Chronobiologic study of the dynamic electrocardiogram in healthy athletes with frequent ventricular ectopic beats

The chronobiologic analysis has been applied to Dynamic ECG data in order to verify whether or not a circadian rhythm for heart rate (HR) and ventricular ectopic beats (VEB's) can be detected in athletes with frequent ventricular arrhythmia (range 169-2120 VEB's/hour). The study was carried out on 10 athletes (7 males and 3 females, aged 11-23 years), taking part in various sports, asymptomatic but characterized by a frequent VEB's. Data have been analysed by means of cosinor method. A circadian rhythm for HR was documented. A circadian rhythm for VEB's was validated in all but one of the athletes. The circadian acrophases for HR occur early in the afternoon. The circadian acrophases for VEB's are prominently diurnal (7 out of 10 cases). The VEB's circadian crest is not associated with the physical activity supporting a relative independency of the rhythmic generator of VEB's.     

Clinical assessment of respiratory sinus arrhythmia by computerized analysis of RR interval and respiration.

Heart rate variability (HRV) and respiratory sinus arrhythmia (RSA) are often considered as interchangeable terms. However, the application of power spectral analysis to describe spontaneous fluctuations in heart period has clearly shown that RSA is only a part of HRV, and that in specific situations their respective patterns may diverge. In order to quantify the RSA we have used a mathematical method based on combined spectral analysis of respiration and RR interval (cross-correlation function), and evaluated its performance in terms of reproducibility, sensitivity to parasympathetic withdrawal and in clinical evaluation of autonomic function. Compared to other indices of HRV the cross-correlation between RR interval and respiration showed a greater sensitivity to parasympathetic withdrawal, better reproducibility and a high sensitivity in detecting autonomic dysfunction in diabetic patients. These findings suggest that specific indices of RSA, such as the cross-correlation, can be a valid tool for the diagnostic approach to cardiac autonomic dysfunction.     

冠心病患者窦性心率震荡与心率变异性和室性早搏关系的探讨

目的探讨冠心病患者的窦性心率震荡(HRT)及其与心率变异性(HRV)和室性早搏之间的关系。方法86例冠心病患者行24h动态心电图检查,计算机自动测定HRT的两个参数震荡初始(TO)和震荡斜率(TS)、HRV时域和频域指标及室性早搏数目。结果冠心病患者的HRT减弱,HRV降低,且TO与时域指标SDNN和SDANN及频域指标LF和LF/HF明显相关(p<0.05),TS与时域指标SDNN和RMSSD及频域指标HF和LF/HF及室性早搏数目明显相关(p<0.05)。结论冠心病患者的HRT现象减弱,且HRT与HRV及室性早搏数目明显相关。HRT应当是一种较HRV更好预测高危冠心病患者的无创性检查方法。     

Scatterplots of RR and RT interval variability bring evidence for diverse non-linear dynamics of heart rate and ventricular repolarization duration in coronary heart disease.

OBJECTIVE: QT interval prolongation and increased spatial QT dispersion are important factors increasing the risk in coronary heart disease. The authors studied the spontaneous beat-to-beat variability of ventricular repolarization (RT intervals) in normal subjects and in patients after myocardial infarction (MI) in order to define the determinants of abnormal temporal dispersion. METHODS: Seventy-six patients with a history of MI (17 female, 59 male, aged 52 +/- 10 years) comprised the study group. Forty-seven patients had preserved left ventricular ejection fraction (EF > or = 40%, MI-A) and 29 patients had left ventricular dysfunction (EF < 40%, MI-B). Twenty healthy volunteers (6 female, 14 male, aged 25 +/- 5 years) were included as the control group. An ECG signal of 512 heartbeats was recorded in the supine position. After analogue-to-digital conversion (16 bit, 2 kHz), the fiducial points of the R wave and T wave were determined. The RR and RT variability (V) assessed in the time domain as the standard deviations of RR and RT (ms), as well as the coefficients of scatterplots of RR and RT intervals. RESULTS: As expected, the standard deviation of RR was significantly reduced in MI patients. The magnitude of RTV in the time domain was similar in the controls and in both subgroups of MI patients. The complexity of heart rate variability (HRV) was slightly, but significantly, reduced in the MI-B group, but not significantly in the MI-A heart group. The complexity of RTV behaved in the opposite manner, being increased in both MI subgroups with the lower mean in the MI-B patients. The different behaviour of HRV and RTV was indicated by the increased ratio of RR/RT coefficients, which reached a significantly greater value in the MI-B group. CONCLUSION: The authors have described different patterns of scatterplot of short-term HRV and RTV in normal subjects, which confirmed that RTV is a less complex phenomenon than HRV. In patients after MI, the complexity of HRV diminishes, while the complexity of RTV increases. These opposing changes are more pronounced in patients with left ventricular dysfunction. A possible prognostic value of this feature is unknown and remains to be elucidated in future prospective studies.     

