What Should We Use for the Functional Assessment of Coronary Lesions in Severe Aortic Stenosis?

This systematic analysis measured intracoronary pressure in different phases of the cardiac cycle and flow velocity in patients with severe aortic stenosis and coronary artery disease, who were scheduled for transcatheter aortic valve replacement (TAVR). The aim was to determine the impact of aortic stenosis on: 1) flow, at different phases; 2) hyperemic coronary flow; 3) fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) measurements (the most commonly used tools in clinical practice to define stenosis severity).

A significant proportion (up to half) of patients with severe aortic stenosis have concomitant coronary artery disease. The effect of valve disease on flow, coronary pressure, and the established clinical indices of stenosis is yet to be studied.

This work included 28 patients with 30 lesions, in whom intracoronary pressure and flow assessments were performed at rest and during hyperemia immediately before and after TAVR.

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Flow during the wave-free period of diastole did not change significantly after TAVR (29.78 ± 14.9 cm/s vs. 30.81 ± 19.6 cm/s; p = 0.64), unlike whole-cycle hyperemic flow, which increased significantly after the procedure (33.44 ± 13.4 cm/s pre-TAVR vs. 40.33 ± 17.4 cm/s post-TAVR; p = 0.006). The latter was secondary to an increase in systolic hyperemic flow after TAVR.

iFR values did not change after aortic valve replacement (0.88 ± 0.09 pre-TAVR vs. 0.88 ± 0.09 post-TAVR; p = 0.73), unlike FFR values, which decreased significantly after TAVR (0.87 ± 0.08 pre-TAVR vs. 0.85 ± 0.09 post-TAVR; p = 0.001). In consequence, we finally have a reliable tool (iFR) for the invasive assessment of intermediate lesions in severe aortic stenosis.

Conclusion

Both systolic and hyperemic coronary flow increase significantly after TAVR, so that hyperemic indices including systole (FFR) underestimate the severity of coronary stenosis in patients with severe aortic stenosis.

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Flow during the wave-free period of diastole does not change, which suggests that measurements taken during this specific period (iFR) are not vulnerable to confounding effects or changes caused by aortic valve stenosis. For these patients, iFR seems to be the standard.

Original title: 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.

Reference: Yousif Ahmad et al. J Am Coll Cardiol Intv 2018, article in press.

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