Atrial Fibrillation May Make HCM Even More Dangerous

The role of atrial fibrillation in hypertrophic cardiomyopathy (HCM) is unclear. There’s a body of research that has shown that patients with HCM with atrial fibrillation are at increased risk of mortality related to heart failure and other serious consequences such as stroke. But several years ago, a retrospective study published in Circulationof more than 1,500 hypertrophic cardiomyopathy patients at the Tufts Medical Center Hypertrophic Cardiomyopathy Institute in Boston found otherwise. About 20% of the 1,500 patients had atrial fibrillation, and the researchers found no difference in outcome between HCM patients with atrial fibrillation and those without.

But a Japanese research team led by Toru Kubo, M.D., Ph.D., of Kochi Medical School paint a different picture in findings published this month in ESC Heart Failure, the open-access journal of the Heart Failure Association of the European Society of Cardiology. They argue that findings from their study of 293 HCM patients suggest that atrial fibrillation is not just a marker of poorer outcomes for HCM patients but may have a causative role in adverse outcomes although they were also careful to note that their observational study can’t prove a cause and effect. One implication of their findings, they say, is a need for more careful management of atrial fibrillation in HCM patients, particularly those for whom atrial fibrillation has been newly diagnosed.

Their study was based on data collected from a registry of cardiomyopathy patients in the Kochi prefecture, a rural area on the Shikoku Island in southern Japan. As they were entered into the registry, 86 of the 293 patients (29%) had documented atrial fibrillation. The patients with atrial fibrillation at registration were more symptomatic than those without it. They also had more advanced left atrial and ventricular remodeling. During an average follow-up period of six years, the HCM patients with atrial fibrillation also had an increased risk of adverse events related to HCM.

Chart from study in ESC Health Failure shows that the rate of adverse events among those with new-onset atrial fibrillation quickly matches the rate among the HCM patients who had an atrial fibrillation diagnosis when they were entered into a registry of myopathy patients.

But in their findings reported in ESC Heart Failure, the Japanese researchers zeroed in on the 31 patients who developed atrial fibrillation during the follow-up period. More than half (55%) of those new onset cases had an adverse event related to HCM. They highlighted the finding that the rate of adverse events in the new onset group soon matched the rate among those diagnosed with atrial fibrillation when they were entered into the registry. That rate and the way it converges with the rate among those with a diagnosis of atrial fibrillation at registration suggests that atrial fibrillation may increase the chances of adverse events among patients with HCM, said Kubo and the other researchers.

“Given that AF (atrial fibrillation) might be a trigger for worsening disease condition in HCM, aggressive intervention such as AF catheter ablation or the Maze procedure at surgical myectomy can improve outcomes,” they wrote in ESC Heart Failure.

They acknowledged their study’s limitation, which included a relatively small group of patients and the lack of systematic monitoring for atrial fibrillation, which could mean that some cases of atrial fibrillation were not diagnosed.