Abstract

Background: Disturbances of blood rheology may create unfavorable changes of blood flow. The present study was performed to reveal possible hemorheologic abnormalities in primary pulmonary hypertension.

Methods: Six patients with primary pulmonary hypertension (PPH) and 10 healthy controls of comparable age and smoking habits were studied. Blood viscosity was studied with a computer-controlled rotational viscometer, at natural hematocrit and at standardized hematocrit (45%). A capillary U-tube was used for plasma viscosity studies. Blood cell filterability was measured by theSt. George's Filtrometer (according to Dormandy et a1). Nucleopore filters of 5 (erythrocytes) and 8 (leukocytes) micrometers were used.

Results: Whole blood viscosity in PPH patients was higher than in controls at four different shear rates (p<0.025-0.005). This was partly due to a higher concentration of red cells in the patients. After standardization to 45%  however, the difference was still there at the highest shear rate used (40 s-1). It was also found that the passage time for erythrocytes through the filter was increased in the patient group, indicating decreased erythrocyte deformability. There were no significant differences between the groups in plasma viscosity, plasma fibrinogen, concentration of leukocytes, or leukocyte deformability.

Conclusions: Patients with PPH show increased whole blood viscosity values. This is partly explained by an increased hematocrit. It is also found, however, that the deformability of erythrocytes in these patients is decreased. These changes may influence blood flow in an unfavorable way. Therapeutic measures against hemorheologic disturbances may be a possible complement to the commonly used vasodilatory treatment.