Effects of anaesthesia on acute ischaemic arrhythmias and epicardial electrograms in the pig heart in situ.

STUDY

OBJECTIVE

The aim of the study was to assess the influence of general anaesthesia on electrocardiographic and arrhythmogenic responses to left anterior descending coronary artery occlusion.

DESIGN

Pigs weighing 18-20 kg were anaesthetised with alpha chloralose 100 mg.kg-1 (n = 9) or thiopentone 30 mg.kg-1 (n = 9) and the arrhythmogenic effects of coronary artery occlusion were examined by sequential electrocardiographic measurements every 5 min and arrhythmia analysis every minute over a 60 min period.

RESULTS

alpha Chloralose predisposed to lower ST segment elevation (analysis of variance for repeated measurements p less than 0.002), less marked epicardial conduction delay (p less than 0.01) with slower progression to monophasic potentials, and in contrast, to a greater number of episodes of ventricular premature beats (p less than 0.005), ventricular tachycardia (51 v 32 episodes), and ventricular fibrillation (6 v 2 pigs) than barbiturate anaesthesia.

CONCLUSIONS

alpha Chloralose and barbiturates exerted opposite electrocardiographic and arrhythmogenic effects in a porcine model of acute myocardial ischaemia. Due to its proarrhythmic effect chloralose should probably be used in studies dealing with spontaneous and induced ischaemic arrhythmias.