Circadian Heart Rate Variability Research Articles

Delayed improvement of autonomic nervous abnormality after the Maze procedure: time and frequency domain analysis of heart rate variability using 24 hour Holter monitoring

ObjectiveTo analyse heart rate variability in patients with atrial fibrillation after the Maze procedure, to investigate whether the procedure damages the cardiac autonomic fibres supplying the sinus node.Design and patientsTime...

Autonomic dysfunction in systemic sclerosis: time and frequency domain 24 hour heart rate variability analysis.

To evaluate the autonomic nervous control of the heart in patients with systemic sclerosis (SSc), spontaneous heart rate variability was investigated by means of time-domain and spectrum analysis of 24 h ECG ambulatory recordings in 30 SSc patients (four males, aged 45.2 +/- 9 yr, mean +/- S.D., range 27-60) and 30 age-matched healthy subjects. A significantly higher heart rate (P < 0.01) and lower circadian and spectral indices of heart rate variability (P < 0.01) were observed in SSc patients, compared with controls. A predictive value of age (P = 0.002), tachycardia (P = 0.002), circadian heart rate variability (P = 0.0025) and spectral power values (P = 0.005) for patient mortality was found. Moreover, the relative risk of death was higher (P = 0.05) in older subjects with circulating anti-Scl70. These abnormalities, detectable by a feasible, non-invasive diagnostic approach, indicate the presence of autonomic cardiac neuropathy in SSc patients.

Time-series analysis of long-term ambulatory myocardial ischemia: Effects of β-adrenergic and calcium channel blockade

We have previously demonstrated the utility of time-series analysis applied to 72-hour ambulatory electrocardiographic data in patients with coronary artery disease. The present investigation applied time-series analysis to long-term (120-hour) ambulatory electrocardiographic data to determine the minimal period of monitoring needed (1) to detect periodicity of ischemia-related variables in ambulatory patients, (2) to describe auto-correlation and cross-correlation functions for heart rate and ischemia, and (3) to describe the effects of β-adrenergic and calcium channel blockade on circadian characteristics and coupling of heart rate and ischemia. A double-blind crossover design was used to obtain 120-hour recordings during placebo, atenolol (200 mg/day), and diltiazem (360 mg/day) administration. During all three treatment periods, distinct circadian variation of heart rate was documented by autocorrelation and Fourier analysis. Ischemia did not exhibit clear periodicity as indexed by autocorrelation in any period; however, it was coupled to heart rate in all treatment periods as reflected in cross-correlation analysis. Although diltiazem did not quantitatively alter the circadian characteristics of heart rate or ischemia, atenolol produced a shift in the coupling between remaining ischemia and heart rate in time. Significant autocorrelation was detected for all treatment periods after 72 hours of monitoring, suggesting that 72 hours is the minimum amount of time needed for analysis of ambulatory electrocardiographic data in patients with coronary artery disease.

Quality of life and circadian variation of heart rate and heart rate variability in short‐term survivors and nonsurvivors after acute myocardial infarction

The purpose of this study was the simultaneous examination of the quality of life and changes in heart rate (HR) variables of patients immediately following acute myocardial infarction (AMI). Quality of life, estimated on a rating scale assessing the patients' well-being, as well as the circadian rhythm of their HR and HR variability, were determined within the first 3 days and at approximately 3 weeks after admission and the results were related to survival. The quality of life within the first 3 days post AMI was low in both the surviving (n = 42) and the nonsurviving (n = 5) patients but only the scores of the survivors increased significantly over the following three weeks. The HR of the survivors, initially lower than that of the nonsurvivors, decreased significantly at 3 weeks and a normal circadian pattern had developed. The HR variability of the survivors within the first 3 days was significantly higher than that of the nonsurvivors and had developed a clear circadian pattern after 3 weeks. It is concluded that in patients with AMI such diverse clinical aspects as quality of life and circadian patterns of HR and HR variability can be assessed meaningfully immediately post AMI and may find common expression in changes in sympathovagal balance.

