Undetected silent AF is present in 3% of 75-year-olds



AMSTERDAM – A first-of-its-kind mass screening program identified fully 5% of 75- to 76-year-old Swedes as having untreated atrial fibrillation.

Three percent of the aged participants in the ongoing STROKESTOP study had previously unidentified silent atrial fibrillation (AF). Another 2% had been diagnosed with AF but were not on oral anticoagulation despite their substantial stroke risk, Dr. Emma Svennberg reported at the annual congress of the European Society of Cardiology.

The idea behind the screening program was to screen people at an age when the prevalence of AF is very high and yet there is sufficient remaining life expectancy that they could expect to gain substantial benefit from oral anticoagulation therapy for protection against cardioembolic stroke, explained Dr. Svennberg, a cardiologist at the Karolinska Institute, Stockholm.

Dr. Emma Svennberg

The STROKESTOP study tested a novel mass screening strategy in which more than 6,000 Swedish 75- and 76-year-olds without known AF were issued a hand-held ECG device. Twice a day for 2 weeks they placed both thumbs on the device for 30 seconds to generate an ECG, which was transmitted to a central database. Compliance in this older age group was extremely high, although 1% of the ECGs were uninterpretable due to tremor, Parkinson’s disease, or other age-related physical infirmities.

Other mass screening programs have relied upon a single screening ECG. That’s a reliable means of detecting individuals with permanent AF, but very much hit-or-miss in those with paroxysmal AF, she noted.

Oral anticoagulant therapy was offered to all STROKESTOP participants found to have untreated AF. More than 90% of them accepted it. They are being prospectively followed for 5 years in the second phase of the STROKESTOP study, which will compare rates of ischemic stroke, major bleeding, mortality, and dementia in that group to a control group of 14,381 Swedish 75- and 76-year-olds – in the same two regions of the country – who were not invited to the screening program.

The prevalence of known AF in subjects invited to the screening program was 8.9%.

Dr. Robert Hatala

Individuals with AF have a fivefold increased risk of ischemic stroke, regardless of whether their atrial arrhythmia is silent or symptomatic. Oral anticoagulation therapy cuts that risk by close to 70%. Among patients with AF discharged from the hospital after a stroke, 70% die or become disabled. Yet undertreatment is common – in Sweden, as elsewhere, fewer than half of AF patients whose risk scores warrant anticoagulation therapy are on it, according to Dr. Svennberg.

Dr. Robert Hatala, session cochair, said one of the important messages of STROKESTOP is that you can’t find silent AF if you don’t look for it.

That’s why current ESC practice guidelines recommend that all patients aged 65 or older have their pulse taken at every physician visit, with an ECG to be ordered when any irregularities are detected, added Dr. Hatala, head of cardiology and director of the arrhythmia and pacing center at Slovak Medical University, Bratislava, Slovakia.

Dr. Svennberg said she and her coinvestigators are in the midst of a randomized trial comparing this low-tech screening method to the approach used in STROKESTOP involving 2 weeks of intermittent ECGs using a hand-held loaner device.

Dr. Hans-Christoph Diener, ESC spokesperson, predicted in an interview that physicians can soon expect to see a huge influx of patients with newly discovered silent AF. The impetus will be the much-anticipated introduction of the Apple iWatch, which he said could happen later this year.

"The detection of silent atrial fibrillation is going to change very quickly. This watch will have a device in it which measures pulse, and it has software which detects atrial fibrillation. More features are available for people with various diseases: It can measure oxygen saturation, pulse, blood pressure. They’ve even developed a chip to measure glucose transdermally. It’s amazing," said Dr. Diener, professor and chair of the department of neurology at the University of Duisburg-Essen, Germany.

The STROKESTOP study is supported by the Heart and Lung Foundation of Sweden and government research funds. Dr. Svennberg reported that she has received lecture fees from Merck Sharp & Dohme.

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