Differences in Heart Rate Dynamics Before the Spontaneous Onset of Long and Short Episodes of Paroxysmal Atrial Fibrillation

Background: Altered heart rate (HR) dynamics precede the spontaneous onset of atrial fibrillation (AF), but the factors related to the perpetuation and duration of paroxysmal AF episodes are not well established. This study was designed to test the hypothesis that HR dynamics preceding the onset of (AF) may influence the duration of AF. Methods: Traditional time and frequency domain HR variability indices, along with a short‐term fractal scaling exponent (α₁) and approximate entropy (ApEn), were analyzed in 20‐minute intervals before 92 episodes of spontaneous paroxysmal AF in 22 patients without structural heart disease. AF episodes were divided into two groups according to the duration of the arrhythmia episodes. Results: The high‐frequency (HF) spectral component in normalized units (nu) of heart rate variability was higher and low‐frequency (LF) component lower before long (> 200 s, n = 41) compared to short (< 200 s, n = 51) AF episodes (HF nu; 40.1 ± 14.8 vs 31.5 ± 16.4, P < 0.0001 and LF nu; 59.9 ± 14.8 vs 68.5 ± 16.4, P < 0.0001). Short‐term scaling exponent values also were lower before long compared to short AF episodes (e.g., α₁; 1.12 ± 0.21 vs 1.24 ± 0.23, P < 0.0001). Women had a larger number of long AF episodes than men, but the duration of AF was not related to any other clinical or demographic features or antiarrhythmic medication. Conclusion: Increased HF oscillations and decreased short‐term correlation properties of R‐R intervals, reflecting altered sympathovagal balance before the onset of AF, predispose to perpetuation of spontaneous arrhythmia episodes in patients with vulnerability to paroxysmal AF and without structural heart disease. A.N.E. 2001;6(2):134–142     

Abnormalities in Fractal Heart Rate Dynamics in Chagas Disease

Background and Methods: In order to study fractal HR dynamics in Chagas disease, we performed detrended fluctuation analysis (DFA)—along with analysis of power‐law β slope (β index) and standard deviation of N–N intervals (SDNN)—in edited and unedited (with ventricular premature beats — VPBs, only in DFA analysis) series of R‐R intervals from Holter monitoring of healthy controls (Group 0, n = 27) and Chagas disease patients with left ventricular (LV) ejection fraction >50% (Group 1, n = 137) and with LV ejection fraction <50% (Group 2, n = 23). Results: When analyzed from the edited R‐R interval data, the long‐term scaling exponent α₂ is altered both among the Chagas patients with and without LV dysfunction. The short‐term scaling exponent α₁ was higher in Group 1 Chagas patients as compared to controls (P < 0.01) and did not differ between Group 2 and controls. In unedited R‐R interval series, α₁ was significantly reduced in Group 2 Chagas patients (0.55 ± 0.002) as compared to controls (0.90 ± 0.002) and Group 1 (0.91 ± 0.003) (P < 0.001), but did not differ between Group 1 and controls. Similarly α₂ was lower in Group 2 compared to other groups (P < 0.001). SDNN did not differ between the groups, but the β index derived from 1/f model was reduced both in Group 1 and 2 Chagas patients as compared to controls (P < 0.01). There was strong correlation (rs = 0.82; P < 0.001) between the β and α₂ index from edited series. There was an inverse correlation (rs =?0.63, P < 0.01) between the number of VPBs and α₁ index of unedited series. Conclusions: The long‐term fractal HR dynamics altered in chagasic patients with and without LV dysfunction could be an early sign of autonomic dysfunction. Patients with impaired LV function show marked alterations in short‐term fractal HR dynamics toward more random behavior, mainly due to frequent ectopy. Prospective studies are necessary to define the value of these indices as predictors of death in Chagas disease.     

