Quantitative myocardial perfusion during stress echocardiography predicted cardiac damage and adverse events in symptomatic moderate aortic stenosis in a prospective study

Background With the advent of lower risk transcatheter procedures in severe aortic stenosis (AS), valve intervention in less severe, but potentially haemodynamically significant symptomatic moderate AS, is being contemplated both for therapeutic and prognostic reasons. Numerous factors have been assessed to improve understanding of the haemodynamic impact of moderate AS and therefore improve risk stratification. Myocardial blood flow reserve (MBFR) is a useful marker of microvascular disease which has been associated with adverse outcome. Stress echocardiography (SE) with MBFR assessment has not been previously used for risk stratification in symptomatic moderate AS. Purpose We sought to determine the value of SE with quantitative myocardial perfusion assessment in patients with symptomatic moderate AS. Methods In a prospective study 100 consecutive patients with symptomatic moderate AS [aortic valve area (AVA) = 1-1.4cm2 and aortic valve mean gradient (AVMG) < 40mmHg] and normal left ventricular ejection fraction, underwent contrast-enhanced SE for simultaneous assessment of function and perfusion and were then followed up at 1 year with transthoracic echocardiography (TTE) and at 4 years for all-cause mortality and aortic valve intervention. The stage of cardiac damage was assessed at baseline and at the 1-year TTE follow-up. MBFR was calculated using quantitative myocardial perfusion assessment during SE. Results The mean age of the study population was 77 ± 10 years. All patients had symptoms of shortness of breath on exertion. At rest the mean AVA was 1.17 ± 0.14cm2 and AVMG 19 ± 7mmHg. During follow-up there were 29 (29%) deaths, and 16 (16%) patients underwent aortic valve intervention. At 1-year TTE follow-up there was significant increase in the LV mass and relative wall thickness (increase by 11 ± 48g- p= 0.03, and 0.04 ± 0.13- p= 0.01 respectively). Progression in cardiac remodelling with increasing proportions of patients with concentric and eccentric hypertrophy was also observed (p< 0.001). Although the AS remained moderate (AVMG 22 ± 10mmHg and AVA 1.16 ± 0.26cm2), there was significant progression in the cardiac damage stage at follow-up TTE compared to baseline (p< 0.001) (Figure 1). The MBFR and the adjusted to LV mass MBFR (MBFRLVmass) were low 1.52 ± 0.56 and 0.87 ± 0.40 respectively. Low MBFRLVmass was a significant independent predictor of progression in cardiac damage at 1-year TTE follow-up (OR 3.78, 95% CI 1.05-13.58, p= 0.04) and poor outcome (death and aortic valve intervention at 4 years) (HR 0.34, 95%CI 0.12-0.99, p= 0.048). Conclusions In patients with symptomatic moderate AS LV remodelling and stage of cardiac damage progress significantly at 1-year of follow-up without concordant significant AS progression. MBFRLVmass assessed during contrast-enhanced SE was low indicating presence of microvascular/myocardial disease and a significant predictor of progression of cardiac damage and adverse outcome.