Left ventricular hypercontractility and ST segment depression in patients with syndrome X

Objectives. This study was designed to assess the relation between rest left ventricular function and exercise capacity in patients with syndrome X.Background. Clinical observation has suggested that some patients with syndrome X have a rest left ventricular cjetion fraction. In this study we determined the relation between left ventricular ejection fraction and exercise capacity and the electrocardiographic (ECG) changes that develop on exercise.Methods. The pattern of left ventricular function, exercise capacity and 24-h ambulatory ECG monitoring were studied in 37 patients (9 men, 28 women; mean age 52 ± 7 years) with syndrome X (angina with normal coronary arteries and a positive exercise test result). All patients had normal findings on echocardiogram and rest ECG. All treatment was discontinued for ≥ 48 h. Left ventricular ejection fraction was determined by computerised analysis of the left ventricular angiogram. In patients with syndrome X, exercise duration and heart rate were measured at 1-mm ST segment depression and at peak exercise.Results. Left ventricular hypercontractility (ejection fraction ≥ 80%) was observed in 12 patients (32%) (group 1), whereas 25 patients (68%) had normal left ventricular contraction (group 2). The time to 1-mm ST depression on exercise testing was significantly earlier in group 1 than in group 2 (5.13 ± 1.03 vs. 10.76 ± 0.63 min, respectively, p < 0.001). The magnitude of the ST segment depression at peak exercise was significantly greater in group 1 than in group 2 (2.03 ± 0.2 vs. 1.33 ± 0.05 mm, respectively, p < 0.001). The mean time for ST segment depression to normalize was significantly greater in group 1 than in group 2 (4.76 ± 0.78 vs. 3.16 ± 0.39 min, respectively, p < 0.05). Linear regression analysis of all patients with syndrome X showed a significant correlation between exercise duration and ejection fraction (r = 0.55, p < 0.001). The mean circadian variation of heart rate and episodes of ST segment depression on 24-h ambulatory ECG monitoring were similar in the two groups of patients.Conclusions. These findings indicate that approximately one third of patients with chest pain, normal coronary angiograms and a positive exercise test have left ventricular hypercontractility, and this is associated with the development of ST segment depression at a lower heart rate and work load and a longer time to normalization of ST segment depression after exercise.

Parasympathetic activity is a major modulator of the circadian variability of heart rate in healthy subjects and in patients with coronary artery disease or diabetes mellitus

Autonomic heart rate control was assessed by power spectral analysis of heart rate variability in 24-hour ambulatory electrocardiographic recordings from 23 healthy subjects, 14 patients with coronary artery disease without cardiac dysfunction, and 14 patients with diabetes mellitus. The log value of the ratio of the low-frequency component (LF = 0.04 to 0.15 Hz) to the high-frequency component (HF = 0.15 to 0.5 Hz) and logHF were employed as indexes of sympathetic and parasympathetic activity, respectively. Diurnal and nocturnal logLF, logHF, and log(LF/HF) values were calculated for heart rates of 60, 70, and 80 beats/min. Intergroup differences among these three variables were not significant at any heart rate. Although a heart rate-related decrease in logHF was generally observed, the relationship between log(LF/HF) and heart rate was not consistent. The correlation between diurnal and nocturnal logHF values was significant at all three heart rates (r = 0.63, 0.87, and 0.59), whereas the diurnal log(LF/HF) was correlated with the nocturnal value only at 70 beats/min (r = 0.77). These results suggest that the heart rate during normal daily activities is a reliable indicator of parasympathetic tone, if not sympathetic tone, in healthy subjects and patients with coronary artery disease or diabetes mellitus.

Circadian rhythms of blood pressure after liver transplantation.

Twenty-four-hour systolic blood pressure, diastolic blood pressure, and heart rate profiles were recorded in 17 liver-transplanted patients by noninvasive ambulatory monitoring and were analyzed with the periodogram method. These recordings were compared with those of control subjects matched for age, sex, and daytime ambulatory blood pressure. Abnormal blood pressure patterns were found in seven of the 17 patients, whereas the other 10 patients had circadian blood pressure profiles that were not different from those of control subjects. These two groups of liver-transplanted patients did not differ in age, sex, oral dose of cyclosporine, specific serum cyclosporine level, and proportion of patients receiving azathioprine and antihypertensive medications. In contrast, the daily oral dose of prednisolone was significantly higher (p < 0.001) in the seven patients with abnormal circadian blood pressure patterns. Moreover, only the daily oral dose of prednisolone was inversely correlated with the magnitude of the nighttime systolic and diastolic blood pressure decrease (r = -0.64 and r = -0.66, p < 0.01). In contrast to blood pressure, patients and control subjects had similar circadian heart rate variations. We conclude that exogenous glucocorticoid administration may have a dose-dependent effect on the nighttime blood pressure fall and may play an important role in the pathogenesis of the abnormal circadian blood pressure profiles observed in liver-transplanted patients.

