FLOW RATE NOT STROKE VOLUME IS A SUPERIOR PROGNOSTIC MARKER OF TRANSORTIC FLOW AND FLOW RESERVE IN PATIENTS WITH LOW-FLOW LOW-GRADIENT AORTIC STENOSIS UNDERGOING LOW-DOSE DOBUTAMINE ECHOCARDIOGRAPHY

Comparison of transvalvular flow rate in aortic stenosis subtypes

OBJECTIVES

Evaluate ET and TVFR in normal patients, PLFLGAS, LGLFAS, and classic pre and post TAVR.

BACKGROUND

Severe aortic stenosis (AS) is defined echocardiographically. Generating a pressure gradient to meet diagnostic criteria is dependent on left ventricular contractility, stroke volume, and ejection time.  Abnormalities in these decrease the mean pressure gradient across the valve creating pathology termed low flow, low gradient AS. This occurs in two subtypes, low ejection fraction LFLGAS and paradoxical LFLGAS (PLFLGAS), in which EF is normal but stroke volume is < 35 ml/m² . Paradoxical LFLGAS is difficult to diagnose and does not have a confirmatory echocardiographic parameter. Transvalvular flow rate (TVFR), which is defined as stroke volume divided by the ejection time, provides a direct measure of flow across the aortic valve.

METHODS

A retrospective study of patients who underwent transcatheter aortic valve replacement (TAVR) at the University of Cincinnati Medical Center between 2016 and 2019 was performed. Patients were classified by AS subtype. ET and TVFR were measured pre and post TAVR and statistically compared using SPSS statistics software and ANOVA analysis.

RESULTS

Pre TAVR TVFR in the normal population, severe AS population, and LFLGAS were not significantly different. The pre TAVR TVFR in paradoxical LFLGAS patients was significantly lower than other groups. TVFR improved to the greatest degree post TAVR in PLFLGAS but did not meet statistical significance.

CONCLUSIONS

The significantly lower TVFR demonstrated in PLFLGAS provides a comprehensive, direct measurement of aortic valve hemodynamics and PLFLGAS pathology and can aid in diagnosis.