Prognostic value of left atrial size in hypertensive African Americans undergoing stress echocardiography

Abstract

Background: Left atrial (LA) enlargement is a marker of increased risk in the general population undergoing stress echocardiography. African American (AA) patients with hypertension are known to have less atrial remodeling than whites with hypertension. The prognostic impact of LA enlargement in AA with hypertension undergoing stress echocardiography is uncertain.

Aim: To investigate the prognostic value of LA size in hypertensive AA patients undergoing stress echocardiography.

Methods: This retrospective outcomes study enrolled 583 consecutive hypertensive AA patients who underwent stress echocardiography over a 2.5-year period. Clinical characteristics including cardiovascular risk factors, stress and echocardiographic data were collected from the electronic health record of a large community hospital. Treadmill exercise and Dobutamine protocols were conducted based on standard practices. Patients were followed for all-cause mortality. The optimal cutoff value of antero-posterior LA diameter for mortality was assessed by receiver operating characteristic analysis. Cox regression was used to determine variables associated with outcome.

Results: The mean age was 57 ± 12 years. LA dilatation was present in 9% (54) of patients (LA anteroposterior ≥ 2.4 cm/m²). There were 85 deaths (15%) during 4.5 ± 1.7 years of follow-up. LA diameter indexed for body surface area had an area under the curve of 0.72 ± 0.03 (optimal cut-point of 2.05 cm/m²). Variables independently associated with mortality included age [P = 0.004, hazard ratio (HR) 1.34 (1.10-1.64)], tobacco use [P = 0.001, HR 2.59 (1.51-4.44)], left ventricular hypertrophy [P = 0.001 , HR 2.14 (1.35-3.39)], Dobutamine stress [P = 0.003, HR 2.12 (1.29-3.47)], heart failure history [P = 0.031, HR 1.76 (1.05-2.94)], LA diameter ≥ 2.05 cm/m² [P = 0.027, HR 1.73 (1.06-2.82)], and an abnormal stress echocardiogram [P = 0.033, HR 1.67 (1.04-2.68)]. LA diameter as a continuous variable was also independently associated with mortality but LA size ≥ 2.40 cm/m² was not.

Conclusion: LA enlargement is infrequent in hypertensive AA patients when traditional reference values are used. LA enlargement is independently associated with mortality when a lower than "normal" threshold (≥ 2.05 cm/m²) is used.

Keywords: African American; Hypertension; Left atrial enlargement; Mortality; Stress echocardiography.

Figure 1

Comparison of sensitivity and specificity of left atrial diameter index cut-points. Sensitivity, specificity, and the summation of sensitivity and specificity are plotted for left atrial diameter index at 0.05 cm/m² intervals. Sensitivity is shown in blue, specificity is shown in red, and the summation of the two is shown in green. The reference upper and lower limits of normal (2.4 cm/m² and 1.5 cm/m², respectively) are indicated with dashed lines. The optimal cut-point that maximizes sensitivity and specificity was 2.05 cm/m² and is indicated with an asterisk (*) on the graph.

Figure 2

Kaplan Meier curve. Cumulative survival estimates are compared between patients with left atrial (LA) diameter index values above (blue line, LA index < 2.05) and below (red line, LA index ≥ 2.05) the optimal cut-point that maximizes sensitivity and specificity for death. LA: Left atrial.