THE LEFT ATRIUM IN HYPERTENSION: A SYMBOL OF MORTALITY AND MORBIDITY?

The importance of the left atrium in cardiac pathophysiology is perhaps a little undervalued. Indeed, left atrial size and/or function has been implicated in a number of cardiovascular and cerebrovascular disorders as being either causal or as an indirect marker(s) of disease [1]. For example, the Framingham study reported that left atrial enlargement was a significant predictor of stroke in men and death in both sexes; indeed, for every 10-mm increase in left atrial size, the relative risk of stroke was 2.4 in men and 1.4 in women, whilst the relative risk of death was 1.3 in men and 1.4 in women [2]. This relation of left atrial enlargement to stroke and death appeared to be partially mediated by left ventricular mass [1]. In contrast, Di Tullio et al [3] reported that left atrial enlargement was associated with an increased risk of ischemic stroke in an ethnically mixed population, even after adjustment for other risk factors, including left ventricular hypertrophy. Left atrial size is also the principal independent predictor of prognosis in patients with dilated cardiomyopathy, where those with left atrial dilatation have an increase in mortality and a worse clinical outcome [4]. Finally, left atrial enlargement (≥4.8 cm) is an independent risk factor for the development of left atrial thrombi in patients with mitral stenosis [5], increasing the potential for stroke and thromboembolism. With the potential mortality and morbidity associated with left atrial enlargement, its quantification is therefore important. Various methods such as electrocardiography (ECG), echocardiography (both transthoracic and transoesophageal), chest xray, cardiac angiography and magnetic resonance imaging of the heart have been used to assess left atrial size. However, the ECG is not be as reliable as echocardiography, with no consistent agreement between the ECG diagnosis of left atrial enlargement and the left atrial cavity size as measured by echocardiography [6]. On the chest x-ray, the left atrium is larger than 5.0 cm in diameter if the carinal angle was 100 degrees or greater [7]. Whether left atrial diameter by echocardiography corresponds well with left atrial volume is slightly controversial.