My View of Internal Cardioversion and Cellular Memory Reset

Recently, EP MedSystems ALERT® Catheter System for internal cardioversion received FDA Pre-Market Approval. From our experience, we know that many patients are better candidates for internal cardioversion over external cardioversion, such as those who may not be optimal patients for anesthesia, many of the obese patients, and those which have active implantable devices like pacemakers subject to reprogramming. We're pleased that internal cardioversion can now be added to various therapies available to assist atrial fibrillation patients. I found myself explaining the ALERT® System and the intrinsic nature of sinus rhythm to an interested lay person, where I gave the standard domino theory: Dominoes falling down is an analogy about the propagation of depolarization. I realized then, that my explanation, while maybe sounding good to the lay person, never extends to the more mysterious process of repolarization. In fact, when analyzed, the organized individually self-standing-back-up behavior of all the dominoes is the greater miracle, especially if they can all stand back up without any premature re-triggering of the falling down. Within the heart, there clearly must be a regulation mechanism because the heart system shows regulated behavior. In particular, repolarization patterns tend to mirror depolarization, and repolarization will adjust itself slowly over time when a pacemaker is implanted. Thus, it seems the cells are self adjusting, most likely based upon their immediate neighbors. I believe that a defibrillation shock causes a reset of the adjustments back to the nominal, and particularly those cells that have drifted away from the group and are following themselves to trouble. My best analogy of cardiac defibrillation is of a truly large and spread out marching band, where the director cannot be seen by the players. The band can still hold rhythm by each member watching around himself, and the beat propagates outward from the fastest player. Each player has a self-adjusting metronome of when they can look around for the next beat. Trouble can occur when a drummer plays one beat and then quickly sees another player starting the same beat, without waiting long enough, and plays another beat. His wait metronome then makes a small adjustment. The others around him are variously swayed by this and can either ignore it or are sucked in. Eventually, you can have various (small or large) regions off in their own rhythm, even in the presence of otherwise disciplined playing. The offbeat groups may be inaudible to the observers. A defibrillation shock is like setting off a stick of dynamite, which causes the band to fall to the ground and stop playing, and lose any sense of what had been going on, including their ideas about how quickly they should look for the next beat. This minimizes the difficulty for the strong-willed player to actually get control by resynchronizing and resetting the repolarization-time regulation mechanism of any and all (even tiny) pockets of phase drifters, even if they are not visible to the world. The important point is that internal cardioversion seems to have better results than external shocks, especially for lengthening the time between bouts of atrial fibrillation in the chronic patient. Many physicians have observed this, but could not explain why. Well, I think this is big news, because until now, a defibrillation shock is a defibrillation shock; it either works or not. The difference between an external shock and an internal one is the difference between a hand grenade and a full stick of dynamite. The hand grenade, or external shock, simply does not knock down all of the band members. One hundred percent of the cells are not reset. An internal shock, on the other hand, applies its energy directly to the problem (i.e., the heart muscle itself), knocks over all the band members, and achieves resynchronization in 100% of all cardiac cells.