Transcutaneous cardiac pacing: determination of myocardial injury in a canine model

Transcutaneous cardiac pacing holds promise as the initial cardiac pacing technique for emergency patients. Determination of the extent of myocardial injury associated with the use of commercial transcutaneous pacemaker devices has been limited. This study was undertaken to document electrocardiographic, enzymatic, and histologic changes following transcutaneous pacing. Ten mongrel dogs were paced with a transcutaneous cardiac pacemaker for 30 minutes. Electrical pulses of 100 mA lasting 20 ms each were delivered at a rate of 80/min via cutaneous electrodes on the anterior and posterior thorax. Myocardial damage was assessed by serial electrocardiograms (ECGs), serial creatine kinase (CK) determinations with myocardial band (MB) fractionation, and gross and microscopic pathologic examination. Double blind reading of the ECGs showed no significant changes after pacing. CK levels peaked an average of 78 units over baseline levels at 4 hours; however, there was no rise in the CK MB fraction. Pathologic examination revealed micro-infarcts adjacent to intramural vessels in 5 animals, but no clinically significant myocardial injury in the 10 dogs. The absence of enzymatic, cardiographic, and clinically significant pathologic findings was statistically significant (P less than .05). Transcutaneous pacing at low currents and for short periods appears to be a safe technique. This pacing technique deserves further evaluation, and may hold promise as a clinical tool during resuscitation.