CardioNerds (Dr. Kelly Arps, Dr. Colin Blumenthal, Dr. Dan Ambinder, and Dr. Teodora Donisan) discuss the screening, detection, and diagnosis of atrial fibrillation (AF) with Dr. Ben Freedman. AF is frequently undiagnosed and its first manifestation can be a debilitating stroke. European and American guidelines differ slightly with regards to guidelines for AF screening in asymptomatic individuals. There are multiple methods available to screen for AF; the setting and the clinical scenario can help guide the choice. Consumer-led screening has its own challenges, as it can detect AF in a younger population where we should prioritize aggressive management of risk factors and comorbidities. There is uncertainty regarding the minimum AF burden that increases thromboembolic risk, however a high CHAD₂S₂-VASc score remains the strongest predictor of stroke risk independent of AF burden. Perioperative AF associated with non-cardiac surgery has increased risk of future stroke and adverse cardiac outcomes and should likely be treated as a new diagnosis of chronic AF.   

This CardioNerds Atrial Fibrillation series is a multi-institutional collaboration made possible by contributions of stellar fellow leads and expert faculty from several programs, led by series co-chairs, Dr. Kelly Arps and Dr. Colin Blumenthal.

This series is supported by an educational grant from the Bristol Myers Squibb and Pfizer Alliance. All CardioNerds content is planned, produced, and reviewed solely by CardioNerds.

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Pearls and Quotes – Screening, Detection, and Diagnosis of Atrial Fibrillation

1. “Stroke is a poor early sign of AF.”  
   
   1. AF remains frequently undiagnosed and there remains uncertainty about the optimal target population and screening methodology.  
      
   
   
2. “We have to tailor AF screening to the purpose we’re using it for”  
   
   1. If in a primary care setting, check the pulse. If the goal is to exclude high-risk AF –  handheld ECG for heart rhythm snapshots are appropriate. If the goal is to identify or exclude AF with a high level of certainty, continuous monitors are necessary for greater sensitivity. 
      
   
   
3. Consumer-led screening is performed by (mostly young) individuals using commercial monitors and smart watches, facilitating earlier recognition of paroxysmal AF in this population. In these cases, we should prioritize aggressive management of risk factors and comorbidities to reduce the risk of progression to persistent AF. 
   
4. There is no specific cutoff for AF duration which has been identified to predict elevated stroke risk; AF is likely both a risk factor and a risk marker for stroke, suggesting an underlying atrial myopathy. 
   
5. Non-cardiac surgeries and procedures can be considered “AF stress tests.” If AF occurs in these settings, it is usually more clinically significant and has a higher risk of stroke and death than AF associated with cardiac surgeries. 
   

Notes – Screening, Detection, and Diagnosis of Atrial Fibrillation

Notes drafted by Dr. Teodora Donisan and reviewed by Dr. Kelly Arps

1. Why is it important to screen for AF and who should be screened? 

AF is frequently undiagnosed and its first manifestation can be a debilitating stroke or death. Let’s go over a few numbers: 

• 15% of people with AF are currently undiagnosed and 75% of those individuals would be eligible for anticoagulation.¹   
  
• 10-38% of individuals with ischemic strokes are found to have AF as a plausible cause, and the true proportion may be even higher, given difficulties in detecting intermittent AF.² 
  

Current guideline recommendations:  

• European guidelines: opportunistic screening for AF is recommended for individuals ≥65 years old.³ 
  

• American guidelines: AF screening is recommended in patients with cryptogenic strokes and those with device-recorded atrial high-rate episodes.⁴ 
  

Opportunistic screening for AF can be done by checking the pulse or noticing the irregular heart rate on blood pressure monitors. When AF is found by opportunistic screening at a single time point, it is usually persistent AF. Continuous ambulatory heart rhythm monitoring can identify shorter episodes of paroxysmal AF, perhaps earlier in the AF disease course.  

