Monitoring the voltage of the myocardium during cardioplegia arrest

Electrical activity was monitored with specially designed plunge electrodes in 19 animals undergoing 3 h of cardioplegic arrest. Electrical activity was recorded on electromagnetic tane and intramyocardial voltage was monitored with an inline voltmeter. Haemodvnamic function was assessed before bypass and following 3 h of ischaemia and 45 min of reperfusion. Intramyocardial voltage during normothermic fibrillation measured 2.4 ±0.4 mv. Infusion of cardioplegia initiated a complete electrical arrest in all animals and reduced intramyocardial voltage to 33 ± 7 pv. Small amplitude electrical activity was present in 9 of 19 animals. Intramyocardial voltage increased to 108 ±12 pv with the onset of small amplitude electrical activity and spectral analysis of the wave form indicated that the fundamental frequency was in the range of 3.08 Hz. Small amplitude electrical activity during cardioplegic arrest was associated with significant post-arrest depression of left ventricular function. Our data confirms that the presence of small amplitude electrical activity impairs myocardial functional recovery and suggests that continuous intramyocardial voltage monitoring may be used to guide the administration of cardioplegia during cardioplegic arrest. [Eur J Cardio- tnorac Surg (1989) 3:203-208].