[Transthoracic dopllerographic assessment of the relative coronary reserve in the norm and in the presence of isolated hemodynamically significant stenoses of the left anterior descending coronary artery].

Comparison of velocity parameters of blood flow and absolute coronary reserve (absCR) in the left anterior descending and posterior interventricular coronary arteries (ADCA and PICA) with calculation of relative coronary reserve (relCR) and determination of its normative values was carried out with the help of transthoracic echocardiography in 29 healthy volunteers (mean age 40+/-13 years). Assessment of the role of absCR and relCR in ADCA in diagnostics of hemodynamically significant stenoses of this vessel was performed in 88 patients with syndrome of cardiac pain (mean age 40+/-12 years). Coronary angiography was used as a reference method. Coronary blood flow in distal segments of ADCA and PICA was measured at baseline and during infusion of a vasodilator (dipyridamole up to 0.84 mg/kg as intravenous infusion). AbsCR for each of these arteries was determined as ratio of hyperemic peak diastolic blood flow velocity and its baseline value. Lowering of absCR was diagnosed at its level <2.0). RelCR was calculated only for ADCA as ratio of absCR of ADCA and PICA. It was established that parameters of coronary blood flow and absCR level in healthy volunteers in ADA and PICA had no significant differences. Therefore these vessels were considered referent for each other. In the norm relCR in ADA was 1.09+/-0.36 (95% confidence interval from 0.95 to 1.23). We proved that ADA abs CR in <2.0 served as predictor of ADA stenosis >50% with sensitivity 89% and specificity 85%. However 22% of subjects with lowering of absCR had ADA stenoses <50%, microvascular involvement, or belonged to the group of healthy volunteers. It was established that ADA relCR <0.80 in patients with ADA absCR <2.0 was a sensitive and specific sign of isolated ADA stenosis >50%.