Posted on 08/24/2012

HALIFAX, NOVA SCOTIA--Real-world primary prevention using implantable cardioverter-defibrillators (ICDs) conferred a significant survival benefit for patients at risk for sudden cardiac death, Canadian researchers found.

Among patients who had an ICD placed, the hazard ratio for all-cause mortality was 0.46, according to Ratika Parkash, MD, from the Queen Elizabeth II Health Sciences Center in Halifax, Nova Scotia, and colleagues.

In addition, after adjustment for factors such as age, drug therapies, ejection fraction, and propensity score, a significant difference in mortality remained, the researchers reported in the August issue of Circulation: Arrhythmia and Electrophysiology.

Clear benefits have been demonstrated in clinical trials for the use of ICDs as primary prevention in patients with conditions such as congestive heart failure and acute coronary syndrome, but it has not previously been shown if real-world clinical use would echo those results.

Moreover, the increasing numbers of patients who survive these events -- and the exploding senior population in general who could be candidates for ICDs -- "increases the importance of understanding the magnitude of benefit that may be expected and the importance of appropriately applying this therapy," the researchers stated.

So they undertook a comparison of a cohort of 290 patients from a comprehensive ICD registry and a second cohort from a registry of all patients in the province hospitalized with congestive heart failure or an acute coronary syndrome.

Among the second group, which included 717 patients, 116 (16%) received an ICD, while the remaining 601 were considered a no-ICD group in the study analysis.

The rate of 5-year survival among patients in the ICD group was 78.6%, compared with 61.2% for patients with no ICD. After adjustment for propensity quintile to control for variables that might influence the decision to use the device, the 5-year survival was 78.8% among patients with ICDs and 66.5% for those without. Accordingly, mortality rates in the ICD and non-ICD groups at 5 years were 21% and 33%, which translates into a 43% decrease in all-cause mortality risk, according to the researchers.

During a mean follow-up of 2.7 years, 26% of patients with an ICD had had an appropriate treatment from the device, either a shock or pacing to prevent tachycardia.

"The mortality benefit in the ICD may well be derived from the potential life-saving therapies from their implantable defibrillator," the researchers observed.

Survival in this study associated with ICD use was higher than in the clinical trials, possibly because of the lengthy follow-up, they noted.

"ICDs can have a significant impact on quality of life because of both appropriate and inappropriate shocks," Parkash and colleagues cautioned.

Nonetheless, in an accompanying editorial, Rachel Lampert, MD, of Yale University, commented on the contribution of studies such as this.

"This and other observational studies complement the well-known [randomized controlled trials], showing improved survival with primary prevention ICDs to provide compelling evidence that the benefit of primary prevention ICDs can and should be generalized to the real world," she wrote.


SOURCE: MedPage Today