The Association between Whole Blood Viscosity and Coronary Collateral Circulation in Patients with Chronic Total Occlusion

Background and Objectives: Coronary collateral circulation (CCC) has been attributed as inborn bypass mechanisms supporting ischemic myocardium. Various factors have been postulated in CCC. Whole blood viscosity (WBV) has been an underappreciated entity despite close relationships between multiple cardiovascular diseases. WBV can be calculated with a validated equation from hematocrit and total plasma protein levels for a low and high shear rate. On the grounds, we aimed to evaluate the association between WBV and CCC in patients with chronic total occlusion. Subjects and Methods: A total of 371 patients diagnosed as having at least one major, chronic total occluded coronary artery were included. 197 patients with good CCC (Rentrop 2 and 3) composed the patient group. The poor collateral group consisted of 174 patients (Rentrop grade 0 and 1). Results: Patients with poor CCC had higher WBV values for a low-shear rate (LSR) ($69.5{\pm}8.7$ vs. $60.1{\pm}9.8$, p<0.001) and high-shear rate (HSR) ($17.0{\pm}2.0$ vs. $16.4{\pm}1.8$, p<0.001) than the good collateral group. Correlation analysis demonstrated a significant negative correlation between the grade of CCC and WBV for LSR (${\beta}=0.597$, p<0.001) and HSR (${\beta}=0.494$, p<0.001). WBV for LSR (${\beta}=0.476$, p<0.001) and HSR (${\beta}=0.407$, p<0.001) had a significant correlation with the synergy between percutaneous coronary intervention with taxus and cardiac surgery (SYNTAX) score. A multivariate analysis showed that the WBV for both shear rates were independent risk factors of poor CCC (WBV at LSR, OR: 1.362 CI 95%: 1.095-1.741 p<0.001 and WBV at HSR, 1.251 CI 95%: 1.180-1.347 p<0.001). Conclusion: WBV has been demonstrated as the overlooked predictor of poor coronary collateralization. WBV seemed to be associated with microvascular perfusion and angiogenesis process impairing CCC development.