Objective: Analysis of different indices of blood pressure (BP) variability using the ambulatory blood pressure monitoring (ABPM) method in two populations of hypertensive patients (HTA Group) and normotensive volunteers (NOR Group).
Setting: Noninvasive prospective ambulatory study to assess the alterations of the circadian blood pressure profile through ABPM indices of blood pressure variability.
Patients: Patients with the diagnosis of essential arterial hypertension referred for clinical investigation to the Cardiology Department of Egas Moniz Hospital in Lisbon.
Material and methods: 40 hypertensive patients (HTA Group) and 30 normal subjects (NOR Group) were included in this study. We calculated the short and long term variability indices. The short term variability indices were the casual and mean immediate BP deviation, percentage of BP peaks and BP peak relative deviation and maximal range variation. Some clinical and general factors considered were namely age, gender, height, weight, body area and index, mean and casual systolic-diastolic blood pressure.
Results: Concerning systolic blood pressure in hypertension Vs normal groups respectively, the casual BP deviation was 15 +/- 4 mmHg and 7 +/- 4 mmHg (p 0.003), the mean immediate BP deviation was 18.5 +/- 4 mmHg and 7.5 +/- 3 mmHg (p 0.002), the percentage of BP peaks was 27 +/- 6% (p < 0.001), the percentage of BP peak area was 29 +/- 7% and 6 +/- 3% (p 0.001) and the percentage of relative deviation was 14 +/- 4% and 8 +/- 3% (p 0.03). For diastolic blood pressure all differences were not statistically significant between the two groups and the same happened for systolic blood pressure in relation to standard deviation and maximal range variation. Among these parameters and general and clinical characteristics, the systolic mean and casual blood pressure level showed an acceptable correlation with mean immediate deviation (R = 0.54/0.49), percentage of BP peaks (R = 0.56/0.49) and percentage of BP peak area (R = 0.60/0.53).
Conclusions: Blood pressure variability can be adequately evaluated through the method of ambulatory blood pressure monitoring. Some variability indices can be extracted from the 24 hour curves of ambulatory blood pressure monitoring. Long-term variability indices are not related to the level of blood pressure. In the hypertension group we found a greater variability concerning short term indices, namely immediate deviation, percentage and are of peak curve.