S-37-4: TRANSCATHETER AORTIC VALVE REPLACEMENT DOES NOT RESULT IN SUSTAINED LOAD TRANSFER WITH INCREASED VASCULAR LOAD

Abstract

Objectives: Transcatheter aortic valve replacement (TAVR) is an effective treatment for aortic stenosis (AS) by reducing the load placed on the left ventricle (LV) by the stenotic valve. Although systolic pressure is reported to increase in 50% of individuals after TAVR, its effects on steady and pulsatile vascular load represented by the systemic vascular resistance (SVR) and impedance of the proximal ascending aorta (Zc) respectively is less well understood. Using a previously validated non-invasive load estimation technique, we investigated the valvulo-arterial interaction in AS patients pre- and post-TAVR. Design and Method: In AS patients being assessed for TAVR, the proximal thoracic aorta flows, LV volume and function were recorded using 3T cardiac magnetic resonance (CMR) using phase-contrast velocity quantification. Simultaneous radial tonometric pressure was acquired during CMR and brachial cuff pressure was recorded. Aortic pressure was derived offline using SphygmoCor 8.1 (AtCor Medical, Sydney) from radial pressure, and calibrated to brachial pressure. Flow was acquired at 5 cm above the aortic valve at the level of the pulmonary artery bifurcation to avoid flow artefact from the TAVR prosthesis. Baseline and follow-up measurements were made before and after treatment with TAVR. Values pre- and post-TAVR were compared, and indices of pulsatile arterial load were calculated using frequency domain analysis. Results: A total of 17 patients (mean age 80 ± 6 years, 7 females) were recruited, with a median follow up of 54.5 days post-TAVR. In the post-TAVR measurements, a significant improvement in aortic peak volumetric flow (336 ± 79 ml/s vs 389 ± 110 ml, P = 0.011) was observed with an associated reduction in peak aortic velocity (189 ± 65 cm/s vs 126 ± 24 cm/s, P = 0.002). However, there was no statistical difference in heart rate (70 ± 9 beats per minute vs 68 ± 12 beats per minute), mean central aortic pressure (98 ± 13mmHg vs 99 ± 11mmHg), or the steady vascular load parameters of SVR (1860 ± 513 dynes.s/cm5 vs 1999 ± 561 dynes. s/cm5, P = 0.284) and pulsatile load Zc of the aorta (119 ± 51 dynes.s/cm5 vs 106 ± 43 dynes.s/cm5, P = 0.102). Conclusion: TAVR relieves valvular obstruction but does not result in significant alterations of vascular load in the short to medium term. The previously reported acute load transfer immediately following TAVR appears to resolve with time. Further study examining the effect of TAVR on external LV work may help to elucidate the energy consumption by the vascular system after correction of valvular obstruction from AS.