PubMed · 14285161
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B PHIBBS. 1965. MONITORED EXERCISE ELECTROCARDIOGRAMS.. https://pubmed.ncbi.nlm.nih.gov/14285161/
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Depressed heart rate variability (HRV) is a powerful independent predictor of a poor outcome in patients with chronic and stable congestive heart failure (CHF). However, the prognostic value of HRV analysis in patients hospitalized for decompensated CHF is not known. The aim of this study was to investigate whether HRV parameters obtained during admission for decompensated CHF could predict survival after hospital discharge. We studied 199 patients (131 men, aged 60 +/- 14 years) with a previous diagnosis of New York Heart Association class III or IV CHF who were admitted to the hospital for decompensated CHF. Twenty-four-hour Holter recordings were obtained on admission, and measures of HRV were calculated in the time and frequency domain. During a mean follow-up of 312 +/- 150 days, 40 patients (21.1%) died. Kaplan-Meier analysis indicated that patients with SD of the RR intervals over a 24-hour period (p = 0.027), SD of all 5-minute mean RR intervals (p = 0.043), total power (p = 0.022), and ultra-low-frequency power (p = 0.008) in the lower tertile were at a higher risk of death. In a multivariate Cox regression model, the same indexes in the lower tertile were independent predictors of mortality: SD of the RR intervals over a 24-hour period (risk ratio [RR] 2.2, 95% confidence interval [CI] 1.05 to 4.3, p = 0.036), SD of all 5-minute mean RR intervals (RR 2.1, 95% CI 1.05 to 4.2, p = 0.04), total power (RR 2.2, 95% CI 1.08 to 4.2, p = 0.03), and ultra-low-frequency power (RR 2.6, 95% CI 1.3 to 5.3, p = 0.007). Therefore, the severity of autonomic perturbations during hospital admission for CHF decompensation, as reflected by measures of overall HRV, can predict survival after hospital discharge. Together with previous studies, our findings suggest that indexes of overall HRV provide useful prognostic information in the full spectrum of CHF severity.
PURPOSE OF REVIEW: Recent progress in understanding the role of the autonomic nervous system in the development of cardiac arrhythmias is reviewed. The focus is on the translation of basic principles of neural control of heart rhythm that have emerged from experimental studies to clinical applications. RECENT FINDINGS: Recent studies have made significant strides in defining the function of intrinsic cardiac innervation and the importance of nerve sprouting in electrical remodeling. A recurring theme is that heterogeneity of sympathetic innervation in response to injury is highly arrhythmogenic. In addition, both sympathetic and parasympathetic influences on ion channel activity have been found to accentuate electrical heterogeneities and thus to contribute to arrhythmogenesis in the long QT and Brugada syndromes. In the clinic, heart rate variability continues to be a useful tool in delineating pathophysiologic changes that result from the progression of heart disease and the impact of diabetic neuropathy. Heart rate turbulence, a noninvasive indicator of baroreceptor sensitivity, has emerged as a simple, practical tool to assess risk for cardiovascular mortality in patients with ischemic heart disease and heart failure. Evidence of the proarrhythmic influence of behavioral stress has been further bolstered by defibrillator discharge studies and ambulatory ECG-based T-wave alternans measurement. SUMMARY: The results of recent investigations underscore the importance of the autonomic influences as triggers of arrhythmia and provide important mechanistic insights into the ionic and cellular mechanisms involved.
PURPOSE OF REVIEW: Continued growth in the elderly population and expanding indications have resulted in a progressive increase in the number of implants of pacemakers and defibrillators. Concomitant with these expanding numbers, more leads require removal, due especially to mechanical dysfunction, the need to upgrade to more complex devices, or local or systemic infection. Further, leads have become more complex, particularly for defibrillator systems, resulting in the development of powered extraction sheaths to expedite their removal. For these reasons, it is important to understand the expanding indications, procedural aspects, and limitations of arrhythmia device extraction. RECENT FINDINGS: Expanded indications for lead extraction include upgrade to more complex systems, particularly pacemaker to defibrillator or biventricular device, extraction through occluded vasculature to produce a conduit for reimplantation, more frequent removal due to vascular overload with multiple leads, and a finite frequency of infection, occurring particularly with device replacement or revision. Powered sheaths now include laser and electrocautery systems, both improving the ease of lead explantation. SUMMARY: Complication rates remain low but constant with extraction of larger numbers of leads using new technologies. Expansion of the use of biventricular systems, with implantation of coronary sinus electrodes, will continue to challenge lead extraction in terms of technology and safety. Design of leads that are easier to remove remains of paramount importance.