Non-invasive assessment of coronary flow reserve in distal left circumflex coronary artery in patients with angiographically normal coronary tree.

Nine patients (pts) with angiographically normal coronary arteries were submitted to absolute coronary flow reserve (CFR) in the distal left circumflex (LCx) coronary artery (specifically in the marginal branch that was insonified by a modified four-chamber view) using a novel non-invasive method (base-adenosine transthoracic echo Doppler in convergent color Doppler mode ). CFR in the distal left anterior descending coronary artery was attained as well using the same Doppler modality. Results: In this non consecutive series of patients blood flow velocity in LCx was adequately recorded at baseline and during adenosine infusion. However blood flow velocity recording in the LCx was more difficult to attain during hyperemic phase than during the basal one; in fact it was attained only in the pre-tachicardic phase of the hyperemia in 4 pts (45%). CFR attained in the LCx strictly concorded with that attained in the left anterior descending coronary artery territory (R= 0.94, p<0.001) (see graph) so relative CFR was close to 1 (0,96 +/-0.08). Conclusion: In this preliminary non-consecutive study CFR in LCx seems feasible enough to have clinical potential value. Its strict agreement with LAD CFR over a wide range of values in patients with angiographically normal coronary arteries and expected homogeneous microcirculatory function indicate its potential higly reliability in terms of pathophysiology assessment of coronary function.