Causes of Markedly Dilated Left and Right Atria

Primary Pathophysiologic Mechanisms

• The European Society of Cardiology recommends considering pressure overload and volume overload as the two fundamental pathways that frequently coexist in atrial dilation, with mitral stenosis creating direct left atrial pressure overload, and left ventricular diastolic dysfunction elevating left ventricular end-diastolic pressure 1, 2
• The American Heart Association suggests that systolic heart failure with reduced ejection fraction commonly causes left atrial enlargement through sustained elevation of filling pressures, with the severity of stenosis accounting for 38% of left atrial size changes 1, 3

Volume Overload Conditions

• The European Heart Journal states that mitral regurgitation causes direct volume overload as blood flows backward into the left atrium during systole, with the atrium receiving both normal pulmonary venous return and the regurgitant volume 1

Biventricular Heart Failure Manifestations

• The European Heart Journal recommends evaluating left ventricular function, including systolic function and diastolic function, and assessing right ventricular function, which commonly accompanies left-sided pathology 2, 4, 5, 6, 7
• The American College of Cardiology suggests that right ventricular failure contributes to right atrial dilation through increased right ventricular size, decreased systolic function, and high right atrial pressure with dilated inferior vena cava 4, 5, 6, 7

Clinical Algorithm for Determining Etiology

• The European Society of Cardiology recommends systematically evaluating the etiology of markedly dilated left and right atria by documenting rhythm status, assessing mitral valve, evaluating left ventricular function, assessing right ventricular function, and quantifying hemodynamics 1, 2, 4, 5, 6, 7