Abstract Body (Do not enter title and authors here): Introduction: Slow coronary flow (SCF) is a coronary microvascular disorder characterized by delayed opacification of coronary vessels on angiography in the absence of obstructive epicardial coronary artery disease (CAD). Many patients with SCF suffer from angina-like chest pain and are frequently referred for angiography following abnormal cardiac stress tests. Although the clinical and pathological features of SCF have been previously described, the effect of SCF on cardiac function remains an area of active investigation.
Methods: We performed a single-center retrospective cohort study of 145 adults with angiographically confirmed SCF, defined by prolonged TIMI frame count, and absence of obstructive epicardial CAD. Demographic, historical, procedural and transthoracic echo (TTE) data was collected by review of electronic medical records. These patients were compared to a matched control group with normal coronary flow and no evidence of obstructive epicardial disease on angiography.
Results: Analysis of TTE parameters of patients with SCF demonstrated no impairment of left ventricular systolic function in our study population (LVEF 54.11 ± 3.43%). However, we found that a higher proportion of patients with SCF demonstrated diastolic dysfunction when compared to controls (49.7% vs 13.5%, P<0.0001). Multinomial logistic regression demonstrated SCF is independently associated with diastolic dysfunction, adjusting for age, sex, hypertension, diabetes, hyperlipidemia and smoking (coefficient: 2.50, p-value=0.001). Patients with SCF also exhibited dilation of the LA as evidenced by the increased LA volume index in patients with SCF compared to controls (34.00 ± 4.93 vs 28.58 ± 0.81 mL/m², P<0.0001).
Conclusions: Our results demonstrate that SCF is independently associated with left ventricular diastolic dysfunction and left atrial dilation in patients without obstructive epicardial coronary disease. These findings suggest that SCF may reflect underlying microvascular disease severe enough to impair myocardial relaxation and elevate filling pressures. Given the prevalence of diastolic dysfunction and the increasing recognition of coronary microvascular dysfunction as a contributor to cardiovascular morbidity, SCF may serve as an important early clinical indicator. Future studies are needed to determine whether therapies aimed at improving microvascular function correlate with the reversal of diastolic dysfunction in this population.