<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Back pain and can you explain it in depth? [/INST] Back pain is pain felt in the back. It may be classified as neck pain (cervical), middle back pain (thoracic), lower back pain (lumbar) or coccydynia (tailbone or sacral pain) based on the segment affected. The lumbar area is the most common area affected. An episode of back pain may be acute, subacute or chronic depending on the duration. The pain may be characterized as a dull ache, shooting or piercing pain or a burning sensation. Discomfort can radiate to the arms and hands as well as the legs or feet, and may include numbness or weakness in the legs and arms.
The majority of back pain is nonspecific and idiopathic. Common underlying mechanisms include degenerative or traumatic changes to the discs and facet joints, which can then cause secondary pain in the muscles and nerves and referred pain to the bones, joints and extremities. Diseases and inflammation of the gallbladder, pancreas, aorta and kidneys may also cause referred pain in the back. Tumors of the vertebrae, neural tissues and adjacent structures can also manifest as back pain.
Back pain is common; approximately nine of ten adults experiencing it at some point in their lives, and five of ten working adults experience back pain each year. Some estimate that as many of 95% of people will experience back pain at some point in their lifetime. It is the most common cause of chronic pain and is a major contributor to missed work and disability. For most individuals, back pain is self-limiting. Most people with back pain do not experience chronic severe pain but rather persistent or intermittent pain that is mild or moderate. In most cases of herniated disks and stenosis, rest, injections or surgery have similar general pain-resolution outcomes on average after one year. In the United States, acute low back pain is the fifth most common reason for physician visits and causes 40% of missed work days. It is the single leading cause of disability worldwide.

Classification
Back pain is classified in terms of duration of symptoms.
Acute back pain lasts <6 weeks
Subacute back pain lasts between 6 and 12 weeks.
Chronic back pain lasts for greater than 12 weeks.

Causes
There are many causes of back pain, including blood vessels, internal organs, infections, mechanical and autoimmune causes. Approximately 90 percent of people with back pain are diagnosed with nonspecific, idiopathic acute pain with no identifiable underlying pathology. In approximately 10 percent of people, a cause can be identified through diagnostic imaging. Fewer than two percent of cases are attributed to secondary factors, with metastatic cancers and serious infections, such as spinal osteomyelitis and epidural abscesses, accounting for approximately one percent.

Nonspecific
In as many as 90 percent of cases, no physiological causes or abnormalities on diagnostic tests can be found. Nonspecific back pain can result from back strain or sprains, which can cause peripheral injury to muscle or ligaments. Many patients cannot identify the events or activities that may have caused the strain. The pain can present acutely but in some cases can persist, leading to chronic pain.
Chronic back pain in people with otherwise normal scans can result from central sensitization, in which an initial injury causes a longer-lasting state of heightened sensitivity to pain. This persistent state maintains pain even after the initial injury has healed. Treatment of sensitization may involve low doses of antidepressants and directed rehabilitation such as physical therapy.

Spinal disc disease
Spinal disc disease occurs when the nucleus pulposus, a gel-like material in the inner core of the vertebral disc, ruptures. Rupturing of the nucleus pulposus can lead to compression of nerve roots. Symptoms may be unilateral or bilateral, and correlate to the region of the spine affected. The most common region for spinal disk disease is at L4–L5 or L5–S1. The risk for lumbar disc disease is increased in overweight individuals because of the increased compressive force on the nucleus pulposus, and is twice as likely to occur in men. A 2002 study found that lifestyle factors such as night-shift work and lack of physical activity can also increase the risk of lumbar disc disease.
Severe spinal-cord compression is considered a surgical emergency and requires decompression to preserve motor and sensory function. Cauda equina syndrome involves severe compression of the cauda equina and presents initially with pain followed by motor and sensory. Bladder incontinence is seen in later stages of cauda equina syndrome.

Degenerative disease
Spondylosis, or degenerative arthritis of the spine, occurs when the intervertebral disc undergoes degenerative changes, causing the disc to fail at cushioning the vertebrae. There is an association between intervertebral disc space narrowing and lumbar spine pain. The space between the vertebrae becomes more narrow, resulting in compression and irritation of the nerves.Spondylolithesis is the anterior shift of one vertebra compared to the neighboring vertebra. It is associated with age-related degenerative changes as well as trauma and congenital anomalies.
Spinal stenosis can occur in cases of severe spondylosis, spondylotheisis and age-associated thickening of the ligamentum flavum. Spinal stenosis involves narrowing of the spinal canal and typically presents in patients greater than 60 years of age. Neurogenic claudication can occur in cases of severe lumbar spinal stenosis and presents with symptoms of pain in the lower back, buttock or leg that is worsened by standing and relieved by sitting.
Vertebral compression fractures occur in four percent of patients presenting with lower back pain. Risk factors include age, female gender, history of osteoporosis, and chronic glucocorticoid use. Fractures can occur as a result of trauma but in many cases can be asymptomatic.

Infection
Common infectious causes of back pain include osteomyelitis, septic discitis, paraspinal abscess and epidural abscess. Infectious causes that lead to back pain involve various structures surrounding the spine.Osteomyelitis is the bacterial infection of the bone. Vertebral osteomyelitis is most commonly caused by staphylococci. Risk factors include skin infection, urinary tract infection, IV catheter use, IV drug use, previous endocarditis and lung disease.
Spinal epidural abscess is commonly caused by severe infection with bacteremia. Risk factors include recent administration of epidurals, IV drug use or recent infection.

