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Prediction of cardiac structure and function by repeated clinic and ambulatory blood pressure
R H Fagard1, J A Staessen, L Thijs
1Department of Molecular and Cardiovascular Research, Faculty of Medicine, University of Leuven KUL, Belgium.
Insights
Increasing blood pressure measurements improve correlations with left ventricular mass and wall thickness. However, repeated measurements decrease the added predictive value of 24-hour ambulatory blood pressure monitoring.
Area of Science:
- Cardiology
- Hypertension Research
- Medical Imaging
Background:
- Discrepancies exist regarding the strength of associations between left ventricular characteristics and clinic blood pressure.
- The superiority of ambulatory over clinic blood pressure measurements and the significance of diurnal blood pressure variations remain debated.
Purpose of the Study:
- To investigate the impact of repeated clinic and ambulatory blood pressure measurements on left ventricular characteristics.
- To clarify the relationships between different blood pressure measurement methods and cardiac structure/function in hypertensive individuals.
Main Methods:
- Imaging echocardiography and Doppler velocimetry were used in 74 hypertensive patients.
- Clinic blood pressure was measured multiple times using automated and conventional devices.
- 24-hour ambulatory blood pressure monitoring was performed.
Main Results:
- Partial correlation coefficients between left ventricular mass/wall thickness and clinic blood pressure strengthened with an increased number of measurements.
- Average 24-hour blood pressure was significantly related to cardiac structure, but its additional predictive power diminished with more clinic measurements.
- Daytime blood pressure showed a stronger association with cardiac structure than nighttime pressure; gender differences were observed in the importance of nighttime pressure.
Conclusions:
- Repeated clinic blood pressure measurements enhance the correlation with left ventricular mass and wall thickness.
- The incremental predictive value of 24-hour ambulatory blood pressure monitoring decreases as the number of clinic measurements increases.
- Nighttime blood pressure and its fall are important, with gender-specific variations, irrespective of the definition of day/night.
Abstract:
We performed imaging echocardiography, Doppler velocimetry, and repeated clinic and ambulatory blood pressure measurements in 74 hypertensive individuals to clarify why reports differ on the strength of the relationships of left ventricular characteristics with clinic blood pressure, on the superiority of ambulatory over clinic pressure, and on the importance of day-time and nighttime pressures. Clinic pressure was measured five times with an automated device and five times with the conventional technique on 2 different days. The partial correlation coefficients of left ventricular mass and wall thickness with the first automated systolic and diastolic clinic pressures amounted to .38 to .45 (P < .001), improved with increasing numbers of measurements, and reached .56 to .58 for the average of 10 automated pressure determinations. Similar trends were observed for conventional clinic pressures. Average 24-hour pressures were significantly related to mass and wall thickness (partial r = .50 to .61, P < .001) and explained 3% to 6% (systolic) and 5% to 12% (diastolic) of the variance of cardiac structure in addition to the first automated or conventional clinic pressure (P < .05). However, when 10 clinic measurements were averaged, only diastolic 24-hour pressure added information over and above clinic pressure (P < .05); the additional explained variance was larger with regard to the conventional (+4% for mass and +7% for wall thickness) rather than the automated (+3% for wall thickness only) pressures. Mass and wall thickness were more closely related to day-time than nighttime pressures and were not independently related to day-night differences in pressure, except when men and women were considered separately; the results were similar when four different definitions of day and night were applied. Finally, the weak association of left ventricular diastolic function with blood pressure did not improve on repeated clinic or ambulatory blood pressure measurements. In conclusion, increasing numbers of measurements strengthen the relationships of clinic pressure with left ventricular mass and wall thickness and, conversely, diminish the additional predictive power of 24-hour blood pressure. The importance of nighttime pressure and of the nighttime pressure fall does not seem to depend on the definition of day and night but differs in men and women.