Short- versus long-term ECG recordings for the assessment of non-linear heart rate variability parameters after beating heart myocardial revascularization
Department of Cardiac Surgery, University Clinical Center Maribor, Slovenia. Computers in Biology and Medicine
(Impact Factor: 1.24).
01/2009; 39(1):79-87. DOI: 10.1016/j.compbiomed.2008.11.005
Non-linear analyses of heart rate dynamics reveal subtle changes not evident from conventional heart rate variability measures. Traditionally, the information was inferred from 24-hour ECG recordings, making it less suitable for clinical application. Moreover, only few studies have attempted to evaluate the reliability of non-linear analyses in relation to varying proportion of artifacts in tracings. In 67 patients revascularized with beating-heart technique, fractal dimension and detrended fluctuation analyses were obtained from 24-hour Holter and 15-minute high-resolution ECG recordings pre and postoperatively. We found strong correlations of non-linear indices between 24-hour and 15-minute recordings (0.54-0.77, p<0.001), unaffected by proportion of artifacts.
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ABSTRACT: The application of continuous positive airway pressure (CPAP) produces important hemodynamic alterations, which can influence breathing pattern (BP) and heart rate variability (HRV). The aim of this study was to evaluate the effects of different levels of CPAP on postoperative BP and HRV after coronary artery bypass grafting (CABG) surgery and the impact of CABG surgery on these variables. Eighteen patients undergoing CABG were evaluated postoperatively during spontaneous breathing (SB) and application of four levels of CPAP applied in random order: sham (3 cmH₂O), 5 cmH₂O, 8 cmH₂O, and 12 cmH₂O. HRV was analyzed in time and frequency domains and by nonlinear methods and BP was analyzed in different variables (breathing frequency, inspiratory tidal volume, inspiratory and expiratory time, total breath time, fractional inspiratory time, percent rib cage inspiratory contribution to tidal volume, phase relation during inspiration, phase relation during expiration). There was significant postoperative impairment in HRV and BP after CABG surgery compared to the preoperative period and improvement of DFAα1, DFAα2 and SD2 indexes, and ventilatory variables during postoperative CPAP application, with a greater effect when 8 and 12 cmH₂O were applied. A positive correlation (P < 0.05 and r = 0.64; Spearman) was found between DFAα1 and inspiratory time to the delta of 12 cmH₂O and SB of HRV and respiratory values. Acute application of CPAP was able to alter cardiac autonomic nervous system control and BP of patients undergoing CABG surgery and 8 and 12 cmH₂O of CPAP provided the best performance of pulmonary and cardiac autonomic functions.
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Alcohol dependence is associated with an increased likelihood of cardiac events. Reductions in heart rate variability (HRV) may be one mechanism linking dependence with these events. HRV may also be related to poor social functioning and the lack of impulse control commonly observed in alcohol-dependent individuals. However, prior studies on the impact of alcohol dependence on HRV have reported contradictory findings highlighting the need for a meta-analysis.
Studies comparing short-term HRV in alcohol-dependent populations and healthy controls who were nondependent were considered for meta-analysis. Only studies reporting findings from participants without cardiovascular disease were included in the analysis.
Meta-analyses were based on 6 articles that fulfilled inclusion criteria, comprising a total of 177 alcohol-dependent participants and 216 nondependent participants. Alcohol-dependent participants displayed reduced HRV (Hedges' g = -0.6, p > 0.001) in comparison with nondependent participants. No differences were observed between the summary effect sizes obtained from different HRV domains (Q = 1.19, p = 0.55).
Alcohol dependence is associated with reduced HRV, an effect associated with a medium effect size. Findings highlight the importance of monitoring alcohol-dependent patients for cardiac disease and emphasize the need for cardiovascular risk reduction strategies in these patients.
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