Left atrial enlargement – A prevalent marker of hypertensive heart disease

Left atrial (LA) enlargement is a common and early sign of hypertensive heart disease, which may be detected by electrocardiography or more accurately by echocardiography (1,2). LA enlargement may reflect structural or functional hypertensive heart disease, and is commonly found independently of presence of other echocardiographic signs of hypertensive heart disease, like concentric left ventricular (LV) remodeling or LV hypertrophy, as demonstrated by Milan et al. in the present issue of Blood Pressure (3). Thus, routine echocardiographic assessment of subclinical hypertensive heart disease should not be limited to diagnosis of LV hypertrophy, but also include measurement of LA size as well as LV geometry and function.

Although LA enlargement is most commonly related to increased wall tension because of increased filling pressure, both unmodifiable and modifiable predictors of LA size have been identified in hypertensive populations (4–6). In particular, older age and female gender have been associated with increased prevalence of LA enlargement (4), whereas African American men have smaller LA than their Caucasian counterparts, which has been linked to the lower risk for stroke in blacks (4,7). Other well-known covariates of LA size in hypertension are obesity, diabetes mellitus, metabolic syndrome, sleep apnea, LV hypertrophy, particularly of eccentric type, and systolic or diastolic LV dysfunction (4–7). From studies of change in LA size during antihypertensive treatment, treatment with diuretics and losartan have been proved to be superior in inducing reduction in LA size, which leads to a subsequent lower risk for cardiovascular events (5,8). In particular, reduction in LA size has been associated with lower incidence of new-onset atrial fibrillation (9).

When echocardiography is used for cardiovascular risk assessment, it is critical that guideline conventions and correct formulas are used to assess LA size and LV mass and geometry. Following the joint European Association of Echocardiography and American Society of Echocardiography (ASE) chamber quantification guidelines (10), LA size may be measured as anterior-posterior diameter in parasternal long-axis view or as LA area or volume using apical four-chamber or combined four- and two-chamber views (10). The latter method is recommended by the current echocardiographic chamber quantification guidelines, as LA may enlarge asymmetrically, which may not be accurately captured from a simple anterior–posterior LA diameter measurement. From this, prevalence of LA enlargement may vary within the same population, depending on the measurement used. To avoid overestimation of LA diameter by erroneously including the variable extent of fat tissue between the LA and aortic root in the linear measurement, LA anterior–posterior diameter should be measured from the trailing edge of the posterior aortic/anterior LA wall complex (10). Of note, LA diameter was not measured in this fashion in the study by Milan et al. (3).

The prognostic importance of different measures of LA size is well demonstrated. Larger LA anterior–posterior diameter predicted higher total mortality and higher risk for ischemic stroke in the Atherosclerosis Risk in Community (ARIC) study, which mainly included hypertensive African Americans (11). Larger LA diameter also predicted increased cardiovascular morbidity and mortality in hypertensive patients with LV hypertrophy on the electrocardiogram (2). LA volume was demonstrated as a better predictor of cardiovascular events than LA area and LA anterior–posterior diameter in a group of 423 unselected patients from the Mayo Clinic echocardiography laboratory, particular in patients with sinus rhythm (12). However, whether LA volume is superior to LA diameter in predicting prognosis in hypertension remains unknown.

Conflict of interest: None.