Electrophysiological effects of carvedilol administration in patients with dilated cardiomyopathy.
OBJECTIVE
Several studies suggest the clinical efficacy of carvedilol in reducing atrial and ventricular arrhythmias in patients with left ventricular dysfunction (LVD) due to congestive heart failure (CHF) or following myocardial infarction. However, the mechanisms supporting its antiarrhythmic efficacy have been derived from experimental studies. In this prospective, placebo-controlled trial we examined the electrophysiological effects of a high oral dose of carvedilol in patients with CHF and LVD due to non-ischemic dilated cardiomyopathy.


METHODS
Thirty-one patients with stable CHF underwent electrophysiological study and were randomly assigned to treatment with carvedilol or placebo. After 2 months of treatment the study was repeated.


RESULTS
Carvedilol prolonged almost all conduction times. In the same group atrial and ventricular effective refractory periods were significantly prolonged, while the parameters of repolarization remained virtually unchanged. The prolongation of refractoriness was most pronounced in the atrium. The change in ventricular refractoriness was correlated with ejection fraction (r = 0.94, p < 0.01) suggesting that patients with more preserved left ventricular function responded to treatment with greater prolongation.


CONCLUSIONS
Even after a short period of administration carvedilol has marked and diffused electrophysiological effects that would be beneficial for patients with CHF and may contribute to the positive outcome of clinical trials.
Kanoupakis
Emmanuel M
EM
Cardiology Department, Heraklion University Hospital, Heraklion, Crete, Greece.
Manios
Emmanuel G
EG
Mavrakis
Hercules E
HE
Kallergis
Eleftherios M
EM
Lyrarakis
George M
GM
Koutalas
Emmanuel P
EP
Vardas
Panos E
PE
D000200:Action Potentials / Q000187:drug effects; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000368:Aged; D001794:Blood Pressure / Q000187:drug effects; D002227:Carbazoles / Q000627:therapeutic use*; D002311:Cardiomyopathy, Dilated / Q000188:drug therapy* / Q000503:physiopathology*; D002316:Cardiotonic Agents / Q000627:therapeutic use; D000077261:Carvedilol; D016757:Death, Sudden, Cardiac / Q000517:prevention & control; D004562:Electrocardiography / Q000187:drug effects; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011412:Propanolamines / Q000627:therapeutic use*; D012032:Refractory Period, Electrophysiological / Q000187:drug effects; D012306:Risk; D012849:Sinoatrial Node / Q000187:drug effects; D013318:Stroke Volume / Q000187:drug effects / Q000502:physiology; D017180:Tachycardia, Ventricular / Q000188:drug therapy / Q000503:physiopathology; D016277:Ventricular Function, Left / Q000187:drug effects; D016278:Ventricular Function, Right / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D002227:Carbazoles; D002316:Cardiotonic Agents; D011412:Propanolamines; D000077261:Carvedilol