Ventriküler Septal Defekt

The heart has two atria and two ventricles, a right and a left one. Defects that arise from a congenital malformation in the region called the ventricular septum — the partition that separates the right and the left ventricle from one another — are termed ventricular septal defects (VSD).

Types of ventricular septal defect

• Perimembranous / paramembranous / conoventricular VSD. The most common type, accounting for approximately 80% of all VSDs. It is located in the membranous septum, with possible extension into the inlet, the trabecular or the outlet septum, and lies adjacent to the tricuspid and the aortic valve. Aneurysms of the membranous septum are frequent and may result in partial or complete closure. This type can be closed by the transcatheter method, without surgery.
• Muscular / trabecular VSD. Up to 15–20% of cases. The defect is completely surrounded by muscle, may be found at various locations and is frequently multiple. Spontaneous closure is frequent; when the defect remains open, it can be closed by the transcatheter method, without surgery.
• Outlet VSD (supracristal / subarterial / subpulmonary / infundibular / conal / doubly committed juxta-arterial). Approximately 5% of cases. It is located beneath the semilunar valves, in the conal or outlet septum, and is often associated with progressive aortic regurgitation (AR) due to prolapse of an aortic cusp, usually the right one.
• Inlet / AV canal / AVSD-type VSD. Located in the inlet of the ventricular septum, immediately inferior to the atrioventricular (AV) valve apparatus; it typically occurs in Down syndrome.
• Post-myocardial infarction VSD (VSD after a heart attack). A serious complication of myocardial infarction, typically seen after infarctions in patients who received neither thrombolytic therapy nor primary percutaneous coronary intervention (PCI). It is usually located in the muscular septum. In the presence of haemodynamic compromise, it requires emergency treatment. Surgery is the first-line option, but the sutures of the surgical patch may fail to hold because that area is necrotic. Device therapy may be used as an alternative, although reported closure rates with a device are also low in published series. If haemodynamics are not compromised and it is possible to wait one or two weeks, device therapy may offer a considerable advantage over surgery.

The left ventricle is the chamber that pumps the blood oxygenated in the lungs to the whole body, whereas the right ventricle is the main structure that pumps the deoxygenated blood returning from the body to the lungs to be oxygenated. When there is a defect in the ventricular septum that separates the two ventricles, part of the oxygenated blood that should be pumped to the body crosses this defect and mixes with the deoxygenated blood in the right ventricle. The volume of this shunt is directly proportional to the size of the defect.

In the presence of a VSD, blood that has already been oxygenated but has shunted into the right ventricle through the defect is pumped to the lungs a second time to be oxygenated, and this imposes an additional workload on the lungs.

If the defect goes unrecognised and remains open, it may in later years lead to enlargement of the right heart chambers, to severe heart failure and to pulmonary hypertension. As pulmonary vascular pressure and resistance rise, the shunt — which is left-to-right at the outset — may reverse and become right-to-left, so that deoxygenated rather than oxygenated blood is delivered to the body. Serious arrhythmias may also develop, and the jet flow across the defect may cause endocarditis, inflammation of the endocardium that lines the inner surface of the heart, leading to bacteraemia and septicaemia. Left untreated, these complications may prove fatal.

As stated above, the most common types of VSD in the population are the perimembranous and the muscular types, and these defects can be closed without open surgery. In the past, the only treatment for a VSD was the surgical suturing of a patch over it; today, in children and in adults alike, perimembranous and muscular VSDs can be closed by the transcatheter method with dedicated devices in the catheterisation laboratory, without open surgery. For the other, less common types of VSD we continue to recommend open surgery.

How is the diagnosis made?

