Hemorheological abnormalities and their associations with coronary blood flow in patients with cardiac syndrome X: A comparison between males and females

Aim: The role of elevated whole blood viscosity (WBV) in the pathogenesis of atherosclerosis is well known. We sought to investigate the gender differences in the association between WBV, coronary blood flow and tissue oxygen delivery index (TODI) in cardiac syndrome X (CSX). Methods: Forty-six CSX patients and 14 healthy volunteers were enrolled. The coronary flow parameters were obtained with transthoracic Doppler echocardiography and WBV was measured (at high-shear and low-shear rates of 300s^-1 and 5s^-1, respectively) using a scanning capillary tube viscometer. TODI was determined from the ratio of hematocrit to WBV measured at a low-shear rate of 5s^-1. Results: In male patients, the mean diastolic coronary flow velocity (CFV) and diastolic velocity time integral (VTI) were significantly decreased compared to control group (all p<0.05) and the WBV showed significant negative correlation with peak systolic CFV (r = -'0.559 at 300s^-1, r = -'0.438 at 5s^-1), mean systolic CFV (r = -'0.577 at 300s^-1, r = -'0.488 at 5s^-1), systolic VTI (r = -'0.576 at 300s^-1, r = -'0.530 at 5s^-1) and diastolic VTI (r = -'0.553 at 300s^-1, r = -'0.551 at 5s^-1) (all p<0.01). Meanwhile, although female patients showed no significant relationships between WBV and coronary flow parameters, TODI were significantly decreased compared to the control group (3.64 ± 0.34 vs. 4.07 ± 0.38%/centipoises (cP), respectively, p=0.008). Conclusion: Our study suggests that there are gender-related differences in the pathogenesis of microvascular angina and gender-specific approaches for CSX patients might be needed.