QT interval dynamics and heart rate variability preceding a case of cardiac arrest.

A 71 year old man with hypertensive heart disease and chronic renal failure was wearing a Holter monitor when he had a cardiac arrest. He had ventricular fibrillation (VF) and died despite prompt resuscitation. In the 15 minutes preceding the VF there was a sudden increase in heart rate, followed by a brief period of atrial fibrillation leading to ventricular tachycardia, which in turn rapidly degenerated into VF. The QT interval and heart rate variability were studied half hourly over the seven hours preceding the cardiac arrest, using a computerised Holter system. A further detailed analysis was performed over the final hour before the cardiac arrest. An abrupt increase in the steepness of the QT/RR slope, a prolonged QTc, and a reduction in the heart rate variability were observed in the interval that immediately preceded the onset of the terminal rhythm disturbance.     

伴长RR间期的慢性心房颤动患者心率特点

慢性心房颤动 (房颤 )是临床上最常见的心律失常之一[1] ,部分患者伴有长ＲＲ间期或心动过缓 ,对此类患者是否需要植入心脏起搏器或用药物调整心率 ?为此 ,我们做了前瞻性研究 ,对 5 6例患者进行了 4～ 4 5年临床动态心电图随访。资料和方法　病例选择 :从 1997年至今的门诊及住院的器质性心脏病合并慢性房颤者筛选 5 6例患者。入选标准 :动态心电图记录到 2 4ｈ内 >1 3ｓ的ＲＲ间期 3次以上 ,或平均心室率在 6 0次 /ｍｉｎ以下者。排除洋地黄中毒、使用β受体阻滞剂、和甲状腺功能减退者。患者无黑或晕厥现象 ,其中男性 4 0例 ,女性 16…     

Circadian rhythms of heart rate and premature ventricular beats in the aged

The chronobiological analysis by means of the cosinor method on the dynamic electrocardiographic tracings of 30 subjects aged over 65 years with no clinical or instrumental signs of heart disease revealed a significant circadian rhythm of heart rate with acrophase in the early afternoon. When compared with a group of 30 young adult subjects, the elderly exhibited only a non-significant reduction of the rhythm amplitude. Elderly patients with heart disease exhibited a similar chronobiological pattern of heart rate. Premature ventricular beats (PVBs) were present in all subjects and occurred mostly during the day. A significant circadian rhythm was present only in elderly heart patients with 30-150 PVBs/h. The circadian distribution of PVBs showed significant interindividual differences with nocturnal acrophase in about one third of the patients. The chronobiological analysis can represent the basis for a more appropriate therapeutic approach to the elderly with PVBs.     

Relationship between heart rate turbulence and heart rate, heart rate variability, and number of ventricular premature beats in coronary patients

