Characterization of the in vivo cardiac electrophysiologic effects of high-dose cocaine in closed-chest, anesthetized dogs with normal hearts.
OBJECTIVE
To characterize the cardiac electrophysiologic effects of cocaine.


METHODS
In 8 dogs (9-13 kg), electrophysiologic parameters and programmed stimulation were undertaken using transvenous catheters at baseline, and after cocaine intravenous infusion (12 mg/kg bolus followed by 0.22 mg/kg/min for 25 minutes).


RESULTS
Cocaine plasma levels (n=5) rose to 6.73 +/- 0.56 mg/mL. Cocaine did not affect sinus cycle length and arterial pressure. Cocaine prolonged P wave duration (54 +/- 6 vs 73 +/- 4 ms, P<0.001), PR interval (115 +/- 17 vs 164 +/- 15 ms, P<0.001), QRS duration (62 +/- 10 vs 88 +/- 14 ms, P<0.001), and QTc interval (344 +/- 28 vs 403 +/- 62 ms, P=0.03) but not JT interval (193 +/- 35 vs 226 +/- 53 ms, NS). Cocaine prolonged PA (9 +/- 6 vs 23 +/- 8 ms, P<0.001), AH (73 +/- 16 vs 92 +/- 15 ms; P=0.03), and HV (35 +/- 5 vs 45 +/- 3 ms; P<0.001) intervals and Wenckebach point (247 +/- 26 vs 280 +/- 28 ms, P=0.04). An increase occurred in atrial (138 +/- 8 vs 184 +/- 20 ms; P<0.001) and ventricular (160 +/- 15 vs 187 +/- 25 ms; P=0.03) refractoriness at a cycle length of 300 ms. Atrial arrhythmias were not induced in any dog. Ventricular fibrillation (VF) was induced in 2/8 dogs at baseline and 4/8 dogs after cocaine.


CONCLUSIONS
High doses of cocaine exert significant class I effects and seem to enhance inducibility of VF but not of atrial arrhythmias.
Fenelon
Guilherme
G
Paulista School of Medicine, Federal University of São Paulo, São Paulo, SP, Brazil. guilhermefenelon@uol.com.br
Uchoa
Júlio
J
Otobone
José Roberto
JR
Reis
Marcos
M
do Amaral
José Luiz Gomes
JL
de Paola
Angelo A V
AA
D000758:Anesthesia; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology*; D004285:Dogs; D004562:Electrocardiography; D004594:Electrophysiology; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006439:Hemodynamics; D008297:Male; D014693:Ventricular Fibrillation / Q000139:chemically induced
D000779:Anesthetics, Local; D003042:Cocaine