Pseudoaneurysm of the mitral-aortic intervalvular fibrosa is rare, particularly in children, and is potentially fatal. This article presents two cases of pediatric mitral-aortic intervalvular fibrosa pseudoaneurysm: one secondary to infective endocarditis and the other confirmed to be congenital in nature. The characteristic echocardiographic manifestations of mitral-aortic intervalvular fibrosa pseudoaneurysm demonstrated in this study will enhance diagnostic efficacy and guide early clinical intervention.

Pseudoaneurysms of the mitral-aortic intervalvular fibrosa can rupture and form fistulous communications between the left ventricle and left atrium. Pulmonary venous systolic flow reversal in such cases reflects elevated left atrial pressure due to shunting. This finding, particularly in the setting of endocarditis, is not specific for severe mitral regurgitation.