Heart Rate Turbulence for Prediction of Heart Transplantation and Mortality in Chronic Heart Failure

Background: Previous studies have shown conflicting results about the value of heart rate turbulence (HRT) for risk stratification of patients (pts) with chronic heart failure (CHF). We prospectively evaluated the relation between HRT and progression toward end‐stage heart failure or all‐cause mortality in patients with CHF. Methods: HRT was assessed from 24‐hour Holter recordings in 110 pts with CHF (54 in NYHA class II, 56 in class III–IV; left ventricular ejection fraction (LVEF) 30%± 10%) on optimal pharmacotherapy and quantified as turbulence onset (TO,%), turbulence slope (TS, ms/RR interval), and turbulence timing (beginning of RR sequence for calculation of TS, TT). TO ≥ 0%, TS ≤ 2.5 ms/RR, and TT >10 were considered abnormal. End point was development of end‐stage CHF requiring heart transplantation (OHT) or all‐cause mortality. Results: During a follow‐up of 5.8 ± 1.3 years, 24 pts died and 10 required OHT. TO, TS, TT, and both (TO and TS) were abnormal in 35%, 50%, 30%, and 25% of all patients, respectively. Patients with at least one relatively preserved HRT parameter (TO, TS, or TT) (n = 98) had 5‐year event‐free rate of 83% compared to 33% of those in whom all three parameters were abnormal (n = 12). In multivariate Cox regression analysis, the most powerful predictor of end point events was heart rate variability (SDNN < 70 ms, hazard ratio (HR) 9.41, P < 0.001), followed by LVEF ≤ 35% (HR 6.23), TT ≥ 10 (HR 3.14), and TO ≥ 0 (HR 2.54, P < 0.05). Conclusion : In patients with CHF on optimal pharmacotherapy, HRT can help to predict those at risk for progression toward OHT or death of all causes. Ann Noninvasive Electrocardiol 2010;15(3):230–237     

卡维地洛对慢性心衰患者糖、脂代谢的影响

目的观察卡维地洛对慢性心衰患者的疗效及其对血糖,血脂代谢的影响。方法入选CHF患者59例,随机分为对照组:应用常规抗CHF治疗组(30例)和卡维地洛组(29例),后者在常规抗CHF治疗基础上加用卡维地洛,疗程为24周,治疗前后均测定左室舒张末期内径(LVDd)和收缩末期内径(LVDs)、左室射血分数(LVEF)、空腹血糖(FBS)、糖化血红蛋白(HbAlc)、血脂。结果卡维地洛组改善LVDd、LVDs和LVEF均优于常规抗CHF治疗组(P<0.01),治疗后卡维地络组TC、LDL-C较对照组降低(P<0.05)。结论卡维地洛可有效改善CHF患者的心功能,对糖、脂代谢有一定的益处。     

Influence of Atropine on Fractal and Complexity Measures of Heart Rate Variability

Background: Measurement of short‐term fractal‐like correlation properties of heart rate dynamics has been shown to be a useful prognostic indicator of adverse events in cardiac patients. Complexity measurements of heart rate variability (HRV) have already provided important information in many cardiac conditions. However, data on the physiological background of these newer nonlinear measures of HRV are limited. Methods: Nine healthy subjects (aged from 22 to 35 years, 6 males, 3 females) had an electro‐cardiographic (ECG) recording during controlled breathing in supine position. HRV was analyzed for 5 min periods before and after intravenous injection of 0.6 mg of atropine using conventional HRV measures and newer nonlinear HRV measures including the short‐term scaling exponent (a,) and approximate entropy (ApEn). Results: The short‐term scaling exponent a₁ increased significantly after atropine injection (1.01 ± 0.23 vs 1.43 ± 0.19, P = 0.001). There was no significant difference between ApEn values before and after atropine injection (0.87 ± 0.17 vs 0.70 ± 0.31, respectively, P = 0.27). At baseline before atropine administration, a₁ had a significant negative correlation with SDNN, RMSSD, and HF (r = ‐0.70, ‐0.76, ‐0.67, respectively, P <0.05 for all), and a significant positive correlation with heart rate (r = 0.76, P < 0.05). After atropine injection, a, did not have significant correlation with any of the HRV parameters or heart rate. There were no significant correlations between ApEn and any of the HRV measures or heart rate either before or after atropine administration. Conclusions: Vagal tone has an important influence on the values of the short‐term scaling exponent a,. However, vagal modulation is not a major determinant of the values of ApEn. A.N.E. 2002;7(4):326–331     

Effects and Significance of Premature Beats on Fractal Correlation Properties of R‐R Interval Dynamics

