Biomedical subjects
Publications and source records attributed to H Ijiri.
A case of exercise-induced idiopathic ventricular tachycardia (VT) arose from the left ventricular outflow tract. The QRS morphology of the VT was Rs pattern in V1 and R pattern in the lateral leads with inferior axis. The pacing at the superior interventricular septum near the mitral anulus produced the best pace mapping. Radiofrequency application to this site suppressed the VT.
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.
We evaluated the circadian variation and exercise stress response patterns of blood pressure (BP) in elderly patients with essential hypertension. Ambulatory BP monitoring for 48 hours every 30 minutes, and treadmill exercise test using a Bruce protocol at PM 3 to 5 were performed in 49 untreated patients with hypertension. Mean daytime (awake), and night-time (sleeping) systolic BP (SBP) and diastolic BP (DBP) values were analyzed by reviewing the patients' diaries, and the nocturnal reduction rate (NRR) of SBP and DBP were calculated according to the following formula. NRR (%) = [(daytime mean-nighttime mean)/daytime mean] x 100. The patients were divided into two groups according to the presence (dipper, n = 25) or absence (non-dipper, n = 24) of a reduction in both SBP and DBP during the night by an average of more than 10% of the daytime BP. Mean values of SBP and DBP measured over 48 hours in the dipper and non-dipper groups were similar. Responses of SBP to dynamic exercise at 2 to 5 minutes in the non-dipper group were significantly smaller than those in the dipper group (p < 0.05). Non-dipper patients with hypertension responded to dynamic exercise stress with smaller increases in SBP than did those in the dipper group. The differences in BP responses to exercise may affect the circadian blood pressure profile in dipper and non-dipper elderly patients with essential hypertension.
Traditionally the therapy for coronary heart disease has been focused on the "how-to" problem. However, the clustering of cardiovascular events around the specific time of the day has been clarified. To solve the problems of the clustering would give us the clue to treat the coronary heart disease timely and in time. Therefore, the research has been stressed to solve "when-to" problem. The circadian variabilities in coronary heart disease has been clarified to be the function of the biologic time. Therefore, three problems were discussed in this paper. 1) The circadian variabilities in biology should be assessed based on the biologic zero hour rather than the mid-night of the mechanical clock. Our concept of the biologic zero hours has been proposed to answer this problem. 2) Daily health care with circadian order and harmony for the prevention of the coronary risk factors should be recommended as the prevention of the acute coronary risk factors as the trigger mechanism of the cardiovascular events. 3) The chronotherapy to chronic coronary risk factors such as hypertension was discussed, In hypertension the anti-hypertensive therapy should be customized individually adjusting the circadian variability of blood pressure with the proper selection of agents and time of the administration.
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.
The aim of this study was to assess the effect of menopause on circadian profile of blood pressure (BP) and heart rate (HR) in the normotensive pre- and postmenopausal women. Systolic BP (SBP), diagnostic BP (DBP) and HR were monitored every 30 min for 48 hrs using noninvasive ambulatory BP monitoring in 24 premenopausal and 40 postmenopausal women. Mean 48-hours, daytime (awake), and nighttime (sleeping) SBP, DBP and HR values were analyzed by reviewing the patients' diaries, and the nocturnal reduction rate (NRR) of SBP, DBP and HR were calculated according to the following formula. NRR (%9 = [(daytime mean-nighttime mean)/daytime mean] x 100. The study subjects were then divided into two groups according to the presence (dipper) or absence (nondipper) of a significant reduction in nocturnal BP (> 10%). Mean SBP, DBP and HR measured over 48 hours were similar between the premenopausal and the postmenopausal group. The NRR of DBP and HR in the postmenopausal group were significantly smaller than those in the premenopausal group (17.1 +/- 6.0% vs. 13.5 +/- 7.0%, 241.1 +/- 6.0% vs. 19.8 +/- 9.0%: p < 0.05). There tended to be higher prevalence of nondipper in the postmenopausal (37%) than in the premenopausal group (29%).