In the past, the diagnosis of a VSD rested solely on the murmur found at physical examination and on the electrocardiographic findings; today it is readily established with the highly advanced ultrasound systems known as echocardiography. Transthoracic echocardiography, performed simply by placing an ultrasound probe on the anterior chest wall, usually confirms the diagnosis. Transoesophageal echocardiography (TEE) — performed by having the patient swallow a probe that is then positioned in the oesophagus — must always follow, in order to determine whether the defect is suitable for transcatheter closure, to measure, particularly in the perimembranous type, the distance between the rims of the defect and the aortic valve, and to establish whether the rims of the VSD are able to support a closure device. Once colour Doppler jets across the ventricular septum have been detected with two-dimensional TEE, real-time three-dimensional TEE usually confirms the definitive diagnosis. Contrast left ventriculography, performed in the catheterisation laboratory, is likewise one of the indispensable investigations in the diagnosis and treatment of a VSD: it defines the location of the defect, shows whether an aneurysm is present and, in the perimembranous type, confirms the distance from the aortic valve.

How is percutaneous transcatheter VSD closure performed?

The femoral veins in the groin carry the deoxygenated blood of the legs and of the lower body to the right side of the heart through the inferior vena cava. The femoral artery in the groin is one of the main vessels through which the aorta and, from there, the left ventricle can be reached. In the catheterisation laboratory, the femoral artery and the femoral vein are punctured with a fine needle and two sheaths are placed, one in the artery and one in the vein.

Through the sheath in the left femoral artery, a dedicated catheter and atraumatic guidewires are advanced into the aorta and from there into the left ventricle. With dedicated catheters and wires, the defect between the ventricles is crossed and the right ventricle is reached from the left ventricle. The wire is then advanced from the right ventricle as far as the mid portion of the pulmonary artery.

Through the sheath in the right femoral vein, a dedicated snare system is advanced through the inferior vena cava and the right ventricle into the pulmonary artery. This snare is used to grasp the wire that was previously delivered from the left femoral artery, passed through the defect between the ventricles and advanced into the pulmonary artery. The captured wire is pulled out through the venous sheath, and an arteriovenous wire loop is thereby created.

This loop must always be created, because it increases the stability and the control of the device delivery system within the body; it is the cornerstone of the transcatheter procedure.

Once the arteriovenous loop is in place, the delivery system of the VSD closure device is advanced over it from the right femoral vein. After the right ventricle has been reached, the system is passed through the defect between the ventricles into the left ventricle and from there into the aorta.

Once the system has been stabilised in the aorta, the wire forming the loop is withdrawn from the arterial side. Under fluoroscopic guidance, the system is pulled back from the aorta into the portion of the left ventricle called the apex. Then, under fluoroscopic and two- or three-dimensional echocardiographic guidance, the distal end of the left disc of the closure device — which may be described as a kind of “double-disc” device — is deployed in the left ventricle; the system is withdrawn slightly further so that the waist of the device lies exactly within the defect, and the right disc is then deployed in the right ventricle, closing the defect completely.

Once a dedicated manoeuvre has confirmed that the device is seated exactly across the defect, it is released from its delivery cable and left in place. After the procedure, the surfaces of the device become covered spontaneously, within approximately six months to one year, by endothelium, the body’s own surface lining.

Are there any complications of the transcatheter method, or any side effects of the closure devices?

Compared with open surgery, the complications of treatment performed by the transcatheter method are far less frequent. Complications that may arise during open surgery — major bleeding, the consequences of prolonged anaesthesia, and trauma to vessels and cardiac chambers — are not commonly encountered. The cosmetic advantage of a procedure carried out without opening the chest, through nothing more than needle punctures and the placement of sheaths in both groins, is also evident. Most of these devices are manufactured from special shape-memory metals known as nitinol. No side effect of the devices has been reported other than in patients with a nickel allergy. However, in procedures performed by operators who have not been trained in this field, the device may dislodge and embolise into the cardiac chambers if appropriate measurements have not been made or an appropriate device has not been selected. Dedicated snares able to capture a device within the body have been manufactured for precisely such an event, and the device can be retrieved with them without difficulty. Other complications, such as bleeding, air embolism and pericardial effusion or tamponade, may arise during the procedure, albeit very rarely; compared with open surgery, their occurrence is extremely rare.

Can a new defect develop around a defect that was previously closed with a patch at open surgery? Can these defects be closed without a second open operation?

Rarely, defects may develop around the patches used in the treatment of a VSD. In such cases, taking the patient to open surgery a second time may be hazardous. If these defects are of a suitable type, they can be treated by the transcatheter method, without the need for repeat open surgery.