Intensive home-based exercise training in cardiac rehabilitation increases exercise capacity and heart rate variability.

BACKGROUND: Reduced heart rate variability (HRV) is a risk factor for cardiac death. Animal studies have shown increased HRV and reduced mortality after physical training. We evaluated the change in exercise capacity and HRV in cardiac rehabilitation patients, randomised to routine or home-based intensive training. The design was prospective, stratified randomisation with pre-specified subgroup analysis. METHODS: Maximal bicycle exercise test and 24-h Holter were performed 1 (baseline), 4 and 12 months after myocardial infarction (MI) or coronary artery by-pass surgery (CABG). Patients were randomised to physical training either two (N) or six (I) times per week for 3 months Sixty-two patients (43 MI and 19 CABG patients) were evaluated. RESULTS: Exercise capacity increased significantly more after 3 months of training in group I (mean (S.E.)); 29.0 (3.4) vs. 7.2 (2.6) watts, P<0.001). One year later the difference in exercise capacity remained (26.5 (3.3) vs. 11.8 (3.8) watts, P<0.001). Global HRV measurements SDNN and SDANN increased significantly more in group I after training (17.1 (5.6) vs. 1.7 (3.7) and 16.2 (4.9) vs. 2.8 (3.1) ms, P<0.05) and 1 year later the differences were still significant. Subgroup analysis showed more pronounced HRV response in CABG than MI patients. CONCLUSION: Intensive exercise training in cardiac rehabilitation increases exercise capacity and global HRV, which could be of prognostic significance.     

Traditional and nonlinear heart rate variability are each independently associated with mortality after myocardial infarction

INTRODUCTION: Decreased heart rate variability (HRV) and abnormal nonlinear HRV shortly after myocardial infarction (MI) are risk factors for mortality. Traditional HRV predicts mortality in patients with a range of times post-MI, but the association of nonlinear HRV and outcome in this population is unknown. METHODS AND RESULTS: HRV was determined from 740 tapes recorded before antiarrhythmic therapy in Cardiac Arrhythmia Suppression Trial patients with ventricular premature contractions (VPCs) suppressed on the first randomized treatment. Patients were 70 +/- 121 days post-MI. Follow up was 362 +/- 241 days (70 deaths). The association between traditional time and frequency-domain HRV and mortality and nonlinear HRV and mortality were compared for the entire population (ALL), those without coronary artery bypass graft post-MI (no CABG), and those without CABG or diabetes (no CABG, no DIAB) using univariate and multivariate Cox regression analysis. Strength of association was compared by P values and Wald Chi-square values. Nonlinear HRV included short-term fractal scaling exponent, power law slope, and SD12 (Poincare dimension). For ALL and for no CABG, increased daytime SD12 had the strongest association with mortality (P=0.002 ALL and P <0.001 no CABG). For no CABG, no DIAB increased 24-hour SD12 hours had the strongest association (P <0.001) with mortality. Upon multivariate analysis, increased SD12, decreased ln ULF (ultra low frequency), and history of prior MI and history of congestive heart failure each remained in the model. CONCLUSION: Nonlinear HRV is associated with mortality post-MI. However, as with traditional HRV, this is diluted by CABG surgery post-MI and by diabetes. Results suggest that decreased long-term HRV and increased randomness of heart rate are each independent risk factors for mortality post-MI.     

Clinical and demographic determinants of heart rate variability in patients post myocardial infarction: insights from the cardiac arrhythmia suppression trial (CAST)

BACKGROUND: Clinical and demographic determinants of heart rate variability (HRV), an almost universal predictor of increased mortality, have not been systematically investigated in patients post myocardial infarction (MI). HYPOTHESIS: The study was undertaken to evaluate the relationship between pretreatment clinical and demographic variables and HRV in the Cardiac Arrhythmia Suppression Trial (CAST). METHODS: CAST patients were post MI and had > or =6 ventricular premature complexes/h on pretreatment recording. Patients in this substudy (n = 769) had usable pretreatment and suppression tapes and were successfully randomized on the first antiarrhythmic treatment. Tapes were rescanned; only time domain HRV was reported because many tapes lacked the calibrated timing signal needed for accurate frequency domain analysis. Independent predictors of HRV were determined by stepwise selection. RESULTS: Coronary artery bypass graft surgery (CABG) after the qualifying MI was the strongest determinant of HRV. The markedly decreased HRV associated with CABG was not associated with increased mortality. Ejection fraction and diabetes were also independent predictors of HRV. Other predictors for some indices of HRV included beta-blocker use, gender, time from MI to Holter, history of CABG before the qualifying MI, and systolic blood pressure. Decreased HRV did not predict mortality for the entire group. For patients without CABG or diabetes, decreased standard deviation of all NN intervals (SDANN) predicted mortality. Clinical and demographic factors accounted for 31% of the variance in the average of normal-to-normal intervals (AVGNN) and 13-26% of the variance in other HRV indices. CONCLUSIONS: Heart rate variability post MI is largely independent of clinical and demographic factors. Antecedent CABG dramatically reduces HRV. Recognition of this is necessary to prevent misclassification of risk in patients post infarct.     