Cancer
Spread of cancer to the bone or spinal cord can lead to back pain. Bone is one of the most common sites of metastatic lesions. Patients typically have a history of malignancy. Common types of cancer that present with back pain include multiple myeloma, lymphoma, leukemia, spinal cord tumors, primary vertebral tumors and prostate cancer. Back pain is present in 29% of patients with systemic cancer. Unlike other causes of back pain that commonly affect the lumbar spine, the thoracic spine is most commonly affected. The pain can be associated with systemic symptoms such as weight loss, chills, fever, nausea and vomiting. Unlike other causes of back pain, neoplasm-associated back pain is constant, dull, poorly localized and worsens with rest. Metastasis to the bone also increases the risk of spinal-cord compression or vertebral fractures that require emergency surgical treatment.

Autoimmune
Inflammatory arthritides such as ankylosing spondylitis, psoriatic arthritis, rheumatoid arthritis and systemic lupus erythematosus can all cause varying levels of joint destruction. Among the inflammatory arthritides, ankylosing spondylitis is most closely associated with back pain because of the inflammatory destruction of the bony components of the spine. Ankylosing spondylitis is common in young men and presents with a range of possible symptoms such as uveitis, psoriasis and inflammatory bowel disease.

Referred pain
Back pain can also be referred from another source. Referred pain occurs when pain is felt at a location different than the source of the pain. Disease processes that can present with back pain include pancreatitis, kidney stones, severe urinary tract infections and abdominal aortic aneurysms.

Risk factors
Heavy lifting, obesity, sedentary lifestyle and lack of exercise can increase the risk of back pain. Cigarette smokers are more likely to experience back pain than are nonsmokers. Poor posture and weight gain in pregnancy are also risk factors for back pain. In general, fatigue can worsen pain.A few studies suggest that psychosocial factors such as work-related stress and dysfunctional family relationships may correlate more closely with back pain than do structural abnormalities revealed in X-rays and other medical imaging scans.
While back pain physical effects can range from muscle aching to a shooting, burning, or stabbing sensation.  It can radiate pain down the legs and have pain increased by bending, twisting, lifting, standing, or walking. While the physical effects of back pain are always at the forefront back pain also has other psychological effects. Back Pain has been linked to depression, anxiety, stress, and avoidance behaviors due to mentally not being able to cope with the physical pain. “Both acute and chronic back pain can be associated with psychological distress in the form of anxiety (worries, stress) or depression (sadness, discouragement). Psychological distress is a common reaction to the suffering aspects of acute back pain, even when symptoms are short-term and not medically serious [35]’( (IASP, 2021)

Diagnosis
Initial assessment of back pain consists of a history and physical examination. Important characterizing features of back pain include location, duration, severity, history of prior back pain and possible trauma. Other important components of the patient history include age, physical trauma, prior history of cancer, fever, weight loss, urinary incontinence, progressive weakness or expanding sensory changes, which can indicate a medically urgent condition.Physical examination of the back should assess for posture and deformities. Pain elicited by palpating certain structures may be helpful in localizing the affected area. A neurologic exam is needed to assess for changes in gait, sensation and motor function.
Determining if there are radicular symptoms, such as pain, numbness or weakness that radiate down limbs, is important for differentiating between central and peripheral causes of back pain. The straight leg test is a maneuver used to determine the presence of lumbosacral radiculopathy, which occurs when there is irritation in the nerve root that causes neurologic symptoms such as numbness and tingling. Non-radicular back pain is most commonly caused by injury to the spinal muscles or ligaments, degenerative spinal disease or a herniated disc. Disc herniation and foraminal stenosis are the most common causes of radiculopathy.Imaging of the spine and laboratory tests is not recommended during the acute phase. This assumes that there is no reason to expect that the patient has an underlying problem. In most cases, the pain subsides naturally after several weeks. People who seek diagnosis through imaging are typically less likely to receive a better outcome than are those who wait for the condition to resolve.

Imaging
Magnetic resonance imaging (MRI) is the preferred modality for the evaluation of back pain and visualization of bone, soft tissue, nerves and ligaments. X-rays are a less costly initial option offered to patients with a low clinical suspicion of infection or malignancy, and they are combined with laboratory studies for interpretation.
Imaging is not needed for the majority of patients with back pain. In cases of acute back pain, MRI is recommended for those with major risk factors or clinical suspicion of cancer, spinal infection or severe progressive neurological deficits. For patients with subacute to chronic back pain, MRI is recommended if minor risk factors exist for cancer, ankylosing spondylitis or vertebral compression fracture, or if significant trauma or symptomatic spinal stenosis is present.Early imaging studies during the acute phase do not improve care or prognosis. Imaging findings are not correlated with severity or outcome.

Laboratory studies
Laboratory studies are employed when there are suspicions of autoimmune causes, infection or malignancy. Laboratory testing may include white blood cell (WBC) count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).
Elevated ESR could indicate infection, malignancy, chronic disease, inflammation, trauma or tissue ischemia.
Elevated CRP levels are associated with infection.

Red flags
Imaging is not typically needed in the initial diagnosis or treatment of back pain. However, if there are certain "red flag" symptoms present, plain radiographs (X-ray), CT scan or magnetic resonance imaging may be recommended. These red flags include:
History of cancer
Unexplained weight loss
Immunosuppression
Urinary infection
Intravenous drug use
Prolonged use of corticosteroids
Back pain not improved with conservative management
History of significant trauma
Minor fall or heavy lift in a potentially osteoporotic or elderly individual
Acute onset of urinary retention, overflow incontinence, loss of anal sphincter tone, or fecal incontinence
Saddle anesthesia
Global or progressive motor weakness in the lower limbs

Prevention
Moderate-quality evidence exists that suggests that the combination of education and exercise may reduce an individuals risk of developing an episode of low back pain. Lesser-quality evidence points to exercise alone as a possible deterrent to the risk of the condition.

