Experimental Measures of Ventricular Activation and Synchrony

Background: A widened QRS complex as a primary indication for cardiac resynchronization therapy (CRT) for heart failure patients has been reported to be an inconsistent indicator for dyssynchronous ventricular activation. The purpose of this study was to conduct a detailed experimental investigation of total ventricular activation time (TVAT), determine how to measure it accurately, and compare it to the commonly used measure of QRS width. In addition, we investigated a measure of electrical synchrony and determined its relationship to the duration of ventricular activation. Methods: Unipolar electrograms (EGs) were recorded from the myocardial volume using plunge needle electrodes, from the epicardial surface using sock electrode arrays, and from the surface of an electrolytic torso-shaped tank. EGs were analyzed to determine a root mean square (RMS)-based measure of ventricular activation and electrical ventricular synchrony. Results: The RMS-based technique provided an accurate means of measuring TVAT from unipolar EGs recorded from the heart, the entire tank surface, or the precordial leads. In normal canine hearts, a quantification of ventricular electrical synchrony (VES) for normal ventricular activation showed that the ventricles activate, on average, within 3 ms of each other with the left typically activating first. Conclusion: Conclusions from this study are: (1) ventricular activation was reflected accurately by the RMS width obtained from direct cardiac measurements and from precordial leads on the tank surface and (2) VES was not strongly correlated with TVAT. (PACE 2008; 31:1560-1570).