Correlation between cardiac autonomic activity and compromise of left ventricular function in dilated cardiomyopathy

In recent years, evaluation of cardiac autonomic activity by means of heart rate variability (HRV) determination and baroreflex sensitivity (BRS) testing has become readily available. The results of the ATRAMI (Autonomic Tone and Reflexes After Myocardial Infarction) study showed that both diminished HRV and baro-reflex sensitivity are associated with poor outcome in patients after myocardial infarction. In contrast to patients with coronary disease little information is available concerning cardiac autonomic activity in idiopathic dilated cardiomyopathy (IDC). Therefore, HRV and BRS were assessed in 160 patients with IDC and preserved sinus rhythm in order to investigate the relationship between HRV, BRS, and left ventricular ejection fraction. Time domain indices of HRV were computed from 24-hour digital Holter recordings. BRS testing was performed using the noninvasive phenylephrine method. Mean standard deviation of all normal RR intervals (SDNN) of the whole study population was 112 +/- 46 ms. A well preserved HRV (SDNN > 105 ms) was found in 74 patients (46%), a moderately decreased HRV (SDNN 70-105 ms) in 59 patients (37%), and a severely decreased HRV (SDNN < 70 ms) in 27 patients (17%). Mean BRS was 7.5 +/- 5.0 ms/mm Hg. A well preserved BRS (> 6 ms/mm Hg) was present in 78 patients (57%), a moderately decreased BRS (3-6 ms/mm Hg) was present in 38 patients (28%), and a severely decreased BRS (< 3 ms/mm Hg) in 21 patients (15%). There was only a weak correlation between SDNN and BRS (r = 0.19; p < 0.05). A weak correlation was found for SDNN and left ventricular ejection fraction (r = 0.29; p < 0.05). There was no significant correlation between BRS and left ventricular ejection fraction (r = 0.14). In summary, there was only a weak correlation between the HRV, BRS, and left ventricular ejection fraction in patients with IDC suggesting that these 3 variables may be independent predictors of sudden death in IDC. The relative prognostic value of these variables and other potential risk predictors including the presence of arrhythmias on Holter, microvolt T wave alternans, QTc dispersion, and signal-averaged ECG is currently under investigation in a large prospective observational study (Marburg Cardiomyopathy Study (MACAS)) during 5-year follow-up at our institution.     

心室晚电位、心率变异对急性心肌梗死患者心律失常事件发生的预测价值

目的 了解心率变异(HRV)、心室晚电位(VLP)在预测急性心肌梗死(AMI)预后的价值。方法 40例AMI患者HRV(SDNN)、VLP测定,与40例正常人进行对比分析。结果 AMI组SDNN(87.9±25.07ms)与对照组(13.37±35.96ms)比较明显减低(P<0.001),AMI组VLP阳性(11例)与正常组(1例)比较明显增高(P<0.01)。梗塞患者室性心律失常事件组与非事件组HRV(SDNN)、VLP比较相差显著(P<0.005)。对心律失常事件发生预测方面,HRV特异性为93.55％,相对危险性为10.50,VLP敏感性为44.4％。二者结合特异性、相对危险性增加。结论 二项指标均有独立的预测价值,如同时检测可望提高阳性预测值。     

Predictive value of heart rate variability for the recurrence of chronic atrial fibrillation after electrical cardioversion

BACKGROUND: The relation between heart rate variability (HRV) and occurrence of atrial fibrillation (AF) in paroxysmal AF has been well studied, but there are controversial observations regarding the relation of HRV parameters to the recurrence of chronic AF after cardioversion. HYPOTHESIS: The present study compared HRV parameters of patients with chronic AF on the second day of cardioversion with a healthy control group and investigated their predictive value for AF recurrence. METHODS: Forty-one patients with chronic AF (> 3 months), who had various underlying cardiovascular disorders, were enrolled to the study. Of these, 31 patients were successfully cardioverted by external direct current shock, but 27 patients fulfilled the entry criteria. Twenty healthy subjects served as a control group. On the second day of restoration of sinus rhythm, 24-h Holter recording was obtained and the following time-domain indices of HRV were measured: SDNN (the standard deviation of the mean RR interval expressed in ms), SDANN (the SD of the averages of RR intervals in all 5-min segments of the 24-h recording), rMSSD (the root mean square of differences of successive RR intervals), and pNN50 (the percentage of adjacent RR intervals that differed by more than 50 ms). Patients were followed-up for 6 weeks for recurrence of AF. RESULTS: After cardioversion, SDNN and SDANN were found to be significantly lower in the AF group than in the control group (86.4 +/- 31.7 ms vs. 142.1 +/- 40.2 ms, and 57 +/- 17.4 ms vs. 124.4 +/- 37.7 ms, p < 0.001 and p < 0.001, respectively). The indices of vagal modulation of heart rate (rMSS and pNN50) were not different between the AF group and the control group. Recurrence of AF was observed in 15 patients. In these patients, all HRV parameters were significantly depressed compared with those with maintained sinus rhythm. Logistic regression analysis revealed that only decreased pNN50 was an independent predictor of AF relapse (relative risk = 1.5, p = 0.02, 95% confidence interval 1.1-2.2). There was also a trend toward a shortened SDNN as a predictor of AF recurrences. CONCLUSION: Suppressed HRV parameters and decreased vagal tone are probably a risk factor for AF recurrences after cardioversion to sinus rhythm in a specific subset of patients with chronic AF.     

