Abstract 45: Hemodynamic and Clinical Determinants of Coronary Sinus Flow in Patients Referred for Cardiac Catheterization

Background: Coronary sinus blood flow (CSBF) can be used as a measure of total coronary blood flow. Hemodynamic and clinical determinants of coronary sinus flow are not well investigated. Decreased CSBF is expected in obstructive coronary artery disease (CAD) and elevated left ventricular end-diastolic pressure (LVEDP). Material and Methods: A prospective cohort study of patients referred for cardiac catheterization was performed. CSBF (ml/min) was measured non-invasively as a product of heart rate, coronary sinus cross-sectional area (obtained in modified apical 4 chamber view), and coronary sinus time velocity integral (obtained in modified right ventricular inflow view). In patients with normal sinus rhythm and preserved atrial contraction, retrograde diastolic CSBF was subtracted from forward CSBF. Repeated measures ANOVA and chi-square analyses were used. Results: Study cohort consisted of 39 patients (19 females, 63+/-11 years old, 9 with diabetes, 30 with hypertension (HTN) and 6 with atrial fibrillation). CSBF was obtained in 24 (61%) patients. CSBF was increased in patients with normal blood pressure (1353+/-862 vs. 647+/-397 in patients with HTN, p=0.011) and in patients with right atrial (RA) pressure exceeding 5 mmHg (1228+/-654 vs. 478+/-356 in RA pressure less than 5 mmHg, p=0.002). HTN appeared to be a less important determinant of CSBF than RA pressure (RAP) in multiple ANOVA comparison (HTN p=0.643, RAP p=0.005, Figure). There was also a trend towards decreased CSBF in patients with diabetes (647 +/-507 vs. 937 +/-685 ml/min in patients without diabetes, p=0.327) and /or obstructive CAD (663+/-381 vs. 832+/-748 ml/min in non-obstructive CAD or normal coronaries, p=0.613) and females (680+/-419 vs. 1095+/-828 ml/min in males, p=0.119). There was no significant correlation between CSBF and LVEDP. Discussion and Conclusions: Coronary sinus blood flow is determined by patient morbidities and central hemodynamic parameters. CSBF tends to be lower in patients with obstructive CAD, diabetes and/or HTN. Increased RA pressure and systemic HTN are associated with augmented CSBF. We speculate that effects of RA pressure on CSBF are reflective of preload and intrathoracic pressure parameters. Increased intrathoracic pressure may augment coronary blood flow by compression of the aorta and improved coronary perfusion gradient.