Invasive assessment of coronary flow reserve impairment in severe aortic stenosis and ecochadiographic correlations

Objectives and background: Patients with aortic stenosis (AS) may have impaired coronary flow reserve (CFR) despite angiographically normal coronary arteries. This is the first report of invasive thermodilution-derived CFR and IMR in patients with AS and their associations with echocardiographic parameters for AS assessment.

Methods: Thirty-six consecutive severe AS patients and ten patients without AS underwent prospectively cardiac catheterization and coronary physiological parameters were determined in the left anterior descending (LAD). Mean transit time (Tmn), a surrogate of absolute coronary flow, was obtained from the coronary thermodilution curve.

Results: In AS patients we found a high LAD flow at rest (Tmn _rest 0.55±0.3 vs 0.99±0.4, p=0.01) and a low flow at hyperemia (Tmn_hyp 0.44±0.2 vs 27.7±0.1, p=0.02) and consequently a severe CFR impairment (1.4±0.4 vs 3.8±1.4, p<0.001) compared with controls. An elevated index of microvascular resistance (IMR) (32.7±16 vs 17.8±6.5, p=0.01) and a low baseline microvascular coronary resistance (48.1±29 vs 84±34, p=0.02) were also found. In AS patients there were significant correlations between CFR and left ventricular mass index (r=-0.32; p=0.02), and the ratio of acceleration time to ejection time (AT/ET) (r=-0.4; p=0.01) a non-flow dependent echocardiographic parameter for AS assessment. Multiple linear stepwise regression analysis showed that AT/ET (β=-0.441, p=0.019) was the only independently variable associated with CFR CONCLUSIONS: In severe AS, invasive CFR shows a progressive decrease with AS severity and a good correlation with echocardiographic parameters of AS, especially with flow-independent ones.