Background: Premature beats (PBs) have been considered as artifacts producing a bias in the traditional analysis of heart rate (HR) variability. We assessed the effects and significance of PBs on fractal scaling exponents in healthy subjects and patients with a recent myocardial infarction (AMI). Methods: Artificial PBs were first generated into a time series of pure sinus beats in 20 healthy subjects and 20 post‐AMI patients. Thereafter, a case‐control approach was used to compare the prognostic significance of edited and nonedited fractal scaling exponents in a random elderly population and in a post‐AMI population. Detrended fluctuation analysis (DFA) was used to measure the short‐term (α₁) and long‐term (α₂) fractal scaling exponents. Results: Artificial PBs caused a more pronounced reduction of α₁ value among the post‐AMI patients than the healthy subjects, for example, if >0.25% of the beats were premature a >25% decrease in the α₁ was observed in post‐AMI patients, but 4% of the premature beats were needed to cause a 25% reduction in α₁ in healthy subjects. Both edited (1.01 ± 0.31 vs 1.19 ± 0.27, P < 0.01) and unedited α₁ (0.71 ± 0.33 vs 0.89 ± 0.36, P < 0.05) differed between the patients who died (n = 42) and those who survived (n = 42) after an AMI. In the general population, only unedited α₁ differed significantly between survivors and those who died (0.96 ± 0.19 vs 0.83 ± 0.27, P < 0.05). Conclusions: Unedited premature beats result in an increase in the randomness of short‐term R‐R interval dynamics, particularly in post‐AMI patients. Premature beats must not necessarily be edited when fractal analysis is used for risk stratification.     

Effect of Beta‐Blockade on Autonomic Modulation of Heart Rate and Neurohormonal Profile in Decompensated Heart Failure

Background: One of the putative mechanisms for the salutary effects of beta‐blockers in patients with congestive heart failure (CHF) is their ability to improve autonomic dysfunction. However, patients with profound neurohumoral abnormalities derive little survival benefit from beta‐blockers. The purpose of the current study was to evaluate the effect of beta‐blockers on heart rate variability (HRV) in decompensated CHF. Methods: Time and frequency domain HRV indices were obtained from 24‐hour Holter recordings and compared to assess the role of beta‐blockade in 199 patients (mean age 60 ± 14 years) with decompensated CHF. Neurohormonal differences were assessed by measuring norepinephrine, endothelin‐1, tumor necrosis factor‐a, and interleukin‐6 in a subset of 64 patients. Results: All HRV indices were markedly suppressed but were substantially higher in patients who were on beta‐blockers. Time domain measures of parasympathetic cardiac activity, the percentage of R‐R intervals with > 50 ms variation (4.9 ± 0.6 vs 7.7 ± 1.2%, P = 0.006) and the square root of mean squared differences of successive R‐R intervals (22.7 ± 2.0 vs 31.6 ± 4.1 ms, P = 0.004), were higher in the beta‐blocker group. Spectral analysis revealed that the total power and the ultra‐low frequency power were significantly higher in patients on beta‐blockers (82% and 59%, respectively). The high frequency power, a spectral index of parasympathetic modulation, was 41% higher in the beta‐blocker group (121 ± 25 vs 171 ± 27 ms2, P = 0.02). Norepinephrine and interleukin‐6 levels were substantially lower in patients on beta‐blockers (28% and 61%, respectively). However, these differences did not reach statistical significance. Conclusions: Beta‐blockers improve the impaired cardiac autonomic regulation during high sympathetic stress of decompensated CHF. This effect may play an important role in protecting the myocardium and preventing arrhythmias during transient increases in sympathetic activity. A.N.E. 2001;6(2):98–106     

Resting Heart Rate and Chronotropic Response to Exercise: Prognostic Implications in Heart Failure Across the Left Ventricular Ejection Fraction Spectrum

Background:

We studied the relationship between resting heart rate (HR), chronotropic response to exercise, and clinical outcomes in patients with heart failure (HF) across the spectrum of left ventricle ejection fraction (LVEF).

