How should I treat atrial septal defects in adults?

A significant secundum atrial septal defect (ASD) will result in volume and pressure overload of the right heart and may be associated with reduced exercise tolerance, shortness of breath and palpitations from atrial arrhythmias especially atrial fibrillation/flutter. Pulmonary vascular disease is a late complication, rarely seen before the fourth or fifth decade. The clinical suspicion of an ASD is confirmed by transoesophageal echocardiography as transthoracic images are usually inadequate. The presence of tricuspid regurgitation permits accurate assessment of right heart pressures, otherwise right heart catheterisation is required. Coronary angiography is indicated in patients over 40 years of age.

Indications for closure include symptoms (exercise intolerance, arrhythmias), right heart volume overload on echocardiography, the presence of a significant shunt (>2:1) or cryptogenic cerebrovascular events, especially associated with aneurysm of the oval foramen and right to left shunting demonstrated on contrast echocardiography during a Valsalva manoeuvre. Preoperative arrhythmias may persist after closure of the ASD but are associated with fewer symptoms. Reduction in left ventricular compliance due to e.g. hypertension/myocardial infarction will increase the left to right shunt through an ASD.

Closure of an ASD requires either surgery or transcatheter intervention. The results of surgery are excellent with little or no operative mortality in the absence of risk factors, e.g. pulmonary hypertension, co-morbidity. However, it requires a surgical scar, cardiopulmonary bypass and hospital stay of approximately 3–5 days. There is a small but definite risk of pericardial effusion with the potential for cardiac tamponade following closure of an atrial septal defect. The aetiology is poorly understood.

Transcatheter occlusion of ASDs is now established practice. Several occlusion devices are available. Their efficacy and ease of deployment have been demonstrated although long term data are lacking. It is possible to close ASDs with a stretched diameter of up to 34mm in size, providing there is a sufficient rim of atrial tissue. Our policy is to perform a transoesophageal echocardiogram under general anaesthesia with plans to proceed to device closure if the defect is suitable. Transoesophageal echocardiography is invaluable in guiding correct placement of the exposure. Heparin and antibiotics are administered during the procedure and intravenous heparinisation is used for the first 24 hours following deployment. Aspirin is administered for six weeks and then stopped, by which time the device will be covered by endothelial tissue. Mechanical problems seen with some earlier devices have not been encountered with the latest range. Medium term results have been encouraging.