In patients with unexplained stroke we have different ways to search for occult AF: 

• In the hospital: all patients should have 72h of ECG monitoring. There is evidence that nurse-led ECG surveillance detects more paroxysmal AF earlier and more frequently than 24-hour Holter recordings.⁵  
  
• After discharge: if clinical suspicion for occult AF is high (e.g., cerebral imaging concerning for cardioembolic source, evidence of left atrial enlargement, elevated BNP), consider more prolonged monitoring via cutaneous patches, multiple Holter recordings, or implantable cardiac monitors. 
  

2. What tools are currently available to screen for AF? 

There are multiple tools available for AF screening: pulse palpation, oscillometry, and ambulatory heart rhythm ECG monitoring with external or subcutaneous devices. Handheld ECG devices are very convenient options, as they can diagnose AF in 30 seconds directly, whereas other methods such as oscillometry would ultimately require ECG confirmation. 

• If in the office for a quick screen: check the pulse; 
  
• If you’re looking for high-burden AF: handheld one-time ECG; 
  
• If you’re looking to identify or rule out AF with a high degree of certainty: continuous monitoring with transcutaneous patch or implantable monitor. 
  

3. How should commercial monitor/smart watch data be incorporated into clinical practice? 

We need to be aware of the population who have access to and more often use these modern technologies; use is unequally distributed around the world and across the age span.⁶ These devices are most often used by people who are 35-40 years old, not the typical population for whom AF screening may be more impactful. If we do identify AF in these younger individuals, starting anticoagulation may not be indicated. It is important, however, to emphasize more aggressive management of risk factors and comorbidities (e.g., weight loss, diet, exercise, alcohol reduction, hypertension control, screening for and treating prediabetes and diabetes, screening for obstructive sleep apnea, and assessing thyroid function) to reduce the risk of AF progression. 

4. How much atrial fibrillation is clinically relevant? 

There is uncertainty regarding the minimum AF burden that increases the thromboembolic risk above an individual’s baseline risk, with studies exploring durations of ≥ 5 minutes to ≥ 24 hours.^7,8 Several studies show that there isn’t a clear temporal relationship between device-detected high-rate episodes and strokes either, with only a small number of patients experiencing arrhythmia in the month before a stroke.⁹ 

• The CHA₂DS₂-VASc score is very important when discussing thromboembolic risk: if it is low, then the risk of stroke is low; if it is high, risk of stroke is higher, even if there is a low burden of AF. 
  
• AF is likely both a risk factor and a risk marker for stroke, suggesting an underlying atrial myopathy. This would explain why a specific cutoff point for AF duration is not necessarily relevant to predict stroke risk. 
  

5. How should clinicians approach peri-operative AF? 

Perioperative AF is associated with increased perioperative morbidity, higher stroke rates, more readmissions, and lower survival.¹⁰ The significance of AF is different depending on the type of surgery: 

• With AF after cardiac surgery (which involves opening the pericardium and direct irritation of the atria), the incidence of perioperative AF is greater (20-30%). Roughly 25% of patients with AF after CABG experience asymptomatic recurrent AF episodes during the first month after the procedure.¹¹ Many individuals with AF after cardiac surgery do not go on to have chronic AF. 
  
• With AF after general surgery, the chance of chronic AF and future risk of adverse events are significantly elevated, as AF should not be a direct result of the procedure itself and instead likely represents a previously undiagnosed atrial myopathy. Consider noncardiac procedures as an “AF stress test”.   
  

Give this information, we should strongly consider anticoagulation after identifying AF associated with non-cardiac surgeries or procedures, when indicated by the CHA2DS2-VASc score. We should start anticoagulation in individuals with AF associated with cardiac surgeries only if there are other risk factors or clini

Opportunistic screening for AF can be done by checking the pulse or noticing the irregular heart rate on blood pressure monitors. When AF is found by opportunistic screening at a single time point, it is usually persistent AF. Continuous ambulatory heart rhythm monitoring can identify shorter episodes of paroxysmal AF, perhaps earlier in the AF disease course.  

