Left atrial volume and function in Cavalier King Charles spaniels at different ACVIM stages

The correct assessment of left atrial size and function is essential to evaluate the severity of degenerative mitral valve disease in dogs. Evaluate left atrial (LA) dimension and function in Cavalier King Charles Spaniel (CKCS) at different ACVIM stages and the accuracy of linear and volumetric indexes to assess LA enlargement. One hundred and ninety-eight privately owned CKCS. Multicentric prospective observational cross-sectional study. Dogs underwent an echocardiographic exam for breed screening or cardiac examination. Linear and volumetric echocardiographic LA size and function indexes were compared between classes. Dogs were allocated as follows: 43 in class ACVIM A, 58 ACVIM B1, 55 ACVIM B2, and 42 ACVIM C/D. Only LA anteroposterior diameter normalized on body weight (LADn) and LA maximal, minimal and P volumes (LAV max , LAV min , LAV P ) differed across all pairwise comparisons. Active LA emptying fraction (aLAEF) was higher in class B1 compared to class A ( P < .001), and then decreased in class C/D compared to class B2 (P < .001). This suggests an increase in the left atrial active component due to the Frank-Starling mechanism in ACVIM B1 dogs, and the presence of atrial dysfunction in symptomatic dogs. The LADn and LAV are higher in CKCS in class ACVIM B1 compared to class ACVIM A, suggesting the presence of LA remodelling at the early stages of the disease. Atrial dysfunction is evident in symptomatic dogs. • Left atrial remodelling is an important progression marker in dogs with myxomatous mitral valve disease. • Early atrial remodeling in Cavalier King Charles Spaniels can be detected by measuring left atrial diameter and volume. • Symptomatic Cavalier King Charles spaniels exhibit evident atrial dysfunction.