PO-703-07 IMPROVED LEFT VENTRICULAR EJECTION FRACTION AND STROKE VOLUME WITH HIS BUNDLE PACING ARE ASSOCIATED WITH HIGHER MAGNITUDES OF GLOBAL LONGITUDINAL AND CIRCUMFERENTIAL STRAINS

Abstract

In recently reported clinical studies, His bundle pacing (HBP) improved cardiac function in patients with pre-existing heart failure. The effect of HBP vs RBP on global longitudinal strain (GLS), global circumferential strain (GCS), and global radial strain (GRS) in the absence of pre-existing heart failure has not yet been explored. To investigate whether the improved systolic function observed with HBP compared to RVP results in higher magnitudes of myocardial GLS, GCS, and GRS. Seven healthy adult mixed breed hounds (25 to 35 kg) were anesthetized, and pacing leads were implanted in the right atrium (RA), RV apex, and the HB region. Echocardiographic data were recorded for each pacing configuration to assess the left ventricular function. Finally, 2-D tissue tracking analysis was performed to estimate GLS from the 4-chamber apical views and GCS and GRS from short-axis views. Consistent with prior reports,HBP significantly improved both LVEF (Fig. A) and stroke volume (Fig. B). Similarly, HBP showed higher magnitudes for GLS and GCS than RVP, as shown in Fig. C and Fig. D, respectively. Interestingly, the GRS outcome for both HBP and RVP revealed a minimal difference (Fig. E). Compared to the RAP, HBP showed similar hemodynamic and strain measurements (GLS, GCS, and GRS). The paired comparisons in this canine study under the same experimental conditions demonstrate an increase in longitudinal and circumferential strain (but not radial strain) with HBP relative to RVP. These results indicate that systolic improvements mediated by HBP are driven by longitudinal and circumferential rather than radial strain.