Atrial fibrillation

Introduction

• Atrial fibrillation is a supraventricular tachyarrhythmia with uncoordinated atrial electrical activation and consequently ineffective atrial contraction and irregular ventricular conduction
• A standard 12-lead ECG recording or a single-lead ECG tracing of >30 s showing heart rhythm with no discernible repeating P waves and irregular RR intervals is required to establish the diagnosis of AF
• AF is the most common sustained cardiac arrhythmia in adults and is associated with substantial morbidity and mortality. The currently estimated prevalence of AF in adults is between 2% and 4%, and a 2-3-fold rise is expected

Possible causes of atrial fibrillation

• Atrial pressure elevation – Systemic hypertension, Pulmonary hypertension, Mitral or tricuspid valve disease,  Myocardial disease, cardiomyopathy,  Semilunar valvular abnormalities 
• Atrial ischaemia - coronary artery disease
• Inflammatory or infiltrative atrial disease – Pericarditis, Amyloidosis, Myocarditis, Age-induced atrial fibrotic changes
• Intoxicants – Alcohol, Carbon monoxide
• Increased sympathetic activity – Hyperthyroidism, Pheochromocytoma, Anxiety, Exertion-induced
• Postoperative - Cardiac and pulmonary surgery, Cardiac trauma, Hypoxia, Pneumonia
• Congenital heart disease, particularly atrial septal defect, channelopathy

Classification

Five patterns of AF are distinguished, based on presentation, duration, and spontaneous termination of AF episodes:

1) First diagnosed - AF not diagnosed before

2) Paroxysmal - AF that terminates spontaneously or with intervention within 7 days of onset.

3) Persistent - AF sustained > 7 days‍

4) Long-standing persistent - Continuous AF > 12 months

5) Permanent - AF that is accepted by the patient and physician, and no further attempts to restore/maintain sinus rhythm will be undertaken.

Electrophysiological mechanisms of AF include focal mechanisms and re-entry, from a single or multiple sources (mainly from pulmonary veins). In focal AF, one or more rapidly firing foci cause fibrillatory conduction over the atria. AF produced by re-entry may involve one or more circuits.

ECG features

• Irregularly irregular R-R intervals – no repetitive pattern
• Absence of distinct repeating P waves
• Irregular atrial activation
• There may be evidence of an old myocardial infarction, left atrial and ventricular hypertrophy, pericardial disease, cardiomyopathy and ventricular preexcitation 

Atrial fibrillation in Wolff-Parkinson-White syndrome

• Paroxysmal AF has been found in almost 50% of patients with WPW
• Typically young patients with no structural disease of the heart
• These patients may benefit from treatment of their preexcitation with catheter ablation of their accessory pathway. Many of these patients do not have further AF once their accessory pathway is eliminated.
• Atrial fibrillation in combination with ventricular preexcitation through the accessory pathway may degenerate into FBI = Fast Broad Irregular tachycardia
• atrial fibrillation with fast ventricular response over an accessory pathway
• potentially life-threatening arrhythmia – due to 1:1 conduction the ventricular rate may be very rapid (even >300bpm) and it can degenerate into ventricular fibrillation!

ECG of atrial fibrillation in WPW

• irregular wide complex tachycardia
• ventricular rate >200 bpm
• QRS complexes usually have variable morphology – APs bypassing the AV node can produce wide and bizarre looking complexes
• axis remains stable
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ECG 1 Atrial fibrillation with Right bundle branch block (RBBB)

• no visible P waves
• irregular rhythm – no R-R interval is the same
• ventricular rate around 125 bpm
• Right bundle branch block – QRS 150ms, rSR pattern in V1, slurred S wave in lateral leads – I, aVL, V5, V6
  

ECG 2 Atrial fibrillation with RBBB + LAH

• no visible P waves
• irregular rhythm, ventricular rate around 75 bpm
• Right bundle branch block – QRS duration 140ms, M shaped QRS in V1, slurred S wave in leads I and V6
• Left anterior fascicular block – axis -80° > left axis deviation

