Brief Communication
Transcatheter intravascular stent placement to relieve supravalvular pulmonic stenosis

https://doi.org/10.1016/j.jvc.2006.01.004Get rights and content

Abstract

Valvular pulmonic stenosis has been successfully treated in dogs via minimally invasive transcatheter balloon dilation procedures for almost 20 years. Supravalvular pulmonic stenosis however is not amenable to balloon dilation procedures. Although several surgical procedures are described for treatment of pulmonic stenosis, the morbidity and mortality of these procedures are significantly higher than for transcatheter approaches.

Two cases of supravalvular pulmonic stenosis are presented, one acquired and one congenital, which were successfully treated with transcatheter intravascular stent placement. The procedure alleviated the stenotic lesion and resolved clinical signs.

Introduction

Congenital heart disease has been reported to occur in 0.46 to 0.85% of dogs, with pulmonic stenosis accounting for 11–23% of these patients.1, 2, 3 Acquired pulmonic stenosis, although rare, has also been reported to occur due to mass lesions obstructing the right ventricular outflow tract.4 Congenital pulmonic stenosis is over represented in several breeds including the English Bulldog, Scottish Terrier, Wirehaired Fox Terrier, Miniature Schnauzer, West Highland White Terrier, Chihuahua, Jack Russell Terrier, Boxer, Beagle, Mastiff and Samoyed.1, 2, 5 Inheritance has been demonstrated in several breeds, with a polygenic mode of transmission.6

Pulmonic stenosis has been classified as either subvalvular, valvular or supravalvular.1, 7 Valvular pulmonic stenosis is most common and can be due to either commissural fusion or dysplasia of the valve cusps, with or without hypoplasia of the valve annulus.7, 8, 9 Primary supravalvular and subvalvular lesions are less common. Infundibular hypertrophy, although reported as a primary lesion, is most commonly secondary to right ventricular hypertrophy which develops in response to the pressure overload imposed by a primary subvalvular, valvular or supravalvular lesion.7 Several systems for estimating the severity of pulmonic stenosis have been reported; most reports define severe pulmonic stenosis as a Doppler derived pressure gradient greater than 80 mmHg.c,10, 11 Relief of severe pulmonic stenosis, with balloon dilation, has been shown to relieve clinical signs and increase survival in dogs.c11

Balloon dilation to relieve valvular stenosis due to commissural fusion has been widely reported in the veterinary literature.d,12, 13, 14, 15, 16 To date commissural fusion is the only lesion which has been shown to consistently respond to balloon dilation in veterinary patients. In those patients in which balloon dilation is not appropriate, a number of palliative surgical procedures have been reported.10, 17, 18, 19 However, regardless of procedure, the morbidity and mortality associated with surgery is significantly greater than that of catheter based procedures.10, 17, 18, 19

Transcatheter intravascular stent placement has been reported for the correction of both acquired and congenital supravalvular pulmonic stenosis in humans.20, 21 This report describes the successful use of transcatheter intravascular stent placement for relief of supravalvular pulmonic stenosis in two dogs.

Section snippets

Methods

All echocardiograms were obtained with a Vivid 5 echocardiographic recorder.e Two-dimensional, M-mode and Doppler measurements were performed with 10/4.4 and 3.6/1.5 MHz phased array sector transducers. Echocardiographic measurements were made according to accepted previously reported standards.22, 23 M-mode measurements were performed in triplicate and averaged.

Six-lead ECG was recorded using an EKG unit

Case history 1

An 11 month-old male intact Cocker Spaniel (11.2 kg) was referred to Colorado State University Veterinary School with an incidental murmur noted by the referring veterinarian. The dog was asymptomatic according to the owner.

On auscultation, a grade V/VI holosystolic left basilar murmur was evident, with a palpable thrill over the left cranial thorax. All other cardiovascular findings were within normal limits on physical examination.

Echocardiography showed severe right ventricular hypertrophy, a

Discussion

Since the first report of its use,25 balloon dilation has rapidly become the standard of care in veterinary practice for treatment of valvular pulmonic stenosis.d,12, 13, 14, 15, 16 Application of balloon dilation is limited to valvular pulmonic stenosis where commissural fusion is the major abnormality. Many surgical options exist for treatment of pulmonic stenosis;10, 17, 18, 19 however due to the increased morbidity and mortality of these procedures they are often reserved for those animals

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      Such an issue could have easily prevented the proper placement of the stent across the membrane. Griffiths et al. reported the use of a balloon-in-balloon catheter to deliver an intravascular stent within the pulmonary artery in two dogs.21 In these cases, the inner balloon was dilated initially to engage the stent, preventing dislocation and aiding in correct “dog bone” inflation of the outer balloon.

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