32 Occlusion of Septal Defects

Atrial Septal Defect

Basics

At approximately 8 % of all congenital heart defects, atrial septal defect (ASD) is one of the most common. Many patients only become symptomatic as adults. Major signs and symptoms associated with ASD are right ventricular failure and pulmonary hypertension with dyspnea and peripheral edema. Other complaints are supraventricular arrhythmias or recurrent pulmonary infections. Women are 1.5 to 2.5 times more frequently affected than men. Anatomically three forms can be differentiated (Fig. 32.1):

Septum primum defect (ASD type 1): variant of an atrioventricular defect, most often with involvement of the AV valves (cleft formation).

Septum secundum defect (ASD type 2): the most frequent form, it is a true defect in the fossa ovalis, associated in ~25 % with partial anomalous pulmonary venous return.

Sinus venosus defect: ~11 % of all ASDs, always associated with partial anomalous pulmonary venous return.

Clinical findings are a fixed, wide split in the second heart sound and an early systolic murmur in the left parasternal region in the second to third intercostal space. The ECG shows right axis deviation and a rSR′ configuration or a complete right bundle branch block. The chest radiograph shows signs of right ventricular overload and an enlarged pulmonary segment as a result of right ventricular volume overload. The definitive diagnostic modality is echocardiography (transthoracic [TTE] and transesophageal [TEE]). It provides information on the morphology of the defect and on the anatomy of the pulmonary veins (anomalous return?), as well as on concomitant heart defects and intracavitary thrombi. Doppler and color Doppler echocardiography as well as contrast echocardiography (wash-out phenomenon) are used to assess the shunt. Invasive catheterization of both the right and left heart provides hemodynamic quantification of the shunt and can detect other comorbidities. Alternatively, cardiac MRI also allows imaging of the morphology and, with phase contrast imaging, the left-to-right shunt can be quantified.

Fig. 32.1 Different types of atrial septal defects (ASD). SVC, superior vena cava; IVC, inferior vena cava.

Pulmonary arterial resistance is markedly less than systemic resistance ASD occlusion is not indicated or is contraindicated for

Numerous systems are available for interventional occlusion. The Amplatzer septal occluder (St. Jude Medical, St. Paul, MN, USA) is the system most commonly used. It is a prefabricated, self-centering device made of nitinol wire available in various sizes (Fig. 34.2). Alternatives include the Helex occluder (Gore Medical, Flagstaff, AZ, USA), the Occlutech occluder (Occlutech International AB, Helsingborg, Sweden), and the Atriasept occluder (Cardia, Inc., Eagan, MN, USA). For patients with a multifenestrated ASD, which previously could only be treated surgically, there are now also interventional options available.

The occluders of the individual manufacturers are available in different sizes from 4 to almost 40 mm. The diameter of the left and right atrial disks vary with the diameter of the connection waists. The breadth of the connection waists is 3 to 4 mm.

The following materials are required for the procedure:

8F to 12F sheath, depending on the defect and device size

5F to 7F multipurpose diagnostic catheter

Amplatz Super Stiff Guidewire, 300 cm, J-tip

Sizing balloon with 25, 30, or 40 mm diameter (depending on defect size) with radiopaque markers for calibration

Long 8F to 12F sheath/delivery system

Occlusion system in different sizes

Fig. 32.2 Amplatzer Septal Occluder with the connecting waist, which occludes the defect, the left and right atrial disks, and the screwed-on cable.

Measure the waist of the expanded balloon by echocardiography and by angiography after calibration (either using the radiopaque markers on the sizing balloon or, preferably, using a previously imaged calibration sphere → balloon-stretched diameter of the defect) (Fig. 32.3).

Perform measurements in several planes.

Confirm with color Doppler that the defect is completely occluded by the expanded balloon.

Select the appropriately sized occluder:

– In the size of the balloon-stretched diameter of the defect or rounded up to the next larger disk size (e.g., when 17.3 mm is measured, implantation of an 18-mm disk)

– If an aortic septal rim is lacking or only very narrow, the occluder should be selected two to three sizes (not 2–3mm) larger (i.e., for an 18.5-mm defect a size 24 occluder)

The occluder is screwed onto the delivery cable and is introduced into the supplied loading sheath submerged in a water bath to reduce the chance of air entrapment in the delivery system.

Place the long sheath (diameter depends on occluder size) transseptally into the left atrium and remove the Amplatz wire.

If ventilated: increase PEEP to 10 mm Hg.

The loading sheath with the occluder is connected to the long sheath without introducing air. Then advance the occluder to the end of the sheath.

Fig. 32.3 Measurement of the defect with a sizing balloon and determination of the balloon-stretched diameter at the waist of the balloon. The measurement is done using both TEE and the angiographic image.

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