Chapter 83 Ventricular Septal Defect and Repair
PATHOPHYSIOLOGY
A ventricular septal defect (VSD) is a communication or abnormal opening between the right and left ventricles of the heart. VSDs are classified according to location in the ventricular septum as either membranous or muscular. The size of the communication varies widely. Many small, muscular VSDs close spontaneously. The defect is frequently associated with other cardiac defects such as transposition of the great arteries, pulmonary stenosis, atrial septal defect, and coarctation of the aorta. The altered physiology can be described as follows:
1. Pressure is higher in the left ventricle, and thus oxygenated blood shunts from the left ventricle to the right ventricle.
2. Increased blood volume is pumped into the lungs, which eventually may become congested with blood. Over time, this may lead to increased pulmonary vascular resistance.
3. If the pulmonary resistance is high, right ventricular pressure may increase, causing a reversal of the shunt. The unoxygenated blood then flows from the right ventricle to the left, which produces cyanosis (Eisenmenger’s syndrome).
INCIDENCE
1. VSD is the most common congenital heart defect, occurring at a rate of 2 per 1000 live births and accounting for 20% of all congenital heart defects.
2. VSD is also the most common congenital heart defect in children with chromosomal abnormalities such as Down syndrome.
4. Congenital heart defects are more common in the offspring of those who had a VSD.
CLINICAL MANIFESTATIONS
1. Loud systolic murmur generally heard best at left lower sternal border; the size of the defect does not correlate with intensity of the murmur, since louder murmurs may be associated with smaller defects.
2. Thrill may be palpable at left lower sternal border.
3. Signs and symptoms vary with size of the defect and pressure differences between the right and left ventricle.
COMPLICATIONS
1. Cardiac: CHF, development of aortic insufficiency or pulmonary stenosis, progressive pulmonary vascular disease, damage to ventricular conduction system
Postoperative Complications
1. Cardiac: aortic insufficiency, tricuspid insufficiency, electrocardiogram (ECG) changes such as right bundle branch block, arrhythmias including heart block, ventricular dysfunction with potential for low cardiac output (especially if pulmonary hypertension and/or ventriculotomy), residual VSD
3. Growth and development: neurodevelopmental sequelae of cardiopulmonary bypass
LABORATORY AND DIAGNOSTIC TESTS
Refer to Appendix D for normal values and ranges of laboratory and diagnostic tests.
1. Chest radiograph—varying degrees of cardiomegaly, with increased pulmonary vascular markings
2. ECG—normal with a small VSD; may have left ventricular hypertrophy (LVH) with larger defects
3. Echocardiogram—to identify size and location of defect, identify associated defects, and estimate the magnitude of the left to right shunt
4. Cardiac catheterization—may not be required unless there are other associated defects or concerns regarding elevated pulmonary vascular resistance
5. Preoperative laboratory data
