News:Defribillators: Systematic Review of ICDs for Adults with LV Systolic Dysfunction
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August 23, 2007 By Scott P. Williams [1]
Edmonton, Canada: A systematic review of 12 randomized, controlled trials and 76 observational studies, all published between 1980 and 27 April, 2007, concludes that implantable cardiac defibrillators (ICDs) are efficacious and effective in reducing mortality among adults with left ventricular (LV) systolic dysfunction, although the majority of patients are never administered a shock. The paper was published in the most recent issue of Annals of Internal Medicine.
Ezekowitz et al. selected original research studies for the review to determine the efficacy of ICDs in treating patients with LV systolic dysfunction, as well as the effectiveness and safety of the devices when used in clinical practice. The research group defined the efficacy of ICDs as “the risks and benefits of [the] therapy when tested under ideal circumstances,” while the effectiveness of the devices was defined as “the risks and benefits of [the] therapy under usual clinical practice conditions.”
The original research studies incorporated in the systematic review all included at least 25 patients, and reported mortality or peri- or post-implantation complications with ICDs in adult patients. Further, for the purpose of the review, LV systolic dysfunction was defined by patients demonstrating a left ventricular ejection fraction less than or equal to 35%.
The efficacy of ICDs was determined based upon the mortality data from 12 randomized, controlled trials, which encompassed a total of 8516 patients. From these trials Ezekowitz and colleagues observed a 20% reduction in mortality among patients with LV systolic dysfunction (95% CI, 10% to 29%).
The data used to support the efficacy of ICDs was expanded upon with the addition of data from observational studies and randomized, controlled trials that did not report efficacy outcomes. These additional studies increased the number of patients to 26,840, and were used to evaluate the effectiveness of ICDs. Overall the effectiveness data yielded results similar to the efficacy data, with the observational studies displaying a 46% reduction in mortality (95% CI, 32% to 57%).
A total of 64 randomized, controlled trials and observational studies were used to evaluate the safety of ICDs. Ezekowitz et al. demonstrate that ICDs are generally safe for use in every day clinical practice. The research group observed an occurrence of 1.4 device malfunctions, 1.5 lead problems, and 0.6 implant site infections per one hundred patients. Additionally there was 99% success rate of implantation, and a 1.2% rate of peri-implantation death.
Although the research group concludes that ICDs are generally efficacious, effective and safe for use in clinical practice, they do state that the use of the devices involves some underappreciated risks. These risks include the possibility of inappropriate shocks or the chance of the device delivering no therapeutic discharges to the patient. Coupled together these two risks can lead to a decline in the quality of life for an ICD recipient.
The study was limited by the short duration and infrequent reporting of nonfatal outcomes among the studies reviewed. Additionally the lack of individual-patient data prevented the research group from exploring the benefits of ICDs among subgroups.
Overall, the study suggests that although ICDs are generally efficacious, effective and safe in clinical practice, there are a large number of ICD patients that never receive a therapeutic discharge. Therefore, further research on what makes a patient an ideal candidate for ICD implantation should further maximize the benefit of the devices while minimizing the patient’s risk.
<biblio> Justin A. Ezekowitz, MB, BCh, MSc; Brian H. Rowe, MD, MSc; Donna M. Dryden, PhD; Nicola Hooton, MPH; Ben Vandermeer, MSc; Carol Spooner, BScN, MSc; and Finlay A. McAlister, MD, MSc. Systematic Review: Implantable Cardioverter Defibrillators for Adults with Left Ventricular Systolic Dysfunction. Annnals of Internal Medicine. 21 August 2007. Volume 147, Issue 4: 251-262. </biblio>
