The aim of this study was to identify the relationship of QT dispersion on 12-lead electrocardiograms and left ventricular mass index on echocardiograms associated with the circadian rhythm of blood pressure (BP). Heart rate and BP were monitored every 30 min for 48 h in 62 patients with essential hypertension using an ambulatory BP monitoring device. The patients were divided into four groups according to gender and circadian BP pattern (nocturnal BP dipper or nondipper). The patients were classified as dippers if their daytime BP decreased by at least 10% during the night and all the other subjects were classified as nondippers. Age, body mass index, and 48-h mean BP were similar among the four groups. During the night-rest period, the systolic and diastolic BP were significantly decreased in dipper-type hypertensives. The maximum QTc interval and QTc dispersion were longer in nondippers than in dippers. Left ventricular mass index (LVMI) had a tendency to increase in nondippers. The nocturnal reduction of BP significantly correlated with QTc dispersion and LVMI. The QTc dispersion significantly correlated with LVMI and interventricular septum thickness.

The aim of this study was to identify differences in the patterns of efficacy and duration of effect by diltiazem given in different dosage forms and schedules. Blood pressure (BP) and heart rate (HR) were monitored before and after treatment by ambulatory blood pressure monitoring for 48 h every 30 min. Patients were divided for treatment assignment into 4 groups -nocturnal BP dippers and nondippers. In dipper hypertension, diltiazem-retard at 08:00 (n = 7) had the most marked antihypertensive effects during nighttime rest (SBP; 136 +/- 14/118 +/- 9 mmHg, p < 0.01 before vs. after treatment). Diltiazem-retard at 19:00 (n = 6) exerted greatest effect during daytime activity (152 +/- 7/139 +/- 6, p < 0.01) with inhibition of the morning BP rise. Diltiazem (t.i.d., n = 5) had the best effect during daytime activity (151 +/- 16/136 +/- 9, p < 0.05). However, in nondipper hypertensive patients, diltiazem (t.i.d., n = 8) had the most pronounced antihypertensive effects during nightly rest (144 +/- 12/127 +/- 12, p < 0.05). Evening medication with diltiazem retard appears to be more efficacious than the other dosage schedules.

We investigated the influence of thyroid hormones on the circadian blood pressure (BP) and heart rate (HR) variations in 12 normotensive subjects and 12 normotensive patients with mild hyperthyroidism. BP and HR were monitored every 30 minutes for 48 h, and electrocardiograms (ECGs) were recorded to measure the RR interval of the ECGs. We analyzed the circadian BP and HR variations, HR variability, and the morning rise in BP and HR. There was no significant difference in the average 24 h BP between groups. HR and pulse pressure were higher in the hyperthyroid group than in the control group. Though the circadian BP pattern was similar in both groups, HR decreased at night in the control group, but not in the hyperthyroid group. Spectrum analysis of the RR interval showed no increase in the high-frequency (HF) component at night in patients with hyperthyroidism. The HR did not show a morning rise in the hyperthyroid group. These findings indicate that the circadian rhythm of HR was not preserved in patients with mild hyperthyroidism. The circadian BP rhythm was similar in normotensive subjects and normotensive patients with mild hyperthyroidism, suggesting that it resulted from factors other than thyroid hormone.

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