"This study highlights that many older individuals in primary care practices have subclinical AF and don't know it," Dr. David Gladstone of the University of Toronto Department of Medicine told Reuters Health by email. "At the hospital, we regularly see patients who have suffered catastrophic embolic strokes attributed to previously-unrecognized AF."
"We found that one in 20 seniors over age 75 with a history of hypertension had AF that was identified by screening," he said. "Half of the ECG-detected AF cases had episodes lasting more than six hours, with some lasting many days. The screening intervention led to anticoagulation in 75% of patients with screen-detected AF - a finding that we interpret as potentially clinically significant with the potential to prevent future strokes, stroke-related disability and dementia."
"However," he added, "widespread AF screening is not yet ready for prime time because the scientific evidence is still accumulating...Trials will need to determine its effects on hard clinical outcomes and the benefits will need to outweigh the risks and costs."
As reported in JAMA Cardiology, Dr. Gladstone and colleagues randomized 856 older adults from 48 primary care practices to standard care (routine clinical follow-up plus a pulse check and heart auscultation at baseline and six months) or screening.
In addition to standard care, the screening group received a two-week continuous electrocardiographic (cECG) patch monitor to wear at baseline and at three months. The screening group also received automated home blood pressure machines with oscillometric AF screening capability to use twice-daily during the cECG monitoring periods.
The median cECG wear time over the study period was 27.4 days.
As Dr. Gladstone indicated, in the primary analysis, AF was detected in 5.3% of the screening group versus 0.5% in the control group (relative risk, 11.2; number needed to screen, 21).
Of those with cECG-detected AF, median total time spent in AF was 6.3 hours, and the longest episode had a median duration of 5.7 hours.
Anticoagulation was initiated in 15 of 20 patients (75%) with cECG-detected AF; by six months, anticoagulant therapy had been prescribed for 18 participants (4.1%) in the screening group versus four (0.9%) in the control group (relative risk, 4.4).
Twice-daily AF screening using a home BP monitor had a sensitivity of 35%, specificity of 81%, positive predictive value of 8.9%, and negative predictive value of 95.9%.
Adverse skin reactions requiring premature discontinuation of cECG monitoring occurred in five patients (1.2%).
Dr. Gladstone said, "One of the main concerns related to AF screening is that it could lead to overdiagnosis and overtreatment of very low-risk patients with AF, thereby increasing bleeding risks without expected benefit. We don't want patients to be overtreated, but at the same time we don't want patients who may be at risk to be undertreated either."
"For now," he concluded, "clinical equipoise for anticoagulation exists for subclinical AF of less than 24 hours' duration."
Dr. Roopinder Sandhu of Cedars-Sinai Hospital in Los Angeles, coauthor of a related editorial, commented by email to Reuters Health that the study "helps to address an important gap that exists with regards to optimal screening method, population and setting."
That said, she noted, "There are major gaps that exist in our current evidence for AF screening that the study does not address and among the most important are (1) the clinical significance of screen-detected AF and whether oral anticoagulation therapy to prevent stroke provides a net clinical benefit; and (2) what are the harms of screening."
"False positive results may lead to inappropriate or overprescribing of oral anticoagulation, unnecessary testing, and anxiety," she said. "Ongoing research will help to further our understanding of these issues."
The study was funded in part by Boehringer Ingelheim, Microlife Corp, ManthaMed, and iRhythm. Two coauthors received fees from Boehringer Ingelheim.
SOURCE: https://bit.ly/3r5yzpT JAMA Cardiology, online February 24, 2021
By Marilynn Larkin
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