The Left Atrium Makes Headlines

Abstract

The associations of left atrial (LA) enlargement with chronic diastolic dysfunction1Nagueh S.F. Appleton C.P. Gillebert T.C. et al.Recommendations for the evaluation of left ventricular diastolic function by echocardiography.J Am Soc Echocardiogr. 2009; 22: 107-133Abstract Full Text Full Text PDF PubMed Scopus (2482) Google Scholar and increased mortality in various cardiac conditions2Moller J.E. Hillis G.S. Oh J.K. et al.Left atrial volume: a powerful predictor of survival after acute myocardial infarction.Circulation. 2003; 107: 2207-2212Crossref PubMed Scopus (573) Google Scholar,3Essayagh B. Antoine C. Benfari G. et al.Prognostic implications of left atrial enlargement in degenerative mitral regurgitation.J Am Coll Cardiol. 2019; 74: 858-870Crossref PubMed Scopus (30) Google Scholar have long been recognized. However, the LA's active and complex relationship with total cardiac performance has only more recently become appreciated. This issue of JASE includes four important papers on LA remodeling and mechanics.4Nuzzi V. Raafs A. Manca P. et al.Left atrial reverse remodeling in dilated cardiomyopathy.J Am Soc Echocardiogr. 2023; 36: 154-162Abstract Full Text Full Text PDF Google Scholar, 5Montero-Cabezas J.M. Abou R. Chimed S. et al.Effects of atrial ischemia on left atrial remodeling in patients with ST segment elevation myocardial infarction.J Am Soc Echocardiogr. 2023; 36: 163-171Abstract Full Text Full Text PDF Google Scholar, 6Meucci M.C. Reinders M.E.J. Groeneweg K.E. et al.Left atrial structural and functional response in kidney transplant recipients treated with mesenchymal stromal cell therapy and early tacrolimus withdrawal.J Am Soc Echocardiogr. 2023; 36: 172-179Abstract Full Text Full Text PDF Google Scholar, 7Cho D.-H. Kim Y.G. Choi J. et al.Atrial cardiomyopathy with impaired functional reserve in patients with paroxysmal atrial fibrillation.J Am Soc Echocardiogr. 2023; 36: 180-188Abstract Full Text Full Text PDF Google Scholar In a large cohort of consecutive patients with dilated cardiomyopathy treated according to guidelines, Nuzzi et al.4Nuzzi V. Raafs A. Manca P. et al.Left atrial reverse remodeling in dilated cardiomyopathy.J Am Soc Echocardiogr. 2023; 36: 154-162Abstract Full Text Full Text PDF Google Scholar have explored the relationship of LA reverse remodeling and outcome. After exclusion of 4% of the study population because of poor acoustic windows, 560 patients from tertiary care centers in Trieste and Maastricht had LA volume index (LAVI) assessment by the biplane disk summation method at baseline and 1-year follow-up. Intra- and interobserver variability of measurement were excellent. The study group included 35% women, age was 52 ± 13 years, and ejection fraction was 31% ± 10% at baseline. The LAVI was 45 ± 18 mL/m2 and >34 mL/m2 in 69%. Left atrial reverse remodeling was defined as LAVI ≤ 34 mL/m2 and a change of ≥10%. After one year of medical therapy, LAVI decreased in 67%, with a median change of –24%, and the criteria for LA reverse remodeling were met in 31%. During a median follow-up of 65 months, change in LAVI was linearly associated with death, heart transplantation, and heart failure hospitalization after adjustment for age, baseline LAVI, left ventricular ejection fraction, mitral regurgitation, atrial fibrillation (AFib), and therapy. This supports the utility of LAVI measurement in the assessment of patients with dilated cardiomyopathy. In future work, it will be important to consider the relationship of LA remodeling with the parameters of diastolic function, blood pressure control, and specific heart failure therapy. In patients with ST-elevation myocardial infarction, the impact of atrial ischemia resulting from impaired coronary flow in the dominant coronary artery branch (CAB) on LA anatomical and functional remodeling was assessed.5Montero-Cabezas J.M. Abou R. Chimed S. et al.Effects of atrial ischemia on left atrial remodeling in patients with ST segment elevation myocardial infarction.J Am Soc Echocardiogr. 2023; 36: 163-171Abstract Full Text Full Text PDF Google Scholar Sixty-nine patients with impaired flow in the dominant CAB were compared with an age- and sex-matched control group of 138 patients with normal CAB flow. Echocardiographic LA remodeling was evaluated with transthoracic echocardiography at baseline and at 6 and 12 months. Among patients with impaired CAB flow, LA strain reservoir, conduit, and booster pump functions were lower at baseline and remained impaired at follow-up. Although LA maximal volume was similar in both groups at baseline, in those with impaired flow, LA volumes were larger at six months, and this difference was sustained at one year. Thus, in this example of ischemic atrial disease, LA functional changes preceded anatomic remodeling. Kidney transplant recipients were randomized to autologous bone marrow-derived mesenchymal stromal cell therapy (MSC) versus standard tacrolimus dosing, and echocardiographic parameters were compared by Meucci et al.6Meucci M.C. Reinders M.E.J. Groeneweg K.E. et al.Left atrial structural and functional response in kidney transplant recipients treated with mesenchymal stromal cell therapy and early tacrolimus withdrawal.J Am Soc Echocardiogr. 