Preserved heart rate variability identifies low-risk patients with nonischemic dilated cardiomyopathy: results from the DEFINITE trial.

BACKGROUND: The recent expansion of indications for prophylactic implantable cardioverter-defibrillator (ICD) placement in subjects with nonischemic dilated cardiomyopathy has raised concerns about the cost-effectiveness of this therapy. OBJECTIVES: The purpose of this study was to identify low-risk patients with nonischemic dilated cardiomyopathy who may not require prophylactic ICD placement. METHODS: This was a prospective study of 274 participants in the Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial, a randomized controlled trial that evaluated the role of prophylactic ICD placement in patients with nonischemic dilated cardiomyopathy. The patients underwent 24-hour Holter recording for analysis of heart rate variability (HRV). The primary HRV variable was the standard deviation of normal R-R intervals (SDNN). Patients with atrial fibrillation and frequent ventricular ectopy (>25% of beats) were excluded from HRV analysis (23% of patients). SDNN was categorized in tertiles, and Kaplan-Meier analysis was performed to compare survival in the three tertiles and excluded patients. RESULTS: The study population was 73% male, with a mean age of 59 +/- 12 years and mean left ventricular ejection fraction of 21% +/- 6%. After 3-year follow-up, significant differences in mortality rates were observed: SDNN >113 ms: 0 (0%), SDNN 81-113 ms: 5 (7%), SDNN <81 ms: 7 (10%), excluded patients: 11 (17%) (P = .03). There were no deaths in the tertile with SDNN >113 ms regardless of treatment assignment (ICD vs control). CONCLUSION: Patients with nonischemic dilated cardiomyopathy and preserved HRV have an excellent prognosis and may not benefit from prophylactic ICD placement. Patients with severely depressed HRV and patients who are excluded from HRV analysis because of atrial fibrillation and frequent ventricular ectopy have the highest mortality.     

Depressed Heart Rate Variability as an Independent Predictor of Death in Chronic Congestive Heart Failure Secondary to Ischemic or Idiopathic Dilated Cardiomyopathy

After acute myocardial infarction, depressed heart rate variability (HRV) has been proven to be a powerful independent predictor of a poor outcome. Although patients with chronic congestive heart failure (CHF) have also markedly impaired HRV, the prognostic value of HRV analysis in these patients remains unknown. The aim of this study was to investigate whether HRV parameters could predict survival in 102 consecutive patients with moderate to severe CHF (90 men, mean age 58 years, New York Heart Association [NYHA] class II to IV, CHF due to idiopathic dilated cardiomyopathy in 24 patients and ischemic heart disease in 78 patients, ejection fraction [EF], 26%; peak oxygen consumption, 16.9 ml/kg/min) after exclusion of patients in atrial fibrilation with diabetes or with chronic renal failure. In the prognostic analysis (Cox proportional-hazards model, Kaplan-Meier survival analysis), the following factors were investigated: age, CHF etiology, NYHA class, EF, peak oxygen consumption, presence of ventricular tachycardia on Holter monitoring, and HRV measures derived from 24-hour electrocardiography monitoring, calculated in the time (standard deviation of all normal RR intervals [SDNN], standard deviation of 5-minute RR intervals [SDANN], mean of all 5-minute standard deviations of RR intervals [SD], root-mean-square of difference of successive RR intervals [rMSSD], and percentage of adjacent RR intervals >50 ms different [pNN50]) and frequency domain (total power [TP], power within low-frequency band [LF], and power within high-frequency band [HF]). During follow-up of 584 ± 405 days (365 days in all who survived), 19 patients (19%) died (mean time to death: 307 ± 315 days, range 3 to 989). Cox's univariate analysis identified the following factors to be predictors of death: NYHA (p = 0.003), peak oxygen consumption (p = 0.01), EF (p = 0.02), ventricular tachycardia on Holter monitoring (p = 0.05), and among HRV measures: SDNN (p = 0.004), SDANN (p = 0.003), SD (p = 0.02), and LF (p = 0.003). In multivariate analysis, HRV parameters (SDNN, SDANN, LF) were found to predict survival independently of NYHA functional class, EF, peak oxygen consumption, and ventricular tachycardia on Holter monitoring. The Kaplan-Meier survival curves revealed SDNN <100 ms to be a useful risk factor; 1-year survival in patients with SDNN <100 ms was 78% when compared with 95% in those with SDNN >100 ms (p = 0.008). The coexistence of SDNN <100 ms and a peak oxygen consumption <14 ml/kg/min allowed identification of a group of 18 patients with a particularly poor prognosis (1-year survival 63% vs 94% in the remaining patients, p <0.001). We conclude that depressed HRV on 24-hour ambulatory electrocardiography monitoring is an independent risk factor for a poor prognosis in patients with CHF. Whether analysis of HRV could be recommended in the risk stratification for better management of patients with CHF needs further investigation.

