Age Likely Explains Pacemaker vs ICD Survival Difference in HF

Daniel M. Keller, PhD

April 14, 2022

Pacemakers do not result in lower survival than implantable cardiac defibrillator (ICD) devices in patients undergoing cardiac resynchronization therapy (CRT) for heart failure, a large health claims analysis suggests.

Unadjusted data gave a survival edge to defibrillator devices, but when adjusted for age, there was no difference, indicating that age differences accounted for most of the observed survival difference.

For patients who have had a previous life-threatening arrhythmia, an ICD is imperative, but this group is a small minority of patients implanted with a CRT device. So the question remains whether most CRT patients should receive a device with defibrillator function, with its potential complications, particularly inappropriate shocks, the emotional stress they may cause, as well as significant added cost.

With a lack of head-to-head evidence and recommendations for individual decision-making in this area, even in recent separate heart failure and pacing guidelines of the European Society of Cardiology, there is uncertainty over which kind of device to use. "And this is reflected in huge variations in clinical practice," Nikolaos Dagres, MD, Heart Center of Leipzig, Germany, told attendees at the European Heart Rhythm Association (EHRA) 2022 Congress in Copenhagen.

So, based on conflicting observational data and uncertainty of whether defibrillation capability improves prognosis of patients undergoing CRT for heart failure, investigators conducted the Re-evaluation of Optimal Re-synchronisation Therapy in Patients With Chronic Heart Failure (RESET-CRT) study, a publicly funded project in Germany. This retrospective, observational part of the study involved 2722 patients who received a CRT-defibrillator (CRT-D) and 847 patients who received a CRT-pacemaker (CRT-P) from 2014 to 2019.

"The observational path was conducted in parallel with the ongoing randomized trial, aiming to compare the survival in health claims data of one large German statutory health insurance…[and] applying the same inclusion and exclusion criteria as in the [RESET-CRT] randomized trial," Dagres said.

The participants had symptomatic chronic heart failure from ischemic or nonischemic cardiomyopathy, were in New York Heart Association class II, III, or ambulatory IV, had a left ventricular ejection fraction of at least 35%, and were on optimal medical therapy for at least 3 months. Excluded were patients with indications for implantation for secondary prevention and those with a previous CRT implantation.

Age and Death

At baseline, the average age of the CRT-P group was 76.7 years and of the CRT-D group was 69.9 years. Renal dysfunction stage III (35% vs 28%) and stage IV (7% vs 4%) were more common in CRT-P than in CRT-D patients, whereas diabetes was more common in CRT-D patients (36% vs 32%). Atrial fibrillation was more prevalent in the CRT-P group than in the CRT-D group (59% vs 41%), reflecting what is seen in clinical practice, Dagres noted.

At a median follow-up of 2.4 years, 24% of the CRT-P group had died, compared with 19% of the CRT-D group (unadjusted hazard ratio [HR], 1.63; < .001), the raw data indicating a significant survival benefit for CRT-D.

"But adjusting just for age...this difference became not significant," (HR, 1.13; P =.165), Dagres said. "And adjusting for further comorbidities, it disappeared completely with a hazard ratio of 0.99 (P = .89), meaning an almost identical survival of the two populations."

When the groups were stratified by age — 65 years or younger, 65 to 75 years, and older than 75 years — no significant difference between CRT-D and CRT-P in the cumulative incidence of death was observed in any of the three groups (P for interaction = .598).

"Age differences accounted in our study for the greatest part of the observed survival difference," he said. "These results corroborate the need for a randomized comparison."

The study was published online April 3 in the European Heart Journal to coincide with the presentation.

Cecilia Linde, MD, PhD, Karolinska Institute, Stockholm, commented that it is not "self-evident that everybody should get an ICD" and that if patients were properly informed about who will benefit from them and what the risks are, they may not even want such therapy. "But doctors follow the guidelines...unevenly across Europe. Up to 75%, on average, do implant a CRT-D."

The study used data from Barmer, a large statutory health insurer that covers about one-tenth of the German population. The dataset comprised patients with ischemic heart disease and those with dilated cardiomyopathy. About 75% of them had received a CRT-D and the rest, a CRT-P. "So the method there is quite highly justified. You did analyze it with sophisticated methods," Linde told Dagres.

She noted that the CRT-P patients were nearly 7 years older than in the CRT-D patients, had somewhat lower renal function, and had more atrial fibrillation, but otherwise the groups were largely equivalent, with 25% to 27% having nonischemic cardiomyopathy, respectively.

Reiterating the conclusion that age mainly accounted for any higher mortality, even in younger age groups, with some effect of comorbidities, Linde said that it "further spurs us to be very careful when we select a CRT-D or a CRT-P, and there we have help from the EHRA guidelines, from the heart failure guidelines, which balance the risk of sudden versus nonsudden cardiac death."

As for limitations of the study, she noted that the Barmer health insurance database does not give information about things that are predictive of CRT response, such as Q wave, left ventricular ejection fraction, "or if indeed anybody was upgraded from a CRT-P to CRT-D."

Linde said randomized clinical trials as part of RESET-CRT that compare CRT-D with CRT-P in patients on optimal medical therapy will better guide choice of modalities. Until then, practitioners will need to mainly rely on clinical judgment in selecting patients for each device.

The study was funded by the Innovation Committee of the Federal Joint Committee (G-BA) of Germany. Dagres reported no conflicts of interest. Linde disclosed research grants from the Swedish Heart-Lung-Foundation and Stockholm County Council, the Swedish Royal Academy of Science, and Roche Diagnostics; and speaker honoraria from Astra-Zeneca, Bayer, Boehringer Ingelheim, Novartis, Vifor, Medtronic, Abbott, Micropore, and Impulse Dynamics.

Eur Heart J. Published online April 3, 2022. Full text

European Heart Rhythm Association (EHRA) 2022.

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