Impaired coronary flow reserve as a marker of microvascular dysfunction to predict long-term cardiovascular outcomes, acute coronary syndrome and the development of heart failure.

BACKGROUND

In the absence of obstructive coronary narrowing, impaired coronary flow reserve (CFR) represents coronary microvascular dysfunction. Transthoracic Doppler echocardiography (TTDE) allows non-invasive measurement of CFR in the left anterior descending (LAD) artery. This study aimed to assess the prognostic value of TTDE-derived CFR (as a marker of microvascular function) in predicting long-term cardiovascular events, acute coronary syndrome (ACS) events, and the development of heart failure (HF).

METHODS AND RESULTS

This study consisted of 272 patients with coronary artery disease not involving obstructive narrowing (≥50%) in the LAD. Patients underwent TTDE examination for CFR measurement in the LAD. During the follow-up period of 4.0±1.9 years, 32 patients (12%) had cardiovascular events. Cox proportional hazard analysis identified lower CFR as an independent risk factor of cardiovascular events (P<0.001), ACS events (P=0.008), and HF development (P=0.003). A CFR less than 2.4 was the best cut-off value for predicting all events (area under the curve=0.82). CFR excellently predicted the development of HF (area under the curve=0.95), but not ACS events (area under the curve=0.67).

CONCLUSIONS

This TTDE study demonstrated that CFR was a significant and independent determinant of long-term cardiovascular events, ACS events and HF in patients with coronary artery disease. A CFR greater than 2.0 was not suitable to predict a favorable long-term outcome, even in the absence of obstructive coronary narrowing.