Optimized Left Ventricular Endocardial Stimulation Is Superior to Optimized Epicardial Stimulation in Ischemic Patients With Poor Response to Cardiac Resynchronization Therapy

Abstract

ObjectivesThe purpose of this study was to identify the optimal pacing site for the left ventricular (LV) lead in ischemic patients with poor response to cardiac resynchronization therapy (CRT).BackgroundLV endocardial pacing may offer benefit over conventional CRT in ischemic patients.MethodsWe performed cardiac magnetic resonance, invasive electroanatomic mapping (EAM), and measured the acute hemodynamic response (AHR) in patients with existing CRT systems.ResultsIn all, 135 epicardial and endocardial pacing sites were tested in 8 patients. Endocardial pacing was superior to epicardial pacing with respect to mean AHR (% change in dP/dtmax vs. baseline) (11.81 [-7.2 to 44.6] vs. 6.55 [-11.0 to 19.7]; p = 0.025). This was associated with a similar first ventricular depolarization (Q-LV) (75 ms [13 to 161 ms] vs. 75 ms [25 to 129 ms]; p = 0.354), shorter stimulation–QRS duration (15 ms [7 to 43 ms] vs. 19 ms [5 to 66 ms]; p = 0.010) and shorter paced QRS duration (149 ms [95 to 218 ms] vs. 171 ms [120 to 235 ms]; p < 0.001). The mean best achievable AHR was higher with endocardial pacing (25.64 ± 14.74% vs. 12.64 ± 6.76%; p = 0.044). Furthermore, AHR was significantly greater pacing the same site endocardially versus epicardially (15.2 ± 10.7% vs. 7.6 ± 6.3%; p = 0.014) with a shorter paced QRS duration (137 ± 22 ms vs. 166 ± 30 ms; p < 0.001) despite a similar Q-LV (70 ± 38 ms vs. 79 ± 34 ms; p = 0.512). Lack of capture due to areas of scar (corroborated by EAM and cardiac magnetic resonance) was associated with a poor AHR.ConclusionsIn ischemic patients with poor CRT response, biventricular endocardial pacing is superior to epicardial pacing. This may reflect accessibility to sites that cannot be reached via coronary sinus anatomy and/or by access to more rapidly conducting tissue. Furthermore, guidance to the optimal LV pacing site may be aided by modalities such as cardiac magnetic resonance to target delayed activating sites while avoiding scar.

Optimal site selection and image fusion guidance technology to facilitate cardiac resynchronization therapy

“…Theoretically, the site of latest activation should exhibit the most dyssynchrony and as such would represent an ideal pacing site. While some work appears to confirm the site of LEA is synonymous with the optimal pacing site [21], more recent analysis has shown optimal site exhibits late but not supremely delayed activation [100]. Sites demonstrating excessively delayed activity may in fact merely represent distal activation occurring within islands of non-viable tissue.…”

“…There is also no consensus as to whether delivering BiV pacing at a site which achieves a narrowing of the paced QRS is associated with improvements in hemodynamics. While some work has shown a correlation between narrowing of the QRS and improvements in AHR [100], this finding has not been consistently replicated [21]. …”

“…It is also associated with a higher implant success rates, less phrenic nerve stimulation, and far greater access to different pacing sites. The optimal LV endocardial pacing site displays marked inter- and intra-patient variability and while some argue that any endocardial pacing site will invariably prove superior to epicardial stimulation, research has shown that suboptimal BiV ENDO CRT can achieve hemodynamic improvements inferior to those associated with empirically positioned BiV EPI CRT [100]. As such, while endocardial pacing affords the freedom to perform LV stimulation at a customizable location, site selection is even more critical in order to maximize the potential benefits associated with this technique.…”

Splinting and mechanical disruption of the mitral valve apparatus by an endocardial left ventricular lead while delivering cardiac resynchronization therapy

“…There is evidence from both animal and clinical studies that, compared to epicardial stimulation, LV endocardial stimulation by activating the ventricular myocardium in a more physiological fashion may deliver superior electrical and hemodynamic properties and be less likely to cause phrenic nerve stimulation 2, 3, 4, 5. For a select group of patients who have failed conventional CRT delivered via an epicardial LV lead, this approach may be of value.…”

Cardiac resynchronisation therapy: current indications, management and basic troubleshooting

“…Finally, LV endocardial stimulation has been proposed and implemented in small studies of CRT where coronary sinus lead placement has failed 49. More recently, a comparison of multiple endocardial and epicardial LV stimulation sites in a series of patients with a poor response to CRT (online supplementary file 1) demonstrated superior haemodynamic responses to endocardial stimulation 50 …”