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Study finds high rate of subclinical AF using implantable cardiac monitor

By Nicole MacKee
Subclinical atrial fibrillation (AF) may be present in as many as 40% of older patients at high risk of AF and stroke, according to research presented at the recent European Society of Cardiology Congress, in Barcelona.

The industry-sponsored REVEAL AF study – also reported in JAMA Cardiology – enrolled 446 participants with a CHADS2 score of 3 or greater (or a score of 2 with at least one additional risk factor, such as coronary artery disease, sleep apnoea or chronic obstructive pulmonary disease). About 90% of these participants had nonspecific symptoms – such as fatigue, dyspnoea and/or palpitations – that may be compatible with AF. Of these participants, 385 received an implantable cardiac monitor.

After 18 months, 29.3% of participants with an implantable cardiac monitor had experienced AF lasting six or more minutes, and by 30 months, 40.0% of patients had had at least one episode of AF lasting six minutes or more.

The median age of participants was 71.5 years, and the researchers found that the median time from the insertion of the device to first AF episode was 123 days.

Of the patients with AF, 13 (10.2%) had one or more episode lasting 24 hours or longer, and 72 (56.3%) were prescribed anticoagulation therapy.

At 18 months, the researchers found a similar incidence of AF among those with CHADS2 scores of 2 (24.7%), 3 (32.7%) and 4 or greater (31.7%).

Professor Garry Jennings, the National Heart Foundation of Australia’s Chief Medical Advisor, said the rate of AF detected in the study was ‘very high’, but consistent with other data.

‘It is generally quite plausible,’ Professor Jennings told Cardiology Today. ‘The selection of people with a high CHADS2 score may be the key.’

The author of an accompanying editorial in JAMA Cardiology noted that the high rate of incident AF detected in the study suggested that screening with implantable cardiac monitors may be a ‘potentially attractive stroke prevention strategy’.

Professor Jennings agreed. ‘The implications of AF detected in this way [warrants further investigation], but given the clear association of AF with stroke in people with a high CHADS2 score and the catastrophic consequences of a stroke event this is a priority area for further research.’

Professor Jennings acknowledged that overdiagnosis was a possibility given the sensitivity of implantable cardiac monitors.

‘It may be that AF detected in this way is less likely to lead to stroke, but given the potential consequences, I would be inclined to play safe and assume it does,’ he said.
JAMA Cardiol 2017; doi: 10.1001/jamacardio.2017.3180.
JAMA Cardiol 2017; doi: 10.1001/jamacardio.2017.3203.

Picture credit: © Science Source/Monica Schroeder/