2023; 36: 172-179Abstract Full Text Full Text PDF Google Scholar Between 4 and 24 weeks after transplantation, indexed minimal LA volume increased in the tacrolimus group but remained unchanged in the MSC group, in which blood pressure control was better. Moreover, those in the MSC group had a benefit in terms of LA emptying fraction and reservoir strain even after adjustment for changes in blood pressure over time. In a novel study using submaximal supine bicycle exercise echocardiography, Cho et al.7Cho D.-H. Kim Y.G. Choi J. et al.Atrial cardiomyopathy with impaired functional reserve in patients with paroxysmal atrial fibrillation.J Am Soc Echocardiogr. 2023; 36: 180-188Abstract Full Text Full Text PDF Google Scholar compared 61 patients with paroxysmal AFib undergoing radiofrequency catheter ablation and 38 healthy controls. Patients with AFib were divided into two groups according to LAVI. Exercise-induced increases in LA reservoir strain were attenuated in all patients with AFib. Left atrial functional reserve index was lower in the AFib patients with enlarged LAVI and was associated with recurrent AFib. Larger studies are needed to confirm the importance of exercise-induced changes in LA volume and function with outcome. This topic has been addressed in recent important studies. Among 666 patients with secondary mitral regurgitation of grade 2 or more severity, LA reservoir strain was independently associated with mortality during a median follow-up of five years, providing incremental prognostic value over LAVI and LV global longitudinal strain.8Stassen J. Namazi F. van der Bill P. et al.Left atrial reservoir function and outcomes in secondary mitral regurgitation.J Am Soc Echocardiogr. 2022; 35: 477-485Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar In 125 patients with rheumatic mitral stenosis and without a history of AFib, LA reservoir strain and strain rate were associated with the development of AFib at follow-up.9Stassen J. Burcher S.C. Namazi F. et al.Left atrial deformation imaging and atrial fibrillation in patients with rheumatic mitral stenosis.J Am Soc Echocardiogr. 2022; 35: 486-494Abstract Full Text Full Text PDF Scopus (0) Google Scholar In 594 hospitalized patients with nonvalvular AFib followed for 33 ± 21 months, LAVI and reduced LA emptying fraction were associated with AFib rehospitalization and mortality.10Bhat A. Gan G.C.H. Chen H.H.L. et al.Association of left atrial metrics with atrial fibrillation rehospitalization and adverse cardiovascular outcomes in patients with nonvalvular atrial fibrillation following index hospitalization.J Am Soc Echocardiogr. 2021; 34: 1046-1055Abstract Full Text Full Text PDF PubMed Scopus (3) Google Scholar Among 291 patients with cryptogenic stroke and 20 ± 14 months of follow-up, LA reservoir and booster strain were independently associated with recurrent stroke.11Bhat A. Chen H.H.L. Khanna S. et al.Diagnostic and prognostic value of left atrial function in identification of cardioembolism and prediction of outcomes in patients with cryptogenic stroke.J Am Soc Echocardiogr. 2022; 35: 1064-1076Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar In 792 patients who underwent catheter ablation for AFib, not only LAVI but also emptying fraction and expansion index were associated with cardiac hospitalization, stroke, or death during a median follow-up of 7.5 years,12Wen S. Pislaru S.V. Lin G. et al.Association of postprocedural left atrial volume and reservoir function with outcomes in patients with atrial fibrillation undergoing catheter ablation.J Am Soc Echocardiogr. 2022; 35: 818-828Abstract Full Text Full Text PDF Scopus (0) Google Scholar independent of AFib recurrence. Further studies are needed to see whether, by improving risk stratification, measurement of LA mechanics can impact the outcome of patients with valve disease, cryptogenic stroke, and AFib. These new papers augment our understanding of the LA and its important role in overall cardiac function. I look forward to future studies that continue to explore and validate these new insights.