It has been reported that imbibing red wine increases coronary blood flow reserve acutely. In the absence of changes in coronary driving pressure, any increases in coronary blood flow reserve should occur through a decrease in capillary resistance, which in turn is determined by capillary dimensions and whole-blood viscosity. Since alcohol intake is unlikely to acutely change capillary dimensions, we hypothesized that it must increase coronary blood flow reserve by reducing whole-blood viscosity.
Forty-five normal subjects were randomly assigned to water (n = 12), vodka (n = 11), white wine (n = 11), and red wine (n = 11). Myocardial blood flow reserve was measured at baseline and after up to 2 weeks of beverage consumption using myocardial contrast echocardiography. In addition, whole-blood viscosity and its principal determinants (haematocrit; erythrocyte deformability, mobility, and charge; plasma fibrinogen; and total serum protein, glucose, and lipids) were also measured. Systolic and diastolic blood pressure and heart rate did not change between the two examinations either at rest or following dipyridamole infusion. Neither did myocardial blood flow reserve nor whole-blood viscosity or any of its determinants. Only high-density lipoprotein-2 increased for all alcohol consumers (12.4 ± 5.3 vs. 10.9 ± 4.7, P = 0.007).
It is concluded that modest alcohol consumption for up to 2 weeks does not increase myocardial blood flow reserve. It also does not alter whole-blood viscosity or any of its principal determinants. Therefore, the beneficial cardiovascular effects of modest alcohol consumption over 1–2 weeks cannot be attributed either to its effect on the coronary microcirculation or haemorheology.
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