Three dimensional biatrial expansion index as an independent predictor of outcome in dilated cardiomyopathy

Abstract Background Left atrial expansion index (LAEI) is a marker of left ventricular (LV) diastolic dysfunction and an outcome predictor in heart failure (HF). However, the role of the right atrial expansion index (RAEI) in the setting of left-sided HF is incompletely understood. Purpose We sought to evaluate the left, right and combined bi-atrial expansion index (BAEI) with three-dimensional (3D) echocardiography in a cohort of patients with dilated cardiomyopathy (DCM) and to assess their prognostic role. Methods We enrolled 121 consecutive patients (mean age 59±14 years, 74% men) with DCM in sinus rhythm, who underwent 3D echocardiography and were prospectively followed for 19±11 months for an endpoint of death, nonfatal cardiac arrest and HF hospitalization. As previously described, for the left atrium (LA), LAEI was measured as (3D LA Vmax – 3D LA Vmin) x 100/3D LA Vmin, where Vmax was the maximal end-systolic atrial volume and Vmin was the minimal end-diastolic atrial volume. For the right atrium (RA), RAEI was calculated as (3D RA Vmax – 3D RA Vmin) x 100/3D RA Vmin. BAEI was defined as the sum of LAEI and RAEI. Results 55 patients (46%) reached the endpoint: there were 27 deaths, 5 nonfatal cardiac arrests and 23 readmissions for HF. Patients with adverse outcome had lower LAEI (52±25 vs. 63±36, p=0.047), lower RAEI (57±29 vs. 70±32, p=0.02), lower BAEI (108±46 vs. 133±55, p=0.008). In univariate Cox regression, all three expansion indices were predictors of adverse events: HR=3.23 [95% CI, 1.45-7.20], p=0.004 for LAEI, HR=2.12 [95% CI, 1.24-3.61], p=0.006 for RAEI, HR=3.99 [95% CI, 1.70-9.36], p=0.001 for BAEI. We constructed a multivariable model with well-established event predictors in DCM and one expansion index at a time. After adjustment for age, left ventricular ejection fraction, mitral regurgitation severity and pulmonary artery systolic pressure, all three expansion indices remained independent predictors of the composite endpoint: HR=2.75 [95% CI, 1.18-6.38], p=0.02 for LAEI, HR=1.86 [95% CI, 1.04-3.31], p=0.04 for RAEI, HR=3.53 [95% CI, 1.46-8.51], p=0.005 for BAEI. BAEI yielded the highest incremental prognostic power (likelihood ratio chi2 test=14, p=0.03) on top of the baseline model consisting of age, left ventricular ejection fraction, mitral regurgitation severity and pulmonary artery systolic pressure (likelihood ratio chi2 test=9). Conclusion In DCM, 3D atrial expansion indices are significantly lower in patients with major adverse events, reflecting a more impaired atrial reservoir dysfunction. Both LAEI, RAEI and BAEI were independent outcome predictors in patients with DCM. Combining the left and right atrial expansion indices might improve risk stratification, since BAEI had the highest predictive value after adjustment for confounders.