Microcirculatory dysfunction in cardiac syndrome X: role of abnormal blood rheology.

ABSTRACT

OBJECTIVE: Cardiac syndrome X (CSX) is of clinical interest, yet the underlying pathophysiological mechanisms have not been fully elucidated. It is well known that elevated blood viscosity and red blood cell (RBC) aggregation can adversely affect microcirculatory blood flow. The present study was designed to explore whether CSX is associated with abnormalities of blood rheology. METHODS: Blood samples were obtained from 152 adult angina patients undergoing diagnostic coronary angiography; geometric and flow-velocity data were obtained. Rheologic measurements were performed in a blinded manner; 21 subjects were later identified with CSX. Hemorheologic and clinical laboratory data were compared to 21 age- and gender-matched healthy controls. RESULTS: CSX patients had markedly abnormal blood rheology (1) higher RBC aggregation and aggregability as judged by erythrocyte sedimentation rate and Myrenne indices at stasis and low shear (p < 0.001) and (2) elevated hematocrit-corrected blood viscosity, plasma viscosity (p < 0.001), and yield stress (p < 0.01). White blood cell counts and high-sensitivity C-reactive protein levels were significantly elevated in CSX; coronary-flow velocities were below normal. CONCLUSIONS: Abnormal hemorheologic parameters exist in subjects with CSX and may contribute to the pathophysiology of the disease, presumably via adversely affecting blood flow in the coronary microcirculation. Therapeutic measures aimed at normalizing blood rheology and hence microcirculatory flow should be explored.