Heart Rate Variability in Risk Stratification of Cardiac Patients

Heart rate (HR) variability has been extensively studied in cardiac patients, especially in patients surviving an acute myocardial infarction (AMI) and also in patients with congestive heart failure (CHF) or left ventricular (LV) dysfunction. The majority of studies have shown that patients with reduced or abnormal HR variability have an increased risk of mortality within a few years after an AMI or after a diagnosis of CHF/LV dysfunction. Various measures of HR dynamics, such as time-domain, spectral, and non-linear measures of HR variability have been used in risk stratification. The prognostic power of various measures, except of those reflecting rapid R–R interval oscillations, has been almost identical, albeit some non-linear HR variability measures, such as short-term fractal scaling exponent have provided somewhat better prognostic information than the others. Abnormal HR variability predicts both sudden and non-sudden cardiac death. Because of remodeling of the arrhythmia substrate after AMI, early measurement of HR variability to identify those at high risk should likely be repeated later in order to assess the risk of fatal arrhythmia events. Future randomized trials using HR variability/turbulence as one of the pre-defined inclusion criteria will show whether routine measurement of HR variability/turbulence will become a routine clinical tool for risk stratification of cardiac patients.     

Comparative long term effects of nebivolol and carvedilol in hypertensive heart failure patients

Background

Beta-blockers improve left ventricular (LV) systolic function and prognosis in patients with chronic heart failure (CHF), but their different pleiotropic properties may influence their cardiovascular effects. This open-label study compared the effects of long-term treatment with nebivolol versus carvedilol on LV ejection fraction (LVEF), in hypertensive CHF patients. Secondary end points were to assess the effect of the 2 beta-blockers on exercise capacity and clinical outcome.

Methods and Results

A total of 160 hypertensive CHF patients, with LVEF <40% and in New York Heart Association (NYHA) functional class I, II, or III, were randomly assigned to receive nebivolol or carvedilol for 24 months. At baseline and at the end of treatment, all patients underwent clinical evaluation, echocardiography, and 6-minute walking test. The target doses were 10 mg/d for nebivolol and 50 mg/d for carvedilol. Compared with baseline values, LVEF increased by a similar extent in the carvedilol (C) and nebivolol (N) groups (C from 36.1% (SD 1.5%) to 40.9% (SD 1.9%), P < .001; N from 34.1% (SD 1.8%) to 38.5% (SF 2.2%), P < .001). Heart rate and NYHA functional class decreased significantly in both groups, and the 6-minute walking distance increased (C from 420 m (SD 104 m) to 490 m (SD 115 m), P < .001; N from 421 m (SD 118 m) to 487 m (SD 138 m), P < .001). During 24 months, 21 carvedilol recipients (26%) and 18 nebivolol recipients (22%) had cardiac events, including 3 and 4 deaths, respectively.

Conclusion

In the long term, nebivolol and carvedilol appear to be similarly effective in the treatment of hypertensive patients with CHF.     

Baseline Heart Rate Variability Predicts Clinical Events in Heart Failure Patients Implanted with Cardiac Resynchronization Therapy: Validation by Means of Related Complexity Index

Background: Studies on the physiology of the cardiovascular system suggest that generation of the heart rate (HR) signal is governed by nonlinear dynamics. Linear and nonlinear indices of HR variability (HRV) have been shown to predict outcome in heart failure (HF). Aim of the present study is to assess if a HR‐related complexity predicts adverse clinical and cardiovascular events at 1 year in patients implanted with cardiac resynchronization therapy (CRT). Methods: In sixty patients implanted with CRT (Renewal), 24‐hour HR data were retrieved at patient discharge and 1‐year follow‐up. A set of linear indices of HRV were considered: mean HR, standard deviation of normal beat to normal beat (SDANN), and HR footprint. Two novel nonlinear indices were calculated by means of a specific algorithm (OntoSpace): HR‐complexity (HR‐Co) and HR‐entropy (HR‐En). Predictors of adverse clinical outcome (functional class deterioration or major hospitalizations for cardiovascular causes or all‐cause mortality) and of HRV recovery were sought by means of multivariate analysis. Results: HR‐Co and HR‐En were found to be highly correlated with the other traditional indices of HRV. Lower baseline values of complexity were associated with adverse clinical outcomes (hazard ratio [HR] 0.71; 95% confidence interval [CI] 0.54–0.95; P < 0.02). Conclusion: Complexity and entropy indices, calculated from 24‐hour normal beat to normal beat (RR) intervals well represent patient's autonomic function. In this limited set of data, HF patients with lower baseline complexity‐related indices, representing a more compromised autonomic function, present worse clinical outcome at 1‐year follow‐up. Ann Noninvasive Electrocardiol 2010;15(4):301–307     

Fractal analysis and time- and frequency-domain measures of heart rate variability as predictors of mortality in patients with heart failure

