ABC of Atrial Fibrillation: AETIOLOGY, PATHOPHYSIOLOGY, AND CLINICAL FEATURES

doi:10.1136/bmj.311.7017.1425

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ABC of Atrial Fibrillation: AETIOLOGY, PATHOPHYSIOLOGY, AND CLINICAL FEATURES

BMJ

1995; 311 doi: 10.1136/bmj.311.7017.1425 (Published 25 November 1995)

Cite this as: BMJ 1995;311:1425

Aetiology

Ischaemic heart disease

Ischaemic heart disease is probably the most common underlying cause of atrial fibrillation in Britain. In addition, the fast ventricular rate due to atrial fibrillation may cause angina, leading to cardiac ischaemia and heart failure. Atrial fibrillation may complicate acute myocardial infarction in 10-15% of cases and is often a marker of extensive myocardial damage and a poor prognosis, with increased mortality. If atrial fibrillation occurs with an acute myocardial infarction, it tends to occur in the first 24 hours and is usually self limiting. Patients should be observed unless fast atrial fibrillation occurs or the patient is haemodynamically compromised.

Atrial fibrillation is also a marker of underlying ventricular dysfunction and a compromised myocardium. Many years after myocardial infarction, ventricular scarring and dilatation often predispose to atrial fibrillation and congestive heart failure.

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Hypertension

Hypertension accounted for about half of the cases of atrial fibrillation in the Framingham study. Hypertension contributes to the complications of stroke and thromboembolism in such patients, especially if left ventricular hypertrophy is present. Electrocardiography is useful for screening for left ventricular hypertrophy (for example, with the criteria of Sokolow and Lyon--S wave in V1 and R wave in V5 or V6 of >/=35 mm), and if the electrocardiogram is abnormal the echocardiogram will invariably show left ventricular hypertrophy. Left ventricular hypertrophy on echocardiography is defined by calculating the left ventricular mass index.

Left ventricular hypertrophy is considered to be present if the left ventricular mass index is >131 g/m² in men and >110 g/m²in women

Atrial fibrillation may be secondary to left atrial dilatation, which occurs in hypertensive patients, as a consequence of reduced left ventricular compliance. In addition, hypertension may be associated with underlying coronary artery disease, which itself is a risk for atrial fibrillation and thromboembolism.

M mode echocardiograms showing left ventricular …