Atrial Septal Defect Creation

Pulmonary hypertension (HTN) with end-stage pulmonary vascular disease results in right heart failure, low output, and death, with few therapeutic options other than lung transplantation. Opening of the atrial septum (most common), ventricular septum, or ductus arteriosus allows for right-to-left shunt decompression of the right heart volume and pressure at the expense of systemic desaturation. Opening of the atrial septum is the preferred approach in most patients because of the relative ease and safety. Despite the decrease in systemic saturation with opening of the atrial septum, left heart loading is augmented, enhancing cardiac output and improving peripheral O ₂ delivery. An optimal balance must be struck, because too much right-to-left shunting (too large a defect) results in profound desaturation with a marked decrease in tissue O ₂ delivery and exacerbates symptoms severely, to the point of death. After creation of a right-to-left shunt resulting in this physiologic tradeoff, clinical evidence has shown an improvement in symptoms, exercise tolerance, right ventricular function, and possibly improved survival. Clinical improvement can be sustained for many years. Interventional techniques now allow for an easy, safe nonsurgical option for this palliative therapy in patients.

Nonsurgical opening of the atrial septum was first described in 1966 by Rashkind and Miller for palliative treatment of neonates with transposition of the great arteries, creating a left-to-right shunt at the atrial level to improve systemic saturations. This treatment remains in use for stabilization of neonates in anticipation of corrective surgical repair. The technique was expanded to treat older patients with transposition by the development of a “blade” catheter by Park et al in 1975. These techniques rapidly expanded to treat a variety of infants and children who had congenital defects with atrial septal restriction, such as mitral atresia and anomalous pulmonary venous return. In 1983, Rich and Lam applied the Park blade followed by a Rashkind atrial septostomy to a 28-year-old patient with end-stage pulmonary HTN for symptomatic palliation. Since then, newer techniques, including oversized static balloon dilation, cutting balloon dilation, stent implantation, and fenestrated device implantation have been used. This chapter details preferred techniques for atrial septal defect (ASD) creation, including cutting balloon dilation with large static balloon postdilation, stent implantation, and fenestrated device implantation.

21.1 Patient Selection/Indications

Patients receiving medical therapy for symptomatic end-stage pulmonary HTN who are awaiting transplant remain the primary group who benefits from opening of the atrial septum ( Table 21–1 ). Syncope in the setting of severe pulmonary HTN carries a significant mortality risk. Wait times for lung transplantation remain long with limited survival to transplant. Patients who have pulmonary HTN but are not transplant candidates yet are symptomatic while receiving maximal medical therapy may also benefit from atrial septal opening with improvement in symptoms.

TABLE 21–1

Indications for Atrial Septal Defect Creation

Group	Shunt	Indications	Goal
Symptomatic Pulmonary HTN	R to L	PVR > 4 on 3 agents, syncope	Sat 80-85
Pulmonary HTN + ASD	R to L	Minimum PVR > 4, ASD > 15 mm	Sat 90-95
Failing Fontan	R to L	PLE on maximum medical therapy	Sat 80-85
LVAD support	L to R	LAp > 20, LA distension on echo	LAp < RAp + 5

ASD, Atrial septal defect; HTN, hypertension; L, left; LA, left atrial; LAp, left atrial pressure; LVAD, left ventricular assist device; PLE, protein losing enteropathy; PVR, pulmonary vascular resistance; R, right; RAp, right atrial pressure; Sat, saturation.

A second group of patients, much less common, are those who develop severe pulmonary HTN in the setting of a large secundum ASD. Most of these patients should have their ASD closed completely, but there are a select few whose limited response to maximal medical therapy and test balloon occlusion suggest a small residual defect may be beneficial. Definitive indications for this subset of patients remains in evolution, but ASD closure with creation of a residual fenestration may be considered in those with a minimal pulmonary vascular resistance (PVR) of more than 4 Wood units and an ASD larger than 10 to 15 mm in diameter.

Creation of a right-to-left shunt at the atrial level is also used in congenital cardiac patients with failing single ventricle physiology. These patients are typically surgically corrected with a total cavopulmonary connection, commonly referred to as a Fontan repair. In this setting the inferior vena cava (IVC) and superior vena cava (SVC) are directly connected to the pulmonary arteries for passive flow through the lungs. Cardiac or pulmonary failure results in IVC pressure elevation, causing a condition known as protein-losing enteropathy. When medical management fails, cardiac transplant is the only option. The creation of a communication between the Fontan circuit (physiologically the right atrium) and the left atrium with the development of a right-to-left shunt is an effective palliative treatment in some patients to improve protein-losing enteropathy. Clinical indications in this group of patients include the diagnosis of protein-losing enteropathy (low serum albumin and elevated stool α-1-antitrypsin) despite maximal medical therapy (e.g., diuretics, afterload reduction, pulmonary vasodilators) in patients whose saturations are greater than 90%.

Lastly, patients with severe left ventricular (LV) dysfunction on ventricular assist device with left atrial (LA) HTN will benefit substantially from the creation of an atrial communication. In this setting, unlike others, the intent is for an adequate but transient atrial communication to allow a left-to-right shunt for LA decompression. The goal of defect patency is short, only a few weeks at most, while the ventricular-assist support is needed. To that end the favored technique for defect creation in this subgroup of patients would be cutting balloon with static balloon dilation to allow adequate immediate shunting, with a greater chance of spontaneous closure once the ASD is no longer needed.

21.2 You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here