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Ten top tips - atrial fibrillation

Cardiologists Dr Richard Snowdon and Dr Sean Gomes offer their tips for the diagnosis and management of atrial fibrillation

1. Remember to check the pulse

Assessment of the pulse is a basic examination that may be missed in busy clinic environments. It is essential in patients with cardiac symptoms. Many patients with AF, however, are not symptomatic and are picked up incidentally during routine clinical assessment. Of note, a lack of symptoms does not confer a reduced risk of thromboembolic complications from AF.

2. Arrange a 12-lead ECG for any patient found to have an irregular pulse or complaining of palpitations

While AF may be suspected by irregularity of the pulse, the diagnosis is confirmed by ECG. This simple office test may be diagnostic, but prolonged cardiac monitoring by Holter recorder or cardio memo may be required to make the diagnosis when AF is paroxysmal.

Additionally, other conditions, such as the presence of hypertensive heart disease, previous myocardial infarction and valvular heart disease, may be implied if characteristic ECG changes are identified.

3. Confirm that the diagnosis is atrial fibrillation, not a ‘mimic’

Atrial fibrillation has a characteristic ECG appearance, manifested by irregularly irregular QRS complexes without discernible P-waves. There is usually an undulating baseline, which may be coarse or fine, caused by disorganised atrial activity. Frequent supraventricular extra systoles are a common mimic for atrial fibrillation. This benign phenomenon can be ruled out by careful assessment for presence of a discrete P-wave before each QRS. Atrial flutter/tachycardia with a variable ventricular response may also mimic atrial fibrillation, and while similarities exist in medical management, the distinction is important when considering other treatment options, such as ablation. Although uncommon, multifocal atrial tachycardia may look similar to AF. It is also an irregularly irregular rhythm, but it is characterised by the presence of organised P-waves with multiple morphologies.

4. Be aware of possible triggers for AF

Atrial fibrillation may be triggered by a variety of factors, including infection, electrolyte imbalance, acute respiratory conditions, alcohol, coronary ischaemia and hyperthyroidism. Initial assessment of patients with AF should include clinical assessment for potential precipitating factors, as well as serum electrolytes and thyroid function tests.

5. Check for structural heart disease

Assessment of cardiac structure and function is important in many patients with AF, and echocardiography is the imaging modality of choice. Echo is recommended for patients in whom rhythm control is being considered, and in those with whom there is a high risk or a suspicion of underlying structural/functional heart disease, such as heart failure or a heart murmur. Important findings include left ventricular function and the presence of valvular disease. Mitral valve disease is most commonly associated with AF, although other valve pathologies may co-exist. Left atrial size is of significance in patients referred for AF ablation (see below).

6. Don’t forget to check for heart failure

Heart failure may develop in patients with atrial fibrillation by a variety of mechanisms. Atrial contraction provides approximately 20% of cardiac output. The loss of this can contribute to heart failure in some patients. High ventricular rate during AF is an important factor with respect to development of heart failure due to reduced cardiac filling and impaired haemodynamics. Poor rate control can result in a process termed tachycardia-mediated cardiomyopathy, whereby left ventricular function becomes impaired due to persisting high ventricular rates. It is important to recognise the development of this condition, as it is potentially reversible with enhanced rate control or the restoration of sinus rhythm.

7. Remember to assess the risk of thromboembolism (CHA2DS2-VASc score)

This is important for all patients, including those with paroxysmal atrial fibrillation and in those who are asymptomatic. Assessment of the risk for stroke and other thromboemboli should be made using a validated risk scoring system – the new NICE guidelines on AF recommend the CHA2DS2-VASc score.1 This is a refinement of the CHADS2 score and may allow more accurate assessment of risk. Points are assigned as noted in the table below.