INTRODUCTION: Heart rate variability (HRV) illustrates regulation of the heart by the autonomic nervous system whereas heart rate turbulence (HRT) is believed to reflect baroreflex sensitivity. The aim of this study was to determine the association between HRT and HRV parameters and the relationship between HRT parameters and heart rate and number of ventricular premature beats (VPBs) used to calculate HRT parameters. METHODS AND RESULTS: In 146 patients (117 males and 29 females; mean age 62 years) with coronary artery disease, a 24-hour ECG Holter monitoring was performed to calculate mean heart rate (RR interval), number of VPBs, time- and frequency-domain HRV parameters and two HRT parameters: turbulence onset (TO) and turbulence slope (TS). Univariate and multivariate regression analyses were performed to evaluate the association between tested parameters. Significant correlation between TS and mean RR interval was observed (r = 0.42; p < 0.001), while no association for TO vs. RR interval was found. TS values were significantly higher in patients with less than 10 VPBs/24 hours than in patients with more frequent VPBs. Significant associations between HRT and HRV parameters were found with TS showing stronger correlation with HRV parameters than TO (r value ranging from 0.35 to 0.62 for TS vs. -0.16 to -0.38 for TO). CONCLUSION: HRT parameters correlate strongly with HRV parameters indicating that HRT should be considered as a reflection of both baroreceptors response and overall autonomic tone. Heart rate dependence of turbulence slope indicates the need to adjust this parameter for heart rate.     

QT dispersion in sinus beats and ventricular extrasystoles in normal hearts.

OBJECTIVE--Recent studies have suggested that QT interlead variability (dispersion) on the surface electrocardiogram may have potential as a measure of recovery time dispersion. To test this hypothesis further QT dispersion occurring in sinus beats was compared with that in ventricular extrasystoles. DESIGN--Simultaneous electrocardiograms were recorded at 50 mm/s during sinus rhythm in a drug free state while ventricular extrastimuli were introduced by programmed right ventricular stimulation at different coupling intervals. QT dispersion, defined as the difference between the maximum and minimum QT, was calculated separately for the extrasystoles and preceding and following sinus complexes. To correct for the influence of the number of measurable leads on QT dispersion, an "adjusted" QT dispersion calculated as QT dispersion/square root of the number of measurable leads, was used to compare sinus complexes and extrasystoles. PATIENTS--Nine patients were studied who were undergoing electrophysiological study for investigation of palpitation and were found to have electrically normal ventricles. RESULTS--At all coupling intervals tested "adjusted" QT dispersion was significantly greater in the ventricular extrasystoles than in either the preceding or following sinus complexes. For the coupling interval 350 ms, the 95% confidence intervals for the difference between means was 52 to 78 ms (preceding sinus complex) and 56 to 82 ms (following sinus complex) (p less than 0.00001). There was no correlation between the coupling interval and the magnitude of the "adjusted" QT dispersion. CONCLUSION--These results accord fully with expected differences in ventricular recovery time dispersion and offer further support for the hypothesis that QT dispersion reflects regional variation in ventricular recovery. If substantiated by invasive studies, these findings have wide implications for both the usefulness and the method of QT measurement.     

Effects of sympathetic activation on ventricular ectopic beats in subjects with and without evidence of organic heart disease

In a selected group of 10 apparently healthy subjects and 22 patients with organic heart disease, all with frequent ventricular ectopic beats on Holter monitoring, we assessed the influence of sympathetic activation by comparing the arrhythmogenic effects of a symptom-limited bicycle exercise stress test and 90 degree head up tilt. Tilting reduced ventricular arrhythmias in the normal subjects (-48 +/- 18% from 9 +/- 2 beats min-1, P less than 0.05). Exercise stress testing caused small and insignificant changes in arrhythmias during the early (50-75 W) phases and an almost complete suppression of ventricular ectopic beats in the final stages (-99 +/- 1%, P less than 0.01). In six of the 10 subjects, ventricular arrhythmias reappeared in the early recovery phase. In the 22 patients with organic heart disease, tilting increased ventricular ectopic beats (43 +/- 17% from 9 +/- 3 beats min-1, P less than 0.05); augmented repetitive forms in 12 patients (179 +/- 88% from 1.4 +/- 0.6 per 3 min) and produced repetitive forms in six of the 10 remaining patients who did not show repetitive forms during control conditions. Exercise stress testing caused a marked increase in ectopic activity in the early phase (84 +/- 35%) while the response during the maximal phase of exercise as well as during recovery was related to the effort capabilities. Arrhythmias were increased in 12 patients with limited exercise duration and were reduced in 10 patients with good exercise tolerance. These data indicate that sympathetic activation has different effects on ventricular arrhythmias depending on the clinical setting and that tilting is a useful maneuver to evaluate the arrhythmogenic effects of increased sympathetic activity.     

