Prognostic value of ambulatory blood pressure measurements: further analyses

The value of ambulatory systolic blood pressure as a predictor of the development of cardiovascular complications was investigated in a sample of 761 hypertensive patients who had undergone ambulatory blood pressure monitoring and who were followed for an average of 5.5 years. Of the 695 patients without prior cardiovascular events at entry into the study, 11% subsequently experienced an event during the follow-up period (up to 10 years) compared to 48% of the 102 patients with a prior cardiovascular event. For each patient, a 'predicted' ambulatory systolic blood pressure was calculated, using the patient's office systolic blood pressure and the equation derived from regressing ambulatory on office blood pressure for the entire sample. By subtracting the predicted from the observed ambulatory pressure, a 'residual' ambulatory systolic blood pressure was derived for each patient, as a measure of that portion of the ambulatory pressure that could not be predicted from the office pressure. We used a Cox proportional hazards model to analyse the independent effect of each of the following patient characteristics at entry on the occurrence of subsequent cardiovascular events: sex, age, ECG evidence of left ventricular hypertrophy, hypertensive retinopathy, ambulatory systolic blood pressure, office systolic blood pressure, residual ambulatory systolic blood pressure and subsequent drug therapy. In both groups, with and without a prior cardiovascular event, women, younger patients and those with lower residual ambulatory systolic blood pressure tended to have longer periods of survival without new cardiovascular events. In the group without prior cardiovascular events, a lower office systolic blood pressure and the absence of advanced ECG evidence of left ventricular hypertrophy were also independently predictive of longer event-free survival.(ABSTRACT TRUNCATED AT 250 WORDS)