Study: CRT-D Best When RV Pacing Is Needed

Candidates for right ventricular (RV) pacing with no class I indication for cardiac resynchronization therapy (CRT) still had better outcomes with a CRT defibrillator than a traditional implantable cardioverter defibrillator (ICD), according to a retrospective cohort study.

Compared with dual chamber ICDs, CRT defibrillators were associated with lower rates of 1-year all-cause mortality (13.3% vs 15.7%, adjusted HR 0.70, 95% CI 0.57-0.87) and fewer heart failure hospitalizations (13.5% vs 15.7%, adjusted HR 0.77, 95% CI 0.61-0.97).

Complication rates during implantation came out similar between the two types of devices (10.8% vs 9.3%), reported a group led by Ryan Borne, MD, of the University of Colorado in Aurora, in a study published online in JAMA Network Open.

“While the current study has limitations inherent in observational research, including inability to determine causality, it adds to the limited data that support the more frequent use of CRT among patients with mildly reduced LVEF [left ventricular ejection fraction] and anticipated high RV pacing requirement,” they concluded.

Their study included 3,100 Medicare beneficiaries in the National Cardiovascular Data Registry ICD Registry who received their devices from 2010 to 2016.

That span captured the years before and after the 2013 publication of BLOCK-HF, a trial that showed that patients with a bradycardia pacing indication and mildly reduced LVEF had better outcomes on biventricular pacing over standard RV pacing.

In 2018, CRT gained a class IIa recommendation for such patients in arrhythmia guidelines.

“While the outcome of death was not detectable in BLOCK-HF, we observed an association between CRT-D [CRT defibrillator] and death despite the fact that patients in the current study tended to be older, with lower LVEF and greater burden of comorbidities, including prior MI, hypertension, and diabetes,” according to Borne’s team.

CRT adoption varied substantially across hospitals, but use rose overall from 48.4% in 2010 to 60.9% in 2016 (P<0.01).

For the study, the authors included ICD Registry participants who were likely to require frequent RV pacing but did not have a class I indication for CRT, excluding those with a previous pacemaker or ICD. Outcomes were followed through Medicare claims data.

The 3,100 people included averaged 76.3 years of age at device implant. Four in five were men. Nearly 70% had ischemic heart disease, with a mean LVEF of 31.2%. About 40% had third-degree atrioventricular block and 30% second-degree block.

During the study period, 54.8% underwent CRT defibrillator placement and 45.2% ICD implantation.

Aside from the observational design of the study, its major limitations included the lack of specific information about device interventions (e.g. ICD shocks) and the reliance on data from a voluntary registry that may not be generalizable to non-participating centers, Borne and colleagues noted.

“Further randomized and real-world investigations are warranted to both confirm the findings seen in BLOCK-HF, which would strengthen the recommendation to a class I indication among those with reduced LVEF, and to potentially expand the use of CRT among patients with normal LVEF and the need for frequent RV pacing, particularly those with evidence of electrical dyssynchrony or wide QRS intervals at baseline,” they said.

“Ultimately, the risk of implanting a device with higher procedural complexity and reduction in battery longevity requiring more frequent generator changes needs to be weighed against the potential benefits,” according to the authors.