Linear cardiac output in borderline and sustained hypertension

We assessed the relative contributions of raised cardiac output and increased peripheral resistance to elevation and lability of blood pressure in patients with borderline and sustained hypertension. Ninety-five untreated patients were admitted to hospital for assessment. Using Doppler ultrasound, linear cardiac output was measured as minute distance on the day of admission and 24 h later; blood pressure was measured at the same times, enabling calculation of linear resistance (analogous to peripheral vascular resistance). In sustained, but not borderline, hypertension linear resistance was increased at the first measurement (+ 36%, P less than 0.001), but mean minute distance did not differ significantly from normal in either group. Between the first and second measurements in borderline and sustained hypertension there were significant falls of mean blood pressure (-9%, P less than 0.001 and -4%, P less than 0.01). In borderline, but not sustained, hypertension there was an associated fall of linear resistance (-11%, P less than 0.05); in neither group was there a significant change of minute distance. Both elevation and lability of blood pressure in borderline and sustained hypertension are due more to changes of peripheral resistance than to changes of cardiac output.