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

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.

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.

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.