Research ArticleCardiology

Ventricular stroke work and vascular impedance refine the characterization of patients with aortic stenosis

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Science Translational Medicine  11 Sep 2019:
Vol. 11, Issue 509, eaaw0181
DOI: 10.1126/scitranslmed.aaw0181

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Hard work meets the path of least resistance

Transcatheter aortic valve replacement (TAVR) is a treatment for patients with aortic stenosis (narrow aortic valve) that reduces the transvalvular pressure gradient; however, only some patients experience improved quality of life after the procedure. To understand how valvular, ventricular, and systemic vascular conditions contribute to improvements after TAVR, Ben-Assa et al. studied 70 patients undergoing the procedure. Patients with lower preprocedural vascular impedance and higher left ventricular stroke work had greater improvements in quality of life after TAVR. This suggests that analyzing valve, ventricle, and arterial system hemodynamics could identify patients likely to benefit from TAVR and inform timing of intervention.

Abstract

Aortic stenosis (AS) management is classically guided by symptoms and valvular metrics. However, the natural history of AS is dictated by coupling of the left ventricle, aortic valve, and vascular system. We investigated whether metrics of ventricular and vascular state add to the appreciation of AS state above valve gradient alone. Seventy patients with severe symptomatic AS were prospectively followed from baseline to 30 days after transcatheter aortic valve replacement (TAVR). Quality of life (QOL) was assessed using the Kansas City Cardiomyopathy Questionnaire. Left ventricular stroke work (SWLV) and vascular impedance spectrums were calculated noninvasively using in-house models based on central blood pressure waveforms, along with hemodynamic parameters from echocardiograms. Patients with higher preprocedural SWLV and lower vascular impedance were more likely to experience improved QOL after TAVR. Patients fell into two categories: those who did and those who did not exhibit increase in blood pressure after TAVR. In patients who developed hypertension (19%), vascular impedance increased and SWLV remained unchanged (impedance at zeroth harmonic: Z0, from 3964.4 to 4851.8 dyne·s/cm3, P = 0.039; characteristic impedance: Zc, from 376.2 to 603.2 dyne·s/cm3, P = 0.033). SWLV dropped only in patients who did not develop new hypertension after TAVR (from 1.58 to 1.26 J; P < 0.001). Reduction in valvular pressure gradient after TAVR did not predict change in SWLV (r = 0.213; P = 0.129). Reduction of SWLV after TAVR may be an important metric in management of AS, rather than relying solely on the elimination of transvalvular pressure gradients.

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