Evidence that cocaine slows cardiac conduction by an action on both AV nodal and His-Purkinje tissue in the dog.
The effects of intravenous cocaine (2 mg/kg) were tested on several indices of cardiac electrical activity in sedated dogs. These included sinus rate, PR, AH, and HV intervals; AV nodal effective refractory period (AVNERP); ventricular effective refractory period; QRS duration; and the QT interval. Cocaine induced significant changes in six control animals with an intact-functioning autonomic nervous systems. After pharmacologic autonomic blockade with propranolol plus propantheline, cocaine increased the PR interval (+ 11 +/- 4.0 ms, p less than 0.05), primarily by slowing conduction at the AV nodal level. However, with constant atrial pacing at a rate above the sinus cycle length, prolongation of both the AH and the HV intervals (+ 15 +/- 2.5 and 6.7 +/- 1.7 ms, respectively) occurred. There was also a significant increase in the AVNERP (+ 29 +/- 5.9 ms, p less than 0.05). Consistent with the observed rate-dependent HV prolongation, cocaine decreased the rate of rise of phase 0 of the transmembrane action potential of Purkinje fibers. These data indicate that cocaine impairs cardiac conduction by direct actions on AV nodal and His-Purkinje cells.
Department of Medicine and Pharmacology, Georgetown University School of Medicine, Washington, DC.
C M
CM
Tracy
L
L
Bachenheimer
A
A
Solomon
M M
MM
Cohen
F E
FE
Kuhn
R
R
Jain
P B
PB
Corr
R A
RA
Gillis
D000200:Action Potentials; D000818:Animals; D001283:Atrioventricular Node / Q000503:physiopathology; D001341:Autonomic Nervous System / Q000503:physiopathology; D001794:Blood Pressure; D003042:Cocaine / Q000494:pharmacology*; D004285:Dogs; D004562:Electrocardiography; D006329:Heart Conduction System / Q000187:drug effects / Q000503:physiopathology*; D006339:Heart Rate; D008297:Male; D011690:Purkinje Fibers / Q000187:drug effects / Q000503:physiopathology*
D003042:Cocaine