Cocaine and the Heart
Cocaine is a potent illicit stimulant produced from the leaves of the coca plant. It is widely used in the powder form which is inhaled or in the chunky form which is smoked (crack cocaine). Cocaine is often mixed with other substances to ‘cut’ the pure drug, thereby diluting it. Sometimes these fillers or bulking agents are inert substances while at other time it can be toxic compounds.
Cocaine may also be mixed with other drugs like amphetamines, heroin and morphine for a more potent narcotic effect. Cocaine induces a sense of euphoria due to stimulating a massive release of brain hormones (neurotransmitters) like dopamine which acts on the pleasure and reward center in the brain. It also has a host of other effects on almost every organ and system in the body.
The heart is in constant action throughout life. Sometimes it pumps harder during physical activity and at other times slower when a person is at rest or asleep. The wall of the heart is made up of three layers and the thickest section is smooth muscle known as the myocardium. It has an extensive blood supply through the coronary arteries to ensure an adequate supply of oxygen and nutrients.
The heart has a natural pacemaker that initiates its own electrical impulses. These impulses propagate through the heart wall to ensure that the upper chambers receiving blood (atria) contract separately from the lower chambers (ventricles) that push blood out of the heart. Nerve impulses from the brain and different hormones can also speed up or slow down the heart rate in response to different conditions.
Effects of Cocaine on the Heart
Cocaine has several effects on the body, some of which can be life threatening. It can cause three types of heart problems :
- abnormal heart rhythm (dysrrhythmia)
- death of a portion of the heart muscle (myocardial infarction/heart attack)
- enlargement of the heart with weakening of the walls (dilated cardiomyopathy)
Cocaine use can also cause myocarditis although the exact mechanism is not always understood. Ultimately all these heart problems can culminate in heart failure and eventually lead to death. It is often difficult to separate all three heart problems with cocaine usage as each are closely related.
Cocaine and Dysrrhythmia
Cocaine-induced dysrrhythmia is the most common cause of cocaine-related death that is not associated with trauma. The cardiac cycle is a carefully coordinated process that ensures that the heart fills with blood when its walls relax (diastole) and blood is propelled out of the heart when its walls contract (systole). It is synchronized interplay of events involving the heart muscle, valves, nerves, volume of blood entering and leaving the heart and the resistance of the great blood vessels of the heart.
Abnormal heart rhythm
Cocaine can affect the nerves that comprise the electrical conduction system of the heart in several ways and ultimately disrupt the cardiac cycle. Firstly the neurotransmitters (chemicals) which conduct impulses between the nerve cells leaves one nerve cell to stimulate the next nerve cell along its path. These chemicals have a short duration of action but it is prolonged with cocaine use. This means that its effects are sustained for a longer period. Secondly, cocaine can act as an anesthetic and can block nerve impulses traveling along the conduction system of the heart.
Another mechanism by which cocaine affects the heart is that it can delay the propagation of nerve impulses through the heart wall which allows for different chambers of the heart to contract at specific times in the cardiac cycle. Depending on the extent of the disruption, dysrrhythmias may lead to :
- Rapid heart rate (tachycardia)
- Increased myocardial demand
- Narrowing of the arteries (vasoconstriction)
- High blood pressure (hypertension)
Cocaine and Heart Attacks
Most heart attacks arise with underlying coronary artery disease. These arteries supply blood laden with nutrients and oxygen to the heart wall, especially the demanding muscle layer, the myocardium. In coronary artery disease (CAD), the arteries are narrowed due to the build up of fatty plaques within the wall (atherosclerosis). The blood supply to the heart wall is restricted but in most cases it does not cause any significant problem except when a person is physically active or undergoing psychological stress.
Coronary artery blood flow
A sudden narrowing that causes an almost total occlusion of the artery leads to a heart attack – this may be due to a blood clot or coronary artery spasm. In a heart attack, a portion of the heart wall muscle dies – myocardial infarction. Heart attacks with cocaine use may or may not be related to underlying heart or coronary artery disease. However, regular users of cocaine may develop various chronic types of heart disease that can culminate in a heart attack at some point. In fact long term cocaine use can cause or exacerbate coronary atherosclerosis.
Sometimes cocaine use leads to awareness of underlying heart disease that was asymptomatic up to that point. Even a person without any pre-existing coronary disease may be at risk of a heart attack, sometimes even with once-off use of cocaine. Apart from its effects on the heart and the coronary arteries, cocaine can also affect the blood making it more likely to clot which is an important factor in heart attacks.
- Rapid heart rate (tachycardia)
- Increased myocardial demand
- Atherosclerosis coronary artery
- Vasospasm of the coronary artery (Prinzmetal’s angina)
- Hypercoagulability of the blood
Cocaine and an Enlarged Heart
The heart muscle, myocardium, is the thickest portion of the heart wall. The heart being a muscular pump needs to have muscle that can function adequately throughout life, stretching to receive incoming blood into the heart and contracting to push the blood throughout the body. The myocardium is smooth muscle meaning that it contracts and relaxes without voluntary action. It is controlled by the nerve impulses of the electrical conduction system of the heart. Neurotransmitters from outside the heart can also increase the muscle contractility.
Heart muscle strength and size
Cardiomyopathy is the term for disease of the heart muscle due to various mechanisms. One type of cardiomyopathy that is commonly seen with cocaine use is dilated cardiomyopathy, commonly referred to as heart enlargement. Other types may also arise amongst cocaine users. There are many reasons why cardiomyopathy arises with cocaine use. Ultimately the degree to which heart can stretch and fill with blood or contract and push out blood is affected. To compensate the heart muscle may enlarge but in the process it occupies space and reduces the volume of the chamber. Since less blood can fill the chamber, less blood is pushed out into the circulation.
Cocaine-related cardiomyopathy develops over time (subacute or chronic) and not suddenly (acute) as is the case with a heart attack or dysrrhythmia. It can arise for many of the same reasons why the other heart problems occur. In fact cardiomyopathy may develop as a consequence of preceding dysrrhythmia or heart attacks.
- Heart muscle injury (ischemia) or death (infacrtion).
- Reduced muscle contractility strength
- Decreased cardiac output
- Lower oxygen supply to the heart muscle and rest of the body
Treatment of Cocaine Heart Problems
Stopping cocaine use is the first and main step in the treatment of cocaine-induced heart problems. Some of the heart problems maybe reversible. In fact cardiomyopathy which is often irreversible can reverse in many instances when it is a result of prolonged cocaine use. However, conditions like a myocardial infarction is permanent as the portion of the muscle is dead and scar tissue may develop. Nevertheless stopping cocaine use immediately can prevent any further complications from arising.
Heart problems amongst cocaine users may not always be due to the illicit substance. These patients may have had risk factors for the relevant heart disease and cocaine may have just been an additional risk. It can therefore exacerbate or accelerate the cardiac condition that was probably going to arise in time even without cocaine use. The treatment measures for these specific heart problems is essentially the same for cocaine users and non-users. This includes :
- Drugs to reduce blood pressure and heart muscle contractility.
- Pacemakers to restore the heart rate and rhythm.
- Coronary artery angioplasty and stenting to widen the blood vessel.
- Coronary artery bypass surgery to establish and alternative route for blood flow.