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 hypothesis of differing coronary flow reserve (CFR) of coronary arteries perfusing left ventricular regions with nonuniform myocardial hypertrophy by measuring the relative CFR. METHODS AND RESULTS: Coronary flow velocity was assessed in left anterior descending coronary (LAD) and left circumflex (LCX) arteries in 18 patients with HOCM and marked hypertrophy 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 microg/kg per minute). Relative CFR was estimated as the ratio between absolute CFR 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 reversed 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 rapid 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 correlation between relative CFR and peak systolic outflow tract gradient (r2=.74, P<.001). CONCLUSIONS: Regional distribution of hypertrophy in some patients with HOCM resulted in regional impairment of coronary flow. Relative CFR can be used to estimate regional disturbances of coronary flow and may help in patient selection for new interventional therapeutic techniques.