Management
Nonspecific pain
Patients with uncomplicated back pain should be encouraged to remain active and to return to normal activities.
The management goals when treating back pain are to achieve maximal reduction in pain intensity as rapidly as possible, to restore the individuals ability to function in everyday activities, to help the patient cope with residual pain, to assess for side effects of therapy and to facilitate the patients passage through the legal and socioeconomic impediments to recovery. For many, the goal is to keep the pain at a manageable level to progress with rehabilitation, which then can lead to long-term pain relief. Also, for some people the goal is to use nonsurgical therapies to manage the pain and avoid major surgery, while for others surgery may represent the quickest path to pain relief.Not all treatments work for all conditions or for all individuals with the same condition, and many must try several treatment options to determine what works best for them. The present stage of the condition (acute or chronic) is also a determining factor in the choice of treatment. Only a minority of people with back pain (most estimates are 1–10%) require surgery.

Nonmedical
Back pain is generally first treated with nonpharmacological therapy, as it typically resolves without the use of medication. Superficial heat and massage, acupuncture and spinal manipulation therapy may be recommended.
Heat therapy is useful for back spasms or other conditions. A review concluded that heat therapy can reduce symptoms of acute and subacute low-back pain.
Regular activity and gentle stretching exercises is encouraged in uncomplicated back pain and is associated with better long-term outcomes. Physical therapy to strengthen the muscles in the abdomen and around the spine may also be recommended. These exercises are associated with better patient satisfaction, although they have not been shown to provide functional improvement. However, one review found that exercise is effective for chronic back pain but not for acute pain. Exercise should be performed under the supervision of a healthcare professional.
Massage therapy may provide short-term pain relief, but not functional improvement, for those with acute lower back pain. It may also offer short-term pain relief and functional improvement for those with long-term (chronic) and subacute lower pack pain, but this benefit does not appear to be sustained after six months of treatment. There do not appear to be any serious adverse effects associated with massage.
Acupuncture may provide some relief for back pain. However, further research with stronger evidence is needed.
Spinal manipulation appears similar to other recommended treatments.
"Back school" is an intervention that consists of both education and physical exercises. There is no strong evidence supporting the use of back school for treating acute, subacute, or chronic non-specific back pain.
Insoles appear to be an ineffective treatment intervention.
While traction for back pain is often used in combination with other approaches, there appears to be little or no impact on pain intensity, functional status, global improvement or return to work.

Medication
If nonpharmacological measures are ineffective, medication may be administered.

Non-steroidal anti-inflammatory drugs (NSAIDs) are typically attempted first. NSAIDs have been proven more effective than placebo, and are usually more effective than paracetamol (acetaminophen).
Long-term use of opioids has not been tested to determine whether it is effective or safe for treating chronic lower back pain. For severe back pain not relieved by NSAIDs or acetaminophen, opioids may be used. Opioids may not be better than NSAIDs or antidepressants for chronic back pain with regard to pain relief and gain of function.
Skeletal muscle relaxers may also be used. Their short-term use has been proven effective in the relief of acute back pain. However, the evidence of this effect has been disputed, and these medications do have negative side effects.
For patients with nerve root pain and acute radiculopathy, there is evidence that a single dose of steroids, such as dexamethasone, may provide pain relief.
Epidural corticosteroid injection (ESI) is a procedure in which steroid medications are injected into the epidural space. The steroid medications reduce inflammation and thus decrease pain and improve function. ESI has long been used to both diagnose and treat back pain, although recent studies have shown a lack of efficacy in treating low back pain.

Surgery
Surgery for back pain is typically used as a last resort, when serious neurological deficit is evident. A 2009 systematic review of back surgery studies found that, for certain diagnoses, surgery is moderately better than other common treatments, but the benefits of surgery often decline in the long term.Surgery may sometimes be appropriate for people with severe myelopathy or cauda equina syndrome. Causes of neurological deficits can include spinal disc herniation, spinal stenosis, degenerative disc disease, tumor, infection, and spinal hematomas, all of which can impinge on the nerve roots around the spinal cord. There are multiple surgical options to treat back pain, and these options vary depending on the cause of the pain.
When a herniated disc is compressing the nerve roots, hemi- or partial- laminectomy or discectomy may be performed, in which the material compressing on the nerve is removed. A mutli-level laminectomy can be done to widen the spinal canal in the case of spinal stenosis. A foraminotomy or foraminectomy may also be necessary, if the vertebrae are causing significant nerve root compression. A discectomy is performed when the intervertebral disc has herniated or torn. It involves removing the protruding disc, either a portion of it or all of it, that is placing pressure on the nerve root. Total disc replacement can also be performed, in which the source of the pain (the damaged disc) is removed and replaced, while maintaining spinal mobility. When an entire disc is removed (as in discectomy), or when the vertebrae are unstable, spinal fusion surgery may be performed. Spinal fusion is a procedure in which bone grafts and metal hardware is used to fix together two or more vertebrae, thus preventing the bones of the spinal column from compressing on the spinal cord or nerve roots.If infection, such as a spinal epidural abscess, is the source of the back pain, surgery may be indicated when a trial of antibiotics is ineffective. Surgical evacuation of spinal hematoma can also be attempted, if the blood products fail to break down on their own.

