Objective: To investigate the relationship between isolated nocturnal hypertension and left ventricular hypertrophy.
Methods: In the inhabitants of 14 villages in Jingning County, Zhejiang Province, we performed 24-hour ambulatory blood pressure monitoring with SpaceLab monitors and measured 12-lead resting electrocardiogram using an electronic recording system of GE company. Left ventricular hypertrophy was diagnosed with the criteria of Sokolow-Lyon voltage amplitude and Cornell product. Isolated nocturnal hypertension was defined as a nighttime (from 22:00 to 4:00) blood pressure of > or = 120/70 mm Hg (1 mm Hg = 0.133 kPa). Isolated daytime (from 8:00 to 18:00) hypertension was a diurnal blood pressure of > or = 135/85 mm Hg. When both conditions were present or absent, subjects were classified either as having combined day-night hypertension or as normotensive on ambulatory measurement. Analysis of variance and multiple regressions were used for statistical analysis.
Results: 647 participants (53.9% being female, average age 47.8 years) included 72 patients with isolated nocturnal hypertension, 33 with isolated daytime hypertension and 248 with day-night sustained hypertension. Compared with normotensive subjects, patients with isolated nocturnal hypertension and day-night sustained hypertension had a higher Sokolow-Lyon voltage amplitude and Cornell product. However, after adjustment for sex, age, body mass index, drinking and smoking habits, serum total cholesterol, fasting blood glucose and the use of antihypertensive drugs, only day-night hypertensive patients had a significantly higher Sokolow-Lyon voltage (32.8 mV, P = 0.0003) and Cornell product (1371 mV x ms, P = 0.0004) than normotensive subjects (29.0 mV, 1114 mV x ms). Regardless of whether Sokolow-Lyon or Cornell criteria were used, both nighttime and daytime systolic and diastolic blood pressure were independent risk factors of left ventricular hypertrophy (P < 0.01). However, the prevalence of left ventricular hypertrophy in patients with isolated nocturnal hypertension (23.6%) study was not statistically different from that in normotensives (17.4%, P = 0.24).
Conclusion: In our current cross-sectional study, isolated nocturnal hypertension was not independently related to left ventricular hypertrophy diagnosed with ECG criteria.