Monitoring of the electrical status of the ventricle during cardioplegic arrest.

Present methods used to assess the status of myocardial preservation during cardioplegic arrest include monitoring the peripheral electrocardiogram (ECG) and ventricular myocardial temperature, and visual inspection of the heart to verify complete mechanical arrest. This study was designed to determine if these parameters are adequate to ensure complete electromechanical arrest after the application of standard cardioplegic techniques. The electrical status of the ventricle in adult mongrel dogs was monitored continuously during elective hyperkalemic hypothermic arrest for the presence of electrical activity in either the atrium or ventricle with 25 intramural electrodes, three epicardial reference electrodes, a His bundle catheter, and three peripheral ECGs. Occurrence of ventricular electrical activity was documented in the arrested heart (determined visually) when the peripheral ECG was quiescent; the activity persisted for a significant period of time before electromechanical activity could be detected by standard monitoring techniques. This electrical activity is believed to originate in the lower atrial septum and to conduct through the AV node to the ventricles at myocardial temperatures previously thought to be safe. Thus, continuous monitoring of intramural electrical activity would appear to be a more reliable technique than those currently used to determine the adequacy of myocardial preservation during elective cardioplegic arrest.