Background Objective assessment of the effect of Cardiac Resynchronization Therapy (CRT) is a very difficult clinical task that still has not been fully clarified. The ultra-high-frequency QRS dyssynchrony (DYS) represents a simple ECG derived method that provides information about the ventricular electrical depolarization and thus could become helpful in CRT.
Method The 12-lead ECG (sampling 5kHz/24bits) was measured in 42 consecutive CRT patients. The precordial V1-V6 QRS envelopes were calculated through various frequency ranges from 150 to 1000Hz. The DYS was measured as a difference between soonest and latest activation in V leads. The standard QRS duration (QRSd) was also automatically assessed. All the parameters were assessed before, just after, and 6 months after the CRT during CRT-OFF and CRT-ON. Patients with a relative decrease of 10% and more in the end-systolic volume of the left ventricle were considered CRT responders.
Results In 30 CRT responders, the DYS parameter was significantly lower after 6 months during CRT-OFF compared to state prior CRT (-9±19ms, p<0.05), while interestingly there was no significant DYS change during CRT-ON within 6 months (-1±11ms, NS). On the other hand, there was a clear shortage of DYS just after CRT-ON (-46±23ms, p<0.000001), and 6 months after CRT-ON (-46±21ms, p<0.000001) compared to state before CRT. In 12 CRT non-responders, there were no significant changes in DYS parameter. The QRSd didn’t show any significances in changes before, just after, and 6 months after CRT during CRT-ON and OFF in both CRT groups.
Conclusion The ultra-high-frequency QRS dyssynchrony parameter accurately describes the ventricular conduction pattern and seems to be a superior parameter to simply and quickly assess an immediate as well as long-term (reverse electrical remodeling) effect in CRT. The QRS duration as a descriptor of the ventricular conduction changes induced by CRT does not provide sufficiently valuable information.