Importance of long-acting angiotensin-converting enzyme inhibitors for congestive heart failure

The renin-angiotensin system (RAS) has both localized and systemic effects in the pathophysiology of heart failure. These may lead to structural changes in the heart and blood vessels as well as to more disseminated symptomatology, including vasoconstriction and both satt and water retention. In association with other neurohormonal mechanisms, such as the sympathetic nervous system, these latter effects result in an elevated work load for the heart. The increase in neurohormonal activity, seen in some patients with heart failure, may result in a loss of circadian variation in heart rate and blood pressure and deprive the heart of a needed reduction in work load during the night. The suppression of such neurohormonal activity through the use of long-acting angiotensin-converting enzyme (ACE) inhibitors, such as lisinopril, provides a means of controlling such symptoms. In comparison with short-acting ACE inhibitors, such long-acting suppression of the RAS may have a number of advantages. These include a more sustained increase in exercise duration, improvement in left ventricular ejection fraction, and, speculatively, a better influence on patient mortality.

Effects of left ventricular dysfunction on the circadian variation of ventricular premature complexes in healed myocardial infarction

Circadian variation in the onset of cardiovascular events including sudden cardiac death, myocardial infarction and ventricular arrhythmias has been described. The effect of left ventricular (LV) dysfunction on the circadian variation of ventricular premature complex (VPC) frequency was evaluated in 132 patients with frequent VPCs and reduced LV function after myocardial infarction. Patients were prospectively divided in 2 groups based on LV ejection fraction (EF) (those with LVEF <0.30, and those with LVEF between 0.30 and 0.45). Median hourly VPC frequencies and heart rates were compared between the 2 groups. Subgroup analyses based on treatment with β-adrenoceptor blocking agents and on New York Heart Association functional class were also performed. In patients with LVEF >0.30, a distinct circadian variation of VPCs, and the expected morning increase in VPC frequency were present. In contrast, a distinct circadian variation of VPCs was absent in patients with LVEF ≤0.30. A circadian variation of VPC frequency was also absent in patients with severe symptomatic congestive heart failure (New York Heart Association class III–IV). Treatment with β-adrenoceptor blocking agents was associated with a loss of the circadian variation of VPC frequency. The circadian variation of heart rate was also blunted in the group treated with β-adrenoceptor blocking agents. The proportion of subjects manifesting a positive correlation between heart rate and VPC frequency was tower in subjects with LVEF <-0.30 (26%) than in those with LVEF >0.30 (46%) (p < 0.05). Thus, circadian variation of VPC frequency is absent in patients with severe LV dysfunction.

本態性高血圧症の血圧と心拍数の概日変動に対するｄｉｌｔｉａｚｅｍならびにｎｉｃａｒｄｉｐｉｎｅの効果の差異について

本態性高血圧症の血圧と心拍数の概日変動に対するｄｉｌｔｉａｚｅｍならびにｎｉｃａｒｄｉｐｉｎｅの効果の差異について

本態性高血圧の血圧および心拍数の日内変動に対するｎｉｐｒａｄｉｌｏｌとｍｅｔｏｐｒｏｌｏｌの効果について

本態性高血圧の血圧および心拍数の日内変動に対するｎｉｐｒａｄｉｌｏｌとｍｅｔｏｐｒｏｌｏｌの効果について

Circadian variation of heart rate is affected by environment: a study of continuous electrocardiographic monitoring in members of a symphony orchestra.

Twenty four hour ambulatory ST segment monitoring was performed on 48 members (43 players and five members of the management/technical team) of the British Broadcasting Corporation (BBC) symphony orchestra without a history of cardiac disease. This period included final rehearsals and live performances (for audience and radio) of music by Richard Strauss and Mozart at the Royal Festival Hall (n = 36) and Rachmaninov and Tchaikovsky at the Barbican Arts Centre (n = 21). During the period of monitoring one person (2%) had transient ST segment changes. Mean heart rates were significantly higher during the live performances than during the rehearsals. Mean heart rates during the live performance of Rachmaninov and Tchaikovsky were significantly higher than during Strauss and Mozart in those (n = 6) who were monitored on both occasions. Mean heart rates in the management and technical team were higher than those of the players. The recognised circadian pattern of heart rate, with a peak in the morning waking hours, was altered similarly during both concert days, with a primary peak occurring in the evening hours and a lesser peak in the morning for both musicians and management/technical staff. This study showed that environmental factors are of primary importance in defining the circadian pattern of heart rate. This has important implications when identifying peak periods of cardiovascular stress and tailoring drug treatment for patients with angina pectoris.

