Coronary Hemodynamics in Patients With Severe Aortic Stenosis and Coronary Artery Disease Undergoing Transcatheter Aortic Valve Replacement: Implications for Clinical Indices of Coronary Stenosis Severity

Abstract

Objectives: In this study, a systematic analysis was conducted of phasic intracoronary pressure and flow velocity in patients with severe aortic stenosis (AS) and coronary artery disease, undergoing transcatheter aortic valve replacement (TAVR), to determine how AS affects: 1) phasic coronary flow; 2) hyperemic coronary flow; and 3) the most common clinically used indices of coronary stenosis severity, instantaneous wave-free ratio and fractional flow reserve.

Background: A significant proportion of patients with severe aortic stenosis (AS) have concomitant coronary artery disease. The effect of the valve on coronary pressure, flow, and the established invasive clinical indices of stenosis severity have not been studied.

Methods: Twenty-eight patients (30 lesions, 50.0% men, mean age 82.1 ± 6.5 years) with severe AS and coronary artery disease were included. Intracoronary pressure and flow assessments were performed at rest and during hyperemia immediately before and after TAVR.

Results: Flow during the wave-free period of diastole did not change post-TAVR (29.78 ± 14.9 cm/s vs. 30.81 ± 19.6 cm/s; p = 0.64). Whole-cycle hyperemic flow increased significantly post-TAVR (33.44 ± 13.4 cm/s pre-TAVR vs. 40.33 ± 17.4 cm/s post-TAVR; p = 0.006); this was secondary to significant increases in systolic hyperemic flow post-TAVR (27.67 ± 12.1 cm/s pre-TAVR vs. 34.15 ± 17.5 cm/s post-TAVR; p = 0.02). Instantaneous wave-free ratio values did not change post-TAVR (0.88 ± 0.09 pre-TAVR vs. 0.88 ± 0.09 post-TAVR; p = 0.73), whereas fractional flow reserve decreased significantly post-TAVR (0.87 ± 0.08 pre-TAVR vs. 0.85 ± 0.09 post-TAVR; p = 0.001).

Conclusions: Systolic and hyperemic coronary flow increased significantly post-TAVR; consequently, hyperemic indices that include systole underestimated coronary stenosis severity in patients with severe AS. Flow during the wave-free period of diastole did not change post-TAVR, suggesting that indices calculated during this period are not vulnerable to the confounding effect of the stenotic aortic valve.

Keywords: TAVR; aortic stenosis; coronary flow; fractional flow reserve; instantaneous wave-free ratio.

Graphical abstract

Figure 1

Figure Demonstrating an Example of Invasive Pressure and Doppler Flow Measurements APV = average peak flow velocity; APV-B = average peak flow velocity at baseline; APV-P = average peak flow velocity at peak hyperemia. CFR = coronary flow reserve; FFR = fractional flow reserve; HMR = hyperemic microvascular resistance; HR = heart rate; HSR = hyperemic stenosis resistance; Pa = aortic pressure; Pd = distal coronary pressure.

Figure 2

Outline of the Definitions and Calculations Used for Hemodynamic Parameters Used in the Phasic Analysis

Figure 3

Figure Outlining the Changes in Ejection Fraction, Heart Rate, and Left Ventricular End-Diastolic Pressure Before and After Transcatheter Aortic Valve Replacement The large diamonds denote the mean values, with the error bars denoting the upper and lower 95% confidence intervals.

Figure 4

Coronary Flow Velocity Before and After Transcatheter Aortic Valve Replacement Figure demonstrating the changes in coronary flow before and after transcatheter aortic valve replacement (TAVR). The left side of the graph is resting flow over the whole cardiac cycle (PdPa-flow); the middle side of the graph is resting flow during the wave-period of diastole (iFR-flow); and the right side of the graph is hyperemic flow over the whole cardiac cycle (FFR-flow). Both PdPa-flow and FFR-flow increase significantly more post-TAVR than iFR-flow, which is constant. The bars denote mean values, with the error bars denoting SEs.

Figure 5

Changes in Fractional Flow Reserve and Instantaneous Wave-Free Ratio After Transcatheter Aortic Valve Replacement Figure demonstrating the change in fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) values after transcatheter aortic valve replacement. FFR decreases significantly, whereas iFR remains constant. The bars denote mean values, with the error bars denoting SEs.

Figure 6

Changes in Systolic Coronary Flow After Transcatheter Aortic Valve Replacement Figure demonstrating the changes in systolic coronary flow after transcatheter aortic valve replacement (TAVR). (A) There is a schematic, demonstrating that post-TAVR there is increase in the forward traveling systolic pressure, leading to an increase in systolic coronary flow. There is also a reduction in the compressive forces on the microcirculation post-TAVR; these 2 factors both contribute to a net increase in systolic coronary flow post-TAVR. (B) Statistically significantly increase in systolic coronary flow seen in our study, both at rest and during Hyperemia. The bars denote mean values, with the error bars denoting SEs.

Figure 7

Coronary Hemodynamic Status Before and After Transcatheter Aortic Valve Replacement, Over Both the Fractional Flow Reserve and Instantaneous Wave-Free Ratio Measurement Windows Figure demonstrating the changes in coronary hemodynamic status over the fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) measurement windows. The top row shows the changes in coronary hemodynamics over the FFR window (the whole cardiac cycle during hyperemia): the left panel demonstrates a significant increase in flow, the middle panel demonstrates a significant reduction in resistance; and as a consequence the right panel demonstrates a significant reduction in the FFR value after transcatheter aortic valve replacement (TAVR). The bottom row shows the changes in coronary hemodynamic status over the iFR window (the wave-free period of diastole at rest): the left panel demonstrates constant flow before and after TAVR; the right panel demonstrates a constant iFR value post-TAVR; to achieve the same pressure gradient with the same flow velocity, there is therefore a significant increase in resistance (shown in the middle panel). The bars denote mean values, with the error bars denoting SEs.