Vsd

VENTRICULAR SEPTAL DEFECT Dr Prakash Sapkale

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Ventricular septal defect (VSD) is the second most common cardiac malformation accounting for approximately one fifth of all congenital cardiac anomalies.

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DEVELOPMENT OF INTERVENTRICULAR SEPTUM

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3 Embryological Precursors: 1) Primitive interventricular septum- forms muscular part of the definitive septum 2) Caudal part of the bulbar septum- forms crista of right ventricle 3) Membranous downgrowth from undersurface of AV cushionsmembranous portion of definitive septum

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VSD may occur from maldevelopement of any of these precursors

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PATHOPHYSIOLOGY The functional disturbance caused by a VSD depends primarily on its size and the status of the pulmonary vascular bed rather than on the location of the defect. The magnitude of the shunt is determined by size of the VSD , the level of pulmonary vascular resistance compared with systemic vascular resistance. The magnitude of intracardiac shunts is usually described by the Qp:Qs ratio, where Qp is the pulmonary resistance and Qs is the systemic resistance.

– If the left-to-right shunt is small (Qp:Qs < 1.75:1), the cardiac chambers are not appreciably enlarged, and the pulmonary vascular bed is likely normal. If the shunt is large (Qp:Qs > 2:1), left atrial and LV volume overload occurs, as does right ventricular and pulmonary arterial hypertension. The main pulmonary artery, left atrium, and LV are enlarged. – Restrictive VSD -When a small communication is present (usually <0.5 cm2) – Moderately restrictive VSD- moderate shunt (Qp:Qs = 1.5-2.5:1.0) – large nonrestrictive VSDs (usually >1.0 cm2),

TYPES OF VSD 1)Membranous VSD: • Most common type • Occurs in upper posterior aspect of the septum below the aortic cusps(left) and crista supraventricularis(right) • The bundle of His runs along its posterior edge • 4 types– – – – –

Supracristal VSD (infundibular) (5%) (type I) –located above supraventricularis, just under the annulus of aorta. Type II (80%) Anterior membranous VSD- Fallot’s tetralogy Posterior membranous VSD – uncommon, persistent AV canal anomaly canal-type (Type III )(11%) Gerbode left ventricle to right atrial shunt – maldevelopement of part of AV cushion and the upper part of the ventricular septum

2)Muscular VSD: (4%)(type IV) • One or multiple defects • results from the excessive resorption of septal tissue during the muscular septal formation. • Usually small-loud murmur • Multiple- Swiss cheese VSD

• A = Doubly committed subarterial VSD; • B= perimembranous VSD; • C = inlet or atrioventricular canal–type VSD; • D = muscular VSD.

INVESTIGATIONS •

RADIOLOGY:

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Small VSDs -the chest radiographic results are usually normal.

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Medium-sized VSDs - minimal cardiomegaly and a borderline increase in pulmonary vasculature may be observed.

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Large VSDs -

– the chest radiograph shows gross cardiomegaly with prominence of both ventricles, the left atrium,(visible on lateral radiographs), and the pulmonary artery. The pulmonary vascular markings are increased and frank pulmonary edema, including pleural effusions, may be present. – VSD with pulmonary hypertension- chest radiograph may be normal despite large defect • • • •

Essentially normal-sized heart RV hypertrophy with the cardiac apex rotated slightly upward, to the left, and posteriorly Markedly prominent main PA and adjacent vessels Decreased pulmonary vascularity in outer third of the lung fields

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ECHOCARDIOGRAPHY:

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provides additional physiologic information Dilatation of left ventricle Dilatation of left atrium Tricuspid regurgitation- reflects increased pulmonary artery pressure Doppler gradient from left ventricle to right across VSD- smaller the VSD, more the gradient The size of the defect is often expressed in terms of the size of the aortic root. :

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Defects that approximate the size of the aortic root are classified as large, those one third to two thirds of the diameter of the aorta are classified as moderate, and those less than one third of the aortic root diameter are classified as small.

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Transesophageal echocardiography (TEE) is occasionally used. In the pediatric age group, it is used most often performed intraoperatively to assess the completeness of the repair.

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CT scans may show cardiomegaly, left atrial enlargement, and vascular engorgement.

• MRI : •

MRI is usually used only when ultrasonography is not feasible or when sonographic findings are not diagnostic. • • •

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Morphologic information is provided by ECG-gated spin-echo and cine MRI. Ventricular volumes, mass, and function can be assessed by using cine MRI. The volumes of shunts, valvular function, and pressure gradients across valves and conduits can be estimated by using velocityencoded cine MRI (velocity-flow mapping).

ANGIOCARDIOGRAPHY: Injection of contrast into the LV or main pulmonary artery- LAO or lateral projection Replaced by echocardiography

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