Circadian distribution of the characteristics of ischemic episodes in patients with stable coronary artery disease

To determine the circadian distribution of episodes of myocardial ischemia, studies were performed in 111 patients with chronic stable angina pectoris, positive exercise test results and angiographically proven coronary artery disease. During 24 hours of ambulatory electrocardiographic monitoring, 101 symptomatic and 298 asymptomatic ischemic episodes (ST-segment depression >1 mm, duration >1 minute) were observed. The number of ischemic episodes and the cumulative duration of ischemia showed a circadian variation with the highest values between 8 and 10 A.M. and between 4 and 5 P.M. associated with a similar circadian variation of heart rate. Mean duration of ischemic episodes, maximal amplitude of ST-segment depression during ischemic episodes and increase in heart rate before the onset of ischemic episodes showed no significant circadian variation. Heart rate at the onset of ischemic episodes and maximal heart rate during ischemic episodes were lower between midnight and A.M. than during other times of the day. The morning and afternoon increase in ischemic activity is not paralleled by changes reflecting a decrease in myocardial oxygen supply during these periods (heart rate at onset of ischemia, heart rate increase before onset of ischemia), but is paralleled by a similiar circadian variation of heart rate. The circadian variation in ischemic activity is predominantly based on a comparable variation in myocardial oxygen requirements.

Circadian variations of heart rate, respiratory rate and pulse respiration ratio in routinely examined hospital patients

(1990). Circadian variations of heart rate, respiratory rate and pulse respiration ratio in routinely examined hospital patients. Journal of Interdisciplinary Cycle Research: Vol. 21, No. 3, pp. 198-199.

Circadian Variations of Heart Rate and STIMT Interval: Adaptation for Nighttime Pacing

In order to determine the optimal pacing rate for pacemaker patients at night, 150 normal subjects with regular sinus rhythm and free of manifest heart disease, were studied using 24-hour Holter monitoring. Minimum and average heart rates were analyzed on an hourly basis. The study group was divided into six age groups, 25 subjects each, ranging from 20-29 years to 60-69 years. The minimum heart rate during the night was found to be lower than 65 ppm for all groups. The youngest subjects showed the largest variation in the minimum heart rate. The results suggest that an automatic lowering of the pacing rate during the night would allow for longer periods of sinus rhythm, thereby improving hemodynamic performance and reducing pacemaker power consumption. Suitable sensors for automatic lowering of the pacing rate include inbuilt 24-hour clock systems and the QT interval that lengthens during sleep.

Influence of beta-adrenergic blockade defined by time series analysis on circadian variation of heart rate and ambulatory myocardial ischemia

Extended (72-hour) ambulatory electrocardiographic monitoring was used to enable time series analysis of heart rate and asymptomatic ST-segment depression in 9 patients with severe coronary artery disease. The effects of β 1-adrenergic blockade with optimal dose metoprolol were then assessed. Data were analyzed using Fourier transformation, autocorrelation and cross-correlation to examine possible coupling between heart rate and ischemic electrocardiographic changes. A marked circadian pattern was observed for both heart rate and ambulatory myocardial ischemia, with a period of approximately 24 hours by both Fourier and autocorrelation methods. Cross-correlation revealed heart rate and ischemia to be tightly coupled with a lag of 0 hours during placebo. During β 1 adrenergic blockade the marked circadian variation in heart rate was diminished, although some periodicity in the 24-hour region remained. Ambulatory ischemia was also markedly diminished during β 1-adrenergic blockade; however, some residual ischemia remained that was characterized by a peak spectral activity shifted to a period of 5 to 7 hours. Heart rate and ischemia were not coupled during β 1-adrenergic blockade, as evidenced by lack of significant cross-correlation. Thus, time series analysis suggests close coupling between the variation in heart rate and ambulatory ischemia in patients with severe coronary artery disease. Beta 1-adrenergic blockade can markedly alter the periodic characteristics of and coupling between heart rate and ischemia. Ischemia remaining during β 1-adrenergic blockade may have different spectral characteristics than that predominating during placebo administration. These differences may be manifestations of the heterogenous pathophysiologic mechanisms responsible for ambulatory ischemia and may have therapeutic implications.

