The aim of this study was to test the feasibility and accuracy of transthoracic Doppler echocardiography measurement of coronary flow reserve (CFR) in the left anterior descending coronary artery (LAD) territory in the clinical setting of the acute coronary syndrome.

Transthoracic Doppler echocardiography measurements of CFR were made in 42 consecutive patients in the distal LAD before and during adenosine infusion. The results were validated by coronary angiography. A normal CFR was predefined as a more than 2-fold increase of flow velocity during adenosine infusion.

We were able to detect significant stenosis in the LAD territory with 92% sensitivity and 82% specificity if we considered a stenosis ≥ 50% to be significant. Defining a stenosis of ≥ 70% as significant increased the sensitivity and the negative-predictive value to 100%, with a specificity of 70%.

Measuring CFR using transthoracic Doppler echocardiography is noninvasive, feasible, accurate, and relatively inexpensive. The excellent negative-predictive value of this technique makes it a useful tool for identifying patients who can avoid repeated angiography as a result of suspected subacute LAD restenosis after percutaneous coronary intervention.