**6. Common CHD**

#### **6.1 Ventricular septal defect (VSD)**

VSD is the most common congenital heart defect. It may be an isolated cardiac defect or may be associated with other cardiac defects like ASD, PDA or a part of complex defects (tetralogy, AV canal defect). Communication between two ventricles can be of any size and can occur at any part of septum. Most common type of VSD is peri membranous (also called subaortic or infracristal). Other less common defects are subpulmonary (Supra cristal, infundibular or outlet type), Inlet type (canal type) and muscular. Spontaneous closure is possible in muscular and membranous type of defects.

Smaller defects are not associated with large shunting of blood from left ventricle to right ventricle may not diagnose early in life but they are prone to infective endocarditis. Whereas larger defects cause shunting of blood from left to right ventricle this led to higher pulmonary blood flow and consequently pulmonary congestion. Due to early development of symptoms these patients diagnosed earlier. During systole LV ejects blood not only in the aorta but also in the pulmonary artery causing volume overload of pulmonary vessels, atria and left ventricle. These patients will develop high pulmonary vascular resistance (PVR) and if untreated will leads to Eisemenger.

A device like amplatzer can be placed to close few of these defects by interventional cardiologist. This procedure is performed in the cath lab as a daycare procedure but there are certain criteria needs to be fulfilled. There should be an adequate rim around the defects where amplatzer can be placed. Surgically VSD can be approached through ventricle, aorta, pulmonary artery or right atrium.

#### **Anaesthetic considerations**

Always consider high pulmonary vascular resistance in these patients and be ready to treat high PVR and right ventricular failure by inhaled NO, dobutamine and milrinone. Desirable haemodynamic goals by anaesthetists are to have slightly higher preload and pulmonary vascular resistance while keeping the SVR on the lower side and at the same time maintaining heart rate and contractility. Up to 10% of patients may develop conduction abnormalities after VSD repair which may be transient or permanent.

Intraoperative transesophageal echocardiography (TEE) will be beneficial in recognizing residual defects, intracardiac air and right ventricular function. Smaller VSD are sometimes becomes apparent after closure of large defect. In uncomplicated VSD closure patient can be extubated in the operating room.

#### **6.2 Atrial septal defect (ASD)**

Normally there is no communication between right and left atria due to presence of a septum. This atrial septum composed of septum primum and septum secundum which merges with endocardial cushion, superior and inferior vena cava.

Several types of defects can occur in this septum leading to shunting across. Apart from secundum defect other less common are primum, sinus venosus and coronary sinus type.

Most common defect is **ostium secundum** which usually located in the centre (also called fossa ovalis type) and occurs due to deficient septum primum. It may be single or have several small defects called fenestrated type. Patent foramen ovale commonly seen at the same site in 25 – 30% of normal patients. Usually PFO do not permit left to right shunting but right to left shunting can occurs if right atrial pressure exceeds left atrial pressure (sneezing, valsalva)

**Sinus venosus defect** is usually associated with partial anomalous pulmonary venous drainage and appears either at the junction of superior vena cava and atrial septum (High up) or at the junction of inferior vena cava and septum (located lower part of septum). Repair some time may cause injury to SA node.

**Ostium primum** defect is due to failure of fusion between endocardial cushion and lower part of interatrial septum leading to communication between two atria and usually associated with cleft at anterior mitral leaflet.

**Coronary sinus type** defect is due to absence of wall between left atrium and coronary sinus leading to communication between left and right atrium. It may be associated with persistent left SVC.

Left to right shunting depends on the size of defects and compliance of ventricles as shunting usually occurs during diastole when both mitral and tricuspid valves are open. If the defect is small (less than 5 mm) then it's called restrictive type while larger defects are non restrictive and associated with right atrial dilatation, RV volume overload and increased pulmonary blood flow. Spontaneous closure is possible but most require device closure by cardiologist or surgery.
