Case presentation

A 53-year-old woman was referred for evaluation for lung transplant due to severe pulmonary hypertension in the setting of an atrial septal defect. She noted exertional dyspnea and peripheral edema of 3 years duration, with frequent nonsustained palpitations.

Physical examination revealed mild tachycardia and a resting oxygen saturation of 92% on room air. Jugular veins were distended while sitting, and there was an increased precordial activity with a right ventricular heave. A harsh systolic ejection murmur was present along the left sternal border, but diastole was clear. The abdominal exam was notable for a liver distended 3 centimeters below the right costal margin. Her lower extremities had edema to the ankles but intact peripheral pulses.

A 12-lead surface electrocardiogram demonstrated sinus rhythm with right axis deviation and a narrow RSR’ in V1, consistent with right ventricular enlargement. Transthoracic echocardiography demonstrated a markedly dilated right ventricle (Figure 52-1 and Video 52-1) and a tricuspid regurgitant Doppler signal consistent with severe pulmonary hypertension (Figure 52-2). Subcostal imaging demonstrated an atrial septal defect with significant left-to-right shunt across the atrial septum (Figure 52-3 and Video 52-2). There was normal left ventricular size and systolic function. She was referred for percutaneous closure of the atrial septal defect.

FIGURE 52-1 Parasternal long-axis view showing enlargement of the right ventricle.

FIGURE 52-2 Doppler evaluation found significant tricuspid regurgitation with increased velocities consistent with severe pulmonary hypertension.

FIGURE 52-3 Subcostal image showing flow across the atrial septal defect.

Cardiac catheterization

The procedure was performed using conscious sedation. Vascular access initially consisted of a 6 French sheath in the right femoral artery and both 8 and 11 French sheaths in the right femoral vein. The patient received 4000 U of unfractionated heparin intravenously along with 1 g of cefazolin. A 10.5 French intracardiac echocardiography catheter was then inserted through the 11 French sheath and advanced to the right atrium, allowing imaging and sizing of the atrial septal defect as well as confirming normal pulmonary venous return to the left atrium (Figure 52-4 and Video 52-3). A right and retrograde left-heart catheterization was performed for measurement of hemodynamics and shunt calculation. The pulmonary artery pressure was 95/27 mmHg with a mean of 50 mmHg, and oximetry determined a pulmonary to systemic flow ratio (or Qp:Qs) of 1.5:1 on room air. Pulmonary vascular resistance calculated to 9 Wood units. Repeating the hemodynamic measurements on inhaled epoprostenol at 50 ng/kg/min reduced the pulmonary pressure to 70/25 mmHg with a mean of 38 mmHg, with stable systemic pressures and a Qp:Qs ratio of 2.5:1. With pulmonary vasodilator administration, her pulmonary vascular resistance calculated to 3 Wood units-indexed. Selective coronary angiography demonstrated normal coronaries. The decision was made to occlude her atrial septal defect and maintain her on pulmonary vasodilator therapy.

FIGURE 52-4 This is an intracardiac echocardiogram showing the atrial septal defect (measuring 1.99 cm) (arrow).

The atrial septal defect was first sized with a 34 mm sizing balloon, and the stretch diameter was 24 mm (Figure 52-5). A 24 mm Amplatzer septal occluder was then delivered and its position confirmed satisfactorily by intracardiac echocardiography (Figures 52-6, 52-7 and Video 52-4). Repeat hemodynamics confirmed stable pulmonary and wedge pressures. The patient was then monitored in the intensive care unit before being discharged 24 hours later on oral bosentan and sildenafil therapy.

FIGURE 52-5 A compliant sizing balloon was used to determine the size of the defect.

FIGURE 52-6 Closure device positioned across the atrial septal defect.

FIGURE 52-7 Fluoroscopic appearance of the closure device.

Postprocedural course

At 6-month follow-up, she reported no further dyspnea or other symptoms, and a repeat right-heart catheterization found a pulmonary pressure of 35/17 mmHg with a mean of 21 mmHg. She was then weaned off the oral pulmonary vasodilators and has remained symptom-free for a follow-up period of 5 years.

Discussion

A significant atrial septal defect creates a left-to-right shunt due to the higher compliance of the right ventricle and lower right atrial pressures, with a resultant volume overload of the right heart and pulmonary circulation. The natural history of significant atrial septal defects results in a reduced life expectancy (approximately 57% mortality by age 40) and severe pulmonary hypertension in 22%.^1,2 Previously, correction of such atrial septal defects required a surgical approach with cardiopulmonary bypass. In attempting surgery in patients with elevated pulmonary vascular resistance (≥7 U/m²), significant mortality and morbidity may result, and extremely elevated resistance (≤15 U/m²) has been associated with death.³

The development of percutaneous devices to close atrial septal defects changes this concept as the defect may be closed without the deleterious effects of cardiopulmonary bypass and with the possibility of simultaneously determining the hemodynamic consequences of defect closure. Prior to final deployment, if it is observed that the hemodynamics worsen when there is occlusion of the defect resulting in volume loading of the left ventricle, then the septal occlusion device may be percutaneously removed.

Frequently, percutaneous closure of atrial septal defects is performed with transesophageal guidance under general anesthesia. However, it has been shown that the effects of general anesthesia can raise the mixed venous oxygen saturation and therefore mask the severity of the shunt.⁴

Therefore, when approaching the diagnostic catheterization of a patient with any cardiovascular shunt, use a baseline hemodynamic evaluation to determine Qp:Qs ratio, pulmonary blood flow, and pulmonary vascular resistance under light procedural sedation. If the findings warrant an intervention, guide the intervention by intracardiac echocardiography or, at that point, provide general anesthesia for airway protection during a transesophageal echocardiogram.

Finally, careful decisions must be made when facing the patient with a cardiac shunt and pulmonary hypertension. The utility of newer pulmonary hypertension agents allows the possibility of both a safe shunt occlusion and improved patient outcomes. However, in the patient with persistent right-to-left shunting, occluding the atrial septal defect will only worsen the patient’s outcome and therefore, in these cases, medical therapy alone is warranted.