BALTIMORE, MD — Among heart-failure patients with low left ventricular ejection fraction (LVEF) who received an implantable cardioverter defibrillator (ICD), the EF improved in 40% of patients during follow-up, which was associated with lower all-cause mortality and fewer appropriate shocks, in a new study[1]. However, even among patients whose LVEF improved to >35% during the 4.9-year follow-up, a few patients still had appropriate shocks in this small cohort.
The study by Dr Yiyi Zhang (Johns Hopkins University, Baltimore, MD) and colleagues, based on data from the Prospective Observational Study of Implantable Cardioverter-Defibrillators (PROSE-ICD), was published in the August 4, 2014 issue of the Journal of the American College of Cardiology.
"Since the LVEF is the primary indication by which a patient would get an ICD . . . if the LVEF improves to >35% at the time of the generator exchange [typically at 5 to 7 years after implantation], one could argue that the generator should not be replaced since the original indication . . . is no longer applicable," senior author Dr Alan Cheng (Johns Hopkins University) told heartwire from Medscape.
However, this study showed that "even if a patient's LVEF improves >35%, [he or she] still can experience an appropriate shock . . . [which] suggests that the decision to undergo generator exchange should not be guided solely by the change seen in LVEF until larger studies have been done to confirm or [disprove] our findings," he cautioned.
Dr Kristen Patton (University of Washington, Seattle, WA) who wrote an accompanying editorial[2] agreed, in a comment to heartwire . "I think these data add to what we know, so you can have a nuanced conversation [with a patient and explain] that if the LVEF is pretty normal, the risk of arrhythmia is much lower, but not zero," she said. However, longer, larger trials are needed to help guide the decision of whether a patient still needs ICD therapy. "How much improvement [in LVEF] is enough to say someone is safe without ICD therapy? We really don't know," she said.
LVEF and Appropriate Shocks, All-Cause Mortality
Previous studies have reported that 25% to 40% of patients who receive ICDs for primary prevention of sudden cardiac death improve their LVEF to >35%, but it is still unclear how improved LVEF affects risk of sudden cardiac death, Zhang and colleagues write.
They analyzed data from PROSE-ICD, which enrolled 1189 patients aged 18 to 80 who had systolic heart failure and were referred to four US centers for ICD implants for primary prevention.
A total of 538 patients had LVEF assessed at least once during follow-up and were included in the current analysis.
Of these, 353 patients had an ICD implanted because they had ischemic cardiomyopathy (MI >40 days before implant) with an LVEF <30% and NYHA class 1 to 3 heart failure or they had cardiomyopathy with LVEF <35% and NYHA class 2 or 3 heart failure.
The other 185 patients had a cardiac resynchronization therapy device with defibrillator capacity (CRT-D) implanted because they had LVEF <35% with NYHA class 2 to 4 heart failure.
The patients had an average age of 58.9 years, and most (70%) were men.
During a mean follow-up of 4.9 years, LVEF decreased in 13% of patients, improved in 40% of patients, and was unchanged in 47% of patients.
Patients with worsened LVEF were more likely to be older and have diabetes, ischemic cardiomyopathy, and a higher baseline LVEF.
During follow-up, 27 individuals experienced an appropriate shock and 96 patients died. Compared with patients with an unchanged LVEF, those with an improved LVEF had a significantly lower risk of having an appropriate shock during follow-up (hazard ratio [HR] 0.29; 95% CI 0.11–0.78), after adjustment for multiple variables.
Similarly, patients with an improved LVEF had a significantly lower risk of dying during follow-up (HR 0.33; 95% CI 0.18–0.59).
Among the 126 subjects whose LVEF improved to >35%, only four patients received a shock.
"Unsurprisingly, subjects implanted with biventricular pacing devices were more likely to experience LVEF improvement, but device type did not change the association with outcomes," Patton noted.
"These are small numbers, and the results of this study should be interpreted with appropriate caution," she writes.
Clinical Implications, Call for More Research
"As a cautionary note, we know that heart failure is progressive, and LVEF may improve and then worsen," Patton writes.
Similarly, Cheng advises that "clinicians who follow patients with ICDs should keep in mind that the LVEF is a dynamic measure of heart function," and as it changes, a person's risk for ventricular arrhythmias also changes. "This is perhaps most pertinent when patients with ICDs are faced with the need for a generator exchange . . . especially in patients whose benefit from an ICD is unclear as they get older," he said.
"If an ICD is not replaced, the patient may be unprotected, with catastrophic results," Patton writes. "For some, ICD therapy results in gradual accumulation of complications; for others, a life is saved," she notes, adding that "the perennial problem is in identifying which patient might be in which category.
"Some people want to be protected no matter what the risk is, [while others] shrug and say, 'Hey, I could be hit by a bus tomorrow,' and are okay taking the small risk," she commented. "The hardest conversations are when patients want the doctor to choose."
Other factors beyond LVEF seem to play a role in whether a person still needs an ICD. It would be "overly optimistic" to think that the risk for appropriate shocks would go to zero once LVEF is >35%, which is the "line in the sand" that was established from the large randomized SCD-HeFT clinical study, Cheng noted.
Similarly, Patton commented that "low EF is a marker of increased risk, but just a marker—we can't adequately risk-stratify the general population with normal EF."
Thus, Patton and the researchers both urge continued research to help clarify when it may be safe to forgo ICD-generator replacement.
"Randomized clinical trials of generator replacement in patients whose LVEF improved to >35% are necessary to provide the most convincing evidence as to whether ICD-generator replacement has a positive or negative impact in this particular patient population," Zheng and colleagues conclude.
"Even in this largest series of improved LVEF, there are but 134 subjects," Patton writes. Answering the essential question [should an ICD generator be replaced?] will require longer-term observational follow-up and integration with randomized trial data, in considerably more patients."
Zhang has no relevant financial relationships. Cheng has received honoraria from Boston Scientific, Medtronic, and St Jude Medical for participation in fellows' educational programs and advisory-committee participation. Disclosures for the coauthors are listed in the article. Patton has no relevant financial relationships.
Heartwire from Medscape © 2015 Medscape, LLC
Cite this: Improved LVEF May Negate Need for ICD: More Study Needed - Medscape - Jul 31, 2015.
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