Patients with a total score of 0 are at a low risk of stroke and can be advised to have no anticoagulation. Aspirin is no longer recommended for stroke prevention in patients with atrial fibrillation, and the guideline does not recommend offering antiplatelet therapy to those with a low risk. You should offer oral anticoagulation to those with a score of 2 or above – dabigatran, rivaroxiban or apixaban are the three licensed NOACs.

 ConditionPoints
 C  Congestive heart failure (or left ventricular systolic dysfunction)1
 H Hypertension (including treated hypertension on medication)1
 A2 Age ≥75 years2
 D Diabetes1
 S2 Prior stroke or TIA or thromboembolism2
 V Vascular disease (e.g. peripheral artery disease, myocardial infarction)1
 A Age 65–74 years1
 Sc Sex category (female sex)1

 

8. Decide between rhythm and rate control

Rate control usually involves administration of medications (AV nodal blocking drugs) to control ventricular rate, without aiming to restore sinus rhythm. Drugs include beta-blockers, non-dihydropyridine calcium channel antagonists (diltiazem and verapamil) and digoxin.

Rhythm control refers to measures to restore and maintain sinus rhythm. This may involve anti-arrhythmic medication (such as amiodarone, flecainide or sotalol), DC cardioversion or, in some cases, AF ablation (see below). The decision whether to accept rate control alone or to attempt rhythm control is largely governed by symptoms, as the mortality rates for patients assigned to either strategy are similar.2,3 The pattern of AF is also relevant, however, as rhythm control is more likely to be successful when AF is paroxysmal, and occurs in patients without significant accompanying structural heart diseases or left atrial dilatation.

Patients with no or minimal symptoms can generally be offered rate control alone. Patients with more significant symptoms, despite adequate rate control or where adequate rate control is difficult to achieve, such as paroxysmal AF, may be considered for a rhythm control strategy. All anti-arrhythmic medication carries the potential for side effects, including pro-arrhythmia, and may be associated with a risk for sudden cardiac death. Amiodarone carries less risk for sudden arrhythmic death, but has important long-term extra cardiac side effects, including thyroid dysfunction, pulmonary and hepatic toxicity. Anti-arrhythmic medication therefore requires careful prescription and should be monitored periodically.

9. Don’t forget to manage associated conditions (hypertension, obstructive sleep apnoea, obesity)

These associated conditions promote left atrial dilatation, scarring and remodelling. Management of these conditions limits this process and is important in the prevention of recurrent episodes of AF and progression from a paroxysmal to persistent pattern.

10. Consider referral for AF ablation in selected patients

The cornerstone of AF ablation involves pulmonary vein isolation (PVI). The electrical triggers for AF often arise from the junction between the pulmonary veins and the left atrium. Ablation with radiofrequency energy (similar to electrocautery) or cryotherapy around the entrance to the pulmonary veins creates an obstacle for these triggers, which prevents initiation and maintenance of atrial fibrillation. The success of PVI is approximately 60-70% with a single procedure in selected patients. Good candidates for ablation include patients who are younger, with paroxysmal AF (rather than persistent), and without evidence of structural heart disease (normal left ventricular function and left atrial size). Success rates approach 90% in these patients, if it is accepted that some patients will require up to two repeat ablation procedures.

Dr Richard Snowdon is a consultant cardiologist with special interest in electrophysiology and Dr Sean Gomes is a clinical fellow at the Liverpool Heart and Chest Hospital NHS Foundation Trust.

References

  1. Camm J, Kirchhof P, Lip G et al. Guidelines for the management of atrial fibrillation: the Task Force for the Management of Atrial Fibrillation of the European Society of Cardiology. Eur Heart J 2010;31(19):2369-429
  2. Wyse D, Waldo A, DiMarco J et al. A Comparison of rate control and rhythm control in patients with atrial fibrillation. N Engl J Med 2002;347(23):1825-33
  3. Van Gelder IC, Hagens VE, Bosker HA et al. Rate control versus electrical cardioversion for persistent atrial fibrillation. N Engl J Med 2002;347:1834-40

 

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