In 102 consecutive patients with stable chronic congestive heart failure and sinus rhythm, several heart rate variability measures derived from 24-hour electrocardiographic recording were significant prognostic risk markers, independent of clinical variables (New York Heart Association class, peak oxygen consumption, left ventricular ejection fraction). The coexistence of the standard deviation of all normal RR intervals <100 ms and peak oxygen consumption <14 ml/kg/min had the worst prognosis, and it is concluded that heart rate variability analysis is useful for noninvasive heart transplant assessment.     

Effect of exercise training in patients with heart failure: a pilot study on autonomic balance assessed by heart rate variability.

BACKGROUND: Heart rate variability (HRV) is decreased in patients with congestive heart failure (CHF) and is a prognostic marker in this disease. Exercise training is now regarded as an important part of the treatment of patients with CHF, but the effect on HRV and the association between this effect and the effect on neurohormones are not well assessed. METHODS: Heart rate recording was performed in 12 patients with CHF (mean age 67+/-8 years) with CHF NYHA functional class III, before and after 12 weeks of exercise training. The association with exercise capacity and serum levels of atrial natriuretic peptide was assessed. We also evaluated the correlation between HRV and survival at follow-up 87 months later. RESULTS: At baseline there was a significant correlation between mean heart rate and work performed during max cycle test (r=0.650, P=0.022) and the HRV parameter standard deviation normal to normal (SDNN) (r=0.678, P=0.015). After exercise training there was a significant increase in work performed (30.3+/-14.2 versus 38.1+/-14.1 kJ), 6-min walk test (502+/-88 versus 552+/-59 m, P=0.006) and SDNN (117.3+/-40.7 versus 128.6+/-42.3 ms, P=0.028). At 87 months of follow-up, there was a borderline significant difference between survivors and non-survivors. Only the survivors had a significant increase in SDNN after exercise training. CONCLUSION: This pilot study demonstrates an improvement with regard to parameters for HRV after exercise training in patients with CHF. The study suggests that the positive effect of exercise training in patients with CHF involves an attenuation of the reduced HRV response, and that this improvement might have prognostic significance.     

Heart rate variability in heart failure

BACKGROUND: Heart rate variability (HRV) depicts the functional status of the autonomic nervous system and its effects on sinus node. Recently, HRV analysis has been introduced in patients with heart failure (CHF) to identify those who are at risk of cardiac death. AIM: To analyse HRV in patients with CHF with depressed left ventricular ejection fraction (EF) and to relate HRV parameters to EF, NYHA functional class and other clinical parameters. METHODS: The study group consisted of 105 patients with CHF (88 males, 17 females, mean age 54+/-12 years); 77 patients had ischaemic cardiomyopathy, and 28 - dilated cardiomyopathy. All patients were in NYHA class II-IV and had EF <40%. The mean value of echocardiographically assessed EF was 26.9+/-8.3%. The control group consisted of 30 gender- and age-matched healthy subjects. HRV analysis was performed in the time-domain from 24-hour Holter ECG. RESULTS: All HRV variables were significantly lower in patients with CHF than in controls. Patients with NYHA class II had higher values of SDNN and SDANN than those in class III or IV. Patients with sustained or non-sustained ventricular tachycardia (VT) detected during Holter monitoring had lower SDNN and SDANN values than those without VT. Patients with diabetes had significantly lower SDNN and rMSSD values than the patients without diabetes. Similar results were found when patients with or without hypertension were compared. HRV parameters were similar in patients either with ischaemic or dilated cardiomyopathy. Also the values of EF were similar (27.4+/-8.4 vs 25.0+/-8.3%, respectively, NS). In the whole group of patients with CHF the values of SDNN and SDANN significantly correlated with EF (SDNN p<0.001, r=0.42; SDANN p<0.001, r=0.51). This correlation was stronger in the subset of patients with ischaemic cardiomyopathy (SDNN p=0.002. r=0.54; SDANN p=0.002; r=0.53) than in those with dilated cardiomyopathy (SDNN p=0.012, r=0.23; SDANN p=0.008, r=0.42). A significant negative correlation was found between all HRV parameters and NYHA class (SDNN p<0.001, r = -0.33; SDANN p<0.001, r = -0.38; rMSSD p<0.001, r = -0.13). CONCLUSIONS: HRV is depressed in patients with CHF compared with healthy subjects. Among patients with CHF, HRV is further decreased in patients with more advanced NYHA class, lower EF and in those with diabetes, hypertension or VT on Holter monitoring.     