Time-domain measures of heart rate (HR) variability provide prognostic information among patients with congestive heart failure (CHF). The prognostic power of spectral and fractal analytic methods of HR variability has not been studied in the patients with chronic CHF. The aim of this study was to assess whether traditional and fractal analytic methods of HR variability predict mortality among a population of patients with CHF. The standard deviation of RR intervals, HR variability index, frequency-domain indexes, and the short-term fractal scaling exponent of RR intervals were studied from 24-hour Holter recordings in 499 patients with CHF and left ventricular ejection fraction < or =35%. During a mean follow-up of 665 +/- 374 days, 210 deaths (42%) occurred in this population. Conventional and fractal HR variability indexes predicted mortality by univariate analysis. For example, a short-term fractal scaling exponent <0.90 had a risk ratio (RR) of 1.9 (95% confidence interval [CI] 1.4 to 2.5) and the SD of all RR intervals <80 ms had an RR of 1.7 (95% CI 1.2 to 2.1). After adjusting for age, functional class, medication, and left ventricular ejection fraction in the multivariate proportional-hazards analysis, the reduced short-term fractal exponent remained the independent predictor of mortality, RR 1.4 (95% CI 1.0 to 1.9; p <0.05). All HR variability indexes were more significant univariate predictors of mortality in functional class II than in class III or IV. Among patients with moderate heart failure, HR variability measurements provide prognostic information, but all HR variability indexes fail to provide independent prognostic information in patients with the most severe functional impairment.     

卡维地洛对慢性心力衰竭患者血浆脑钠肽水平的影响

目的观察卡维地洛对慢性心力衰竭患者血浆脑钠肽水平的影响。方法将123例慢性心力衰竭患者随机分为卡维地洛组(62例)和对照组(61例)。治疗后观察脑钠肽和超声心动图的结果。结果卡维地洛组较对照组治疗后血浆脑钠肽水平显著降低(P<0.05);卡维地洛组治疗后左心室射血分数(LVEF)、每搏量以及每分排血量明显增加(P<0.05,P<0.01);卡维地洛组治疗前后患者血浆脑钠肽的下降水平与LVEF增加呈负相关(△LVEF:r=-0.86,P<0.01)。结论卡维地洛能明显改善慢性心力衰竭患者血流动力学,抑制神经内分泌因素的过度激活,改善心功能;血浆脑钠肽水平可作为评价β受体阻滞剂治疗慢性心力衰竭疗效的监测指标之一。     

Efficacy and safety of bisoprolol fumarate compared with carvedilol in Japanese patients with chronic heart failure: results of the randomized,controlled, double-blind,Multistep Administration of bisoprolol IN Chronic Heart Failure II (MAIN-CHF II) study

Bisoprolol fumarate (bisoprolol) is a β-blocker widely used to treat chronic heart failure (CHF). However, few studies have compared its efficacy and safety with those of the widely used β-blocker carvedilol in Japanese patients with CHF. We designed a confirmatory trial of bisoprolol using carvedilol as a control drug; however, the trial was discontinued after an off-label use of bisoprolol was approved during the study. Bisoprolol and carvedilol were administered for 32 weeks in 31 and 28 patients, respectively. The mean maintenance doses of bisoprolol and carvedilol were 3.3 and 13.6 mg/day, respectively, and the mean durations of treatment were 188.2 and 172.9 days, respectively. Heart-rate changes were similar in both groups. The mean changes from baseline to Week 32 in left ventricular (LV) ejection fraction (EF) (bisoprolol vs carvedilol groups; 11.7 % ± 8.6 % vs 10.1 % ± 10.5 %), LV end-diastolic volume (?37.5 ± 48.7 vs ?24.7 ± 29.4 ml), and LV end-systolic volume (?41.9 ± 43.0 vs ?29.3 ± 25.9 ml) revealed a decrease in LV volume and an increase in LVEF in both groups. The cumulative event-free rate for a composite of cardiovascular death or admissions to hospital for worsening of CHF was 92.4 % and 94.7 % in the bisoprolol and carvedilol groups, respectively. Overall, 90.3 % and 85.7 % of patients were titrated up to the maintenance doses of bisoprolol and carvedilol, respectively. Bisoprolol, at half the dose used in other countries, is well tolerated and is as effective as carvedilol for treating Japanese patients with mild to moderate CHF.     

