Atrial fibrillation (AF) is the most common arrhythmia. The prevalence of permanent atrial fibrillation/flutter is 1% and reaches > 5% in octogenarians. Brief episodes of atrial fibrillation/flutter ("paroxysmal") are much more common. A detailed evaluation of the management and investigation of atrial fibrillation has been released by the New Zealand Guidelines Group and is available on the website www.nzgg.org.nz
There should be a high index of suspicion in patients with an irregular heart beat and the diagnosis should be confirmed with an ECG. Initial evaluation includes history, exam, laboratory investigation - thyroid function tests, renal function, INR, electrolytes, liver function, full blood count.
Echocardiography is a central investigation and should be undertaken in nearly all patients to look for underlying unrecognised structural heart disease, assess left ventricular (LV) size, function, hypertrophy and left atrial (LA) size. This information can be important in assessing thromboembolic risk and is necessary prior to initiating antiarrhythmic therapy. Ideally the ventricular rate should be < 100 bpm at the time of the scan to get accurate measurements.
Every patient with atrial fibrillation should have a thromboembolic risk assessment. The overall risk of stroke is 5%/year (3-5 fold higher than those without AF) but is different in various populations (note: there is no difference between chronic and paroxysmal AF). Very high risk populations include rheumatic heart disease (up to 20%/year), prosthetic heart valves, and previous/recent stroke/TIA (12%/year). Traditional intermediate risk factors for stoke include age > 65 , hypertension, heart failure, diabetes, coronary artery disease, and LV impairment on echocardiography. Younger patients with no structural heart disease (lone AF) are at very low risk. Warfarin reduces the risk by 2/3 and aspirin by 1/5. A risk table based on the Framingham database is available in the NZGG Practice Guideline. Warfarin use should be considered prior to a complete risk evaluation, as it can be stopped at a later stage if the risk is low.
The initial assessment of a patient with atrial fibrillation must include considering the probable underlying cause. There are many known causes; these may require urgent treatment in addition to treatment of the rhythm disturbance which has been caused by the problem.
The primary approach to control symptoms in atrial fibrillation is ventricular rate control. Beta-blockers are first line therapy, they are most effective and have proven prognostic benefit in hypertension, IHD and heart failure (which are frequently associated with AF). Verapamil (avoid concomitant use with beta-blockers) or Diltiazem should be used if beta blockers are contraindicated. Digoxin is very useful as a synergistic therapy and can be used in inactive elderly patients as first line therapy, but not used alone for most patients. Rate control is essential even in the absence of symptoms to prevent rate related cardiomyopathy. This should be evaluated at rest and with exercise. The target on clinical evaluation is an apical rate <= 80/min at rest, and <= 110/min with 5-6 minutes gentle exercise. Holter monitoring can be very helpful to assess rate control and should have a target average rate <100.
Attempted maintenance of sinus rhythm (cardioversion-electrical or pharmacologic, anti-arrhythmic therapy) is considered with highly symptomatic patients despite attempts at rate control and often in younger patients. This should be under the supervision of a Cardiologist.