Twenty-four-hour blood pressure load as a surrogate end-point in assessing antihypertensive therapy

To examine the relationships among ambulatory blood pressure, blood pressure load (proportion of elevated blood pressure values over 24-h recording) and indices of hypertensive heart disease (left ventricular mass and left ventricular function) in untreated hypertensive patients. A secondary aim was to evaluate the usefulness of ambulatory blood pressure load in assessing the long-term effects of antihypertensive drug therapy.

Data were obtained from a study of 15 men with moderate to severe essential hypertension who had been treated with a placebo followed by 6-8 months of carvedilol monotherapy (25-75 mg/day). Blood pressure was evaluated by 24-h ambulatory monitoring.

In studies of office or 'white-coat' hypertensives, ambulatory blood pressure has proved a better predictor of target organ involvement than casual (clinic) pressure. Blood pressure loads of > 50% for systolic pressure and > 40% for diastolic pressure are superior to clinic pressures, and also to the usual ambulatory monitoring parameters of mean 24-h, awake and sleeping blood pressure, in predicting left ventricular hypertrophy and abnormal diastolic performance. In the carvedilol study, the mean awake systolic blood pressure load fell from 94 to 43% and the diastolic blood pressure load fell from 84 to 27% with carvedilol treatment (P < 0.001 in both cases). Of the patients treated with carvedilol monotherapy, 60% fell into the lower risk category (< 50% systolic blood pressure and < 40% diastolic blood pressure load).

These data support the use of blood pressure load in clinical studies of mild to moderate essential hypertension as a measure of the efficacy of antihypertensive drugs.