Smoking and respiratory diseases in patients with coronary microvascular dysfunction

Background Coronary microvascular disease (CMD) is common in patients with and without obstructive coronary artery disease, and is associated with adverse clinical outcomes. Respiratory-related variables are associated with pulmonary and systemic microvascular dysfunction, while evidence regarding their relationship with CMD is limited. We aim to evaluate respiratory-related variables as risk factors of CMD. Methods This is an observational, single-center study enrolling consecutive patients undergoing invasive evaluation of coronary microvascular function in the catheterization laboratory. Patients with evidence of obstructive coronary artery disease or with missing data were excluded. Associations between respiratory related variables and indices of CMD were assessed using univariate and multivariate regression models. Results Overall, 266 patients (mean age 67 ±11, 59% females) were included in the current analysis. Of those, 155 (58%) had evidence of CMD. Among the respiratory variables, independent predictors of CMD were current smoking (adjusted OR 2.5, 95% CI 1.2-5, p=0.01) and obstructive sleep apnea (AOR 5.7, 95% CI 1.2-26, p=0.03), while chronic obstructive pulmonary disease was not. Among ever-smokers, higher smoking pack-years was an independent risk factor for CMD (median 35 vs. 25 pack years, AOR 1.09, 95% CI 1.04-1.13, p<0.01), and was associated with higher rates of pathologic index of microcirculatory resistance (IMR) and resistive reserve ratio (RRR). Conclusion In patients undergoing invasive coronary microvascular evaluation, current smoking and obstructive sleep apnea are independently associated with CMD. Among smokers, higher pack-years is a strong predictor for CMD. Our findings should raise awareness for prevention and possible treatment options.