A Prospective Study of Fractional Flow Reserve Assessment of Intermediate Coronary Stenoses in Severe Aortic Stenosis

Coronary artery blockages can reduce blood flow to the heart muscle. Fractional flow reserve (iFR or FFR) assessment is an invasive tool used to determine how much blood flow is reduced. The investigators will perform iFR/FFR on all intermediate coronary stenoses using standard practice, immediately before (at the time of) transcatheter aortic valve replacement (TAVR) and after successful TAVR. The investigators will compare pre- and post-TAVR iFR/FFR values, and assess short-term outcomes. The investigators hypothesize that iFR/FFR values will be consistently and significantly higher pre-TAVR in comparison with post-TAVR for the same lesions.

The purpose of the study is to determine whether iFR assessment gives a valid assessment of coronary hemodynamics in patients with severe aortic stenosis. Several factors confound the interpretation of fractional flow reserve (FFR) in patients with severe aortic stenosis (AS) and intermediate severity coronary stenoses, and the widely accepted cut-off value of 0.80 may not be applicable to this patient population. Coronary flow reserve is known to be attenuated under conditions of left ventricular hypertrophy and severe AS, with one study showing improvement in coronary flow reserve after aortic valve replacement. Left ventricular hypertrophy produces fixed resistance secondary to external compression of the coronary microcirculation. This potentially results in failure to achieve maximal hyperemia with adenosine and can lead to false negative FFR results. Neurohormonal influences in aortic stenosis can further attenuate vasodilator response and potentially result in false negative FFR values. Both of these conditions result in the potential deferral of lesions which may have been hemodynamically significant in the absence of severe AS. At present, there are no studies which have demonstrated validity of FFR measurement in patients with severe AS. Here, the investigators propose a prospective study of iFR/FFR in patients with AS and indeterminate coronary lesions undergoing TAVR to understand the hemodynamic consequences of AS on iFR/FFR. The investigators hypothesize that iFR/FFR values will be consistently and significantly higher pre-TAVR in comparison with post-TAVR for the same lesions.