Pregnancy
About 50% of women experience low back pain during pregnancy. Some studies have suggested that women who have experienced back pain before pregnancy are at a higher risk of experiencing back pain during pregnancy. It may be severe enough to cause significant pain and disability in as many as one third of pregnant women. Back pain typically begins at approximately 18 weeks of gestation and peaks between 24 and 36 weeks. Approximately 16% of women who experience back pain during pregnancy report continued back pain years after pregnancy, indicating that those with significant back pain are at greater risk of back pain following pregnancy.Biomechanical factors of pregnancy shown to be associated with back pain include increased curvature of the lower back, or lumbar lordosis, to support the added weight on the abdomen. Also, the hormone relaxin is released during pregnancy, which softens the structural tissues in the pelvis and lower back to prepare for vaginal delivery. This softening and increased flexibility of the ligaments and joints in the lower back can result in pain. Back pain in pregnancy is often accompanied by radicular symptoms, suggested to be caused by the baby pressing on the sacral plexus and lumbar plexus in the pelvis.Typical factors aggravating the back pain of pregnancy include standing, sitting, forward bending, lifting and walking </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Arrhythmia and can you explain it in depth? [/INST] Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults – is called tachycardia, and a resting heart rate that is too slow – below 60 beats per minute – is called bradycardia. Some types of arrhythmias have no symptoms. Symptoms, when present, may include palpitations or feeling a pause between heartbeats. In more serious cases, there may be lightheadedness, passing out, shortness of breath or chest pain. While most cases of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure. Others may result in sudden death.Arrhythmias are often categorized into four groups: extra beats, supraventricular tachycardias, ventricular arrhythmias and bradyarrhythmias. Extra beats include premature atrial contractions, premature ventricular contractions and premature junctional contractions. Supraventricular tachycardias include atrial fibrillation, atrial flutter and paroxysmal supraventricular tachycardia. Ventricular arrhythmias include ventricular fibrillation and ventricular tachycardia. Bradyarrhythmias are due to sinus node dysfunction or atrioventricular conduction disturbances. Arrhythmias are due to problems with the electrical conduction system of the heart. A number of tests can help with diagnosis, including an electrocardiogram (ECG) and Holter monitor.Many arrhythmias can be effectively treated. Treatments may include medications, medical procedures such as inserting a pacemaker, and surgery. Medications for a fast heart rate may include beta blockers, or antiarrhythmic agents such as procainamide, which attempt to restore a normal heart rhythm. This latter group may have more significant side effects, especially if taken for a long period of time. Pacemakers are often used for slow heart rates. Those with an irregular heartbeat are often treated with blood thinners to reduce the risk of complications. Those who have severe symptoms from an arrhythmia or are medically unstable may receive urgent treatment with a controlled electric shock in the form of cardioversion or defibrillation.Arrhythmia affects millions of people. In Europe and North America, as of 2014, atrial fibrillation affects about 2% to 3% of the population. Atrial fibrillation and atrial flutter resulted in 112,000 deaths in 2013, up from 29,000 in 1990. However, in most recent cases concerning the SARS-CoV‑2 pandemic, cardiac arrhythmias are commonly developed and associated with high morbidity and mortality among patients hospitalized with the COVID-19 infection, due to the infections ability to cause myocardial injury. Sudden cardiac death is the cause of about half of deaths due to cardiovascular disease and about 15% of all deaths globally. About 80% of sudden cardiac death is the result of ventricular arrhythmias. Arrhythmias may occur at any age but are more common among older people. Arrhythmias may also occur in children; however, the normal range for the heart rate varies with age.

Classification
Arrhythmia may be classified by rate (tachycardia, bradycardia), mechanism (automaticity, re-entry, triggered) or duration (isolated premature beats; couplets; runs, that is 3 or more beats;  non-sustained = less than 30 seconds or sustained= over 30 seconds).Arrhythmias are also classified by site of origin:

Atrial arrhythmia
Sinus bradycardia
Sinus arrhythmia
Sinus tachycardia
Premature atrial contractions (PACs)
Wandering atrial pacemaker
Atrial tachycardia
Multifocal atrial tachycardia
Supraventricular tachycardia (SVT)
Atrial flutter
Atrial fibrillation (Afib)
AV nodal reentrant tachycardia

Junctional arrhythmia
AV nodal reentrant tachycardia
Junctional rhythm
Junctional tachycardia
Premature junctional contraction

Ventricular arrhythmia
Premature ventricular contractions (PVCs), sometimes called ventricular extra beats (VEBs)
Premature ventricular beats occurring after every normal beat are termed ventricular bigeminy
PVCs that occur at intervals of 2 normal beats to 1 PVC, or 1 normal beat to 2 PVCs, are termed "PVCs in trigeminy"
Groups of three premature ventricular beats are called triplets and are considered a brief run of non-sustained ventricular tachycardia (NSVT); if the grouping lasts for more than 30 seconds, it is considered sustained ventricular tachycardia (VT).
Accelerated idioventricular rhythm
Monomorphic ventricular tachycardia
Polymorphic ventricular tachycardia
Ventricular fibrillation
Torsades de pointes
Arrhythmogenic right ventricular dysplasia
Re-entry ventricular arrhythmia

Heart blocks
These are also known as AV blocks, because the vast majority of them arise from pathology at the atrioventricular node.  They are the most common causes of bradycardia:
First-degree heart block, which manifests as PR prolongation
Second-degree heart block
Type 1 Second degree heart block, also known as Mobitz I or Wenckebach
Type 2 Second degree heart block, also known as Mobitz II
Third-degree heart block, also known as complete heart blockFirst, second, and third-degree blocks also can occur at the level of the sinoatrial junction. This is referred to as sinoatrial block typically manifesting with various degrees and patterns of sinus bradycardia.