Most ambulatory blood pressure monitoring (ABPM) studies have used a mechanical clock as the reference time, but there is no biologic background for assuming that midnight by the mechanical clock is zero hour by the biologic clock. The aim of this study was to determine the biologic zero hour as the zero reference time by evaluating the circadian rhythm of blood pressure, heart rate, and activity. Twenty healthy medical students (18 men, 2 women, mean age 26 years old) were recruited and blood pressure, heart rate, and physical activity were monitored simultaneously by an ABPM device every 30 min for 48 h. Four concepts of zero time were selected in this study and analyzed regarding biologic zero hour: 24:00 by the mechanical clock (clock time); the time of awakening, based on a diary (diary time); the time of a sudden increment in physical activity in the morning (activity time); and the middle of the total sleeping time, based on the diary (midsleeping time). The awakening time is a better individual index than the mechanical clock, and the midsleeping time as the zero reference point is better than the awakening time. We assessed the reproducibility of the data regarding the circadian troughs between the first and second day. The reproducibility of the day-to-day variation of the blood pressure and heart rate was poor. The reproducibility of physical activity was fairly good, but the magnitude of activity was small. A 48-h monitoring profile is superior to a 24-h monitoring period.
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The purpose of this study was to determine whether thromboxane A2 (TXA2) is involved in the development of ventricular arrhythmias produced by coronary artery occlusion. Ventricular arrhythmias were induced by coronary artery occlusion in 66 male Sprague-Dawley rats. Rats were separated into 4 groups, and saline (n = 19) or CV4151 (a TXA2 synthetase inhibitor)(10 mg/kg, n = 14; 30 mg/kg, n = 15; or 100 mg/kg, n = 18) was injected intravenously 5 min before coronary artery occlusion. The antiarrhythmic effect of CV4151 was assessed in terms of the number of ventricular premature complexes (VPCs), the combined duration of ventricular tachycardia (VT) and ventricular fibrillation (Vf), the incidence of Vf, and the mortality rate within 30 min after occlusion. The total number of VPCs was as follows; control: 1789 +/- 330 beats: 10 mg/kg group: 1289 +/- 302 beats: 30 mg/kg group: 1008 +/- 229 beats: 100 mg/kg group: 986 +/- 275 beats, with no significant differences between groups. The incidence of Vf was significantly reduced in the 30 mg/kg and 100 mg/kg groups, as was the combined duration of VT and Vf and the mortality rate. Our results indicate that the TXA2 synthetase inhibitor CV4151 reduces the incidence of lethal arrhythmias induced by coronary artery occlusion in rats.
We investigated the antiarrhythmic effects of bidisomide (SC-40230), a new class I antiarrhythmic drug, in early-phase ventricular arrhythmias induced by coronary artery occlusion and reperfusion in anesthetized rats. The effects of bidisomide were compared with those of mexiletine (MXT) and disopyramide (DSP), established class I antiarrhythmic drugs. Drugs were administered intravenously, 5 min before induction of coronary occlusion. Bidisomide (5 mg/kg) reduced the number of premature ventricular complexes and the incidence of ventricular tachycardia and ventricular fibrillation similarly to MXT and DSP in rats with ventricular arrhythmias induced by coronary artery occlusion. In rats with ventricular arrhythmias induced by coronary artery reperfusion following a 5-min coronary occlusion, the antiarrhythmic effects of 5 mg/kg of bidisomide were similar to those of the same doses of MXT and DSP. All three drugs significantly slowed the heart rate. Our results suggest that bidisomide may effectively reduce the severity of life-threatening ventricular arrhythmias that occur during acute coronary syndrome.
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Three problems remain to be solved to assess the circadian profile of blood pressure, and night dipper-non-dipper, day-night and morning rise of blood pressure in essential hypertension have been discussed. Both medical and bioengineering issues have been discussed to solve these important problems.
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This paper is an example of the clinical application of chronobiologic methods to the diagnosis of the major killers of modern societies, i.e., hypertension. Passing from the description of the methodology to clinical examples, the article provides convincing evidence of the importance of the chronodiagnostic approach to ambulatory blood pressure monitoring not only for a more accurate diagnosis, but also for a more appropriate therapy.
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