Inflammation and Thrombosis in Patients With Severe Aortic Stenosis After Transcatheter Aortic Valve Replacement (TAVR)

Overview

The central hypothesis of this study is that TAVR leads to platelet deposition and inflammatory cell activation that can be attenuated by the potent anti-platelet and/or pleiotropic effects of ticagrelor. This single center, prospective randomized trial addresses the following specific aims: 1. To determine whether high-potency ADP receptor blockade reduces measures of platelet activation in patients after TAVR. 2. To determine whether high-potency ADP receptor blockade mitigates the pro-thrombotic inflammatory response observed after TAVR.

BACKGROUND Transcatheter Aortic Valve Replacement (TAVR) has emerged as an important alternative to surgical aortic valve replacement. While this technology represents an important advance over medical therapy or surgical AVR in poor operative candidates, the absolute mortality rates remain high, even in the great majority in whom an optimal hemodynamic result is achieved. In the randomized literature, the majority of these patients die within two years and two thirds of these deaths are due to cardiovascular (CV) events. The mechanisms responsible for this limited survival are unclear from the clinical trials completed to date. While persistent valve disease undoubtedly plays a role in a subset of patients, particularly in patients with significant aortic regurgitation, the majority of events are due to non-valve related co-morbidities. The hypothesis of this study is that TAVR results in at least three simultaneous CV insults: 1) the abrupt release of severely elevated left ventricular pressure into a non-compliant systemic vasculature leads to generalized endothelial cell activation, 2) the exposure of the pro-thrombotic and neo-antigenic contents of a degenerated aortic valve (known to histologically resemble atherosclerosis), and 3) the exposure of the replacement valve (bovine valve, stainless steel frame, polyester wrap). The investigators propose that these proximate events lead to platelet activation. Given the important link between thrombosis and inflammation governed by platelet-derived mediators and leukocyte-platelet interactions, they further hypothesize that monocyte activation is mediated, at least in part, by platelet-monocyte interactions, which has been shown to induce the expansion of inflammatory monocytes. Given the pro-thrombotic nature of inflammatory monocytes, they suspect a positive feedback loop may exist via the interplay of these thrombotic -inflammatory mechanisms, which may be abrogated via high potency ADP-receptor blockade. TRIAL DESIGN Primary Objective of the Study This trial is designed to determine whether high-potency ADP-receptor blockade with ticagrelor, compared to standard care with clopidogrel, affects platelet responsiveness and the pattern of prothrombotic monocyte activation seen early after TAVR. Primary and Secondary Outcomes The primary endpoint will be platelet responsiveness: platelet function will be measured one day after TAVR using the VerifyNow P2Y12 assay, and expressed in platelet reactivity units. The key secondary outcome measure will be the percentage of inflammatory monocytes, measured one day after TAVR. Inflammatory monocytes will be determined by flow cytometry, and expressed as a percentage of total monocytes.