Autonomic dysfunction in patients with nocturnal hypoventilation in extrapulmonary restrictive disease.

In chronic obstructive pulmonary disease, persistent hypoxia may be associated with autonomic dysfunction. The effect of nocturnal oxygen desaturation on autonomic function in patients with chest wall deformities and neuromuscular disease is unknown. This study examined the effect of nocturnal oxygen desaturation upon heart rate variability, a sensitive measure of autonomic function. Twenty-seven patients with chest wall deformity or neuromuscular disease underwent analysis of overnight oximetry, blood gases, and 24 h heart rate variability (HRV), specifically the standard deviation of normal-to-normal (SDNN) RR intervals, and the number of increases in successive NN intervals >50 ms (SNN50). Subjects were grouped according to nocturnal arterial oxygen saturation (Sa,O2): group 1 had episodes of Sa,O2 <90%, group 2 had Sa,O2 >90% throughout the night, and group 3 were 27 healthy age-matched controls who also underwent HRV analysis. The mean+/-SD SDNN for group 1 was 79.3+/-23.7 ms, less than group 2 (149.8+/-58.9 ms, p<0.02) and group 3 (155.1+/-37.1 ms, p<0.001). The geometric mean sNN50 was less in group 1 than group 2 (1,530 versus 5,843, p<0.01), but not significantly different from group 3 (2,712, p=0.053). There was no significant difference between groups 2 and 3. Within group 1, both SDNN and sNN50 were significantly lower in those patients with more severe nocturnal hypoxia. The minimum overnight Sa,O2 was the best predictor of abnormal HRV. In conclusion, patients with nocturnal hypoxia have evidence of autonomic dysfunction, even in cases with only transient episodes of nocturnal oxygen desaturation. The severity of autonomic dysfunction is related to the degree of nocturnal oxygen desaturation.     

Heart rate turbulence and left ventricular ejection fraction in Chagas disease.

AIMS: Chagas disease patients often present premature ventricular complexes (PVCs), depression of left ventricular ejection fraction (LVEF) and autonomic dysfunction, which is generally evaluated by heart rate variability (HRV) analysis. As frequent PVCs may complicate HRV computation, we measured heart rate turbulence (HRT) and evaluated the correlation between ejection fraction and HRT or HRV in Chagas disease. METHODS: We studied 30 patients (47+/-11 years, 20 men) with Chagas cardiomyopathy and left ventricular dilatation who underwent clinical evaluation, ejection fraction (EF: 45+/-14%) determination and 24-h Holter monitoring (median PVC=1781). In all patients, the standard deviation of normal RR intervals (SDNN), the square root of the mean square differences of successive RR intervals (RMSSD) and values of turbulence onset (TO) and turbulence slope (TS) were calculated. RESULTS: HRT indices were independent of mean RR interval and presented high correlation with EF: TO (-0.11+/-0.01%, r=-0.60, P<0.001) and TS (5.8+/-3.7 ms/RR-interval, r=0.73, P<0.001). Of HRV parameters, only SDNN, corrected for mean RR interval, showed a weak but not significant correlation with EF (r=0.41). The comparison of HRT/EF and HRV/EF correlation coefficients, indicated the presence of a significant difference (P=0.017). CONCLUSIONS: HRT indices appear to correlate better with EF than SDNN in Chagas disease. Thus, an analysis based on heart rate transient adaptation seems to perform better than HRV in detecting the autonomic alterations that parallel left ventricular dysfunction in Chagas disease patients. The high number of PVCs observed in these patients further support the use of HRT methodology.     

