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Continuous ECG monitoring with an implantable loop recorder detected more cases of asymptomatic atrial fibrillation, but did not reduce the risk of stroke or improve overall survival, according to a randomized controlled trial.

Atrial fibrillation was diagnosed in 477 of 1,501 (31.8%) participants in the monitoring group and 550 of 4,503 (12.2%) participants in the control group (HR 3.17, 95% CI 2.81-3.59, P<0.001), reported Jesper Hastrup Svendsen, MD, of Copenhagen University Hospital in Rigshospitalet.

Detection of atrial fibrillation in the control group was discovered during routine clinic visits, he explained at a press conference during the virtual European Society of Cardiology congress. The study was published simultaneously in .

Oral anticoagulation was initiated in 445 patients (29.7%) in the monitoring group compared with 591 (13.1%) in the control group (HR 2.72, 95% CI 2.41-3.08, P<0.001).

However, greater detection of atrial fibrillation and subsequent use of anticoagulation failed to translate into protecting patients against stroke or death, Svendsen noted.

The primary outcome of stroke or systemic arterial embolism (315 strokes, three embolisms) occurred in 67 patients (4.5%) undergoing monitoring (0.88 events per 100 person-years, 95% CI 0.68-1.12) compared with 251 patients (5.6%) in the control group (1.09 events per 100 person-years, 95% CI 0.96-1.24), a difference that was not significant (HR 0.80, 95% CI 0.61-1.05, P=0.11), Svendsen said.

Cardiovascular death occurred in 43 participants (2.9%) in the monitoring group versus 157 (3.5%) in the control group (HR 0.83, 95% CI 0.59-1.16, P=0.27). Death from any cause occurred in 168 (11.2%) versus 507 (11.3%), respectively (HR 1.00, 95% CI 0.84-1.19, P=1.00).

"In a population of high-risk patients, atrial fibrillation was detected and treated much more often in those undergoing continuous loop recorder monitoring," Svendsen said. "We found a non-significant 20% reduction in risk of stroke, which was not accompanied by a similar reduction in cardiovascular mortality."

"More studies are needed but our findings may suggest that not all atrial fibrillation is worth screening for, and not all screen-detected atrial fibrillation merits anticoagulation," he added.

Commenting on the study, Stefan James, MD, of Uppsala University in Sweden, told 番茄社区app, "Obviously, having symptomatic atrial fibrillation or atrial fibrillation detected at a doctor's office is associated with a very high risk of stroke and should be absolutely treated. But if you are searching for incident short-acting periods of atrial fibrillation, that may be, on a population level, a different type of disease and a different type of risk associated with it. But we also need individual information about the patients so we have an idea of who we need to treat, so we can treat them correctly."

James also noted that there are additional costs with the continuous loop recorder, including the cost of the device, the cost of implanting the device, and the cost of anticoagulation if atrial fibrillation is discovered -- and yet there was no benefit.

"This is another reason why these devices should not be recommended," he said.

Because patients with atrial fibrillation are often asymptomatic and thus remain undiagnosed and untreated, Svendsen and team initiated this study to see if continuous monitoring using an implantable loop recorder, and subsequent anticoagulation if atrial fibrillation was detected, would reduce the risk of stroke or systemic arterial embolism in patients at risk.

Danish national registries were used to identify individuals ages 70 and older with at least one additional stroke risk factor: hypertension, diabetes, heart failure, or previous stroke. Patients with any previous documented history of atrial fibrillation were excluded from the trial. The mean age of participants was 74.7 years, and 47.3% were women. Median duration of monitoring was 39.3 months, and the median follow-up period was 64.5 months.

Under the study protocol, the device continuously recorded the heart's electrical activity. Every night, any ECGs indicating heart rhythm abnormalities were transferred remotely to a server for evaluation by clinicians. If atrial fibrillation lasting more than 6 minutes was diagnosed, patients were advised to start oral anticoagulation. The control group had a telephone consultation with a nurse once a year.

"I think that we should concentrate on addressing our concerns about atrial fibrillation on the patients in this study -- those above the age of 70, and those who have hypertension, diabetes, heart failure, or a prior stroke," suggested press conference moderator Carlos Aguiar, MD, of Hospital Santa Cruz in Lisbon.

"About a third of these people over the ... follow-up actually did have atrial fibrillation," he told 番茄社区app. "We should have conversations with these patients in clinical practice, to make sure they are alert to the signs and symptoms of atrial fibrillation, so they can bring that to the attention of their physicians before they have strokes."

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