Demystifying Complex Coronary Hemodynamics in Patients Undergoing Transcatheter Aortic Valve Replacement

Abstract

T ranscatheter aortic valve replacement (TAVR) has revolutionized the treatment of patients with severe aortic stenosis who are at high risk for traditional surgical intervention.1,2 As the technology matures and experience grows, the applicability of TAVR to lower risk populations is likely and is already being explored. 3 These patients often present with chest pain or exertional dyspnoea in the context of varying degrees of coronary artery disease. An understanding of how the aortic valve affects coronary hemodynamics is becoming increasingly clinically relevant in determining how to manage this coexisting coronary disease. See Article by Wiegerinck et alCreating a model of aortic stenosis is challenging. The pressure loading of the ventricle and coronary arteries varies according to the location of the stenosis. Stenosis at the level of the aortic valve is anatomically below coronary artery inflow; this results in increased afterload of the left ventricle but reduces coronary perfusion pressure. Relief of the stenosis therefore results in an acute reduction in left ventricular enddiastolic pressure, and in most cases, it results in an increase in coronary perfusion. This differs from the traditional systemic hypertension model often generated experimentally in animal models in which a restrictive band is placed around the aorta. 4 In such cases, the stenosis is positioned in the aorta distal to coronary artery inflow; this results in an increase in both left ventricular end-diastolic pressure and coronary perfusion. After removal of the aortic band, both left ventricular end-diastolic pressure and coronary perfusion fall; as a result, the traditional banding model cannot be used to make inferences on the acute effect of relieving aortic stenosis on coronary hemodynamics.The development of TAVR therefore provides a unique model to delineate the coronary hemodynamics of patients with aortic stenosis. In addition to being a model of true aortic stenosis, it permits easy access to the coronaries before and after the procedure for rapid hemodynamic assessment. Previously, TAVR had been performed under general anesthesia, and whilst recently, conscious sedation is increasingly used. Conscious sedation avoids the potentially confounding effect of a general anesthetic, which can manipulate myocardial preload and after-load, and therefore, it may provide a better model to study the effect of severe aortic stenosis on coronary artery hemodynamics.In this issue of Circulation: Cardiovascular Interventions, Wiegerinck et al 5 use the TAVR model to determine how relief of aortic stenosis alters coronary hemodynamics. In a study of 27 patents with aortic stenosis and 28 control patients without aortic stenosis, detailed assessment of coronary flow and microvascular resistance was performed at rest and after intracoronary adenosine administration pre and post TAVR.They demonstrate that in the cohort of patients with no aortic regurgitation post TAVR, hyperemic flow, coronary flow reserve, and hyperemic microvascular resist...

Effect of aortic valve replacement on myocardial perfusion and exercise capacity in patients with severe aortic stenosis

“…Stenosis at the level of the aortic valve is anatomically below the coronary artery in ow resulting in reduced coronary perfusion pressure (23). Previous studies have shown greater CFR impairment with increasing severity of AS and LV remodelling (24).…”

“…Previous studies have shown greater CFR impairment with increasing severity of AS and LV remodelling (24). Relief of the stenosis therefore results in an acute reduction in the left ventricular end diastolic pressure (LVEDP) resulting in increased coronary perfusion (23). Furthermore, the augmentation in coronary ow is linearly related to aortic valve area and coronary perfusion pressure during stress/hyperaemia (6).…”

Assessing coronary disease in patients with severe aortic stenosis: the need for a ‘valid’ gold standard for validation studies?

“…Scarsini and colleagues should be congratulated for attempting to define coronary stenosis severity physiologically in the context of aortic stenosis. Their study contributes to a growing number of studies that are beginning to unpick the complex physiology in these patients 14 . The ability to elucidate coronary stenosis severity independent of aortic valve severity may become increasingly clinically relevant as the use of TAVI increases and it is applied to a larger and lower-risk patient population 15,16 .…”