Clinical and Echocardiographic Features of Primary Infundibular Stenosis with Intact Ventricular Septum in Dogs

Abstract

Background:Primary infundibular stenosis is a rare congenital defect in which the right ventricle is divided into a proximal “high‐pressure” chamber and a distal “low‐pressure” chamber. The condition can be misdiagnosed as ventricular septal defect or valvular pulmonic stenosis and the disease severity underestimated. The purpose of this study was to provide a detailed clinical and echocardiographic description of this anomaly in a series of dogs. Hypothesis:Several anatomic forms of infundibular stenosis exist. High resolution two‐dimensional echocardiography could differentiate 3 gross anatomic substrates. Knowledge of the anatomy of the obstructing lesion could influence options for corrective interventions. Animals:Thirteen dogs examined at the Ontario Veterinary College teaching hospital from 1994 to 2005 with an ultrasound diagnosis of subpulmonic stenasis. Methods:A retrospective review was made of case records from 1994 to 2005. Results:Thirteen dogs were identified as having primary infundibular stenosis, with apparent increased prevalence in Golden Retrievers (8/13, 62%) and Siberian Huskies (3/13, 23%). Three types of infundibular lesions were identified by ultrasound in 11/13 dogs: a fibrous diaphragm (6), fibromuscular (4), and muscular obstruction (1). Two dogs with a fibrous diaphragm underwent direct surgical dilation without the use of cardiopulmonary bypass or inflow occlusion, resulting in substantial reduction of the severity of stenosis. Conclusion and Clinical Importance: Accurate determination of the severity of the stenosis and the anatomy of the obstructing lesion are important in devising a treatment strategy. Recognition of the fibrous diaphragm by echocardiography identifies a subset of dogs potentially amenable to surgical dilation without the need for cardiopulmonary bypass.

Echocardiography

“…388,390,396,[398][399][400][401][402][403] Abnormalities observed by 2D imaging include valvular thickening (dysplasia), fusion along the commissural edges, and varying degrees of annular hypoplasia. 388,390,396,[398][399][400][401][402][403] Abnormalities observed by 2D imaging include valvular thickening (dysplasia), fusion along the commissural edges, and varying degrees of annular hypoplasia.…”

Double-Chambered Right Ventricle in an Old Standard Poodle Dog

“…Anomalous muscle bands or endogenous trabecular hypertrophy may cause abnormal separation (9). Two chambers exist: an inflow chamber with high pressure, and an outflow chamber with low pressure (8)(9)(10)(11). In humans, DCRV is characterized by pressure gradients of over 20 mmHg between the two chambers and is frequently associated with other anomalies, including Ebstein's anomaly, membranous ventricular septal defect, and double-outlet right ventricle (9).…”