Clinical utility of left atrial diameter normalized for body weight in healthy and cardiomyopathic cats

Introduction/Objectives

Left atrial dimensions correlate with body weight (BW) in cats. Atrial dimensions can be obtained from both right parasternal long-axis (RPLAx) and right parasternal short-axis images. However, reference ranges for RPLAx-derived left atrial diameter (LAD) obtained from a large sample of healthy cats are needed. This study measured LAD from the RPLAx view and calculated a normalized value to BW (LADn) and left atrial diameter-to-aortic annulus ratio (LAD:Ao). Study aims included developing prediction intervals for LADn, defining reference intervals for LAD:Ao, and investigating useful cutoffs for these variables for detection of congestive heart failure (CHF) in cats with cardiomyopathy.

Animals, Materials and Methods

Healthy cats (n = 303) and cats with different types of cardiomyopathy (198 preclinical; 71 with CHF). From RPLAx images, the LAD was measured from the interatrial septum to the free wall at end-systole and aortic diameter was measured at the annulus to calculate the LAD:Ao. Linear regression analysis was used to investigate the effect of BW on the LAD. Cutoffs of LADn and LAD:Ao that identified cats with CHF were generated.

Results

The LAD correlated to BW (r = 0.52, P<0.001). The formula to calculate LADn was LAD (mm)/BW (kg)^0.19, while median RPLAx LAD:Ao was 2.0 (95% reference interval: 1.55–2.47). Values of LADn >12.7 and LAD:Ao >2.5 had a sensitivity of 92.8% and 88.7% and a specificity of 91.5% and 93.6%, respectively, in detecting CHF.

Study Limitations

Due to the retrospective design of the study and lack of longitudinal follow-up, the inclusion of cats with occult CM in the healthy group cannot be entirely ruled out.

Conclusions

The LAD correlates with BW in cats. In the evaluation of LA dimension, LADn and LAD:Ao might be preferable to unadjusted LAD, especially in smaller and larger breeds of cats.