# Retrospective Evaluation of End-Diastolic Forward Flow and Restrictive Physiology in One Hundred and Sixty-Four Dogs with Pulmonary Stenosis

## TL;DR

This study examines the link between restrictive right ventricular physiology and severe pulmonary stenosis in dogs, finding that end-diastolic forward flow is associated with more severe disease.

## Contribution

The study is the first to describe end-diastolic forward flow and restrictive physiology in dogs with pulmonary stenosis in veterinary medicine.

## Key findings

- Dogs with end-diastolic forward flow had higher severity of pulmonary stenosis.
- Restrictive right ventricular physiology is common in dogs with severe pulmonary stenosis.
- Type A and B stenosis groups both showed increased disease severity with end-diastolic forward flow.

## Abstract

Pulmonary stenosis is one of the most common congenital cardiac pathologies in dogs. This determines an increase in afterload with consequent right ventricular remodeling with the development of concentric hypertrophy. This pathophysiological mechanism is linked to a reduction in right ventricular diastolic function, which takes on a restrictive aspect with the presence of an anomalous antegrade flow in the late diastolic phase. This study highlights how the restrictiveness of the right ventricle is linked to the presence of a severe pathological condition and is found in patients who present severe right ventricular hypertrophy associated with greater severity of the degree of stenosis with high values of velocity and transvalvular pulmonary gradient.

The study of the function of the right ventricle (RV) is a topic of great interest in the scientific community, and some studies have evaluated parameters of the right ventricular systolic function and have correlated them to various RV pathologies and possible clinical findings. Less information was obtained on the right ventricular diastolic function. In veterinary medicine, the characteristics of the restrictive RV and the presence of end-diastolic forward flow (EDFF) in patients with pulmonary stenosis have not yet been described. This type of flow is an antegrade flow that is observed with the Doppler study of the pulmonary artery and occurs at the end of the diastolic phase. Pulmonary valve stenosis (PVS) is one of the most common congenital heart diseases in dogs. The echocardiographic parameter that is mainly taken as a reference for evaluating the severity of the disease is the peak gradient of the pulmonary antegrade flow. For our retrospective study, we consider a total of 164 dogs with PVS divided into 149 dogs with type A and 15 type B, seen at a reference veterinary clinic from 2020 to 2024. All these dogs underwent echocardiographic examinations to observe the morphological characteristics of the PVS and consider the presence or absence of restrictive RV with EDFF. An independent sample t-test analysis revealed that the severity of PVS is greater in dogs with EDFF, both in the group of patients with type A stenosis and in patients with type B stenosis. This study suggests that RV restrictive physiology is common in dogs with severe PVS.