CHANGES IN PHASIC CORONARY BLOOD-FLOW VELOCITY PROFILE AND RELATIVE CORONARY FLOW RESERVE IN PATIENTS WITH HYPERTROPHIC OBSTRUCTIVE CARDIOMYOPATHY

Background In this study, we both investigated coronary flow velocity in hypertrophic obstructive cardiomyopathy (HOCM) and tested the hypot hesis of differing coronary how reserve (CFR) of coronary arteries per fusing left ventricular regions with nonuniform myocardial hypertrophy by measuring the relative CFR. Methods and Results Coronary flow velo city was assessed in left anterior descending coronary (LAD) and left circumflex (LCx) arteries in 18 patients with HOCM and marked hypertro phy only in the ventricular septum, in 13 patients without obstruction (HCM), and in 9 age- and sex-matched normal subjects at rest, during rapid atrial pacing, and after dobutamine infusion (5 to 30 mu g/kg pe r minute). Relative CFR was estimated as the ratio between absolute CF R of the LAD and absolute CFR of the LCx (LAD/LCx(CF)). At the peak of rapid atrial pacing and during dobutamine stress, LAD/LCx(CF), was re versed in HOCM patients (from 1.25+/-0.11 to 0.82+/-0.07 and 0.79+/-0. 06, respectively), whereas it remained unchanged in control subjects ( from 1.0+/-0.1 to 1.0+/-0.05 and 1.0+/-0.05, respectively; P<.001). In HCM patients, LAD/LCx(CF) at rest was 1.10+/-0.11, whereas during rap id atrial pacing and dobutamine stress, it was 0.92+/-0.08 and 0.90+/- 0.09, respectively. Relative CFR was 0.62+/-0.05 in HOCM patients and 1.05+/-0.05 (P<.001) in normal subjects. There was an inverse correlat ion between relative CFR and peak systolic outflow tract gradient (r(2 )=.74, P<.001). Conclusions Regional distribution of hypertrophy in so me patients with HOCM resulted in regional impairment of coronary flow . Relative CFR can be used to estimate regional disturbances of corona ry flow and may help in patient selection for new interventional thera peutic techniques.