Silent A-fib That Progresses Signals a Higher Heart Failure Risk

When subclinical A-fib detected by implanted devices worsens, patients are at risk for future heart failure, an analysis of the ASSERT trial suggests, revealing a potential opportunity for heading off poor outcomes with lifestyle interventions.

The rate of heart failure hospitalization was higher in patients whose device-detected A-fib progressed to episodes lasting more than 24 hours or to clinically overt A-fib (8.9% vs 2.5% per year; adjusted HR 4.58; 95% CI 1.64-12.80), Jorge Wong, MD (Population Health Research Institute, McMaster University, Hamilton, Canada), and colleagues report in a study published online ahead of the June 12, 2018, issue of the Journal of the American College of Cardiology.

That finding raises the provocative possibility that targeting patients with progressive subclinical A-fib with either intensified heart failure therapy or lifestyle interventions to better control cardiovascular risk factors could reduce admissions for heart failure and maybe even mortality, Wong told TCTMD. He stressed, however, that such an approach would need to be tested in a randomized controlled trial.

The potential for prevention in this situation is tantalizing for N.A. Mark Estes III, MD (Tufts University School of Medicine, Boston, MA), who was not involved in the study.

“This is really an opportunity to prevent progression of A-fib, to prevent progression of heart failure,” he told TCTMD. “There are very few conditions in cardiovascular disease in which we can do really primordial prevention with lifestyle interventions. So I think clinicians should be aware of this new data, they should be aware of the clinical implications of it, and I think that clinical trialists and researchers should also move forward with a trial randomizing patients with subclinical A-fib over 6 minutes to lifestyle interventions versus standards of therapy and see if some of these key outcomes, such as heart failure hospitalizations, really can be influenced.”

There are very few conditions in cardiovascular disease in which we can do really primordial prevention with lifestyle interventions. N.A. Mark Estes III

Much of the focus in managing A-fib has been on preventing stroke, but heart failure remains a big problem, too, affecting about 40% of this population and causing 15% to 30% of deaths. Prior research has established a link between clinical A-fib and heart failure, but less is known about the potential relationship between subclinical A-fib captured by implantable devices and heart failure.

To explore the issue, Wong and colleagues turned to the ASSERT trial, which showed that among older patients with a history of hypertension, no clinical A-fib, and either a pacemaker or defibrillator, subclinical tachyarrhythmias were common and associated with a greater risk of ischemic stroke or systemic embolism. The current analysis focused on the 415 patients (mean age 77; 55% men) whose longest subclinical A-fib episode in the first year after enrollment was between 6 minutes and 24 hours.

Over a mean follow-up of 2 years, 15.7% of these patients progressed to having device-detected A-fib episodes lasting more than 24 hours or to clinical A-fib. Worsening was predicted by older age, higher body mass index, and a longer duration of subclinical A-fib in the first year.

The relationship between progression and heart failure hospitalization was maintained in several sensitivity analyses, including one in which patients with a prior history of heart failure were excluded (adjusted HR 7.06; 95% CI 1.82-27.30).

There were no associations between subclinical A-fib progression and stroke, vascular death, MI, or a composite of those three outcomes, although both the researchers and Estes point out that the study was underpowered for these comparisons.

‘Reasonable’ to Do Lifestyle Modification

Estes noted that prior studies of clinical A-fib show that lifestyle interventions—exercising, eating a healthy diet, and losing weight—lower arrhythmia burden and improve a variety of cardiovascular risk factors, and he said it’s logical to assume that similar benefits would be seen in the setting of subclinical A-fib.

“We don’t have proof from a prospective randomized trial, but the best available data would suggest that if you detect subclinical A-fib . . . intervening with lifestyle modifications would likely decrease progression to hospitalization for heart failure,” Estes said. Though that concept needs to be tested in future studies, it would be reasonable to use such an approach at this point, he added.

“I think certainly if somebody has subclinical A-fib, recommending lifestyle interventions with the hope that it’s going to prevent progression and the hope that it’s going to prevent heart failure hospitalizations is very logical, even though we don’t have the evidence base,” he said.

Wong agreed: “It definitely would be a wise approach. Although it was not proven in a randomized trial, it makes sense to control all the risk factors that we know that lead to atrial fibrillation—obesity, hypertension, sleep apnea, all those things. If we can do better at being more aggressive at targeting those things . . . that may decrease progression of subclinical atrial fibrillation and potentially decrease heart failure admissions.”

Taya Glotzer, MD (Hackensack University Medical Center, NJ), who wrote an editorial accompanying the study, also supports that strategy.

“Detecting subclinical A-fib on an implanted device is akin to having X-ray vision into a patients’ protoplasm, knowing that health is likely not going in the right direction,” she writes. “Therefore, at a minimum, when [it] is detected, lifestyle modifications should be made wherever possible: weight should be lost to modify obesity; therapies to treat sleep apnea should be implemented and used consistently; alcohol excess should be curtailed; smoking should be stopped; glucose levels in diabetics should be carefully controlled; and medications for coexisting conditions such as hypertension should be optimized to prevent disease progression.

“That, in itself, should lead to decreases in hospitalizations and morbidity for both A-fib and congestive heart failure,” Glotzer concludes.