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Circadian systemic haemodynamics in borderline and mild hypertension
1Department of Clinical Physiology, Tampere University Hospital, Finland.
Insights
Circadian hemodynamic changes, particularly increased stroke volume (SV) at night, predict future hypertension. These alterations in cardiovascular function may occur before blood pressure (BP) significantly rises.
Area of Science:
- Cardiovascular Physiology
- Hypertension Research
- Chronobiology
Background:
- Circadian variations in cardiovascular parameters are crucial for maintaining homeostasis.
- Understanding hemodynamic changes preceding hypertension is vital for early detection and intervention.
- Previous studies have explored nocturnal blood pressure dipping, but less is known about other hemodynamic factors.
Purpose of the Study:
- To investigate circadian variations in blood pressure (BP), stroke volume (SV), heart rate (HR), cardiac output (CO), and total peripheral resistance (TPR).
- To identify hemodynamic predictors of future hypertension development.
- To assess longitudinal changes in hemodynamics and their association with hypertension progression.
Main Methods:
- Pulse contour analysis of intra-arterial pulse waves in normotensive (NT), borderline hypertensive (BHT), and hypertensive (HT) men.
- Measurement of BP, SV, HR, CO, and TPR during day and night cycles.
- Longitudinal follow-up assessment of BP after five years, with logistic regression analysis for hypertension development.
Main Results:
- Nocturnal decrease in BP and HR were similar across groups.
- Stroke volume (SV) increased nocturnally in BHT and HT groups, unlike NT group.
- Nocturnal increase in SV was a significant predictor of future hypertension in logistic regression models.
Conclusions:
- Circadian systemic hemodynamics can be altered before significant elevation in blood pressure (BP).
- Nocturnal stroke volume (SV) changes may serve as an early indicator of hypertension development.
- Hemodynamic studies assessing circadian variations show potential for predicting sustained hypertension.
Abstract:
Circadian variations in blood pressure (BP), stroke volume (SV), heart rate (HR), cardiac output (CO) and total peripheral resistance (TPR) were determined by a pulse contour method from the intra-arterial pulse wave in 32 normotensive (NT), 32 borderline hypertensive (BHT) and 31 hypertensive (HT) middle-aged men. Daytime averages were used as the reference levels. The nocturnal decrease in BP and HR were similar in the three groups. In the night, SV did not change in the NT group, but was increased in the BHT and HT groups. The nocturnal increase in SV may reflect reduced venous capacity causing increased cardiac filling. As a consequence of the difference in SV, the nocturnal CO fall was diminished in the HT group as compared with the NT group. Moreover, TPR had a tendency to decrease in the HT group, which may be considered as a baroreflex response to buffer the expected rise in BP. Five years later, 25 NT, 24 BHT and 19 HT subjects were reassessed using casual BP measurements. In the NT and BHT groups, six and 17 subjects, respectively, had progressed to hypertension. In a logistic regression model for those who became HT, the nocturnal increase in SV was a significant predictor for future hypertension. In conclusion, the results suggest that circadian systemic haemodynamics may be altered before BP is markedly elevated, and that haemodynamic studies might be useful in predicting the development of sustained hypertension.