ECG 3  Atrial fibrillation with Left bundle branch block (LBBB)

• no visible P waves
• irregular rhythm, ventricular rate around 90 bpm
• Left bundle branch block – QRS duration 160ms, dominant R waves in I, aVL, V5, V6, deep S waves in V1

ECG 4  FBI = Fast broad irregular tachycardia – atrial fibrillation with preexcitation

• Atrial fibrillation in combination with ventricular preexcitation via an accessory pathway degenerated into FBI
• wide complex tachycardia
• irregular rhythm
• QRS morphology is variable in each lead
• Atrial fibrillation with a 1:1 conduction over a fast-conducting accessory pathway

Management

Management of atrial fibrillation is a complex process that depends on underlying causes, symptoms, duration of atrial fibrillation, structural damage of the atria, comorbidities and age.

Therapy of atrial fibrillation has three goals:

• reduce symptoms
• prevent thromboembolism
• prevent morbidity and mortality

To achieve this, there are 3 approaches:

• rate control
• rhythm control 
• anticoagulation therapy

• Every patient with AF should be evaluated for the need of anticoagulation therapy to prevent systemic embolization (even for the first AF episode)
• CHA2DS2-VASc score- structured, clinical, risk-score-based assessment of individual thrombo-embolic risk, should be performed as the first step in optimal thrombo-embolic risk management in AF patients
• HAS-BLED score – structured risk-score-based bleeding risk assessment, helps to identify non-modifiable and address modifiable bleeding risk factors

Picture 1 European Society of Cardiology Guidelines 2020

References

1. CAMM, A. J., LÜSCHER, T. F., & SERRUYS, P. W. (2009). The ESC textbook of cardiovascular medicine. Oxford, Oxford University Press
2. Hindricks G, Potpara T, Dagres N, Arbelo E, Bax JJ, Blomström-Lundqvist C, Boriani G, Castella M, Dan GA, Dilaveris PE, Fauchier L, Filippatos G, Kalman JM, La Meir M, Lane DA, Lebeau JP, Lettino M, Lip GYH, Pinto FJ, Thomas GN, Valgimigli M, Van Gelder IC, Van Putte BP, Watkins CL; ESC Scientific Document Group. 2020 ESC Guidelines for the diagnosis and management of atrial fibrillation developed in collaboration with the European Association of Cardio-Thoracic Surgery (EACTS). Eur Heart J. 2020 Aug 29:ehaa612. doi: 10.1093/eurheartj/ehaa612. Epub ahead of print. PMID: 32860505.
3. Atrial Fibrillation • LITFL Medical Blog • ECG Library Diagnosis. Life in the Fast Lane • LITFL • Emergency medicine and critical care medical education blog [online]. Copyright © 2021 LITFL [cit. 06.02.2021]. Accessible at: https://litfl.com/atrial-fibrillation-ecg-library/
4. Kapil Kumar, MD (2020), Overview of atrial fibrillation. Gordon M Saperia, MD (Ed.), UpToDate. Retrieved February 5, 2021 from: https://www-uptodate-com.ezproxy.is.cuni.cz/contents/overview-of-atrial-fibrillation?search=atrial%20fibrillation&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1
5. Picture: What is new in the 2020 Guidelines? (2020), from: Gerhard Hindricks, Tatjana Potpara, Nikolaos Dagres, Elena Arbelo, Jeroen J Bax, Carina Blomström-Lundqvist, Giuseppe Boriani, Manuel Castella, Gheorghe-Andrei Dan, Polychronis E Dilaveris, Laurent Fauchier, Gerasimos Filippatos, Jonathan M Kalman, Mark La Meir, Deirdre A Lane, Jean-Pierre Lebeau, Maddalena Lettino, Gregory Y H Lip, Fausto J Pinto, G Neil Thomas, Marco Valgimigli, Isabelle C Van Gelder, Bart P Van Putte, Caroline L Watkins, ESC Scientific Document Group, 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, European Heart Journal, Volume 42, Issue 5, 1 February 2021, Pages 373–498, https://doi.org/10.1093/eurheartj/ehaa612

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