Coronary flow reserve in hypertrophic obstructive cardiomyopathy assessed by intracoronary Doppler catheter

BACKGROUND: In spite of progress in diagnosis and treatment, hypertrophic obstructive cardiomyopathy (HOCM) remains a serious medical problem. Among many issues, the pathophysiology of the coronary circulation in HOCM has not yet been fully examined. AIM: To assess coronary flow reserve in HOCM. METHODS: The study group consisted of 15 patients (6 males, 9 females, mean age 51+/-15 years) with typical echocardiographic signs of HOCM and without stenosis of the coronary arteries. Using an intracoronary Doppler catheter, the average peak velocity and the absolute coronary flow reserve were determined in the proximal, medial and distal parts of the left anterior descending (LAD) and the circumflex coronary artery (Cx) following administration of papaverine, substance P, and during pacing. The coronary square plane was calculated angiographically after substance P injection. The retrograde coronary flow and the relationship between the increase of the coronary square plane and the coronary flow reserve were also examined. RESULTS: Under pharmacological stimulation, higher values of the average peak velocity were observed compared to pacing. A retrograde flow was observed in 8 of 10 patients in the LAD and in 3 of 8 patients in the Cx. The coronary flow reserve was higher under pharmacological stress than during pacing. No relationship was found between the increase of the coronary square plane and the coronary flow reserve. CONCLUSIONS: No decrease in the coronary flow reserve was observed in our patients with HOCM which, however, does not exclude the possibility of ischaemia based on subordinate vessels and microcirculation changes. In the majority of patients a retrograde flow was detected.