Ventricular Septal Defect (VSD)

Introduction

A ventricular septal defect (VSD) is a left-to-right shunt that occurs due to a defect in the interventricular septum of the heart. VSDs are the most common congenital cardiac defect.

Epidemiology

Present in 1/500 live births.

Types

There are 2 types of VSDs depending on the structural pathology present:

1. Perimembranous: membranous septum is deficient. Mostly congenital
2. Muscular: defect in muscular septum. Can be acquired.

Causes

VSDs can be congenital or acquired. Acquired causes include myocardial infarction and trauma. Congenital causes can be associated with Down’s syndrome or congenital rubella syndrome.

Haemodynamics

There is left-to-right shunting of blood, whereby blood from the left ventricle directly enters the right ventricle. This increases pressure in the pulmonary vasculature as the left ventricle generates higher pressures compared to the right ventricle. In addition, there is  increased venous return to the left ventricle since both the peripheral circulation and eventually recirculating blood (via the shunt) end up in the left ventricle.

Eisenmenger’s syndrome

If pulmonary blood flow is very large, there is a progressive obliteration of the pulmonary vasculature. This can eventually lead to pulmonary hypertension and, if the pressure is high enough, right-to-left shunting (when right ventricle pressure exceeds left ventricle pressure).

Clinical features

Small VSDs

Small VSDS are usually asymptomatic and close spontaneously. 90% are no longer patent by the age of 10. However, there is a risk of developing aortic regurgitation and infective endocarditis. May produce a loud pansystolic murmur (referred to as Maladie de Roger, the observation that smaller defects can produce louder murmurs because of increased turbulence).

Large VSDs

Large VSDs can produce dyspnoea, recurrent chest infections and failure to thrive. If heart failure develops, it usually becomes apparent in the first 4-6 weeks of life rather than the immediate postnatal period. Signs include:

• Pansystolic murmur – loudest over tricuspid area
• Thrill over tricuspid area
• Bulging sternum (due to right ventricular hypertrophy)

Investigations

• Chest x-ray: usually normal (may show cardiomegaly in large defects)
• ECG: normal
• Echocardiography: most important investigation for confirming defect

Management

Small defect

No specific treatment required.

Large defect

Initially, manage medically with diuretics and digoxin if heart failure is present. Surgery is the definitive management for VSDs. Surgery is indicated if there is:

• Inadequately controlled heart failure
• Progressive pulmonary hypertension
• Infundibular obstruction
• Infective endocarditis

Complications

• Pulmonary hypertension
• Shunt reversal (Eisenmenger’s syndrome)
• Ventricular septal rupture
• Infective endocarditis
• Aortic regurgitation

Prognosis

Very good in congenital VSD. However, patients with Eisenmenger’s syndrome mostly die at age 20-30.