# Left Atrioventricular Coupling Index: An Echocardiographic Index of Atrioventricular Dysfunction in Dogs with Myxomatous Mitral Valve Disease

## TL;DR

This study introduces a new echocardiographic index to assess heart function in dogs with a specific heart valve disease.

## Contribution

The study introduces the left atrioventricular coupling index (LACi) for evaluating atrioventricular dysfunction in dogs with MMVD.

## Key findings

- LACi-ED and LACi-ES values differ significantly between ACVIM stages in dogs with MMVD.
- LACi-ED and LACi-ES show similar accuracy in identifying MMVD dogs with congestive heart failure.
- LACi does not outperform traditional indices in diagnosing congestive heart failure in MMVD dogs.

## Abstract

Given the close physiological relationship between the left atrium (LA) and left ventricle (LV), an index assessing both chambers simultaneously could be useful for evaluating disease severity. Therefore, we measured the left atrioventricular coupling index (LACi) in healthy dogs and dogs affected by myxomatous mitral valve disease (MMVD). The LACi (LA volume/LV volume*100) at LV end-diastole (LACi-ED) and LV end-systole (LACi-ES) were retrospectively measured in 233 dogs (105 healthy dogs and 128 dogs with MMVD). LACi-ED and LACi-ES differed between ACVIM stages (p < 0.001 and p < 0.02, for all stages) and showed similar accuracy to each other in identifying MMVD dogs with congestive heart failure. Our data suggest that the LACi can be useful in assessing left atrioventricular function in dogs with MMVD, but the diagnostic accuracy in identifying dogs with congestive heart failure is similar to traditional echocardiographic indices. Prospective studies are needed to evaluate the predictive value of this new echocardiographic index in dogs affected by MMVD.

The close physiological relationship between the left atrium (LA) and left ventricle (LV) suggests that an index assessing both the cardiac chambers simultaneously could provide useful information about disease severity. Consequently, investigators have proposed the atrioventricular coupling index (LACi) and demonstrated its utility in predicting the likelihood of atrial fibrillation, heart failure, and other cardiovascular events in humans. No studies have been reported in veterinary medicine. Therefore, we measured the LACi in healthy dogs and dogs affected by myxomatous mitral valve disease (MMVD). Two hundred and thirty-three dogs (105 healthy dogs and 128 dogs with MMVD) were retrospectively included in the study. The LACi (LA volume/LV volume × 100) at LV end-diastole (LACi-ED) and LV end-systole (LACi-ES) of each dog was measured using a monoplane Simpson’s Method of Discs from the left apical four-chamber view. In healthy dogs, LACi-ED and LACi-ES showed no relationship with bodyweight, heart rate and age (R2 < 0.03, for all variables). In MMVD dogs, LACi-ED and LACi-ES differed between ACVIM stages (p < 0.001 and p < 0.02, for all stages). The LACi-ED and LACi-ES had similar accuracy in identifying MMVD dogs with congestive heart failure (area under the curve of 0.920 and 0.906, respectively). Our data suggest that the LACi can be useful in assessing left atrioventricular function in dogs with MMVD but the diagnostic accuracy in identifying dogs with congestive heart failure was not superior to the left atrial-to-aortic ratio. Prospective studies are needed to evaluate the predictive value of this new echocardiographic index in dogs affected by MMVD.