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Pacemaker or Defibrillator? How They Change the Heart’s Rhythm

September 24, 2019

There have been tremendous advancements recently in the evaluation and treatment of heart rhythm disturbances, also known as cardiac arrhythmias. Physicians who specialize in the evaluation and treatment of these electrical disturbances of the heart are known as cardiac electrophysiologists.  Dr. Mark Marieb, System Director of the Electrophysiology Labs for the Hartford HealthCare Heart & Vascular Institute, is such a doctor.

Q: What types of heart rhythm problems do you see in your practice?
These electrical disturbances of cardiac rhythm or arrhythmias are numerous. We evaluate and treat extra heart beats known as premature beats. We deal with slow heart rhythms also known as bradycardia. Fast heart rhythms are also called tachycardia. They can come from the upper chambers or atria and this is called supra-ventricular tachycardia. An irregular and usually rapid rhythm coming from the atria known as atrial fibrillation is extremely important as it is very common, can cause debilitating symptoms, and is an important cause of stroke. Finally, rapid rhythms coming from the lower chambers of the heart known as ventricular tachycardia and fibrillation can be very serious and can lead to cardiac arrest and sudden cardiac death.


Q: Tell us about pacemakers and defibrillators. What are these devices used for? Are there recent advances in these devices?
Pacemakers were first introduced in the late 1950s and defibrillators in the early 1980s. Since then, they have become smaller, last longer, and have more features. They are now able to be wirelessly monitored remotely from the patient’s home, checking things such as the battery, leads and they can also detect arrhythmias. Newer pacemakers and defibrillators are MRI conditional, meaning patients with these devices can now safely undergo MRI scans.

In terms of pacemakers, we are now also using them not only for slow beats, but also to synchronize the beating of both sides of the heart by placing a lead to the left side of the heart and pacing the right and left ventricles simultaneously. This resynchronization can strengthen the heart in certain patients. We are now also using a technique known as HIS bundle pacing, where a pacing lead is placed to capture the normal electrical or bundle system of the heart. It has been shown that this can preserve normal pumping function of the heart. Finally, we are now implanting leadless pacemakers, known as a Micra device; this tiny pacemaker looks like a small bullet and is implanted through a vein directly into the heart, and there are no leads or surgery needed.

In terms of defibrillators, they are now implanted in a similar fashion to pacemakers. However, as opposed to pacemakers which are mostly used to treat slow rhythms, these devices do the opposite; they are used to treat dangerous fast rhythms originating in the lower pumping chambers or ventricles of the heart. These arrhythmias known as ventricular tachycardia and ventricular fibrillation can be very dangerous and can lead to sudden death and cardiac arrest. The defibrillator automatically detects these fast rhythms and delivers a shock to the heart reversing the dangerous rhythm disturbance. These devices also contain a pacemaker as patients often need both functions. One other newer device known as a subcutaneous defibrillator is implanted only under the skin. There are no wires or leads placed within the heart.

Q: Tell us about catheter ablation of cardiac arrhythmias.
I would start by saying that although we have a variety of medications to treat arrhythmias and use them on a daily basis, they are often ineffective and can have side effects. Therefore, ablation has become very popular. This procedure can effectively treat the arrhythmias we have been discussing, including supra-ventricular tachycardia, atrial fibrillation, and ventricular tachycardia. The technique uses catheters that have electrodes on them placed through veins into the heart. Next, mapping is performed, which utilizes specialized computer systems and the electrode catheters to localize the area of heart tissue causing the arrhythmia. Finally, a special catheter is moved to the area of the heart and radio frequency energy is delivered which heats and cauterizes the abnormal heart tissue destroying it. In some instances, the tissue is destroyed by freezing or cryo-ablation as opposed to heating. Typically patients are discharged on the following day.

Q: What do you feel sets the Hartford HealthCare Electrophysiology service apart?
There are several factors that set us apart. We have expanded to a third state-of-the-art electrophysiology lab at Hartford Hospital, and are planning a state-of-the-art facility at MidState Medical Center, where we already implant pacemakers and defibrillators. We have a newly renovated pre-and post-procedure area just around the corner from the labs, leading to excellent continuity of care and patient comfort. All patients are sedated and kept comfortable by our excellent anesthesia staff. To accommodate our increasing patient volume we have recently expanded to a total of 6 other very well trained and talented electrophysiology physicians in our group. Our nurses and technicians are specialized in the care of patients with arrhythmias and in running our complex equipment. Finally, our Hartford HealthCare Heart & Vascular Institute administration have been extremely supportive in all respects. For example, we have four different types of mapping systems to guide us in our ablation procedures.

Learn more about treatment for heart rhythm problems here