CABANA: Ablation Bests Drugs for AF in Racial/Ethnic Minorities

Fran Lowry

July 06, 2021

Catheter ablation appears better than drug therapy for treating atrial fibrillation (AF) in racial and ethnic minorities, according to a new look at CABANA trial data.

CABANA, which was undertaken to compare catheter ablation and rate-control or rhythm-control drug therapy for AF, concluded there was no significant difference between the two strategies in improving the trial's composite primary outcome of death, disabling stroke, serious bleeding, or cardiac arrest.

But a closer look at a subgroup of participants reveals an important difference in outcome among racial and ethnic minorities.

In that group, which made up about 10% of the CABANA study population, catheter ablation was significantly better at treating AF than was drug therapy, producing roughly a 70% relative reduction in the primary endpoint and all-cause mortality.

The benefit for catheter ablation, which was not seen in the nonminority participants, appeared to be due to worse outcomes with drug therapy, the investigators report in an article published July 5 in the Journal of the American College of Cardiology.

Dr Kevin Thomas

"The study really highlights the importance of trying to secure an inclusive and diverse population in clinical trials," lead author Kevin L. Thomas, MD, Duke University Medical Center, Durham, North Carolina, told theheart.org | Medscape Cardiology.

"When we focused on the racial and ethnic minorities who were included in CABANA, the findings were different. This was a surprise," Thomas said.

"The findings from the secondary analysis of CABANA suggest that racial and ethnic minorities that are treated with drugs compared with ablation do worse," he said. "If we can validate this in a larger sample of patients and this does in fact turn out to be true, then we would change how we practice medicine. We would have discussions with these populations about the benefits of ablation over drugs, and this would be important information to help guide our practice."

The investigators analyzed data from 1280 participants enrolled in the North American arm of CABANA. Of these, 127 (9.9%) were of racial or ethnic minorities, as defined by the National Institutes of Health, and were randomly assigned to receive ablation (n = 62) or drug therapy (n = 65).

Compared with nonminorities, participants of racial and ethnic minorities were younger (median age, 65.5 years, vs 68.5 years) and were more likely to have NYHA functional class ≥II symptoms (37.0% vs 22.0%), hypertension (92.1% vs 76.8%), and an ejection fraction <40% (20.8% vs 7.1%).

The overall median follow-up was 54.9 months. Among ethnic and minority participants, the median follow-up was 48 months, compared with 55.5 months for the nonminority participants.

Although there was no significant difference in the primary composite endpoint in the main CABANA trial, among racial and ethnic minorities treated with ablation, there was a 68% relative reduction in the trial's primary endpoint (adjusted hazard ratio [aHR], 0.32; 95% CI, 0.13 – 0.78) and a 72% relative reduction in all-cause mortality (aHR, 0.28; 95% CI, 0.10 – 0.79).

The 4-year Kaplan-Meier primary event rates were similar in both racial/ethnic minority and nonminority groups that received catheter ablation (12.3% vs 9.9%).

However, the 4-year event rate was much higher among racial and ethnic minority participants than nonminority patients who received drug therapy (27.4% vs 9.4%).

The corresponding all-cause 4-year mortality rates were 8.1% and 6.7%, respectively, in the ablation arm and 20.2% and 4.5%, respectively, in the drug arm.

Thomas and colleagues point out that heart failure in racial and ethnic minorities, particularly Black patients, is typically due to hypertensive heart disease, whereas in non-Hispanic White patients, it is overwhelmingly associated with coronary artery disease. "Our results in CABANA, therefore, raise the possibility that the variations in the prevalence of the heart diseases associated with AF might account for differences in the benefits observed with ablation therapy."

Prior data suggest that AF in the setting of heart failure with either reduced or preserved ejection fraction has substantially better clinical outcomes with ablation vs drug therapy, but most studies either do not report racial/ethnic demographics or enroll very low numbers of minorities, they note.

Dr Andrea Russo

Andrea M. Russo, MD, a professor of medicine at Cooper Medical School of Rowan University, Camden, New Jersey, asks why drug therapy might result in worse outcomes in racial and ethnic minorities in an accompanying editorial.

"Those who received ablation did better than those who received drugs, and the main reason for that is not that ablation works better in minorities than nonminorities, it's because drugs are worse in minority patients than they are in nonminority patients. This means that either the way we are using the drugs or the ones that we are using in minority patients are resulting in worse overall outcomes," Russo told theheart.org | Medscape Cardiology.

"The minority patients were younger and yet had more hypertension at baseline. There could be all kinds of factors contributing to their health," she said.

Russo agrees with Thomas on the need to enroll diverse populations in clinical trials.

"Dr Thomas should be commended. He did a fabulous job of looking at this issue. It's only 10% of the group, but it is better than what we have had so far, and this is a start," Russo said. "It's bringing recognition to how important it is to make sure that we include underrepresented populations in these trials, and also that we offer all appropriate therapies to everyone."

Thomas reports financial relationships with Janssen, Pfizer, Biosense Webster. Russo reports no relevant financial relationships. The study was funded by the National Institutes of Health, St. Jude Medical Foundation and Corporation, Biosense Webster, Medtronic, and Boston Scientific.

Correction: An earlier version of the story stated that the 4-year event was much higher among nonminority participants who received drug therapy. The higher event rate was among racial and ethnic minority participants.

J Am Coll Cardiol. 2021;78:126-138 and 139-141. Abstract, Editorial

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