40 The Effect of Altering AV Delay on the Pre-Ejection Period in Patients with Biventricular Pacemakers

Abstract

<h3>Introduction</h3> Left pre-ejection period (LPEP), the interval from onset of ventricular depolarization to the beginning of aortic ejection, is shortened with CRT. We studied the effect of altering AV delay on LPEP in patients with CRT. <h3>Methods</h3> In 16 patients (12 LBBB, 2 RBBB, 2 narrow QRS) AV delay was adjusted while recording invasive and non-invasive BP simultaneously, and the LPEP measured. <h3>Results</h3> With optimal pacing, for 11 LBBB patients, LPEP was shorter than at AAI setting suggesting effective delivery of CRT. As their AV delay lengthened, LPEP shortened with a minimum (‘LPEP optimum’) before lengthening again (Figure 1). In RBBB patients, there was a less clear minimum in LPEP just before intrinsic conduction. In patients with narrow QRS, LPEP was always lengthened with pacing. AV delay minimising LPEP was very similar between invasive and non-invasive pressure measurements: SDD 13.6ms, R² = 0.92. The LPEP optimum was significantly shorter than the AV optimum maximising BP for both invasive (p = 0.023) and non-invasive (p = 0.0034) pressure measurements in patients with LBBB. <h3>Conclusions</h3> LPEP is shortened by CRT in patients with LBBB or RBBB. In patients with narrow QRS, LPEP was never lower than with AAI, suggesting a deleterious effect of CRT. AV settings minimising LPEP are shorter than those maximising BP, perhaps because LPEP addresses 1 intra-cardiac component of the CRT effect, while extra-cardiac BP quantifies the final common pathway.