Increased red blood cell deformability and decreased aggregation as potential adaptive mechanisms in the slow coronary flow phenomenon

OBJECTIVE: At present, the precise pathophysiology of the slow coronary flow phenomenon (SCFP) is still unknown and there is no consensus as to how it should be treated. The rheological factors affect the clinical course of various cardiovascular diseases. We studied the intrinsic properties of blood in the SCFP. MATERIALS AND METHODS: Twenty-six SCFP patients who had angiographically confirmed SCFP, and had otherwise normal epicardial coronary arteries, were included in our study, as were 30 healthy individuals with normal results from arteriography. Red blood cell (RBC) deformability, aggregation, whole-blood viscosity at both native and standard (40%) hematocrit, and plasma viscosity were determined in each individual. The results were analyzed using a Mann-Whitney U-test, an unpaired t-test, and a χ-test, where appropriate. RESULTS: The mean thrombolysis in myocardial infarction frame count was significantly higher in SCFP patients than in the controls. RBC deformability measured at five different shear rates was significantly higher in SCFP patients than in the controls. The RBC aggregation index was lower in SCFP patients. There were no statistically significant differences in RBC aggregation half-time (t1/2) and aggregation amplitude, whole-blood viscosity, and plasma viscosity between the two groups. CONCLUSION: The SCFP is associated with increased RBC deformability and decreased RBC aggregation. These hemorheological alterations, possibly also contributing factors in limiting the pathogenesis, can especially serve as beneficial adaptive mechanisms in the SCFP.