Real-World Ablation Benefits More Modest Than CASTLE-AF Results Indicate

Xiaoxi Yao, PhD

New research from a team of Mayo Clinic physicians is shedding new light on the potential benefits of catheter ablation in heart failure patients with atrial fibrillation (AF).

While CASTLE-AF results indicated catheter ablation resulted in a 38% reduction in risk of death and hospitalization for worsening heart failure, investigators found the effect of ablation to be more modest in real-world settings.

"Randomized clinical trials are the gold standard for evaluating new medical treatments or procedures," said lead investigator Xiaoxi Yao, PhD, a Mayo Clinic health services researcher, in a statement. "However, often their results are not necessarily applicable across a more heterogeneous group of people. Sometimes results cannot be replicated or are simply not as striking when interventions are tested across a broader population."

To expand on the results seen in CASTLE-AF, which contained just 363 individuals, Yao and a team of Mayo Clinic colleagues designed a study to analyze patients with HF and AF from the OptumLabs Data Warehouse. Using this database, investigators identified a study population consisting of 289,831 patients who underwent an ablation procedure (7465) or drug therapy alone (282,366) from 2008 through August 2018.

The mean age of study participants was 73.2±10.3 years and 47.6% were female. Of the individuals in this dataset, which investigators noted was 800 times larger than that of CASTLE-AF, approximately 91% would not have met CASTLE-AF inclusion criteria, 15.5% would have met at least 1 exclusion criteria, and 7.8% would have been eligible for the trial.

The primary outcome of the study was a composite endpoint of all-cause mortality and HF hospitalization. Cox proportional hazards regression was sued by investigators to compare ablation to medical therapy and propensity score overlap weighting was used to balance ablated and drug-treated patients on 90 baseline characteristics.

Analyses revealed ablation was associated with a lower risk of the primary outcome of all-cause mortality and HF hospitalization (0.81, 0.76-0.87, P <.001), and a lower risk of all-cause mortality (HR 0.67, 0.62-0.74, P <.001). However, ablation was not associated with a reduction in risk of HF hospitalizations (HR 1.02, 0.94-1.10, P = .67) or cerebrovascular accident (HR 0.98, 0.82-1.17, P = .81).

When examining outcomes based on trial eligibility, investigators found ablation was associated with a lower risk of the primary endpoint in patients eligible for CASTLE-AF (HR 0.82, 0.70-0.96, P = .01) and those who would have failed to meet inclusion criteria (HR 0.79, 0.73-0.86, P <.001, but not among those who would have been excluded (HR 0.97, 0.81-1.17, P = .75).

Based on the results of their analyses, investigators suggest that while the benefit of ablation was apparent the effects in practice appeared to be attenuated compared to those seen in the CASTLE-AF trial.

"Our study is especially important because it provides complementary evidence in a case where very few clinical trials have been conducted," said Peter Noseworthy, MD, a cardiologist at the Mayo Clinic. "In addition, a large observational study provides a more realistic picture of treatment effects for our everyday patients."

This study, “Generalizability of the CASTLE-AF Trial: Catheter Ablation for Patients with Atrial Fibrillation and Heart Failure in Routine Practice,” in HeartRhythm.