Prognostic value of heart rate variability after acute myocardial infarction in the era of immediate reperfusion

Introduction  The incidence and significance of impaired heart rate variability (HRV) after acute myocardial infarction (AMI) have not yet been evaluated in cohorts of patients in whom early reperfusion was systematically attempted. Therefore, HRV was evaluated in 412 unselected patients with AMI (311 men, mean age: 60±12 years, anterior AMI in 172 patients) treated with direct coronary angioplasty (PTCA) within 12 hours of symptom onset (mean 3.5±2.0 h). Standard deviation of normal RR intervals (SDNN), square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD) and left ventricular ejection fraction (LVEF, mean: 55±15%) were measured 11±9 days after AMI before discharge. Angiotensin-converting enzyme (ACE) inhibitors and beta-blockers were prescribed at discharge in 81.1% and 70.1% of patients, respectively. Results  Mean SDNN was 94±30 ms (range 14–155). SDNN was <50 ms in 7% of patients. Mean RMSSD was 34±32 ms (range 2–234). RMSSD was <15 ms in 21% of patients. Low SDNN (<50 ms) was unrelated to gender, age, infarct location or extension of CHD but was related to low LVEF (p<0.001, logistic regression analysis). During mean follow-up of 4.3±3 years, there were 31 deaths; 24 were cardiac. SDNN was higher in long-term survivors (102±39 ms) as compared to nonsurvivors (81±33 ms, p=0.02) but RMSSD was unrelated to the long-term vital status. Four-year survival of patients with a SDNN <50 ms vs >50 ms was 80% vs 92%, respectively (p<0.001, Kaplan Meier analysis). Low SDNN (odds ratio OR=2.0, p<0.05) but not RMSSD was an independent denominator for long-term mortality as were low LVEF (OR=1.0 decrease in LVEF, p<0.01, proportional hazards model) and age (OR=1.1, p<0.001). Only 3/31 fatalities and 1/24 cardiac deaths were predicted by a SDNN <50 ms and only 5/31 fatalities by a RMSSD <15 ms. Conclusion  The incidence of severely depressed HRV in patients after AMI is low (<10%) in the era of early reperfusion of the infarct vessel using direct PTCA. Mortality in patients with a very low HRV when assessed by SDNN is substantial but the positive predictive value of this parameter is low.      

Do collaterals affect heart rate variability in patients with acute myocardial infarction?

BACKGROUND: The protective effects and the prognostic importance of collaterals during and after acute myocardial infarction (MI) are under debate and heart rate variability (HRV) is a strong predictor of risk of mortality and arrhythmic events after acute MI. We aimed to examine the effects of collateral circulation on HRV in the early period after acute MI. METHODS: Sixty-four patients admitted to our clinics who were diagnosed with acute anterior MI and underwent thrombolytic therapy were enrolled in this study. We applied 24 h Holter monitoring for HRV analysis to all patients and compared the patients with and without collaterals to the infarct-related artery. RESULTS: Mean heart rate, low frequency (LF) (day, night and 24 h) and LF/high frequency (HF) (day, night and 24 h) were higher, SD of all NN intervals (SDNN), root mean square of successive differences (RMSSD), number of NN intervals that differed by more than 50 ms from the adjacent interval divided by the total number of all NN intervals (PNN50) and HF night values were lower in patients without collaterals than in those with collaterals. SDNN was negatively correlated with left anterior descending coronary artery (LAD) stenosis, ventricle score indices and left ventricular ejection fraction (LVEF); LF/HF ratio was positively correlated with ventricle score indices and negatively correlated with LVEF and Thrombolysis in Myocardial Infarction flow grade. Linear regression analysis showed that ventricle score index and coronary collaterals affect HRV and LAD stenosis, ventricle score, LVEF and coronary collaterals affect LF/HF ratio. A SDNN <80 ms increased the development of ventricular arrhythmias in the early period by 4.7 fold, a LF/HF ratio >2.7 increased it by 9.8 fold and a LVEF <35% increased it by 12.8 fold, whereas the presence of well-developed collaterals decreased the arrhythmia development by 2.5 fold. CONCLUSIONS: The collaterals to the infarct-related artery have great impact on HRV, autonomic nervous system activity and the development of ventricular arrhythmias in patients with acute anterior MI. Our results suggest a protective role of collaterals on myocardial electrophysiology in the early period after acute MI.     

Age-adjustment of HRV measures and its prognostic value for risk assessment in patients late after myocardial infarction

