TUESDAY June 18, 2013 — Defibrillators are little devices that monitor every heartbeat, and when a defibrillator detects that a patient has gone into cardiac arrest it will immediately deliver a life-saving shock. But sometimes those shocks can happen for the wrong reasons — and at a surprisingly high rate.
What does it feel like if one of these defibrillators fires? My patients often describe a “shock” from their defibrillator as a bomb going off inside their chest. For most patients, they would gladly exchange a very short and intense burst of pain for extra years of life.
My colleagues and I recently asked the question, What does it mean to a patient and their family if a defibrillator goes off? Today, the results of our large study were published in the leading Journal of the American College of Cardiology.
In this study, we looked at what happened in 3,809 patients who received a shock from their implantable defibrillator. We then compared the outcomes of these 3,809 patients to 3,630 matched defibrillator patients who did not receive a shock.
The results of our study were really quite striking. Here's what we found over the three-year follow-up period of this study:
- If the shock were to end a cardiac arrest (ventricular fibrillation), patients were 2.1 times more likely to die over the next three years.
- If the shock were to stop ventricular tachycardia, patients were 1.7 times more likely to die over the next three years.
- If the shock was from atrial fibrillation, patients were 1.6 times more likely to die over the next three years. It should be noted here that defibrillators are designed not to deliver a shock for atrial fibrillation. However, if the atrial fibrillation is fast enough it can “fool” the defibrillator and a shock will be delivered.
- If the shock was for a very fast benign arrhythmia or a device malfunction (the device was “fooled”), there was no increased risk of dying.
What do these findings mean? While most of the time the defibrillator went off for the right reason (ventricular tachycardia or ventricular fibrillation), 41% of the shocks were because the device was “fooled” by a non-life threatening arrhythmia or device malfunction.
Clearly, these devices are not doing a very good job if they fire for the right reason only 59% of the time. First, in my opinion, this study should be a wake-up call for defibrillator manufacturers to create a more reliable device that is less likely to go off for the wrong reason.
Interpreting the Inappropriate Shock
Second, if a patient receives a shock for any arrhythmia from the ventricles or for atrial fibrillation, this is a cry for help from the patient's heart. These patients are at high risk of dying and need to be evaluated and treated quickly.
Often what we see is that these patients have gone into heart failure or they may have a blockage of one of the arteries in their heart. Thus, patients who have received a shock for a ventricular arrhythmia or atrial fibrillation require prompt medical attention. With a thorough evaluation and treatment, including lifestyle changes, the heart may be given a chance to heal and reduce the risk of premature death.
Third, these results are reassuring in that there was no increased risk of death if the defibrillator went off for a benign rhythm or device malfunction. Furthermore, it helps to answer the long-standing debate among cardiologists as to whether shocks, in and of themselves, are dangerous or not. Fortunately, the danger is not from the shock but rather from the underlying cardiac condition.
At the end of the day, shocks, both appropriate shocks and inappropriate shocks, are just a part of implantable defibrillator therapy. It is my hope that from this study, device manufacturers will work to create better algorithms and software so that these devices are not so easily fooled, and that physicians caring for patients who have received a shock for ventricular fibrillation/tachycardia or atrial fibrillation will realize the significance of this event and take rapid measures to prevent premature death in these patients.
More on Defibrillators
Who needs an implantable defibrillator? Implantable defibrillators are reserved for patients who have already survived a cardiac arrest or who are at high risk for a cardiac arrest. Defibrillators are specifically designed to treat the life-threatening arrhythmias from the ventricles or the lower chambers of the heart.
Arrhythmias of the upper chamber of the heart, like atrial fibrillation, do not require an implantable defibrillator as these arrhythmias are generally not immediately life-threatening.
What is it like to live with an implantable defibrillator? While they generally do not cause much discomfort, patients can certainly feel the implanted device under the skin. If they are in a swimming suit, you can see the outward bulge of the device on their chest.
These devices help many patients feel more secure as they know that every heartbeat is being monitored. For other patients it can be a huge source of anxiety as they never know whether the device is going to deliver a shock.
Unfortunately, however, these devices are not foolproof and sometimes patients receive a shock for a non-life threatening event or a device malfunction, as our new study demonstrates.
John D. Day, MD, is a cardiologist specializing in heart rhythm disorders at the Intermountain Medical Center Heart Institute. He is an upcoming president of the Heart Rhythm Society and is the editor-in-chief of the Journal of Innovations in Cardiac Rhythm Management. He has published more than 100 medical articles and has an upcoming book entitled The Longevity Plan: Lessons Learned from China’s Longevity Village on How to Lose Weight, Feel Great, and Live Healthy to 110.PHOTO CREDIT: Apogee Apogee/Getty Images
Last Updated: 6/18/2013