Relationship between 24-hour blood pressure pattern and left ventricular structure and function in hypertensive Nigerians

Abstract

Objective: Blood pressure variation throughout the day is known to have cardiovascular consequences. Left ventricular (LV) mass is more closely related to 24-hour blood pressure than casual blood pressure. Daytime blood pressure expectedly is higher than that of nighttime under normal circumstances. The effect of 24-hour blood pressure pattern on the left ventricular structure and function has not been examined in hypertensive Nigerians. The aim of our study was to assess the 24-hour blood pressure pattern and its relationship to the LV structure and function in newly diagnosed hypertensives in Nigeria. We hypothesized that 24-hour blood pressure was more related to left ventricular structure than casual blood pressure in hypertensive Nigerians.

Design: Cross-sectional study.

Setting: The study was carried out at the Cardiology Unit of the Department of Medicine, University College Hospital, Ibadan, South West Nigeria.

Participants: Three casual blood pressure measurements were taken, while the participants were resting, using standardized digital blood pressure machine. Mean of the 3 measurements was used to categorize the participants as hypertensives or normotensives (controls). A calibrated Schiller BR-102 ABPM machine was used to measure the 24-hour blood pressure in 210 hypertensives and 202 normotensives (controls). Daytime and nighttime systolic (SBP) and diastolic blood pressures (DBP) were acquired every 20 minutes. Left ventricular mass was indexed by the allometric power of height (height 2.7) and left ventricular hypertrophy was considered present if LVM was > or = 49.2 g/m2.7 in males or > or = 46.7 g/m2.7 in females.

Main outcomes: The hypertensives and the controls were comparable in their demographic characteristics. Among the hypertensives, mean casual blood pressure and mean 24-hour blood pressure (SD) were 165(16)/96(8) mm Hg and 132(22)/84(15) mm Hg, respectively (P < .0001). 24-hour, day- and nighttime blood pressure were statistically related to left ventricular mass and indexed left ventricular mass in the hypertensives (r = .40 and .40, respectively for mean 24-hour SBP; r = .34 and .30, respectively for mean 24-hour DBP; r =.33 and .35, respectively for mean nighttime SBP, and; r = .22 and .24, respectively for mean nighttime DBP. The relationship was significant for mean 24-hour blood pressures but not for mean nighttime blood pressures for normal controls. There was no significant correlation between 24-hour blood pressure and indices of left ventricular function.

Conclusions: Our study has shown a stronger relationship between 24-hour mean blood pressure and left ventricular mass compared with casual blood pressure. However there is no statistical relationship between 24-hour blood pressure and indices of left ventricular systolic and diastolic function.