A Prospective Study of Fractional Flow Reserve Assessment of Intermediate Coronary Stenoses in Severe Aortic Stenosis
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.
Inclusion Criteria:

 -  All patients who have coronary stenoses between 40-70% severity and who have severe
 aortic stenosis undergoing TAVR work-up.

 Exclusion Criteria:

 -  Patients with documented intraprocedural hemodynamic instability, shock, or major
 adverse event (myocardial infarction, aortic rupture/dissection, stroke, left
 ventricular perforation, cardiac arrest).

 -  Contraindication to adenosine, presence of cardiogenic shock, presence of acute
 coronary syndrome.