Sudden arrhythmic death syndrome
Sudden arrhythmic death syndrome (SADS), is a term used as part of sudden unexpected death syndrome to describe sudden death because of cardiac arrest occasioned by an arrhythmia in the presence or absence of any structural heart disease on autopsy. The most common cause of sudden death in the US is coronary artery disease specifically because of poor oxygenation of the heart muscle, that is myocardial ischemia or a heart attack Approximately 180,000 to 250,000 people die suddenly of this cause every year in the US. SADS may occur from other causes. There are many inherited conditions and heart diseases that can affect young people which can subsequently cause sudden death without advance symptoms.Causes of SADS in young people include viral myocarditis, long QT syndrome, Brugada syndrome, Catecholaminergic polymorphic ventricular tachycardia, hypertrophic cardiomyopathy and arrhythmogenic right ventricular dysplasia.

Fetal arrhythmia
Arrhythmias may also occur in the fetus. The normal heart rate of the fetus is between 110 and 160 beats per minute. Any rhythm beyond these limits is abnormal and classed as a fetal arrhythmia. These are mainly the result of premature atrial contractions, usually give no symptoms, and have little consequence. However, around one percent of these will be the result of significant structural damage to the heart.

Signs and symptoms
The term cardiac arrhythmia covers a very large number of very different conditions.The most common symptom of arrhythmia is an awareness of an abnormal heartbeat, called palpitations. These may be infrequent, frequent, or continuous. Some of these arrhythmias are harmless (though distracting for patients) but some of them predispose to adverse outcomes.Some arrhythmias do not cause symptoms and are not associated with increased mortality.  However, some asymptomatic arrhythmias are associated with adverse events.  Examples include a higher risk of blood clotting within the heart and a higher risk of insufficient blood being transported to the heart because of a weak heartbeat. Other increased risks are of embolization and stroke, heart failure, and sudden cardiac death.If an arrhythmia results in a heartbeat that is too fast, too slow, or too weak to supply the bodys needs, this manifests as lower blood pressure and may cause lightheadedness, dizziness, syncope or brain death due to insufficient supply of blood to the brain.Some types of arrhythmia result in cardiac arrest, or sudden death.Medical assessment of the abnormality using an electrocardiogram is one way to diagnose and assess the risk of any given arrhythmia.

Mechanism
Cardiac arrhythmia are caused by one of two major mechanism.  The first of arrhythmia is a result of enhanced or abnormal impulse formation originating at the pacemaker or the His-Purkinje network. The second is due to reentry conduction disturbances.

Diagnostic
Cardiac arrhythmia is often first detected by simple but nonspecific means: auscultation of the heartbeat with a stethoscope, or feeling for peripheral pulses. These cannot usually diagnose specific arrhythmia but can give a general indication of the heart rate and whether it is regular or irregular. Not all the electrical impulses of the heart produce audible or palpable beats; in many cardiac arrhythmias, the premature or abnormal beats do not produce an effective pumping action and are experienced as "skipped" beats.The simplest specific diagnostic test for assessment of heart rhythm is the electrocardiogram (abbreviated ECG or EKG). A Holter monitor is an EKG recorded over a 24-hour period, to detect arrhythmias that may happen briefly and unpredictably throughout the day.A more advanced study of the hearts electrical activity can be performed to assess the source of the aberrant heart beats. This can be accomplished in an electrophysiology study, an endovascular procedure that uses a catheter to "listen" to the electrical activity from within the heart, additionally if the source of the arrhythmias is found, often the abnormal cells can be ablated and the arrhythmia can be permanently corrected. Transesophageal atrial stimulation (TAS) instead uses an electrode inserted through the esophagus to a part where the distance to the posterior wall of the left atrium is only approximately 5–6 mm (remaining constant in people of different age and weight). Transesophageal atrial stimulation can differentiate between atrial flutter, AV nodal reentrant tachycardia and orthodromic atrioventricular reentrant tachycardia. It can also evaluate the risk in people with Wolff–Parkinson–White syndrome, as well as terminate supraventricular tachycardia caused by re-entry.

Differential diagnosis
Normal electrical activity
Each heartbeat originates as an electrical impulse from a small area of tissue in the right atrium of the heart called the sinus node or sinoatrial node (SA node). The impulse initially causes both atria to contract, then activates the atrioventricular node (AV node), which is normally the only electrical connection between the atria and the ventricles (main pumping chambers).  The impulse then spreads through both ventricles via the bundle of His and the Purkinje fibers causing a synchronized contraction of the heart muscle and, thus, the pulse.In adults, the normal resting heart rate ranges from 60 to 90 beats per minute. The resting heart rate in children is much faster. In athletes, however, the resting heart rate can be as slow as 40 beats per minute, and be considered normal.The term sinus arrhythmia refers to a normal phenomenon of alternating mild acceleration and slowing of the heart rate that occurs with breathing in and out respectively.  It is usually quite pronounced in children and steadily decreases with age. This can also be present during meditation breathing exercises that involve deep inhaling and breath holding patterns.

Bradycardias
A slow rhythm (less than 60 beats/min) is labelled bradycardia. This may be caused by a slowed signal from the sinus node (sinus bradycardia), by a pause in the normal activity of the sinus node (sinus arrest), or by blocking of the electrical impulse on its way from the atria to the ventricles (AV block or heart block). Heart block comes in varying degrees and severity. It may be caused by reversible poisoning of the AV node (with drugs that impair conduction) or by irreversible damage to the node. Bradycardias may also be present in the normally functioning heart of endurance athletes or other well-conditioned persons. Bradycardia may also occur in some types of seizures.

