**5.1.3.3 Echocardiogram**

Echocardiographic studies reveal enlarged right ventricle with paradoxical septal motion, particularly well-demonstrable on M-mode echocardiograms. By two-dimensional echocardiogram, the defect can be clearly visualized (Figure 9A). The type of ASD, secundum versus primum can also be delineated by the echocardiographic study. Apical and precordial views may show "septal drop-outs" without an ASD because of thinness of the septum in the region of fossa ovalis. Therefore, only subcostal views should be scrutinized for evidence of ASD. In addition, demonstration of flow across the defect with pulsed Doppler (not shown) and color Doppler (Figure 9B) echocardiography is necessary to avid false positive studied. In adolescents and adults transesophageal echo is needed to make definitive diagnosis of ASD.

Fig. 9. Two dimensional subcostal echocardiographic view of the atrial septum (A) demonstrating a secundum atrial septal defect (ASD) in the mid septum (arrow). Color Doppler imaging shows left-to-right shunt. LA, left atrium; RA, right atrium.

#### **5.1.4 Catheterization and angiography**

Clinical and echocardiographic features are sufficiently characteristic so that cardiac catheterization is not necessary for the diagnosis. However, cardiac catheterization is an integral part of transcatheter occlusion of the ASD.

When catheterization is performed, one will observe step-up in oxygen saturation at the right atrial level. The pulmonary venous, left atrial, left ventricular and aortic saturations are within normal range. In large defects, the pressures in both atria are equal while in small defects, an inter-atrial pressure difference is noted. The right ventricular and pulmonary arterial pressures are usually normal. Calculated pulmonary-to-systemic flow ratio (Qp:Qs) is used to quantitate the degree of shunting and a Qp:Qs in excess of 1.5:1 is considered an indication for closure of ASD.

Congenital Heart Defects – A Review 19

Finally, the defect may be located in the muscular and apical portion of the ventricular septum and may make-up 5% to 20% of all VSDs, depending on the study selected. When multiple muscular defects are seen, it is often referred to as "Swiss-cheese" type of VSD.

The clinical symptomatology is largely dependent upon the size of the VSD. In small defects, the patients are usually asymptomatic and are detected because a cardiac murmur heard on routine examination. Patients with medium and large defects may present with symptoms of congestive heart failure (dyspnea, tachypnea, sweating and failure to gain weight) or with symptoms related to bronchial obstruction and/or respiratory infection.

These, again, depend upon the size of the defect. In small defects the only abnormality is a loud holosystolic murmur (Figure 1 bottom) heard best at the left lower sternal border and is sometimes referred to as "maladie de Roger". Sometimes, the holosystolic murmur may be heard best at left mid and left upper sternal borders, depending upon the direction of the VSD jet. In very small defects, murmur, though begins with first heart sound, may not last

In medium and large defects, the right and left ventricular impulses are increased and somewhat hyperdynamic. A thrill may be felt at the left lower sternal border. The second heart sound is split unless there is pulmonary vascular obstructive disease, in which case a loud single second heart sound is heard. The pulmonary component of the second sound may be normal or increased, depending upon the degree of elevation pulmonary artery pressure. Clicks are unusual for VSD patients although they can be heard in patients whose VSDs are undergoing spontaneous closure by aneurysmal formation of the membranous ventricular septum. A holosystolic murmur is best heard at the left lower sternal border and does not usually radiate although it may be heard widely over the precordium. The intensity of the murmur may vary between grades II-V/Vl. There is no significant variation of this murmur with respiration. This murmur is produced by flow across the VSD. The intensity of the murmur does not bear any consistent relationship with the size of the defect. A grade I-II/Vl mid-diastolic flow rumble may be heard at the apex in patients with medium to large-sized defects and large left-to-right shunts; this murmur is heard best with the bell of the stethoscope. The mid diastolic murmur is due to increased flow across the

The x-ray shows cardiomegaly and increased pulmonary vascular markings if the shunt is

The ECG may be normal in very small defects or may show evidence for left ventricular hypertrophy in small to moderate defects while it may show biventricular or right ventricular hypertrophy in moderate to large defects. Electrocardiographic signs of left atrial

through the entire systole; the shorter the murmur, the smaller is the defect.

mitral valve and usually indicates a Qp:Qs greater than 2:1.

**5.2.3 Noninvasive evaluation** 

**5.2.3.2 Electrocardiogram** 

enlargement may also be seen.

large. Left atrial enlargement may be noted.

**5.2.3.1 Chest x-ray** 

**5.2.1 Symptoms** 

**5.2.2 Physical findings** 

Selective angiography in the right upper pulmonary vein at its junction with the left atrium in a left axial oblique view will reveal location and the size of the ASD. When anomalous pulmonary venous connection is suspected, selective left or right pulmonary arterial angiography should be performed and the levophase of angiogram should be scrutinized for anomalous connections.
