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The Management of Subclinical Atrial Fibrillation: The Pathway to True Medical Expertise

Disclosure: Research grants and speaking fees from Bristol-Meyers-Squibb/Pfizer, Medtronic, Servier, Boston Scientific and Cipher.
Pub Date: Thursday, Nov. 7, 2019
Author: Jeff S. Healey MD, MSc, FRCPC
Affiliation: Population Health Research Institute, McMaster University, Hamilton, Ontario, Canada

Citation

Noseworthy PA, Kaufman ES, Chen LY, Chung MK, Elkind MSV, Joglar JA, Leal MA, McCabe PJ, Pokorney SD, Yao X, on behalf of the American Heart Association Council on Clinical Cardiology Electrocardiography and Arrhythmias Committee, Council on Arteriosclerosis, Thrombosis and Vascular Biology, Council on Cardiovascular and Stroke Nursing, and Stroke Council. Subclinical and device-detected atrial fibrillation: pondering the knowledge gap: a scientific statement from the American Heart Association [published online ahead of print November 7, 2019]. Circulation. doi: 10.1161/CIR.0000000000000740.

Article Text

To become a medical expert, one must go beyond the proficient application of guideline-based care and become an expert at the management of uncertainty. Every day in clinical practice, we are confronted with management dilemmas for which evidence-based medicine [1] cannot give clear guidance. Navigating these routine situations requires the clinician to draw on their experience and the available medical literature; then weigh therapeutic options in terms of their perceived risks and benefits, the degree of uncertainty in these estimates and with a shared decision-making framework that includes patients’ perspectives [2]. It is important that clinicians acknowledge when decisions are made in this fashion, rather than those based on high-quality medical evidence, so that they recognize the knowledge gap and remain receptive to new information. It is even more critical that practice-guidelines and consensus statements highlight these differences, to avoid giving the broader medical community the impression that no new medical evidence is needed.

In the 2019 American Heart Association scientific statement on subclinical atrial fibrillation, Noseworthy and colleagues have done an excellent job to review the medical literature and highlight knowledge gaps pertaining to the role of oral anticoagulation for stroke prevention in this population. [3] They make a clear distinction between clinical and subclinical atrial fibrillation, highlight the prevalence of the latter, and discuss a reasonable approach to anticoagulation use in subclinical atrial fibrillation. This discussion is both thoughtful and comprehensive, but perhaps deserving of two minor clarifications. First, it should be noted that pacemaker patients make up a large proportion of patients identified with subclinical atrial fibrillation, and they are typically elderly [4]. There are good data from the AVERROES trial to show that patients over age 75 years, treated with either aspirin or apixaban have an approximately three-fold increase in major bleeding compared to younger patients [5], which in the context of the lower absolute risk of stroke seen with subclinical atrial fibrillation [4] substantially changes the risk-benefit balance. As Noseworthy states, the CHA2DS2-VASc score also predicts bleeding events, thus the performance of this score may be quite different than in clinical atrial fibrillation.

Elderly patients with subclinical atrial fibrillation are also at risk of stroke from a variety of mechanisms, with data from ASSERT suggesting that only between 25-50% appearing to be embolic in origin [6]. Thus, it is probably overstated to say that any subclinical atrial fibrillation in a patient with a history of stroke requires anticoagulation, although this may be reasonable in those with a clear embolic-appearing stroke [7], or an unclassified ischemic stroke with longer episodes of temporally-associated subclinical atrial fibrillation [8].

In addition to addressing the controversy of anticoagulation in patients with subclinical atrial fibrillation, this scientific statement does an excellent job at describing the looming challenges and opportunities in this field. The statement highlights that the progression of subclinical atrial fibrillation is a strong predictor of incident heart failure [9], which might be amenable to preventive strategies. The writing group has also stressed the important implications that this field, and the ongoing clinical trials [10, 11] have for the controversial topic of population-based atrial fibrillation screening [12]. With the advent of sensitive tools that can screen non-invasively for atrial fibrillation over extended periods of time, understanding the impact of treating short-lasting, low-burden subclinical atrial fibrillation becomes critical if we are to determine what screening strategies may be effective.