Tachycardias
In adults and children over 15, resting heart rate faster than 100 beats per minute is labeled tachycardia.  Tachycardia may result in palpitation; however, tachycardia is not necessarily an arrhythmia. Increased heart rate is a normal response to physical exercise or emotional stress.  This is mediated by the sympathetic nervous system on the sinus node and called sinus tachycardia.  Other conditions that increase sympathetic nervous system activity in the heart include ingested or injected substances, such as caffeine or amphetamines, and an overactive thyroid gland (hyperthyroidism) or anemia.Tachycardia that is not sinus tachycardia usually results from the addition of abnormal impulses to the normal cardiac cycle.  Abnormal impulses can begin by one of three mechanisms: automaticity, re-entry, or triggered activity.  A specialized form of re-entry which is both common and problematic is termed fibrillation.Although the term "tachycardia" has been known for over 160 years, bases for the classification of arrhythmias are still being discussed.

Heart defects
Congenital heart defects are structural or electrical pathway problems in the heart that are present at birth.  Anyone can be affected by this because overall health does not play a role in the problem.  Problems with the electrical pathway of the heart can cause very fast or even deadly arrhythmias.  Wolff–Parkinson–White syndrome is due to an extra pathway in the heart that is made up of electrical muscle tissue.  This tissue allows the electrical impulse, which stimulates the heartbeat, to happen very rapidly.  Right ventricular outflow tract tachycardia is the most common type of ventricular tachycardia in otherwise healthy individuals.  This defect is due to an electrical node in the right ventricle just before the pulmonary artery.  When the node is stimulated, the patient will go into ventricular tachycardia, which does not allow the heart to fill with blood before beating again.  Long QT syndrome is another complex problem in the heart and has been labeled as an independent factor in mortality.    There are multiple methods of treatment for these including cardiac ablations, medication treatment, or lifestyle changes to have less stress and exercise.

Automaticity
Automaticity refers to a cardiac muscle cell firing off an impulse on its own.  All of the cells in the heart have the ability to initiate an action potential; however, only some of these cells are designed to routinely trigger heartbeats.  These cells are found in the conduction system of the heart and include the SA node, AV node, Bundle of His, and Purkinje fibers.  The sinoatrial node is a single specialized location in the atrium that has a higher automaticity (a faster pacemaker) than the rest of the heart and, therefore, is usually responsible for setting the heart rate and initiating each heartbeat.Any part of the heart that initiates an impulse without waiting for the sinoatrial node is called an ectopic focus and is, by definition, a pathological phenomenon. This may cause a single premature beat now and then, or, if the ectopic focus fires more often than the sinoatrial node, it can produce a sustained abnormal rhythm. Rhythms produced by an ectopic focus in the atria, or by the atrioventricular node, are the least dangerous dysrhythmias; but they can still produce a decrease in the hearts pumping efficiency because the signal reaches the various parts of the heart muscle with different timing than usual and can be responsible for poorly coordinated contraction.Conditions that increase automaticity include sympathetic nervous system stimulation and hypoxia. The resulting heart rhythm depends on where the first signal begins: If it is the sinoatrial node, the rhythm remains normal but rapid; if it is an ectopic focus, many types of dysrhythmia may ensue.

Re-entry
Re-entrant arrhythmias occur when an electrical impulse recurrently travels in a tight circle within the heart, rather than moving from one end of the heart to the other and then stopping.Every cardiac cell can transmit impulses of excitation in every direction but will do so only once within a short time. Normally, the action potential impulse will spread through the heart quickly enough that each cell will respond only once.  However, if there is some essential heterogeneity of refractory period or if conduction is abnormally slow in some areas (for example in heart damage) so the myocardial cells are unable to activate the fast sodium channel, part of the impulse will arrive late and potentially be treated as a new impulse. Depending on the timing, this can produce a sustained abnormal circuit rhythm.
As a sort of re-entry, vortices of excitation in the myocardium (autowave vortices) are considered to be the main mechanism of life-threatening cardiac arrhythmias. In particular, the autowave reverberator is common in the thin walls of the atria, sometimes resulting in atrial flutter. Re-entry is also responsible for most paroxysmal supraventricular tachycardia, and dangerous ventricular tachycardia. These types of re-entry circuits are different from WPW syndromes, which utilize abnormal conduction pathways.
Although omega-3 fatty acids from fish oil can be protective against arrhythmias, they can facilitate re-entrant arrhythmias.

Fibrillation
When an entire chamber of the heart is involved in multiple micro-reentry circuits and is, therefore, quivering with chaotic electrical impulses, it is said to be in fibrillation.
Fibrillation can affect the atrium (atrial fibrillation) or the ventricle (ventricular fibrillation): ventricular fibrillation is imminently life-threatening.

Atrial fibrillation affects the upper chambers of the heart, known as the atria. Atrial fibrillation may be due to serious underlying medical conditions and should be evaluated by a physician. It is not typically a medical emergency.
Ventricular fibrillation occurs in the ventricles (lower chambers) of the heart; it is always a medical emergency. If left untreated, ventricular fibrillation (VF, or V-fib) can lead to death within minutes. When a heart goes into V-fib, effective pumping of the blood stops. V-fib is considered a form of cardiac arrest. An affected individual will not survive unless cardiopulmonary resuscitation (CPR) and defibrillation are provided immediately.CPR can prolong the survival of the brain in the lack of a normal pulse, but defibrillation is the only intervention that can restore a healthy heart rhythm. Defibrillation is performed by applying an electric shock to the heart, which resets the cells, permitting a normal beat to re-establish itself.

