Illustration showing various ventricular septal defect pdf of a ventricular septal defects. The extent of the opening may vary from pin size to complete absence of the ventricular septum, creating one common ventricle. The ventricular septum consists of an inferior muscular and superior membranous portion and is extensively innervated with conducting cardiomyocytes.
The membranous portion, which is close to the atrioventricular node, is most commonly affected in adults and older children in the United States. Membranous ventricular septal defects are more common than muscular ventricular septal defects, and are the most common congenital cardiac anomaly. Ventricular septal defect is usually symptomless at birth.
It usually manifests a few weeks after birth. VSD is an acyanotic congenital heart defect, aka a left-to-right shunt, so there are no signs of cyanosis in the early stage. However, uncorrected VSD can increase pulmonary resistance leading to the reversal of the shunt and corresponding cyanosis.
Larger defects may eventually be associated with pulmonary hypertension due to the increased blood flow. Over time this may lead to an Eisenmenger’s syndrome the original VSD operating with a left-to-right shunt, now becomes a right-to-left shunt because of the increased pressures in the pulmonary vascular bed.
Congenital VSDs are frequently associated with other congenital conditions, such as Down syndrome. ASD in humans when one copy is missing.
During ventricular contraction, or systole, some of the blood from the left ventricle leaks into the right ventricle, passes through the lungs and reenters the left ventricle via the pulmonary veins and left atrium. This has two net effects. First, the circuitous refluxing of blood causes volume overload on the left ventricle. In serious cases, the pulmonary arterial pressure can reach levels that equal the systemic pressure.
This reverses the left to right shunt, so that blood then flows from the right ventricle into the left ventricle, resulting in cyanosis, as blood is by-passing the lungs for oxygenation. This effect is more noticeable in patients with larger defects, who may present with breathlessness, poor feeding and failure to thrive in infancy. Patients with smaller defects may be asymptomatic. Four different septal defects exist, with perimembranous most common, outlet, atrioventricular, and muscular less commonly.
Echocardiographic image of a moderate ventricular septal defect in the mid-muscular part of the septum. The trace in the lower left shows the flow during one complete cardiac cycle and the red mark the time in the cardiac cycle that the image was captured.
Colours are used to represent the velocity of the blood. The size and position is typical for a VSD in the newborn period. A VSD can be detected by cardiac auscultation. Classically, a VSD causes a pathognomonic holo- or pansystolic murmur.