Preserved heart rate variability identifies low-risk patients with nonischemic dilated cardiomyopathy: Results from the DEFINITE trial
ABSTRACT 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.
The purpose of this study was to identify low-risk patients with nonischemic dilated cardiomyopathy who may not require prophylactic ICD placement.
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.
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).
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.
SourceAvailable from: Leonida Compostella[Show abstract] [Hide abstract]
ABSTRACT: Background: Cardiac autonomic dysfunction, clinically expressed by reduced heart rate variability (HRV), is present in patients with congestive heart failure (CHF) and is related to the degree of left ventricular dysfunction. In athletes, HRV is an indicator of ability to improve performance. No similar data are available for CHF. Objectives: The aim of this study was to assess whether HRV could predict the capability of CHF patients to improve physical fitness after a short period of exercise-based cardiac rehabilitation (CR). Patients and Methods: This was an observational, non-randomized study, conducted on 57 patients with advanced CHF, admitted to a residential cardiac rehabilitation unit 32 ± 22 days after an episode of acute heart failure. Inclusion criteria were sinus rhythm, stable clinical conditions, no diabetes and ejection fraction ≤ 35%. HRV (time-domain) and mean and minimum heart rate (HR) were evaluated using 24-h Holter at admission. Patients’ physical fitness was evaluated at admission by 6-minute walking test (6MWT) and reassessed after two weeks of intensive exercise-based CR. Exercise capacity was evaluated by a symptom-limited cardiopulmonary exercise test (CPET). Results: Patients with very depressed HRV (SDNN 55.8 ± 10.0 ms) had no improvement in their walking capacity after short CR, walked shorter absolute distances at final 6MWT (348 ± 118 vs. 470 ± 109 m; P = 0.027) and developed a peak-VO2 at CPET significantly lower than patients with greater HRV parameters (11.4 ± 3.7 vs. an average > 16 ± 4 mL/kg/min). Minimum HR, but not mean HR, showed a negative correlation (ρ = -0.319) with CPET performance. Conclusions: In patients with advanced CHF, depressed HRV and higher minimum HR were predictors of poor working capacity after a short period of exercise-based CR. An individualized and intensive rehabilitative intervention should be considered for these patients.12/2014; 3(4):e25237. DOI:10.5812/cardiovascmed.25237
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ABSTRACT: Despite significant therapeutic advancements, heart failure remains a highly prevalent clinical condition associated with significant morbidity and mortality. In 30%-40% patients, the etiology of heart failure is nonischemic. The implantable cardioverter-defibrillator (ICD) is capable of preventing sudden death and decreasing total mortality in patients with nonischemic heart failure. However, a significant number of patients receiving ICD do not receive any kind of therapy during follow-up. Moreover, considering the situation in Brazil and several other countries, ICD cannot be implanted in all patients with nonischemic heart failure. Therefore, there is an urgent need to identify patients at an increased risk of sudden death because these would benefit more than patients at a lower risk, despite the presence of heart failure in both risk groups. In this study, the authors review the primary available methods for the stratification of the risk of sudden death in patients with nonischemic heart failure.Arquivos Brasileiros de Cardiologia 08/2014; DOI:10.5935/abc.20140125 · 1.12 Impact Factor
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ABSTRACT: Cardiac manifestations of Duchenne muscular dystrophy (DMD) include progressive cardiac dysfunction and an elevated resting heart rate (HR). We hypothesized this elevated HR reflects autonomic dysfunction that can be identified by heart rate variability (HRV) analyses which will be associated with myocardial fibrosis by cardiac magnetic resonance imaging (cMR). DMD patients (N = 74) and controls (N = 17) had time and frequency domain HRV analyses calculated via Holter monitoring. Cardiac magnetic resonance imaging was performed on DMD cases only. χ (2) test, T test, ANOVA, and logistic regression were used to perform comparisons between groups. A p value of <0.05 was used for statistical significance. DMD cases had higher resting average HR than controls (99.4 ± 8.9, 85.4 + 6.2, p < 0.001). Among HRV variables, decreases were seen in the following: standard deviation of R to R intervals, the percent RR intervals differing by >50 ms from previous RR interval, the root-meansquare of successive differences of RR intervals, the standard deviation of the mean R to R segment (SDANN), low frequency, and high frequency domain, all p values 0.001. Maximum HR and SDANN most significantly associated with positive LGE on cMR (p = 0.008, p = 0.016). DMD cases on beta blocker had an average HR lower than those not on beta blocker (p = 0.009), but with no difference in HRV analysis. DMD patients have reduced HRV and therefore autonomic dysfunction prior to the onset of heart failure which is associated with myocardial fibrosis.Pediatric Cardiology 11/2014; 36(3). DOI:10.1007/s00246-014-1050-z · 1.55 Impact Factor