Triggered beats
Triggered beats occur when problems at the level of the ion channels in individual heart cells result in abnormal propagation of electrical activity and can lead to a sustained abnormal rhythm. They are relatively rare and can result from the action of anti-arrhythmic drugs, or after depolarizations.

Management
The method of cardiac rhythm management depends firstly on whether the affected person is stable or unstable. Treatments may include physical maneuvers, medications, electricity conversion, or electro- or cryo-cautery.In the United States, people admitted to the hospital with cardiac arrhythmia and conduction disorders with and without complications were admitted to the intensive care unit more than half the time in 2011.

Physical maneuvers
Several physical acts can increase parasympathetic nervous supply to the heart, resulting in blocking of electrical conduction through the AV node.  This can slow down or stop several arrhythmias that originate above or at the AV node (see main article: supraventricular tachycardias).  Parasympathetic nervous supply to the heart is via the vagus nerve, and these maneuvers are collectively known as vagal maneuvers.

Antiarrhythmic drugs
There are many classes of antiarrhythmic medications, with different mechanisms of action and many different individual drugs within these classes.  Although the goal of drug therapy is to prevent arrhythmia, nearly every antiarrhythmic drug has the potential to act as a pro-arrhythmic, and so must be carefully selected and used under medical supervision.

Other drugs
Several groups of drugs slow conduction through the heart, without actually preventing an arrhythmia.  These drugs can be used to "rate control" a fast rhythm and make it physically tolerable for the patient.Some arrhythmias promote blood clotting within the heart and increase the risk of embolus and stroke.  Anticoagulant medications such as warfarin and heparins, and anti-platelet drugs such as aspirin can reduce the risk of clotting.

Electricity
Arrhythmias may also be treated electrically, by applying a shock across the heart – either externally to the chest wall, or internally to the heart via implanted electrodes.Cardioversion is either achieved pharmacologically or via the application of a shock synchronized to the underlying heartbeat.  It is used for the treatment of supraventricular tachycardias. In elective cardioversion, the recipient is usually sedated or lightly anesthetized for the procedure.
Defibrillation differs in that the shock is not synchronized.  It is needed for the chaotic rhythm of ventricular fibrillation and is also used for pulseless ventricular tachycardia </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Urethra and can you explain it in depth? [/INST] The urethra (from Greek οὐρήθρα – ourḗthrā) is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra connects to the urinary meatus above the vagina, whereas in marsupials, the females urethra empties into the urogenital sinus.Females use their urethra only for urinating, but males use their urethra for both urination and ejaculation. The external urethral sphincter is a striated muscle that allows voluntary control over urination. The internal sphincter, formed by the involuntary smooth muscles lining the bladder neck and urethra, receives its nerve supply by the sympathetic division of the autonomic nervous system. The internal sphincter is present both in males and females.

Structure
The urethra is a fibrous and muscular tube which connects the urinary bladder to the external urethral meatus. Its length differs between the sexes, because it passes through the penis in males.

Male
In the human male, the urethra is on average 18 to 20 centimeters (7.1 to 7.9 inches) long and opens at the end of the external urethral meatus.The urethra is divided into four parts in men, named after the location:
There is inadequate data for the typical length of the male urethra; however, a study of 109 men showed an average length of 22.3 cm (SD = 2.4 cm), ranging from 15 cm to 29 cm.

Female
In the human female, the urethra is about 4 cm long, and exits the body between the clitoris and the vagina, extending from the internal to the external urethral orifice. The meatus is located below the clitoris. It is placed behind the symphysis pubis, embedded in the anterior wall of the vagina, and its direction is obliquely downward and forward; it is slightly curved with the concavity directed forward. The proximal two-thirds of the urethra is lined by transitional epithelial cells, while the distal third is lined by stratified squamous epithelial cells.Between the superior and inferior fascia of the urogenital diaphragm, the female urethra is surrounded by the urethral sphincter.

Microanatomy
The cells lining the urethra (the epithelium) start off as transitional cells as it exits the bladder, which are variable layers of flat to cuboidal cells that change shape depending on whether they are compressed by the contents of the urethra. Further along the urethra there are pseudostratified columnar and stratified columnar epithelia. The lining becomes multiple layers of flat cells near the end of the urethra, which is the same as the external skin around it.There are small mucus-secreting urethral glands, as well as bulbo-urethral glands of Cowper, that secret mucous acting to lubricate the urethra.The urethra consists of three coats: muscular, erectile, and mucous, the muscular layer being a continuation of that of the bladder.

Blood and nerve supply and lymphatics
Somatic (conscious) innervation of the external urethral sphincter is supplied by the pudendal nerve.

Development
In the developing embryo, at the hind end lies a cloaca. This, over the fourth to the seventh week, divides into a urogenital sinus and the beginnings of the anal canal, with a wall forming between these two inpouchings called the urorectal septum. The urogenital sinus divides into three parts, with the middle part forming the urethra; the upper part is largest and becomes the urinary bladder, and the lower part then changes depending on the biological sex of the embryo. The cells lining the urethra (the epithelium) come from endoderm, whereas the connective tissue and smooth muscle parts are derived from mesoderm.After the third month, urethra also contributes to the development of associated structures depending on the biological sex of the embryo. In the male, the epithelium multiples to form the prostate. In the female, the upper part of the urethra forms the urethra and paraurethral glands.

Function
Urination
The urethra is the vessel through which urine passes after leaving the bladder. During urination, the smooth muscle lining the urethra relaxes in concert with bladder contraction(s) to forcefully expel the urine in a pressurized stream. Following this, the urethra re-establishes muscle tone by contracting the smooth muscle layer, and the bladder returns to a relaxed, quiescent state. Urethral smooth muscle cells are mechanically coupled to each other to coordinate mechanical force and electrical signaling in an organized, unitary fashion.

