Differential Index: A Simple Time Domain Heart Rate Variability Analysis with Prognostic Implications in Stable Angina Pectoris

Abstract

Objectives: To examine the usefulness of time domain heart rate variability (HRV) measurements by a simple graphical method, the differential index (DI), in prognostic assessments of patients with chronic stable angina pectoris. Methods: HRV measurements in the time domain by DI were compared to conventional measurements of standard deviation of all normal-to-normal intervals (SDNN), percent of differences between adjacent normal RR intervals >50 ms (PNN50) and square root of the mean of the sum of squares of differences between adjacent normal RR intervals (RMSSD) from 24-hour ambulatory electrocardiographic recordings in 678 patients in the Angina Prognosis Study in Stockholm. The patients received double-blind treatment with metoprolol or verapamil. Main outcome measures were cardiovascular death or non-fatal myocardial infarction during follow-up (median 40 months). Results: Patients suffering cardiovascular death (n = 30) had lower DI, SDNN and PNN50 (all p < 0.001). In a multivariate Cox model, DI below median independently predicted cardiovascular death (p = 0.002), as did SDNN (p = 0.016) and PNN50 (p = 0.030), but not RMSSD (p = 0.10). The separation of survival curves was most pronounced and specificity was slightly better with DI. DI and PNN50 increased with metoprolol but not verapamil treatment. Short-term treatment effects were not related to prognosis. Conclusions: Low time domain HRV carries independent prognostic information regarding cardiovascular death in stable angina pectoris. The simple DI method provided equally good or better prognostic information than conventional, more laborious HRV methods.

Development of electrocardiogram intervals during growth of FVB/N neonate mice

“…We found all data points from PND14 onward displayed a value of less than 10%, with most less than 5%. These values are comparable to those found in adult humans in recent studies [34,35]. As with heart rate and heart rate variability, a strong interaction effect was present between gender and age ( P ≤ 0.01).…”

“…Supporting this alternative explanation, data from neonate rats indicates that autonomic neurotransmission continues to develop in the heart from PND4-15 [45], and that pharmacological modulation of the autonomic nervous system has altered/reduced effects in early neonates [46]. In adult mice, we observed pNN6 values to be consistent with control groups of humans in clinical studies [34,35]. Together, these demonstrate that variability parameters can be applied to mice of varying ages in studies of disorders such as sudden infant death syndrome (SIDS), sudden cardiac arrest, atrial fibrillation, aneurysm, congestive heart failure and sustained ventricular tachycardia.…”

“…Measures of variability in heart rate have demonstrated utility as indicators of impaired autonomic function and as signals predictive of adverse cardiac events [35,38-40]. We find heart rate variability to be lower in neonates than in adult mice, with values in young neonates (PND2-4) particularly low.…”

Heart rate variability - current diagnosis of the cardiac autonomic neuropathy. A review

“…3) (ref. 29 ), differential index 30 or scatterplots, determining by the type of points distribution the HRV level (Poincaré or Lorenz plots) (ref. 31 ).…”

Long‐term stability of heart rate variability in chronic stable angina pectoris, and the impact of an acute myocardial infarction

“…In that study, we followed HRV over a period of 3 years (Forslund et al. , 2002; Björkander et al. , 2008).…”