THE AIMS OF OUR STUDY WERE: (1) to establish the normal limit of the heart rate variability (HRV) indices in a healthy population and in its four age-related subgroups, including a new HRV index, HRV fraction; and (2) to analyse the frequency and predictive value of abnormally low HRV in a population of post-infarction patients in respect to the cut-points chosen (raw or age-adjusted). METHODS: Normal population of 296 healthy subjects (81 f, 215 m, aged 47+/-10 years) and post-infarction population of 298 patients (>3 months after acute MI, 65 f, 233 m, aged 56+/-10) were examined. The normal population was divided into 4 subsets based on age at entry: <35, 35-44, 45-54 and >54 years. Based on a 24 h ECG the standard HRV analysis was performed to obtain the following indices: mean RR interval, SDNN and SDANN. A new index of HRV, HRV fraction (HRVF, %) was calculated based on a numerical processing of the RR intervals return map. All patients were followed for 24 months. The endpoints of the study were death (of any reason) and cardiac death. RESULTS: Means and normal limits for SDNN, SDANN and HRVF were: 147+/-36 ms [95% CI 89-220], 136+/-36 ms [79-212] and 53+/-9% [35-68]. The HRV values below the lower normal limit (LNL) were observed in 20-25% of post-MI patients. During a 2 year follow-up there were 36 deaths (total mortality 12.1%), while cardiac mortality was 9.1% (27 cases). The prognostic value of the analysed indices was similar (sens approximately 53-61%, spec approximately 79-84%, PPV 22-26%, NPV 93-94%) irrespective of the cut-points chosen (calculated either for the entire population or age-related). Multivariate Cox regression analysis showed that a decrease of any index below the LNL was associated with a approximately 2.5 and approximately 4-6 times greater risk for death and cardiac death, irrespective of the cut-points chosen. CONCLUSIONS: The age-dependence of the HRV indices does not seem to significantly influence their prognostic value. Thus, a single cut-point of a particular HRV index, based on the entire population, is sufficient to be treated as a risk predictor. In the late phase of myocardial infarction the value of any global HRV index lying below the lower normal limit indicates independently an increased risk of death, especially cardiac death. The new index (HRV fraction) seems to be a promising substitute for currently used standard indices.     

Heart rate variability in hypertrophic obstructive cardiomyopathy: association with functional classification and left ventricular outflow gradients

BACKGROUND: The aim of this study was to investigate cardiac autonomic control in patients with hypertrophic obstructive cardiomyopathy (HOCM) and to assess the indexes of heart rate variability (HRV) in relation to the clinical and echocardiographic features. METHODS AND RESULTS: Twenty-three patients (17 male, six female: mean age 43+/-11) with HOCM and 18 healthy volunteers were included. M-mode and two-dimensional echocardiography, pulsed and continuous-wave Doppler studies were obtained. All patients and volunteers underwent continuous 24-h ambulatory ECG monitoring. Time domain variables considered in this study were standard deviation of mean R-R intervals (SDNN), root mean-squared successive difference (RMSSD) and percentage of cycles differing from the preceding one by more than 50 ms (PNN 50%). Patients were compared to detect associations between indices of heart rate variability, left ventricular outflow tract obstruction and clinical status. Heart rate variability parameters were also correlated with the echocardiographic and clinical characteristics of the patients. Both New York Heart Association (NYHA) functional class I-II patients (group I) and NYHA III-IV patients (group II) had lower values of SDNN, RMSSD and PNN 50% when compared with the control group (P<0.001, P<0.05 and P<0.01, respectively, for group I and P<0.001, P<0.001 and P<0.001, respectively, for group II). Time domain heart rate variability parameters were found to be significantly correlated with the subaortic dynamic obstruction. CONCLUSION: Heart rate variability is reduced in HOCM and well correlated with the degree of subaortic obstruction. Heart rate variability indices are also sensitive markers of the functional status.     

Einflu? von Carvedilol auf die Herzfrequenzvariabilit?t bei Patienten mit dilatativer Kardiomyopathie

The aim of the present study was to assess the effects of carvedilol therapy in addition to conventional heart failure therapy on heart rate variability (HRV) and on left ventricular function in 14 patients with mild to moderate heart failure due to idiopathic dilated cardiomyopathy (IDC). After a 3- to 4-week titration period, carvedilol was titrated up to 50mg daily, or the highest dose tolerated (at least 25mg daily). Maintenance treatment was then continued for 8 weeks. Digital 24-hour Holter recordings were obtained at baseline and after 8 weeks of carvedilol therapy. HRV for the entire 24-hour period was computed in the time domain using the Oxford Medilog Excel 2 analysis system. Measures of HRV included the mean of all coupling intervals between normal beats (RRm), the standard deviation of all normal RR intervals (SDNN), the square root of the mean of the squared differences between adjacent normal RR intervals (rMSSD), and the proportion of adjacent normal RR intervals differing >50 ms (pNN50). Additional treatment with carvedilol induced a significant increase in HRV: SDNN increased from 77+/-21 ms to 110+/-22 ms (p=0.001), rMSSD from 19+/-7 ms to 26+/-7 ms (p=0.02), and mean pNN50-value increased from 1.7+/-1.3% to 5.5+/-4.5% (p<0.01) under therapy with carvedilol. Mean heart rate on carvedilol calculated over 24 hours was 13 beats less than at baseline (75 bpm versus 88 bpm, p<0.01). After 2 months of additional treatment with carvedilol, both hemodynamic and clinical parameters improved: left ventricular ejection fraction increased from 24+/-7% to 30+/-10% (p<0.05), and New York Heart Association class decreased from 2.5+/-0.8 to 1.8+/-0.7 (p<0.05). In summary, eight weeks of additional carvedilol therapy induced a significant increase in HRV parameters related to parasympathetic activity in patients with IDC. Whether increased vagal tone may contribute to the protective effect of carvedilol has to be evaluated by further studies.     

