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1036 Ventricular Septal Defect

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Ventricular Septal Defect Available Client Education
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• Cough (L→R)
BASIC INFORMATION
• Cyanosis (R→L) • Changes consistent with left atrial (LA) and/
or LV enlargement if large L→R shunt or
Definition • Syncope RV enlargement if R→L shunt
Anomalous communication between the right • ± Wide and/or notched Q wave, representing
ventricle (RV) and left ventricle (LV), resulting PHYSICAL EXAM FINDINGS abnormal septal activation
in interventricular shunting of blood • Systolic murmur (grade III-V/VI) heard Echocardiography (confirmatory test of choice):
best over right ventral fourth intercostal • A visible defect in the interventricular septum
Synonyms space (perimembranous VSD); less com- (IVS) may be noted, although small defects
Interventricular septal defect, VSD monly loudest over left base (juxtaarterial often cannot be visualized (see Videos). Beware
VSD) of tissue dropout artifacts mimicking defects.
Epidemiology • If substantial AI is present, a diastolic • L→R VSD: turbulent jet from LV to RV on
SPECIES, AGE, SEX murmur may be heard over the left base. color Doppler echocardiography (see Videos),
• Most common congenital heart defect in • If congestive heart failure (CHF) is present: ± LA and LV enlargement
cats; fourth most common in dogs tachycardia, dyspnea, tachypnea, pulmonary • Peak velocity (in m/s) of VSD jet measured
• Typically diagnosed at a young age (median, crackles with continuous-wave Doppler reflects the
9-12 months) • R→L shunt: cyanosis, generally no murmur pressure gradient (ΔP [mm Hg]) between
• No sex predisposition unless another malformation is present LV and RV according to modified Bernoulli
2
equation (ΔP = 4V ), which generally speaks
GENETICS, BREED PREDISPOSITION Etiology and Pathophysiology to size of defect (small VSD: V > 4.5 m/s;
• Predisposed dog breeds: Akita, basset hound, • Magnitude and direction of shunting and moderate-size VSD: 3 < V < 4.5 m/s; large
bloodhound, English and French bull dog, the clinical consequences depend on size VSD: V < 3 m/s). Beware of underestimation
English springer spaniel, German shepherd, of defect, relative pulmonary and systemic of velocity due to malalignment with the
keeshond (hereditary), terrier breeds (border, vascular resistances, and presence of other VSD jet.
fox, Jack Russell, Lakeland, West Highland cardiopulmonary defects. • R→L VSD: RV hypertrophy, flattening of
white, Yorkshire) • Small, isolated VSDs are most common the IVS, main pulmonary artery dilation
• In cats, domestic shorthairs and Maine coons and may result in minimal overcirculation • ± AI on color and spectral Doppler
most frequently reported and volume overload, whereas significant echocardiography
L→R shunting causes volume overload of
ASSOCIATED DISORDERS pulmonary circulation and left side of the Advanced or Confirmatory Testing
• Concurrent congenital cardiac defects present heart, potentially causing left-sided CHF • Contrast echocardiography (saline bubble
in up to 50% of cases, with pulmonic stenosis and/or pulmonary hypertension (PH). study) to confirm R→L shunt
(PS) and as part of tetralogy of Fallot most • R→L shunting VSD causes systemic arterial • Cardiac catheterization for angiography,
common hypoxemia, leading to erythrocytosis and shunt quantification, and measurement
• Aortic valvular insufficiency (AI) is common hyperviscosity syndrome. of intracardiac pressures (only used pre-/
due to decreased support of aortic valve. intraoperative)
Clinical Presentation DIAGNOSIS
DISEASE FORMS/SUBTYPES Diagnostic Overview TREATMENT
• In dogs and cats, VSD most commonly Although strong clinical suspicion of VSD may Treatment Overview
involve the high membranous septum below be based on physical exam alone, definitive • Often no treatment is required because
the aortic valve on left side and cranial to the diagnosis requires echocardiography. most VSDs are small and do not result in
septal tricuspid valve leaflet on the right side volume overload or other significant clinical
(membranous or perimembranous VSD). Differential Diagnosis consequences.
Less common locations include below the Tricuspid dysplasia (TVD), subaortic stenosis • Treatment of large L→R VSDs is directed at
pulmonic valve (juxtaarterial VSD) and in (SAS), PS, tetralogy of Fallot (of which VSD is decreasing the shunt volume and preventing
the muscular septum (muscular VSD). one component), hypertrophic cardiomyopathy or eliminating the signs of CHF.
• Left-to-right (L→R) shunting across the VSD (HCM) in cats • Treatment of R→L VSDs is directed at
is most common. reducing RV pressure and palliating the
• Right-to-left (R→L, reverse shunting) Initial Database effects of erythrocytosis.
may occur in cases accompanied by other CBC/serum biochemistry panel:
defects that increase RV pressure (e.g., • Typically normal Acute and Chronic Treatment
PS) or rarely with very large VSDs that • Erythrocytosis if R→L shunting L→R VSD with significant left-sided volume
result in pulmonary overcirculation and Thoracic radiographs: overload and risk or presence of CHF:
pulmonary hypertension (Eisenmenger’s • Normal with small VSD • Surgical repair by thoracotomy uncommon
physiology). • Larger L→R VSD: left-sided cardiomegaly, (requires cardiopulmonary bypass, available
pulmonary overcirculation, ± pulmonary at very few referral institutions)
HISTORY, CHIEF COMPLAINT edema, ± right ventricular enlargement • Percutaneous transcatheter repair or hybrid
Frequently it is an incidental finding based on • R→L VSD: right-sided cardiomegaly, variable techniques using a variety of devices have
detection of a heart murmur. In the case of a pulmonary artery pattern (e.g., normal to been described in dogs and may be available
large L→R VSD or in R→L VSD, the following enlarged if PH present; normal or small if at some referral institutions.
may be observed: PS present) • Pulmonary artery banding is a pal-
• Exercise intolerance Electrocardiogram (ECG): often normal (p. liative surgical technique to decrease L→R
• Dyspnea, tachypnea 1096) shunt.

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