Arrhythmias and clinical electrophysiology of the transplanted human heart

The denervated transplanted heart has given us numerous opportunities to assess normal and abnormal electrophysiology and the influence of the autonomic system on these parameters. Observation of baseline electrophysiology of the denervated heart and its response to various physiologic and pharmacologic stimuli has emphasized the role of the parasympathetic system on heart rate and arrhythmia modulation in the normal population. In the transplant patients, the denervated hearts lack the full spectrum of physiologic responses due to the absence of vagally mediated neurostimuli. This results in a higher resting heart rate, sluggish rate response to exercise, and perhaps inadequate response to some commonly used drugs such as atropine and digitalis. Nevertheless, the heart's overall response to physiologic demands and various pharmacologic maneuvers including beta-antagonists and antagonists remains relatively normal and the patient's overall cardiac performance appears to be quite adequate. Thus, despite its shortcomings, the denervated heart provides near normal functional integrity and overall improved quality of life. Arrhythmias are generally a minor problem in these patients. Although there appears to be a high prevalence of various forms of arrhythmias, most present as isolated and insignificant problems. The more severe arrhythmias consist primarily of atrial tachyarrhythmias that are usually associated with acute rejection, and treatment for these arrhythmias never pose serious difficulty. However, sudden death remains an intriguing issue. Clearly, serious ventricular tachyarrhythmias can occur in these patients, arguing against the concept of a primary role of an intact autonomic nervous system for the generation of arrhythmia.(ABSTRACT TRUNCATED AT 250 WORDS)