113例急性心肌梗死心率变异性与恶性心律失常相关性的研究

目的:探讨急性心肌梗死(AMI)患者的心率变异性(HRV)情况与恶性室性心律失常发生率及猝死率的相关性,预测AMI患者的病情及预后。方法:对113例已确诊AMI患者进行24 h动态心电图检查,对HRV进行时域分析(主要参数为全部正常窦性心动周期的标准差-SDNN),监测恶性室性心律失常的发生率,然后随访患者1年。结果:SDNN<50 ms,预测高危险水平的患者31例;SDNN介于50 ms～100 ms,预测中危险水平患者36例;SDNN介于100 ms～150 ms,预测低危险水平患者46例。高危险水平患者组发生恶性室性心律失常19例,猝死6例;中危险水平患者组发生恶性室性心律失常9例,猝死1例;低危险水平患者组发生恶性室性心律失常5例,无猝死。3组患者恶性室性心律失常发生率比较,P<0.05,心脏猝死率比较,P<0.01。结论:HRV减小程度与恶性室性心律失常及猝死发生率有正相关性,HRV在预测AMI患者的危险性及预后起着重要作用。     

Sportmedizinische Aspekte kardialer Risikostratifizierung

The present study investigates the association of the predicted CHD-risk (PROCAM) with the individual endurance capacity and heart rate variability (HRV) in a population-based sample of sedentary elderly. After stratification, in 57 men (48.1+/-9.5 yrs.) with an overall PROCAM-risk <10% (28.7+/-10.9 points) and 22 men (54.5+/-7.7 yrs.) with a coronary 10-year risk > or =10% (50.8+/-5.6 points) cycle ergometries and short-term HRV analysis of time (RRMEAN, SDNN, RMSSD) and frequency domain parameters (LF, HF, TP, LF/HF) were conducted. Additionally the autonomic stress index (SI) was calculated. Nonparametric tests were used for statistical correlation analysis (Spearman rho) and group comparisons (Mann-Whitney). For endurance capacity [W/kg] (r=-0.469, p<0.001), SDNN (r=-0.302, p<0.05), RMSSD (r= -0.311, p<0.05), LF (r=-0.325, p<0.05), HF (r= -0.311, p<0.05) and TP (r= -0.307, p<0.05) negative monotone correlations with the coronary score-risk were determined. Significant positive correlations were calculated for SI (r=0.476, p<0.001). Except for RRMEAN and LF/HF significant group differences (p<0.05) were computed for SDNN (30.0+/-20.0 vs 20.0+/-10.0 ms), RMSSD (22.2+/-18.3 vs 18.0+/-8.7 ms), LF (90.9+/-241.5 vs 41.35+/-81.1 ms(2)), HF (43.0+/-105.1 vs 18.0+/-27.0 ms(2)) and TP (189.0+/-457.1 vs 100.0+/-157.6 ms(2)). Significant differences (p<0.01) were evaluated for exercise capacity (2.4+/-0.5 vs 1.8+/-0.3 W/kg) and SI (90+/-183 vs 322+/-291). The results underline the predictive value of HRV analysis in risk stratification and outline the interrelation of a decreased exercise capacity and autonomic function with a raised individual 10-year cardiac risk. As an independent parameter of the vegetative regulatory state the stress index may contribute to an increased practical relevance of short-time HRV analysis.     

心得安改善短效钙拮抗剂心痛定心率变异性的研究

探讨β受体阻滞剂心得安是否可以改善短效钙拮抗剂心痛定的心率变异性(HRV)。将101例观察对象随机分为对照组(只使用心痛定,n=49)和试验组(使用心痛定和心得安,n=52),分别在服药前及服药后7～10天做24h动态心电图检测,分析HRV指标:正常RR间期的标准差(SDNN)、每5min平均RR间期的标准差(SDANN)、相邻RR之差的均方根(RMSSD)、相邻RR之差>50ms占总窦性心搏的百分数(PNN50)、低频(LF)、高频(HF)、低频和高频比值(LF/HF)。结果:对照组在治疗后心率(HR)加快,SDNN、SDANN显著降低(分别为105.2±31.8msvs126.9±32.0ms、98.9±20.1msvs107.9±19.8ms,P均<0.05),LF、LF/HF升高(分别229.3±77.1Hzvs196.1±64.8Hz、5.4±1.9vs3.8±1.8,P均<0.05),HRV降低;而试验组在治疗后心率无明显改变,SDNN、SDANN、LF、HF升高(分别为140.1±29.8msvs129.1±31.9ms、127.8±21.1msvs108.2±20.1ms、209.8±70.1Hzvs197.3±65.1Hz、148.5±48.8Hzvs123.5±41.0Hz,P均<0.05),LF/HF降低(P<0.05),治疗组HRV升高。结论:心得安能改善短效钙拮抗剂心痛定的HRV。