Abstract
Background: The optimal site for left ventricular (LV) lead placement in cardiac resynchronization therapy (CRT) remains uncertain. Intra-procedural measures for predicting response to CRT have shown mixed results. Hypothesis: This study analyzed intracardiac electrogram (IEGM) characteristics at implant and assessed patients’ response rates (RR) to CRT. Methods: Forty-one consecutive patients undergoing CRT were enrolled. Medically optimized patients in sinus rhythm, with ejection fraction (EF) 34 were included. Right ventricular (RV) leads were positioned mid-septum. LV leads were targeted to the latest mechanical activation on echocardiography. IEGMs were measured, assessing intrinsic RV-to-LV delay (int RV-LV), RV-paced delay (RVp-LV), and LV-paced delay (LVp-RV). The difference between LVp-RV and RVp-LV was recorded as delta-LV. Response was defined as improvement of EF > 10%, reduction in LVEDD > 15% and improvement of ≥1 NYHA class. Results: Overall RR was 79%. LV leads were placed in the target location in 91%. Int RV-LV was 101 ± 14 ms in responders; 78 ± 11 ms in non-responders (p 100 had a RR of 87%; int RV-LV 40 ms had a RR of 56%; delta-LV < 40 ms had a RR of 85%. There was no significant correlation between lead position, DI, QRS duration or EF and IEGM measurements. Conclusions: IEGM measures at implant are easily obtained. Significant intrinsic electrical delay and shorter delta-LV both predict response, even when LV leads are implanted in the targeted mechanically-delayed segment. These assessments of electrical dyssynchrony may be used to determine optimal lead positions and response to CRT.
Highlights
Many multicenter, randomized clinical trials have demonstrated that cardiac resynchronization therapy (CRT) can improve outcomes in the majority of patients with left ventricular (LV) systolic dysfunction and wide QRS complex [1]-[4]
The objectives of this study were to: 1) investigate LV myocardial conduction characteristics using intracardiac electrogram (IEGM) of the right ventricular (RV) and LV leads at the time of CRT implantation; 2) assess the correlation of these measures of electrical dyssynchrony with mechanical dyssynchrony; and 3) determine which electrical parameters result in improved response rates (RR) and predict response to CRT
Interventricular mechanical dyssynchrony (IVMD) was assessed as the difference between the QRS to onset of pulmonary artery flow (QRS-PA) and QRS to onset of aortic flow (QRS-Ao), and dyssynchrony was significant if the IVMD was > 40 ms
Summary
Many multicenter, randomized clinical trials have demonstrated that cardiac resynchronization therapy (CRT) can improve outcomes in the majority of patients with left ventricular (LV) systolic dysfunction and wide QRS complex [1]-[4]. The implant location of the LV lead has been shown to affect mechanical dyssynchrony, response to CRT and overall mortality [7]. Transthoracic echocardiography (TTE) can be used to assist in identifying the area of latest mechanical activation pre-procedure, methods to assess for and find the optimal LV lead position intra-procedurally have had mixed results [13]-[15]. Several studies have measured QRS to LV intracardiac electrogram (IEGM) delays (QLV) and found reasonable correlations with response to CRT [16]. Significant intrinsic electrical delay and shorter delta-LV both predict response, even when LV leads are implanted in the targeted mechanically-delayed segment.
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