Prevalence and characteristics of coronary microvascular dysfunction among chest pain patients in the emergency department

Aims: Coronary microvascular dysfunction (CMD) is common in patients with non-obstructive coronary arteries but has not been described in low-risk symptomatic patients. We therefore assessed the prevalence and characteristics of CMD in low to moderate risk patients with chest pain in an emergency department. Methods and results: We used three-dimensional Rb-82 cardiac positron emission tomography/computed tomography to diagnose coronary artery disease (known or new regional defect, any coronary calcification) and CMD (low coronary flow reserve without coronary artery disease) in chest pain patients after being ruled out for acute myocardial infarction. Exclusions included age 30 years or less, acute myocardial infarction, hemodynamic instability, heart failure and dialysis. Among 195 participants undergoing cardiac positron emission tomography/computed tomography, 42% had CMD, 36% had coronary artery disease and 22% had normal flows; 70% were women and 84% were obese. Patients with CMD and coronary artery disease had significantly lower coronary flow reserve than normal patients (mean coronary flow reserve 1.6 and 1.9 vs. 2.6, respectively, P<0.05). However, CMD patients were younger (mean age 51 vs. 61 years), and had fewer traditional cardiac risk factors (P<0.05) than patients with coronary artery disease. Nearly one third (31%) of patients had a prior emergency department visit for chest pain within three years of index presentation. Women were four times as likely to have CMD as men (adjusted odds ratio 4.2; 95% confidence interval 1.8, 9.6) after controlling for age, race, hypertension, diabetes, smoking, dyslipidemia, obesity and family history of coronary artery disease. Conclusions: Despite their low-risk profile, nearly one half of symptomatic and mostly obese emergency department patients without evidence of myocardial infarction or coronary artery disease had CMD. The results could explain the high rates of return visits associated with chest pain, although their application to the general emergency department population require validation.