Effects of Calcium Antagonist Felodipine on Renal Sympathetic Nerve Activity in Rats with Congestive Heart Failure

In order to assess the effects of dihydropyridine calcium antagonist on sympathetic nerve activity (SNA) in experimental chronic heart failure (CHF), felodipine was given to rats with CHF induced by coronary artery ligation. Anesthetized CHF (n = 7) and sham-operated (n = 9) rats were injected with a bolus dose of felodipine (20 μg/kg) and then infused with felodipine (30 μg/kg/h) for 3 hours. Control CHF rats (n = 8) were given vehicle in the same way. After felodipine treatment, mean blood pressure (MBP) rapidly decreased to 75–85 mmHg, and there was a reflex tachycardia and reflex activation of renal SNA. The heart rate (HR) had returned to baseline level after 3 hours of continuous felodipine infusion, and the SNA returned to baseline level after 2 hours of infusion. At the end of the experiment, renal SNA was 65.4 ± 11.5% of the baseline level in CHF rats receiving felodipine (P < 0.05) and 94.1 ± 22.8% in CHF rats receiving vehicle (P > 0.05), but there was no statistical difference between the two groups. Arterial baroreceptor sensitivity (assessed by phenylephrine infusion), which was impaired in CHF rats (−2.7 ± 0.2 SNA%/mmHg in all CHF rats together vs. −3.6 ± 0.4 in sham-operated rats, P < 0.5) did not differ significantly from that in sham-operated rats during felodipine infusion (−3.2 ± 0.4 in felodipine-treated CHF rats vs. −3.7 ± 0.6 in sham-operated rats) but deteriorated without felodipine treatment (−2.1 ± 0.3 in CHF rats receiving vehicle, P < 0.05). The biphasic renal SNA response during felodipine infusion suggests that felodipine does not cause persistent sympathetic activation and relatively improves baroreceptor sensitivity in CHF rats. This revised version was published online in July 2006 with corrections to the Cover Date.     

Autonomic Markers as Predictors of Nonfatal Acute Coronary Events after Myocardial Infarction

Background: Autonomic markers, such as heart rate variability (HRV), heart rate turbulence (HRT), and baroreflex sensitivity (BRS) provide information on the risk of all‐cause mortality after an acute myocardial infarction (AMI), but their value in predicting nonfatal cardiac events is not well known. Methods: A consecutive series of 675 patients with an AMI were followed up to 30 months. At baseline, the patients underwent a 24‐hour Holter recording, and assessment of BRS using phenylephrine test. Several parameters of HRV and HRT were determined. Results: After the follow‐up, 98 patients (15%) had a nonfatal acute coronary event. Among the studied variables, the short‐term scaling exponent alpha1 (P = 0.002), power‐law slope beta (P = 0.008), low‐frequency component of HRV power spectrum (P < 0.001), turbulence slope (P < 0.001), and BRS (P < 0.001) had the strongest association with the occurrence of nonfatal acute coronary events in univariate comparisons. After adjustment with relevant clinical variables (such as age, gender, ejection fraction, functional class, medication, diabetes) in the Cox proportional hazards model, alpha1 and beta remained as statistically significant predictors of nonfatal acute coronary events (HR = 2.0 [1.2–3.2, 95% CIs, P = 0.006] for alpha1 ≤ 1.025), (HR = 1.9 [1.2–3.1, P = 0.008] for beta ≤–1.507). Conclusion: Several autonomic markers provide information on the risk of recurrent nonfatal coronary events after an AMI. Altered fractal heart rate behavior seems to be the strongest independent predictor of such events.     

Heart rate dynamics before spontaneous onset of ventricular fibrillation in patients with healed myocardial infarcts