Effects of sympathetic activation on ventricular ectopic beats in subjects with and without evidence of organic heart disease

In a selected group of 10 apparently healthy subjects and 22patients with organic heart disease, all with frequent ventricularectopic beats on Holter monitoring, we assessed the influenceof sympathetic activation by comparing the arrhythmogenic effectsof a symptom-limited bicycle exercise stress test and 90°head up tilt. Tilting reduced ventricular arrhythmias in thenormal subjects (–48±18% from 9±2 beatsmin^-1, P<0.05). Exercise stress testing caused small andinsignificant changes in arrhythmias during the early (50–75W) phases and an almost complete suppression of ventricularectopic beats in the final stages (–99±1%, P<0.01).In six of the 10 subjects, ventricular arrhythmias reappearedin the early recovery phase. In the 22 patients with organicheart disease, tilting increased ventricular ectopic beats (43±17%from 9±3 beats min^-1, P<0.05); augmented repetitiveforms in 12 patients (179±88% from 1.4±0.6 per3 min) and produced repetitive forms in six of the 10 remainingpatients who did not show repetitive forms during control conditions.Exercise stress testing caused a marked increase in ectopicactivity in the early phase (84±35%) while the responseduring the maximal phase of exercise as well as during recoverywas related to the effort capabilities. Arrhythmias were increasedin 12 patients with limited exercise duration and were reducedin 10 patients with good exercise tolerance. These data indicatethat sympathetic activation has different effects on ventriculararrhythmias depending on the clinical setting and that tiltingis a useful manoevre to evaluate the arrhythmogenic effectsof increased sympathetic activity.     

QT dispersion in sinus beats and ventricular extrasystoles in normal hearts.

OBJECTIVE--Recent studies have suggested that QT interlead variability (dispersion) on the surface electrocardiogram may have potential as a measure of recovery time dispersion. To test this hypothesis further QT dispersion occurring in sinus beats was compared with that in ventricular extrasystoles. DESIGN--Simultaneous electrocardiograms were recorded at 50 mm/s during sinus rhythm in a drug free state while ventricular extrastimuli were introduced by programmed right ventricular stimulation at different coupling intervals. QT dispersion, defined as the difference between the maximum and minimum QT, was calculated separately for the extrasystoles and preceding and following sinus complexes. To correct for the influence of the number of measurable leads on QT dispersion, an "adjusted" QT dispersion calculated as QT dispersion/square root of the number of measurable leads, was used to compare sinus complexes and extrasystoles. PATIENTS--Nine patients were studied who were undergoing electrophysiological study for investigation of palpitation and were found to have electrically normal ventricles. RESULTS--At all coupling intervals tested "adjusted" QT dispersion was significantly greater in the ventricular extrasystoles than in either the preceding or following sinus complexes. For the coupling interval 350 ms, the 95% confidence intervals for the difference between means was 52 to 78 ms (preceding sinus complex) and 56 to 82 ms (following sinus complex) (p less than 0.00001). There was no correlation between the coupling interval and the magnitude of the "adjusted" QT dispersion. CONCLUSION--These results accord fully with expected differences in ventricular recovery time dispersion and offer further support for the hypothesis that QT dispersion reflects regional variation in ventricular recovery. If substantiated by invasive studies, these findings have wide implications for both the usefulness and the method of QT measurement.     

