Beyond the Segmental Code: Anatomic Diversity and Surgical Pathways in Left Atrial Appendage Isomerism with the {A,L,I} Combination

Background/Objectives: Left atrial appendage isomerism (LAAI) is associated with substantial variation in venous connections and intracardiac anatomy. A subgroup of LAAI patients has L-loop ventricular topology together with a particular great artery relationship—a combination that corresponds historically to Van Praagh’s {A,L,I} segmental notation—but this subgroup has not been separately characterized. We aimed to describe the anatomical spectrum, rhythm and conduction abnormalities, biventricular repair eligibility, and surgical pathways in this subgroup.

Methods

This single-center retrospective study included 15 patients with LAAI, L-loop ventricular topology, and a specific great artery relationship (aorta left-sided, pulmonary artery right-sided)—a combination corresponding historically to Van Praagh’s {A,L,I} notation—evaluated between January 2010 and December 2025. Diagnosis was confirmed independently by echocardiography and cardiac computed tomography in all patients. Anatomical suitability for biventricular repair was determined by multidisciplinary consensus.