Over the course of the past decade, there has been a burgeoning interest in closing septal defects percutaneously. To date, there are now percutaneous closure devices available for the intended closure of ostium secundum atrial septal defects (ASDs) as well as patent foramen ovale (PFO). With the increased interest in these percutaneous procedures, the interventional cardiologist now has an additional set of procedures to master outside the coronary vasculature. This chapter will review the current techniques and devices employed during these specialized procedures.
ASDs are the most common adult congenital cardiac abnormality,1 occurring in about 8% of the adult congenital heart disease population with a slight female predominance (3:2). They are classified by the anatomic location as well as their associations with other local anatomic structures. ASDs can be classified as follows: (1) ostium primum, in which the defect is located inferiorly and is often associated with tricuspid and or mitral valve abnormalities as well as a ventricular septal defect; (2) ostium secundum, in which the defect is related to persistent separation at the midatrial level due to failed fusion during cardiac development; and (3) sinus venosus, in which there is partial anomalous pulmonary venous return due to the septal defect extending superiorly along the atrial septum to include the incoming pulmonary veins. Of these 3 types of ASDs, transcatheter repair is tenable at this time only with the secundum-type defect.
In general, the threshold for closure is dictated by hemodynamic findings. Historical data, largely from the surgical literature, suggest that ASD closure is warranted in patients with a pulmonary/systemic flow ratio (Qp/Qs) of 1.5 or greater. Closure may also be warranted if pulmonary hypertension or early echocardiographic evidence of right ventricular enlargement and/or failure is present. A paradoxical embolus may also be considered to be an indication for closure. Clinically, patients often present with dyspnea on exertion or evidence of right-sided heart failure. It is generally rare to see a cryptogenic neurologic event with an ASD, given that most of the flow early in the process involves left-to-right shunting; as the right heart fails, however, the shunting becomes mixed and even reversed in late-stage disease, with predominantly right-to-left shunting. An electrocardiogram showing incomplete right bundle branch block is common is patients with secundum ASD.
A transesophageal echocardiogram (TEE) is critical in defining the anatomy of the ASD and is useful in determining the potential success of percutaneous closure of a secundum-type defect. An adequate (≥1 mm) anterosuperior aortic rim is important to allow adequate anchoring of the ASD closure device. In addition, the size of the defect and an estimate of the shunt fraction may be helpful in determining the eligibility for closure as well as appropriate balloon sizing. Right ventricular enlargement of at least a mild degree is usually observed. Other important features revolve around the definition of the type of defect and ...