Subclinical atrial fibrillation is a good example of a condition with broad clinical implications, for which there are major management uncertainties. This American Heart Association scientific statement does an exemplary job of highlighting these issues, and proposing a path forward, while stressing the need for new medical knowledge. Highlighting and describing knowledge gaps is a more effective strategy than proposing guidelines with weak recommendations based on low-quality evidence [13], as the latter strategy often leads clinicians to believe that best practice is understood, and further evidence unnecessary. Expert clinicians are often those with the reputation for knowing all of the answers. However, the true expert is one who is able to recognize, profess the limits of their knowledge, while remaining receptive to new information which pushes back these limits.

References

  1. Oxman AD, Sackett DL, Guyatt GH. Users' guides to the medical literature. I. How to get started. The Evidence-Based Medicine Working Group. Jama 1993; 270:2093-2095.
  2. Elwyn G, Frosch D, Thomson R et al. Shared decision making: a model for clinical practice. Journal of general internal medicine 2012; 27:1361-1367.
  3. Noseworthy PA, Kaufman ES, Chen LY, Chung MK, Elkind MSV, Joglar JA, Leal MA, McCabe PJ, Pokorney SD, Yao X, on behalf of the American Heart Association Council on Clinical Cardiology Electrocardiography and Arrhythmias Committee, Council on Arteriosclerosis, Thrombosis and Vascular Biology, Council on Cardiovascular and Stroke Nursing, and Stroke Council. Subclinical and device-detected atrial fibrillation: pondering the knowledge gap: a scientific statement from the American Heart Association [published online ahead of print November 7, 2019]. Circulation. doi: 10.1161/CIR.0000000000000740.
  4. Healey JS, Connolly SJ, Gold MR et al. Subclinical atrial fibrillation and the risk of stroke. The New England journal of medicine 2012; 366:120-129.
  5. Ng KH, Shestakovska O, Connolly SJ et al. Efficacy and safety of apixaban compared with aspirin in the elderly: a subgroup analysis from the AVERROES trial. Age and ageing 2016; 45:77-83.
  6. Perera KS, Sharma M, Connolly SJ et al. Stroke type and severity in patients with subclinical atrial fibrillation: An analysis from the Asymptomatic Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial (ASSERT). American heart journal 2018.
  7. Hart RG, Diener HC, Coutts SB et al. Embolic strokes of undetermined source: the case for a new clinical construct. The Lancet. Neurology 2014; 13:429-438.
  8. Brambatti M, Connolly SJ, Gold MR et al. Temporal relationship between subclinical atrial fibrillation and embolic events. Circulation 2014; 129:2094-2099.
  9. Wong JA, Conen D, Van Gelder IC et al. Progression of Device-Detected Subclinical Atrial Fibrillation and the Risk of Heart Failure. J Am Coll Cardiol 2018; 71:2603-2611.
  10. Lopes RD, Alings M, Connolly SJ et al. Rationale and design of the Apixaban for the Reduction of Thrombo-Embolism in Patients With Device-Detected Sub-Clinical Atrial Fibrillation (ARTESiA) trial. American heart journal 2017; 189:137-145.
  11. Kirchhof P, Blank BF, Calvert M et al. Probing oral anticoagulation in patients with atrial high rate episodes: Rationale and design of the Non-vitamin K antagonist Oral anticoagulants in patients with Atrial High rate episodes (NOAH-AFNET 6) trial. American heart journal 2017; 190:12-18.
  12. Freedman B, Camm J, Calkins H et al. Screening for Atrial Fibrillation: A Report of the AF-SCREEN International Collaboration. Circulation 2017; 135:1851-1867.
  13. Atkins D, Best D, Briss PA et al. Grading quality of evidence and strength of recommendations. BMJ (Clinical research ed.) 2004; 328:1490.

-- The opinions expressed in this commentary are not necessarily those of the editors or of the American Heart Association --