Reversed circadian rhythm of blood pressure in adult spontaneously hypertensive rats.

The diurnal rhythms of blood pressure and heart rate were examined in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) when they were 5-6 weeks old (young), 17-20 weeks old (adult) and 30-32 weeks old (old). Blood pressure was recorded continuously for 24 h in conscious, unrestrained rats. Hourly averages of blood pressure and heart rate were calculated by an on-line computer. The circadian variation of blood pressure and heart rate remained unchanged regardless of age in WKY, but the difference in blood pressure between the daytime average and the night-time average decreased as they grew older. A well-defined circadian variation of blood pressure and heart rate was observed in young rats of both strains, i.e. a nocturnal rise in blood pressure and heart rate. An inverted circadian variation of blood pressure, a nocturnal fall in blood pressure, was observed in adult and old SHR, whereas the ordinary circadian variation of the heart rate remained unchanged. A significant positive correlation was observed between the hourly averages of blood pressure and heart rate in WKY in all the age groups (r = 0.9, P less than 0.001 in each age group) and a weak positive correlation was observed in young SHR (r = 0.6, P less than 0.05, 5-6 weeks old). This positive correlation disappeared in adult and old SHR and, instead, a negative correlation was observed (r = -0.5, P less than 0.02 for 17-20-week-old rats: r = -0.8, P less than 0.001 for 30-32-week-old rats).(ABSTRACT TRUNCATED AT 250 WORDS)

The Effect of Low Dose Carvedilol on Circadian Variation of Blood Pressure in Patients with Essential Hypertension

The effect of once daily low-dose carvedilol on circadian variations of blood pressure (BP) was studied in Japanese patients with mild or moderate essential hypertension. Thirty-one patients were admitted to hospital whose BP was 150/90 mm Hg/day or greater and they participated in the study. After a placebo period of 1 week, 5 or 10 mg carvedilol was given once daily in the morning for 3 to 7 days, and if BP reduction was not sufficient, the dose was increased to 20 mg daily. The blood pressure variation was monitored before and 1, 2, 4, 6, 8, 10, 12, and 24 h after administration of the drug on the last day of placebo and final dose of carvedilol. Of the 31 cases receiving carvedilol once daily, cumulative effectiveness (13 mm Hg reduction in mean BP) was 48.4% at 10 mg/day and 54.8% at 20 mg/day. Both systolic and diastolic pressures decreased significantly and heart rate decreased slightly. There was no significant difference between the standard deviations of BP on the last days of the control period and the carvedilol treatment. The difference between maximum and minimum BP during the day was not significant between the two periods. Circadian variations of heart rate were also not significantly different for the two periods. This indicates that carvedilol did not have any effect on circadian variations of BP and heart rate. The present study also suggests that low-dose carvedilol once daily may be effective in the treatment of hypertension.

Circadian variations of heart rate and premature beats in healthy subjects and in patients with previous myocardial infarction.

Chronobiological analysis of the circadian variations of heart rate, ventricular and atrial ectopies, was carried out on 11 patients with previous myocardial infarction matched with 11 controls. Individual circadian rhythms in heart rate were seen in all the control subjects but only in 6 patients with previous myocardial infarction. The behaviour of the individual circadian rhythms of premature beats was not significantly different between the two groups. A significant group rhythm in ectopies was not demonstrated, nevertheless a trend to higher frequency of arrhythmias during the activity span was detected. These results do not allow to postulate a circadian pattern of arrhythmias common to all the subjects examined. Therefore, the individual circadian behaviour of premature atrial and ventricular beats should be recognized for monitoring antiarrhythmic therapy. A significant group rhythm in heart rate was demonstrated for the two populations studied and linear discriminant analysis showed that the amplitude of this rhythm was significantly lower in patients than in controls. Possibly, myocardial infarction may affect the sinus node function producing a "flattened" range of heart rates during the 24 hours.

Circadian variation in human peripheral blood flow levels and exercise responses.

Circadian variation in heart rate, oral temperature, and in peripheral blood flow levels of humans at rest and during exercise