Heart Rate Variability Fraction Research Articles

Determinants of a Reduced Heart Rate Variability in Chronic Atrial Fibrillation

We aimed to evaluate whether clinical factors, which influence heart rate variability (HRV) in the presence of undisturbed sinus rhythm, have any associations with HRV in patients with permanent atrial fibrillation (AF). One hundred ninety-seven consecutive patients with permanent AF were included (122 males, 75 females, aged 64 ± 11 years, range 25-85). In each patient a 24-hour electrocardiographic recording was performed and an HRV fraction (HRVF)-the index based on scatter plot numerical processing-was calculated. Additionally, standard HRV measures were analyzed. Reduced HRVF was defined as its value lower than lower normal limit. Demographic and clinical factors were examined for their association with a reduced HRVF by means of a univariate and multivariate logistic regression analysis. The reduced HRVF was associated with advanced age, clinical diagnosis of a previous MI or dilated cardiomyopathy, presence of diabetes, depressed left ventricular function, NYHA class > II, treatment regimen, use of digoxin, diuretics or antiarrhythmic agents, nonuse of beta-blockers, and increased heart rate. The independent determinants that sustained after multivariate analysis were: heart rate (per 10 bpm increase, odds ratio 2.77 [1.88-4.07]), age (per 5 years increase 1.43 [1.1-1.85]), depressed left ventricular EF (<30% vs higher 2.26 [1.19-4.31]), and presence of diabetes (3.45 [1.1-10.85]). The HRVF correlated moderately with standard HRV measures. This index showed also the strongest correlation with left ventricular ejection fraction. We concluded that advanced age, left ventricular systolic dysfunction, increased heart rate, and presence of diabetes are cofactors of a reduced HRV in AF patients. Thus, the determinants of heart rate variability in the presence of atrial fibrillation are the same as those in sinus rhythm.

Relationship between R-R interval variation and left ventricular function in sinus rhythm and atrial fibrillation as estimated by means of heart rate variability fraction

Reduced heart rate variability (HRV) is associated with a poor outcome in patients with sinus rhythm (SR) or atrial fibrillation (AF). However, cut-off points for HRV measures differ between SR and AF. We hypothesized that a global index of 24-hour HRV based on evaluation of scatterplot would describe HRV irrespective of cardiac rhythm. 407 patients with ischemic heart disease (317 male, 90 female, mean age 57 ± 9 years) were studied. 331 patients had SR and 76 patients had AF. 24-hour ECGs were recorded, and standard HRV indices were calculated. Scatterplots was used to determine the HRV fraction (HRVF, %). HRV measures were compared in respect to left ventricular ejection fraction (LVEF £ 35% or 〉 35%). Standard HRV measures were higher in AF-patients despite the mean RR interval was lower. In patients with LVEF £ 35%, standard HRV indices were lower in SR group, in AF group only SDNN and RMSSD were reduced. The HRVF was comparably reduced (SR 39.3 ± 15.3%, AF 37.3 ± 17.9%). In patients with LVEF 〉 35%, HRVF did not differ between SR (47.2 ± ± 10.5%) and AF (46.1 ± 12.1%). The HRVF correlated with SDNN and SDANN (~0.85) in SR. Correlations were weaker in AF (~0.6). Standard HRV indices and HRVF showed similar relations with LVEF, but only in AF at the same range. The HRV fraction allows for HRV evaluation irrespective of cardiac rhythm. The index elicited a similar dependence of HRV on left ventricular function in SR and AF.

Heart Rate Variability Fraction—A New Reportable Measure of 24‐Hour R‐R Interval Variation

The scatterplot of R-R intervals has several unique features. Its numerical evaluation may produce a new useful index of global heart rate variability (HRV) from Holter recordings. Two-hundred and ten middle-aged healthy subjects were enrolled in this study. The study was repeated the next day in 165 subjects. Each subject had a 24-hour ECG recording taken. Preprocessed data were transferred into a personal computer and the standard HRV time-domain indices: standard deviation of total normal R-R intervals (SDNN), standard deviation of averaged means of normal R-R intervals over 5-minute periods (SDANN), triangular index (TI), and pNN50 were determined. The scatterplot area (0.2-1.8 second) was divided into 256 boxes, each of 0.1-second interval, and the number of paired R-R intervals was counted. The heart rate variability fraction (HRVF) was calculated as the two highest counts divided by the number of total beats differing from the consecutive beat by <50 ms. The HRVF was obtained by subtracting this fraction from 1, and converting the result to a percentage. The normal value of the HRVF was 52.7 +/- 8.6%. The 2-98% range calculated from the normal probability plot was 35.1-70.3%. The HRVF varied significantly with gender (female 48.7 +/- 8.4% vs male 53.6 +/- 8.6%, P = 0.002). The HRVF correlated with RRI (r = 0.525) and showed a similar or better relationship with SDNN (0.851), SDANN (0.653), and TI (0.845) than did the standard HRV measures with each other. Bland-Altman plot showed a good day-by-day reproducibility of the HRVF, with the intraclass correlation coefficient of 0.839 and a low relative standard error difference (1.8%). We introduced a new index of HRV, which is easy for computation, robust, reproducible, easy to understand, and may overcome the limitations that belong to the standard HRV measures. This index, named HRV fraction, by combining magnitude, distribution, and heart-rate influences, might become a clinically useful index of global HRV.

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 ∼53–61%, spec ∼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 ∼2.5 and ∼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.