Increase in the embedding dimension in electrocardiograms of adult and paediatric patients with ventricular arrhythmia and congestive heart failure.

D. S. ANDRES; I. M. IRURZUN; M. M. DEFEO; J. BLEIZ; E. E. MOLA; D. PEREZ CASAL; J. PAUL

CIRCULATION

LIPPINCOTT WILLIAMS & WILKINS

Año: 2008 vol. 117 p. 103 - 103

0009-7322

Introduction. Human electrocardiograms exhibit complex behavior. The study of the heart rate variability (HRV) in normal and pathological conditions might provide non-invasive insights into the cardiovascular system. Objective a) To test two non-linear HRV indexes: the false nearest neighbor fraction (FNNF10) and the embedding dimension (EDIM) in patients with ventricular ectopic beats (VEB) and congestive heart failure (CHF), and to characterize their changes with age. b) To compare these indexes with the known pNN50 and RMSSD. Methodology Three groups were studied: healthy individuals (control group, CG) ranging from 5 to 74 years old (n83), patients with VEB (n=46) and patients suffering from CHF (n=29). We considered those younger than 16 as pediatric persons. RR-interval time series were obtained from 24-hour Holter recordings and used to determine statistic and non-linear properties of HRV. The false nearest neighbor (FNN) method was used to calculate the EDIM. The FNN curve is constructed as a function of the phase space dimension (DIM), and EDIM is defined as the value of DIM at which it reaches a constant value. The FNN value at a given value of DIM is called false nearest neighbor fraction and its value at DIM=10 (FNNF10) is used as a non-linear measure of the HRV to quantify the departure from a normal behavior. Results In CG values of 7<EDIM<10 were found, independently of age. The FNNF10, pNN50 and RMSSD showed a progressive decrease with age. Between extreme age groups younger than 11 and older than 60, the mean difference showed high statistic significance for the three indexes (p<0.001). The EDIM was higher than normal (EDIM=10) for every patient with more than 3000 VEBs/24h, showing a correlation between EDIM and the number of VEBs/24h. The FNNF10 was progressively incremented in both the VEB and CHF groups. It discriminated between CG, VEB and CHF groups with high statistic significance (p was always 0.0001). The RMSSD showed high discriminative power between CG and CHF or VEB (p<0.0001) for adult population while for children its power was smaller (p<0.01). The pNN50 was unable to distinguish between CG and CHF (p<0.58) and between pediatric CG and VEB (p<0.57). In adults its discriminative power was weaker than the other indexes (p<0.05). Conclusions 1) The FNNF10 decreases with age, but the EDIM, which is related to the number of variables that govern the cardiac dynamics, is independent of age. An increase in the FNNF10 occurs and is associated with VEB and CHF in both adult and pediatric populations and may therefore reflect abnormalities in the left ventricular or autonomic system function. 2) The pNN50 and RMSSD also decrease with age. The performance of the FNNF10 to discriminate between healthy and CHF groups and VEB and CHF is better than that of the RMSSD for children and similar in adults. The pNN50 shows a weak discriminative power for all the groups studied in comparison to the other indexes.