Physiology and Pharmacology of the Transplanted Heart

Heart Transplantation and Altered Drug Response, Part II: Pharmacologic Management of Post‐Transplantation Complications

“…In the normal innervated heart, compensatory reflex tachycardia may be necessary to maintain hemodynamic stability in the presence of excessive vasodilatation. In patients with transplanted hearts, this compensatory mechanism can be blunted or delayed, predisposing the patient to potentially dangerous orthostatic hypotensive episodes 26,27 …”

“…Because it indirectly acts to slow the heart rate, digoxin has no electrophysiologic effect in the transplanted heart and, therefore, cannot be used for ventricular rate control in atrial fibrillation or flutter 26,31 . The positive inotropic effects of digoxin, which are not mediated through the autonomic nervous system, are maintained in the heart patient 26,27 …”

“…CCBs and β‐Blockers. Nondihydropyridine CCBs and β‐blockers can be used for rate control but, due to their potentiated responses in the transplanted heart, care should be taken not to cause substantial decrease in heart rate 27,31 …”

“…Agents that have a direct effect on the denervated heart and have been used to treat arrhythmias include quinidine, procainamide, and mexiletine 26,31,34 . Because the normal and sometimes problematic vagolytic effect from the class Ia agents is lost, the use of these agents in heart transplant patients have resulted in decreased sinus rate and increased AV conduction time 27,31 . Animal studies have shown that amiodarone may have exaggerated effects in the heart transplant recipient.…”

“…Because the effects of β‐blockers and the nondihydropyridine CCBs verapamil and diltiazem may be potentiated in the denervated heart, their use in combination should be discouraged 24,26,27 . Their additive negative inotropic effects on the heart especially in the presence of heart block could be dangerous in the transplanted heart patient when the augmented compensatory mechanisms to maintain hemodynamic stability are impaired 3,26,27 …”