Ejaculation
The male urethra is the conduit for semen during sexual intercourse. Urine is removed before ejaculation by pre-ejaculate fluid – called Cowpers fluid – from the bulbourethral gland.

Clinical significance
Infection of the urethra is urethritis, which often causes purulent urethral discharge. It is most often due to a sexually transmitted infection such as gonorrhoea or chlamydia, and less commonly due to other bacteria such as ureaplasma or mycoplasma; trichomonas vaginalis; or the viruses herpes simplex virus and adenovirus. Investigations such as a gram stain of the discharge might reveal the cause; nucleic acid testing based on the first urine sample passed in a day, or a swab of the urethra sent for bacterial culture and sensitivity may also be used. Treatment usually involves antibiotics that treat both gonorrhoea and chlamydia, as these often occur together. A person being treated for urethritis should not have sex until the infection is treated, so that they do not spread the infection to others. Because of this spread, which may occur during an incubation period before a person gets symptoms, there is often contact tracing so that sexual partners of an affected person can be found and treatment offered.Cancer can also develop in the lining of the urethra. When cancer is present, the most common symptom in an affected person is blood in the urine; a physical medical examination may be otherwise normal, except in late disease. Cancer of the urethra is most often due to cancer of the cells lining the urethra, called transitional cell carcinoma, although it can more rarely occur as a squamous cell carcinoma if the type of cells lining the urethra have changed, such as due to a chronic schistosomiasis infection. Investigations performed usually include collecting a sample of urine for an inspection for malignant cells under a microscope, called cytology, as well as examination with a flexible camera through the urethra, called urethroscopy. If a malignancy is found, a biopsy will be taken, and a CT scan will be performed of other body parts (a CT scan of the chest, abdomen and pelvis) to look for additional metastatic lesions. After the cancer is staged, treatment may involve chemotherapy.

Injury
Passage of kidney stones through the urethra can be painful. Damage to the urethra, such as by kidney stones, chronic infection, cancer, or from catheterisation, can lead to narrowing, called a urethral stricture. The location and structure of the narrowing can be investigated with a medical imaging scan in which dye is injected through the urinary meatus into the urethra, called a retrograde urethrogram </s>


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<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Oligospermia and can you explain it in depth? [/INST] Terms oligospermia, oligozoospermia, and low sperm count refer to semen with a low concentration of sperm and is a common finding in male infertility. Often semen with a decreased sperm concentration may also show significant abnormalities in sperm morphology and motility (technically oligoasthenoteratozoospermia). There has been interest in replacing the descriptive terms used in semen analysis with more quantitative information.

Diagnosis
The diagnosis of oligozoospermia is based on one low count in a semen analysis performed on two occasions. For many decades sperm concentrations of less than 20 million sperm/ml were considered low or oligospermic, recently, however, the WHO reassessed sperm criteria and established a lower reference point, less than 15 million sperm/ml, consistent with the 5th percentile for fertile men. Sperm concentrations fluctuate and oligospermia may be temporary or permanent.
Sources usually classify oligospermia in 3 classes:
Mild: concentrations 10 million – 15 million sperm/mL
Moderate: concentrations 5 million – 10 million sperm/mL
Severe: concentrations less than 5 million sperm/mLThe diagnosis of oligozoospermia requires a work-up via semen analysis (listed in Male infertility).

Causes
There are many causes for oligospermia including:

Pre-testicular causes
Pre-testicular factors refer to conditions that impede adequate support of the testes and include situations of poor hormonal support and poor general health including:

Hypogonadism due to various causes
Drugs, alcohol, smoking
Strenuous riding (bicycle riding, horseback riding)
Medications, including androgens.

Testicular factors
Testicular factors refer to conditions where the testes produces semen of poor quality despite adequate hormonal support and include:

Age
Genetic defects on the Y chromosome
Y chromosome microdeletions
Abnormal set of chromosomes
Klinefelter syndrome
Neoplasm, e.g. seminoma
Cryptorchidism
Varicocele (14% in one study)
Trauma
Hydrocele
Mumps
Malaria
Defects in USP26 enzyme in some casesMast cells releasing inflammatory mediators appear to directly suppress sperm motility in a potentially reversible manner, and may be a common pathophysiological mechanism for several of the above-mentioned factors.

Post-testicular causes
Post-testicular factors decrease male fertility due to conditions that affect the male genital system after testicular sperm production and include defects of the genital tract as well as problems in ejaculation:

Vas deferens obstruction
Lack of Vas deferens, often related to genetic markers for cystic fibrosis
Infection, e.g. prostatitis
Ejaculatory duct obstruction

Idiopathic oligospermia (oligoasthenoteratozoospermia)
In about 30% of infertile men no causative factor is found for their decrease in sperm concentration or quality by common clinical, instrumental, or laboratory means, and the condition is termed "idiopathic" (unexplained). A number of factors may be involved in the genesis of this condition, including age, infectious agents ( such as Chlamydia trachomatis), Y chromosome microdeletions, mitochondrial changes, environmental pollutants, and "subtle" hormonal changes.A review in 2013 came to the result that oligospermia and azoospermia are significantly associated with being overweight (odds ratio 1.1), obese (odds ratio 1.3) and morbidly obese (odds ratio 2.0), but the cause of this is unknown. It found no significant relation between oligospermia and being underweight.

DNA damage
The human breast cancer susceptibility gene 2 (BRCA2) is employed in homologous recombinational repair of DNA damages during meiosis </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Onset and can you explain it in depth? [/INST]  </s>