Systolic coronary flow and hyperemic coronary flow are significantly reduced in severe aortic stenosis (AS) and change significantly post-TAVR, based on findings presented during ESC Congress 2018 and simultaneously published in JACC: Cardiovascular Interventions.

The study analyzed the phasic intracoronary pressure and flow velocity in 28 patients with severe AS and coronary artery disease (CAD) at rest and during hyperemia immediately before and after undergoing TAVR. Results found that flow during the wave-free period of diastole (iFR-flow) did not change post-TAVR, while whole cycle hyperemic flow (FFR-flow) increased significantly. Researchers noted this was secondary to significant increases in systolic hyperemic flow post-TAVR. Additionally, instantaneous wave-free ratio (iFR) values did not change post-TAVR, but fractional flow reserve (FFR) decreased significantly.

Given these findings, researchers note "that hyperemic indices that include systole therefore provide a limited assessment of true coronary stenosis severity in patients with severe aortic stenosis." Meanwhile, because flow during the wave-free period of diastole did not change post-TAVR, "indices calculated during this period many not be vulnerable to the confounding effect of the stenotic aortic valve," they said.

Researchers cautioned that "prospective randomized trials of coronary revascularization in patients with severe AS are required to determine the optimal method of assessing and treating coronary artery disease in this cohort."

On a related note, a separate study, also published in JACC: Cardiovascular Interventions, found a correlation between iFR and FFR in patients with severe AS. Researchers compared iFR values with FFR values and found they exhibit "good correlation with perfusion scintigraphy-identified myocardial ischemia." Based on these results, researchers suggest iFR "could be a safe diagnostic tool for patients with severe AS."

In the case of both studies, Bon-Kwon Koo, MD, PhDa, Arnav Kumar, MDb and Habib Samady, MD, caution in a related editorial about the small size of each study and note that "neither investigated clinical outcomes related to an iFR- or FFR-guided approach to revascularization of CAD in patients with severe AS undergoing TAVR." They write: "Ultimately, although these two studies have provided further insight into the complexity of coronary physiology in severe AS patients, large prospective clinical trials comparing physiology-guided PCI compared to medical therapy are warranted in patients with CAD and severe AS undergoing TAVR. Until then, when encountering lesion assessment in patients with AS, it would be reasonable to 'relax and go with the flow.'"

Clinical Topics: Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention, Valvular Heart Disease, Atherosclerotic Disease (CAD/PAD), Aortic Surgery, Cardiac Surgery and VHD, Interventions and Coronary Artery Disease, Interventions and Structural Heart Disease

Keywords: ESC18, ESC Congress, Aortic Valve Stenosis, Coronary Artery Disease, Transcatheter Aortic Valve Replacement

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