Stroke patients and those with stroke risk factors have been shown to have chronically elevated blood viscosity relative to healthy persons. This increased risk has been attributed to the effect of blood viscosity on cerebrovascular blood flow.
Coull et al. (1991) reported chronically high blood viscosity in 430 subjects with stroke, mini-stroke (TIA), or recognized risk factors for stroke. Diastolic blood viscosity was significantly elevated in stroke patients compared with healthy adults. Between patient groups, those with acute stroke had the highest blood viscosity levels, those with TIA had the second highest, and those with recognized risk factors for stroke had lower blood viscosity levels. The authors concluded that in stroke patients abnormally elevated blood viscosity is chronic. Fisher and Meiselman (1991) reported similar findings. They found significant acute increases in blood viscosity among severe stroke patients.
Fong and Chia (1990) studied blood viscosity in 42 patients with nonembolic cerebral infarction. Blood viscosity, fibrinogen, cholesterol, and triglyceride levels were significantly higher than those of healthy persons, whereas high-density lipoprotein cholesterol (HDL-c) levels in the patients were significantly lower. In this study, blood viscosity was positively correlated with hematocrit and fibrinogen, while negatively correlated with HDL-c.
Di Perri et al. (1985) evaluated 106 patients with acute and chronic cerebrovascular diseases. Blood samples were drawn within six hours of the onset of the vascular syndrome. The authors reported that the onset of the vascular storm was associated with marked increases in blood viscosity and fibrinogen, while blood filterability
(a measure of red blood cell deformability) was significantly decreased. Acute stroke regressed with the progressive reduction of hemodynamic abnormalities, providing evidence for the association between cerebrovascular disease and hemodynamic alterations.
Resch et al. (1992) asked whether abnormalities in blood viscosity predict a poor prognosis for subsequent cardiovascular events in stroke survivors. They followed 625 survivors of a first stroke for an average of two years. Altogether, 85 patients (13.6%) had a heart attack or a second stroke or died as a result of a cardiovascular event. Blood viscosity and fibrinogen were higher in patients who had subsequent cardiovascular events than in those who did not.
Ernst et al. (1991) reported that pathologic blood flow properties and elevated blood viscosity lead to deterioration in the prognosis of patients with “arteriosclerotic diseases,” especially after a stroke. They concluded that in patients who survived a first stroke, elevated blood viscosity is a risk factor that is independent of other accepted risk factors.