Background: Both atherosclerosis and plaque rupture are closely associated with wall shear stress (WSS). Although WSS is determined by the product of whole blood viscosity (WBV) and shear rate, there have been few studies for the direct measurement of WBV at the coronary artery. The aim of the study was to measure and compare WBVs between acute coronary syndrome (ACS) and non-ACS patients and also between coronary and peripheral arteries in ACS patients.
Methods: Consecutive 38 patients who underwent diagnostic coronary angiography were enrolled (62.2±9.2 years, 22 males) and were divided to two groups [Group I = non-ACS (n=16), Group II = ACS (n = 22)]. The Group II was consisted of unstable angina (n=13) and acute myocardial infarction (n=9) patients. Three blood samples were obtained from each patient at left and right coronary artery ostia and femoral artery prior to diagnostic coronary angiography (i.e., at least 10 s after the test injection of a contrast medium). Diastolic and systolic blood viscosities were measured at shear rates of 1 and 300 s-1, respectively, by a scanning capillary tube viscometer (Bio-Visco Inc., South Korea). Results: The diastolic BVs obtained in Group II were significantly higher than those in Group I for all three blood samples from left coronary (294.2±88.3 vs. 218.6±62.2, p = 0.006), right coronary arteries (296.2±90.1 vs. 238.4±82.4, p = 0.050) and femoral arteries (282.2±75.1 vs. 210.2±57.5, p = 0.003) by 24-34%. The systolic BVs obtained in Group II were significantly higher than those in Group I for blood samples from left coronary artery by 17.7% (42.6±9.5 vs. 36.2±3.9, p = 0.007) and femoral by 14.2% (41.4±8.6 vs. 36.0±3.5, p = 0.014). Conclusions: Both systolic and diastolic blood viscosities were found significantly greater in the left coronary artery in ACS than in non-ACS patients, suggesting the risk of coronary plaque rupture and erosion as well as impaired microcirculation. Further study of WBVs from the distal segment of a diseased coronary artery is recommended to clarify the present results.
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