In patients with unexplained stroke we have different ways to search for occult AF: 

• In the hospital: all patients should have 72h of ECG monitoring. There is evidence that nurse-led ECG surveillance detects more paroxysmal AF earlier and more frequently than 24-hour Holter recordings.⁵  
  
• After discharge: if clinical suspicion for occult AF is high (e.g., cerebral imaging concerning for cardioembolic source, evidence of left atrial enlargement, elevated BNP), consider more prolonged monitoring via cutaneous patches, multiple Holter recordings, or implantable cardiac monitors.  
  

References – Screening, Detection, and Diagnosis of Atrial Fibrillation

1. Turakhia MP, Shafrin J, Bognar K, et al. Estimated prevalence of undiagnosed atrial fibrillation in the United States. PLoS One. 2018;13(4):e0195088. 

2. Friberg L, Rosenqvist M, Lindgren A, Terént A, Norrving B, Asplund K. High prevalence of atrial fibrillation among patients with ischemic stroke. Stroke. 2014;45(9):2599-2605. 

3. Hindricks G, Potpara T, Dagres N, et al. 2020 ESC Guidelines for the diagnosis and management of atrial fibrillation developed in collaboration with the European Association for Cardio-Thoracic Surgery (EACTS): The Task Force for the diagnosis and management of atrial fibrillation of the European Society of Cardiology (ESC) Developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC. Eur Heart J. 2021;42(5):373-498. 

4. January CT, Wann LS, Calkins H, et al. 2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol. 2019;74(1):104-132. 

5. Yan B, Tu H, Lam C, et al. Nurse Led Smartphone Electrographic Monitoring for Atrial Fibrillation after Ischemic Stroke: SPOT-AF. J Stroke. 2020;22(3):387-395. 

6. Turakhia MP, Desai M, Hedlin H, et al. Rationale and design of a large-scale, app-based study to identify cardiac arrhythmias using a smartwatch: The Apple Heart Study. Am Heart J. 2019;207:66-75. 

7. Glotzer TV, Hellkamp AS, Zimmerman J, et al. Atrial high rate episodes detected by pacemaker diagnostics predict death and stroke: report of the Atrial Diagnostics Ancillary Study of the MOde Selection Trial (MOST). Circulation. 2003;107(12):1614-1619. 

8. Healey JS, Connolly SJ, Gold MR, et al. Subclinical atrial fibrillation and the risk of stroke. N Engl J Med. 2012;366(2):120-129. 

9. Freedman B, Camm J, Calkins H, et al. Screening for Atrial Fibrillation: A Report of the AF-SCREEN International Collaboration. Circulation. 2017;135(19):1851-1867. 

10. Bianco V, Kilic A, Yousef S, et al. The long-term impact of postoperative atrial fibrillation after cardiac surgery. J Thorac Cardiovasc Surg. 2022. 

11. Ha ACT, Verma S, Mazer CD, et al. Effect of Continuous Electrocardiogram Monitoring on Detection of Undiagnosed Atrial Fibrillation After Hospitalization for Cardiac Surgery: A Randomized Clinical Trial. JAMA Netw Open. 2021;4(8):e2121867. 

Guest Profiles

Dr. Ben Freedman

Dr. Ben Freedman serves as Director of External Affairs at the Heart Research Institute and Leader of its Heart Rhythm and Stroke Prevention Group, Honorary Professor of Cardiology at The University of Sydney, Charles Perkins Centre. He formed the AF-SCREEN International Collaboration in 2015, which now has over 190 members from 38 countries, including some of the most prolific names in AF research. In 2011 he was awarded the Order of Australia Medal for service to medicine as a clinician, educator, and researcher.

Dr. Teodora Donisan

Teodora Donisan @TDonisan is an internal medicine resident at Beaumont Hospital and rising cardiology fellow at Mayo Clinic. She completed medical school at the Carol Davila University of Medicine and Pharmacy, in her home country of Romania. After medical school, she worked as cardiology resident in Bucharest for 2 years, followed by a research rotation in interventional cardio-oncology at The University of Texas MD Anderson Cancer Center. Teo is passionate about medical education and loves the rush of the cardiac intensive care unit. She dreams of photographing wildlife in all National Parks in the United States.