It has been shown in several studies that silent AF is one of the unrecognized causes of cryptogenic stroke . Diagnosis of silent AF is of great importance in order to decrease ischemic CVS and related morbidity, mortality, disability, and financial loss . Moreover, in patients with a previous cryptogenic stroke, the diagnosis of AF provides the etiology of stroke and generally leads to a change in antithrombotic strategy from antiplatelets to anticoagulation. A recent meta-analysis compared outcomes between patients with asymptomatic and symptomatic AF. The study showed no difference in both general and cardiovascular death risks as well as thromboembolic risk between both groups . Hence, the thromboembolic risk of atrial fibrillation has no relation to symptoms perceived by the patients.
The prevalence of asymptomatic AF depends on the population screened, the device and the duration of monitoring. Consequently, the literature reports a prevalence ranging from 0.5 % in single time point testing, reaching 50% in studies with prolonged continuous ECG monitoring with either surface ECGs or implantable cardiac devices. In a systematic review of AF screening that included 30 studies, single time point pulse palpation or ECG detected 1.4% of undiagnosed AF in adults aged more than 65 years . In the STROKESTOP Study, 7173 Participants without a previous diagnosis of AF underwent intermittent ECG recordings over 2 weeks. 3.0% were found to have AF, and of these, AF was found in 0.5% of the screened population on their first ECG. The use of intermittent ECGs increased new AF detection 4-fold . In the ASSERT study, 2455 participants aged > 65 years with hypertension but no prior history of AF who were receiving a pacemaker. Over a mean 2.5-year follow-up, 34.7% of the patients developed AF. In addition, there was a 2.5-fold increase in the risk of stroke or systemic thromboembolism in patients diagnosed with asymptomatic AF compared to no AF . In a recent study, the estimated prevalence of undiagnosed AF in the USA in 2009 was found to be 700,000 while the total prevalence of AF was 5.3 million, which means 1/8 of all AF patients was undiagnosed. Additional to this data, it was shown that more than half of the population with undiagnosed AF was at moderate to high risk for stroke. The data of this study also showed that the targeted screening strategy may provide benefit especially in the high-risk subgroup of older than 65 years and with multiple CHADS2 risk factors . In a meta-analysis that investigated patients presenting with a stroke or TIA, 7.7% of the patient were diagnosed with atrial fibrillation in the emergency department, with an additional 5.1% during the hospital stay . Our study has supported the previous data showing that the prevalence of undiagnosed AF in patients presented with acute CVS is high given that the monitoring period was just limited to the hospital stay.
Routine pulse self-monitoring in patients over 65 years of age is a class I recommendation in the European Society of Cardiology guidelines for the management of AF to detect silent AF . Despite this high recommendation level, less than 50% of the electrophysiologists who joined the European Heart Rhythm Association survey utilize this method in their daily practice .
It is well established that atrial fibrillation increases stroke risk. This risk can be reduced by anticoagulation. Consecutively, several studies investigated the stroke reduction rate after screening high-risk patients and treating them accordingly afterward. In a large United Kingdom (UK) cohort study , the included 5555 patients with incidentally detected ambulatory AF were shown to have a high risk of developing CVS; that risk can be significantly reduced by anticoagulation treatment as compared to no therapy.
It is estimated that 1 in every 4 patients presenting with stroke or TIA will be diagnosed with AF if systematic, long-term screening is performed . Therefore, after TIA or stroke, most guidelines recommend screening patients for the presence of AF, with 12-lead ECG, Holter monitoring, telemetry, or monitoring devices, but the exact timing and duration of screening with these techniques are undefined. A meta-analysis showed that 1-week ECG monitoring is cost-effective in the diagnosis of silent AF in order to prevent ischemic events recurrence in patients with ischemic stroke . The difficulty is to extend the monitoring opportunity to other groups of patients with AF risk factors. It is obvious that long-term monitoring and routine control of high-risk patients is helpful for detecting silent AF. But unfortunately, the question about cost-effectiveness has no clear answer. To be able to answer all these questions, more investigation and data are needed.
Interest in the issue of detecting silent AF is increasing day by day. However, technology support continues to be one of the most popular topics of recent times.
In a Canadian study, 184 primary care physicians were provided with a KardiaMobile ECG device (AliveCor) for 3 months. Physicians were asked to obtain a single 30-sec ECG recording of all patients seen in their daily practice who were ≥ 65 years old and not previously diagnosed with AF. A total of 7585 patients were screened. AF was detected in 6.2% of the patients . In the Apple Heart Study, 419,297 participants using smart watches with optical sensors were enrolled. Over a median of 117 days of monitoring, 2161 participants (0.52%) received notifications of an irregular pulse. The probability of receiving an irregular pulse notification was low. Among participants who received notification of an irregular pulse, 34% had atrial fibrillation on subsequent ECG patch readings and 84% of notifications were concordant with atrial fibrillation . The results are very promising as with advances in technology diagnosing silent AF could be accomplished with technology that we use on a daily basis.
A limitation of the study is its retrospective nature. However, we enrolled a high number of patients in 4 years, which is like a reflection of real life. Silent AF is not a rare condition, and implementation of good screening programs and new technology can significantly reduce the risk of CVS with appropriate primary prevention by oral anticoagulation therapy. In addition, early detection can decrease the number of disabilities, morbidity, and mortality. However, cost-effectiveness remains to be an unanswered question. We hope that there will be an improvement in silent AF diagnosis and related problems with the help of increasing studies, data, awareness and progressive technology in the near future.