Vasudev G. Ananthram, M.D., is a board-certified cardiologist. He practices with Cardiovascular Health, PLLC, a state-of-the-art treatment facility serving Williamsburg and the surrounding area.

Second Opinion by Vasudev G. Ananthram, M.D. Published: June 2006 Q: My uncle recently suffered a heart attack. I’ve heard the terms pacemaker and defibrillator used interchangeably. What are these devices? What is the difference between the two? A: A pacemaker is a device used to correct abnormally slow heartbeats. It’s a system consisting of two special wires known as leads, and a can that contains a tiny computer chip and a battery with a life span of seven to 10 years. Modern pacemakers are small, lightweight, and more versatile than ever before. Slow heartbeat can result from diminished activity of the natural pacemaker cells in the heart, which together comprise an area called the sinus node. It can also result from poor conduction of the heart’s electrical impulses from its upper chambers to its lower chambers. Symptoms generally include fatigue, shortness of breath and, in some cases, loss of consciousness. To implant a pacemaker, the surgeon inserts the two leads through a vein underneath the collarbone and guides them into the upper and lower chambers of the right side of the heart. The chip and battery, housed inside the can, are placed in a pocket created in the soft tissue below the collarbone. Most patients recover quickly from this procedure, but sometimes an overnight stay at the hospital is required for further observation. With a new pacemaker, patients should avoid raising their arm on the same side as the pacemaker above shoulder-level for at least four weeks. A defibrillator, on the other hand, is a device used to correct fast heart rhythms arising from the lower chambers of the heart. Known as ICDs (implantable cardiac defibrillators), these device systems are similar to pacemakers, except that the can that houses the battery and chip is significantly larger. The procedure to implant a defibrillator, and the recovery time required, is similar to that of a pacemaker. A defibrillator can also function as a pacemaker if necessary. Dangerously fast heart rhythms usually arise in the lower chambers of the heart, known as the ventricles. These rhythms are often fatal (causing sudden death) and include fast heartbeats (ventricular tachycardia) and super-fast, but ineffective heartbeats, known as ventricular fibrillation (not to be confused with atrial fibrillation, which are fast and irregular beats arising from the upper chambers of the heart). The cardiac defibrillator senses any dangerous heart rhythms and is programmed to neutralize them. When it first senses abnormal heartbeats (ventricular tachycardia), the defibrillator fires electrical impulses at a rate higher than the faulty heart rhythm, thus attempting to correct them through a function called overriding. In most cases, a patient feels neither the abnormal heart rhythm nor the device action. If the above action fails to correct the errant heart rhythm, or if the rhythm is ventricular fibrillation (too fast), the device charges and then delivers an electric jolt – neutralizing the fatal heart rhythm – thus, saving a life. Many patients describe the sensation as “being kicked by a mule.” More than one shock may be necessary to correct recurrent or errant heart rhythms. If more than two electrical discharges are necessary, emergency medical help may be needed. If two or less shocks are emitted, a cardiologist should be informed promptly. Not everyone with heart disease will need a defibrillator, but those at high risk for dangerous heart rhythms are candidates for receiving one. This includes patients who have experienced errant heart rhythms in the past and survived, or those who’ve had heart failure with severe disruption of the heart’s pumping ability. Patients with certain congenital heart abnormalities may also be candidates for a defibrillator. There are many other factors to consider, and a discussion with a cardiologist about the risks and benefits is advised. Remember that pacemakers are implantable devices used to correct slow heart rhythms. A pacemaker can improve a patient’s overall quality of life, and in many cases, are life-saving devices. Defibrillators correct life threatening fast heartbeats, and can function as pacemakers when necessary. Although the media publicizes failure of these devices, don’t worry; the instance of malfunction is exceedingly low.

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