Abstract 12395: Nitroglycerin Reduces Pulsatile Arterial Load But Not Steady State Load In Aortic Stenosis Patients Before Or After Transcatheter Aortic Valve Implantation

Abstract

Background: Pulsatile arterial load is represented by the characteristic impedance (Zc) of the ascending aorta. In aortic stenosis (AS) patients, Zc is thought to contribute significantly to left ventricular afterload in addition to aortic transvalvular gradient. We evaluated the effect of nitroglycerin, a potent vasodilator, on Zc non-invasively in AS patients before or after transcatheter aortic valve implantation (TAVI). Methods: Simultaneous aortic pressure from radial arterial tonometry and flow from cardiac magnetic resonance phase contrast imaging were obtained. Radial waveforms were converted to central aortic pressure using SphygmoCor 8.1 (AtCor Medical) and calibrated using brachial cuff values. Zc was derived from aortic pressure and flow by averaging the impedance modulus in frequency domain analysis. Data acquisition was repeated after administration of 300 micrograms of sublingual nitroglycerin to investigate its effect on pulsatile and steady state load. Results: Analysis was performed in 9 AS patients (3 female, age 68-81 years) with a left ventricular ejection fraction > 55%, of whom 5 had undergone recent TAVI. When compared with baseline measurements, nitroglycerin reduced mean arterial pressure (107 ± 11 pre vs 87 ± 5 post, mmHg), central pulse pressure (67 ± 15 pre vs 48 ± 13 post, mmHg), forward stroke volume (83 ± 15 pre vs 70 ± 13 post, ml) and Zc (129 ± 42 pre vs 95 ± 32 post, dynes.cm/s 5 ). However, there was no change in compliance or steady state systemic vascular resistance (2163 ± 445 pre vs 2045 ± 485 post, dynes.cm/s 5 ). Conclusion: Nitroglycerin significantly reduces pulsatile arterial load in AS patients without reducing steady state load. Our non-invasive technique can reliably assess changes in hemodynamic loading conditions, and larger longitudinal paired analysis of nitroglycerin response before and after TAVI may help predict AS patients at risk of poorer outcomes from ventriculo-arterial coupling mismatch following treatment.