Impaired coronary flow velocity reserve is associated with cardiovascular risk factors but not with angina symptoms

Objectives Coronary microvascular dysfunction (CMD) is considered to cause angina pectoris in a large proportion of women with no obstructive coronary artery disease (CAD). However, data supporting a relation between angina pectoris and CMD are limited. We compared CMD in women with angina with asymptomatic women and evaluated the relation between presence of CMD, angina characteristics, cardiovascular risk factors and results of stress testing. Methods In a cross-sectional study, we included 1684 women with angina and <50% coronary artery stenosis on invasive angiography. Asymptomatic women from the community-based Copenhagen City Heart Study served as reference group (n=102). Coronary microvascular function was determined by coronary flow velocity reserve (CFVR) assessed by transthoracic Doppler stress echocardiography. CFVR < 2 was defined as CMD. Symptoms were obtained from standardised angina questionnaires and results of stress testing from health records. Results Median CFVR was 2.33 (IQR 2.00-2.75) in symptomatic women versus 2.60 (2.19-2.95) in asymptomatic (p=0.007). CFVR <2 was found in 25% of symptomatic and in 19% of asymptomatic women. Symptomatic women had a greater risk factor burden. After adjusting for age, hypertension, diabetes, smoking and heart rate the difference in CFVR between groups disappeared (p=0.213). We found no associations between CFVR and angina characteristics, symptom burden or results from stress testing. Conclusions Impaired CFVR is more prevalent in symptomatic than in asymptomatic women and related to the cardiovascular risk factors hypertension, diabetes, smoking and increased heart rate. Neither a positive bicycle test, single photon emission CT stress test nor chest pain characteristics identify women with impaired CFVR among women with angina and no obstructive CAD. Results may question the concept of microvascular angina as currently defined.