The traditional methods of analyzing heart rate (HR) variability have failed to predict imminent ventricular fibrillation (VF). We sought to determine whether new methods of analyzing RR interval variability based on nonlinear dynamics and fractal analysis may help to detect subtle abnormalities in RR interval behavior before the onset of life-threatening arrhythmias. RR interval dynamics were analyzed from 24-hour Holter recordings of 15 patients who experienced VF during electrocardiographic recording. Thirty patients without spontaneous or inducible arrhythmia events served as a control group in this retrospective case control study. Conventional time- and frequency-domain measurements, the short-term fractal scaling exponent (alpha) obtained by detrended fluctuation analysis, and the slope (beta) of the power-law regression line (log power - log frequency, 10(-4)-10(-2) Hz) of RR interval dynamics were determined. The short-term correlation exponent alpha of RR intervals (0.64 +/- 0.19 vs 1.05 +/- 0.12; p <0.001) and the power-law slope beta (-1.63 +/- 0.28 vs -1.31 +/- 0.20, p <0.001) were lower in the patients before the onset of VF than in the control patients, but the SD and the low-frequency spectral components of RR intervals did not differ between the groups. The short-term scaling exponent performed better than any other measurement of HR variability in differentiating between the patients with VF and controls. Altered fractal correlation properties of HR behavior precede the spontaneous onset of VF. Dynamic analysis methods of analyzing RR intervals may help to identify abnormalities in HR behavior before VF.     

卡维地洛治疗充血性心力衰竭的临床研究

目的观察卡维地洛对充血性心力衰竭(CHF)左心功能的影响。方法患冠心病、原发性高血压、扩张型心肌病的CHF患者共174例随机分为治疗组和对照组各87例,治疗组在强心、利尿、血管紧张素转换酶抑制剂(A-CEI)治疗的基础上,每天给卡维地洛6.25~50mg口服治疗,疗程24周。作治疗前、后NYHA分级、心功能的对照。结果治疗后NYHA分级、心功能均得到改善。结论卡维地洛治疗CHF 24周后,能抑制CHF的恶化,改善心功能,改善生活质量。     

Changes in heart rate variability are correlated to hemodynamic improvement with chronic CARVEDILOL therapy in heart failure

BACKGROUND: Reduced heart rate variability (HRV) has been shown to predict mortality in heart failure (CHF). The relationship between improved cardiac function and improvement in HRV has not been previously studied. METHODS AND RESULTS: This was substudy of a randomized, placebo-controlled, double-blinded trial of carvedilol of four months duration. Analysis of HRV was performed on 24-hour Holter monitors obtained at baseline and completion of study. All subjects had symptomatic CHF and an left ventricular ejection fraction (LVEF) <0.35. Study medication was titrated over 1 month to 50 mg/day (< or =75 kg) or 100 mg/day (<75 kg). A total of 17 subjects were randomized to carvedilol and 12 to placebo. Treatment with carvedilol was associated with significant increases in total frequency power, very low frequency power, high frequency power, SDNN, the root-mean square of difference of successive RRs, and pNN50. Change in time and frequency domain measures of HRV had a positive correlation with change in LVEF and negative correlation with change in coronary sinus norepinephrine levels. CONCLUSION: Carvedilol therapy in patients with CHF significantly increased HRV. Change in HRV correlates to improved hemodynamics. This suggests that carvedilol therapy partially normalizes autonomic modulation of heart rate in patients with CHF.     

Waist Circumference but Not Body Mass Index Predicts Long‐Term Mortality in Elderly Subjects with Chronic Heart Failure

OBJECTIVES: To examine whether waist circumference (WC) and body‐mass index (BMI) can predict long‐term mortality in elderly subjects with and without chronic heart failure (CHF). DESIGN: Longitudinal evaluation with a 12‐year follow‐up. SETTING: Campania, a region of southern Italy. PARTICIPANTS: One thousand three hundred thirty‐two subjects aged 65 and older selected from the electoral rolls of Campania. MEASUREMENTS: The relationship between WC or BMI and mortality during a 12‐year follow‐up in 125 subjects with and 1,143 subjects without CHF. RESULTS: Mortality increased as WC increased in elderly subjects without CHF (from 47.8% to 56.7%, P=.01), and the increase was even greater in patients with CHF (from 58.1% to 82.0%, P=.01). In contrast, mortality decreased as BMI increased in elderly subjects without CHF (from 53.8% to 46.1%, P0 =.046) but not in those with CHF. According to Cox regression analysis, BMI protected against long‐term mortality in the absence but not in the presence of CHF. In the absence of CHF, WC was associated with a 2% increased risk of long‐term mortality for each 1‐cm greater WC (Hazard Ratio (HR)=1.02, 95% confidence interval (CI)=1.01–1.03; P<.001), versus 5% increased in the presence of CHF (HR=1.06, 95% CI=1.02–1.10; P<.001). CONCLUSION: WC, but not BMI, is predictive of long‐term mortality in elderly individuals with CHF and to a lesser extent in those without CHF.