European Journal of Cardio-Thoracic Surgery, Vol 7, 186-192, Copyright © 1993 by European Association for Cardio-thoracic Surgery
Lowered threshold for ventricular fibrillation in amiodarone-treated pigs undergoing cardiopulmonary bypass and cardioplegic arrest with St. Thomas' cardioplegic solution
LS Gotzsche, EM Pedersen and PK Paulsen
Institute of Experimental Clinical Research, Skejby University Hospital, Arhus, Denmark.
The antiarrhythmic agent amiodarone has been suspected of causing reduced
cardiac performance after extracorporeal circulation and cardioplegic
arrest in patients. This has recently been confirmed in an experimental
model where pigs were exposed to cardiopulmonary bypass and cold
cardioplegic arrest with Bretschneider's solution. Due to the high
concentration of the cardio-depressant agent procain in Bretschneider's
solution, it could be speculated whether it is the combination of
amiodarone and this solution that may be potentially deleterious, rather
than amiodarone alone. To investigate this, adult pigs (75 +/- 2 kg at
surgery) were treated with amiodarone for 30 +/- 2 days (1400 mg/day: n =
8, untreated controls: n = 4, blind experiment), followed by exposure to
cardiopulmonary bypass with universal cooling to 28 degrees C and topical
cold cardioplegic arrest with St. Thomas' solution for 60 min. Apart from 1
g of calcium (Ca2+) at the end of bypass, no inotropic drugs were
administered. Cardiac reserve was tested by right ventricular pacing (200
beats/min until death or up to 30 min). The two groups did not differ
concerning preload or afterload, heart rate, cardiac output, left
ventricular pressure, arterial pressure or rate of change in left
ventricular relaxation (-dP/dt) before or after bypass was terminated,
while the rate of change in left ventricular contraction (+dP/dt) was lower
in the amiodarone-treated pigs. The time on bypass, before stable
hemodynamics had recovered, was prolonged in amiodarone-treated animals, 46
+/- 4 min versus 31 +/- 3 min in the controls (P < 0.05).(ABSTRACT
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