Wavelet transform for analysis of heart rate variability preceding ventricular arrhythmias in patients with ischemic heart disease

INTRODUCTION: Studies evaluating changes in HRV preceding the onset of ventricular arrhythmias using conventional techniques have shown inconsistent results. Time-frequency analysis of HRV is traditionally performed using short-term Fourier transform (STFT). Wavelet transform (WT) may however be better suited for analyzing non-stationary signals such as heart rate recordings. METHODS AND RESULTS: We studied patients with a history of myocardial infarction implanted with a defibrillator with an extended memory. The RR intervals during the 51 min preceding ventricular events requiring electrical therapy were retrieved, and HRV studied by WT and STFT. 111 episodes of ventricular arrhythmia were retrieved from 41 patients (38 males, age 64 +/- 8 years). Heart rate increased significantly before arrhythmia. There was no significant variation in low frequency / high frequency components (LF/HF) observed for the group as a whole, probably due to a great degree of heterogeneity amongst individuals. A subset of 30 patients also had heart rate recordings performed during normal ICD follow-up. WT did not show any difference in HRV before arrhythmia onset and during control conditions. CONCLUSION: Variations in HRV before onset of ventricular arrhythmias were not apparent in this large dataset, despite use of optimal tools for studying time-frequency analysis.     

Prognostic significance of heart rate turbulence following ventricular premature beats in patients with idiopathic dilated cardiomyopathy

Heart Rate Turbulence in Dilated Cardiomyopathy. INTRODUCTION: The aim of this study was to investigate the prognostic significance of heart rate turbulence (HRT) characterized by HRT onset and slope after ventricular premature beats in patients with idiopathic dilated cardiomyopathy (IDC). METHODS AND RESULTS: Blinded HRT analysis was performed in 242 patients with IDC who were enrolled in the Marburg Cardiomyopathy database between 1992 and 2000. During 41 +/- 23 months of follow-up, 54 patients (22%) died or underwent heart transplant. On Cox univariate regression analysis, abnormal HRT onset, HRT slope, HRT onset combined with HRT slope, left ventricular (LV) ejection fraction, LV size, and New York Heart Association (NYHA) functional class III showed a significant association with total mortality or the need for heart transplant. On multivariate analysis, abnormal HRT onset identified patients without transplant-free survival, as did LV size and NYHA class III heart failure. Major arrhythmic events were observed in 42 patients (17%) during follow-up. On univariate analysis, abnormal HRT onset, HRT onset combined with HRT slope, male sex, NYHA class III, LV ejection fraction, and LV size were associated with a higher incidence of major arrhythmic events. On multivariate analysis, only LV ejection fraction remained as a significant arrhythmia risk predictor, with a relative risk of 2.2 per 10% decrease in ejection fraction (95% confidence interval 1.5-3.2). CONCLUSION: In this selected patient population with IDC, HRT onset is a significant predictor of transplant-free survival, as are LV size and NYHA class. For arrhythmia risk stratification, however, only LV ejection fraction remained a significant risk predictor on multivariate analysis.     

Heart rate turbulence after ventricular and atrial premature beats in subjects without structural heart disease

INTRODUCTION: Studies assessing heart rate (HR) behavior after premature beats have focused on HR responses to ventricular premature beats (VBPs), but there is less information of HR behavior after atrial premature beats (APBs). METHODS AND RESULTS: HR turbulence after VPBs and APBs was first measured in response to ambient APBs and VPBs occurring during 24-hour ambulatory ECG recordings in 29 subjects without structural heart disease, and in response to programmed atrial (AE) and ventricular extrastimuli (VE) in 6 subjects undergoing electrophysiologic (EP) examination. Turbulence onset (TO) was more negative (-2.3 +/- 3.2% vs -0.9 +/- 2.8%, P < 0.01) and turbulence slope (TS) was steeper (11 +/- 11 vs 5.1 +/- 4.1 msec/R-R interval, P < 0.05) after VPBs than APBs. Compared to VPBs, the acceleration of HR after APBs was delayed by one beat, and APBs were associated with a short R-R interval preceding the APB, resulting in a blunted TO. Studies of patients undergoing an EP test confirmed the one-beat delay of HR acceleration and the blunted TO after programmed AE compared to VE (P < 0.05). TO and TS after VPBs were related to baroreflex sensitivity. TO also was related to 24-hour standard deviation of N-N intervals (SDNN). However, the TO or TS following APBs was not related to either SDNN or baroreflex sensitivity. CONCLUSION: HR behavior is different in response to APBs and VBPs among subjects without structural heart disease. Different definitions and calculation formulas should be used in the analysis of HR turbulence after APBs and VPBs.