Atrial Septostomy and Pulmonary Hypertension
Several observations in the 1980’s suggested that adult patients with severe, symptomatic PH who also had a patent foramen ovale had a survival advantage over those who did not.6,7
Improvement in those with atrial defects was postulated to result from the shunt “decompressing” the failing right ventricle, allowing for right to left atrial flow, thereby improving left ventricular preload and thus augmenting cardiac output and oxygen delivery (albeit with overall reduced systemic oxygen saturations). A number of relatively small case series followed, primarily in adults, demonstrating that in the select patient creating an atrial shunt via atrial septostomy (AS) could improve symptoms and possibly serve as a bridge to transplant.8,9 Whether AS improves survival however is less clear due to the lack of control cases. Nonetheless, several studies have argued that when compared to historical controls or calculated survival, patients who underwent AS fared better.9 Studies that look specifically at AS in children are few. One retrospective study reviewed 20 children with a mean age of 8.4 years who underwent AS.10 All were World Health organization functional class (WHO-FC) III or IV, 13 suffered from recurrent syncope. There were no procedural deaths. Post-procedure, functional class improved significantly and syncope was abolished in 12 of the 13 children. With a mean follow-up of 2.1 years, clinical improvement was maintained in 18 of the 20 children. Notably however, despite clinical improvement post-AS, 9 of the children (45%) required the addition of intravenous epoprostenol to their medical regimen. Overall, enough evidence exists to recommend including AS as part of the standard, pediatric PH treatment algorithm for symptomatic children on maximal medical therapy.11 The importance of patient selection and technique in regards to a successful outcome dictate that this relatively high risk procedure (mortality over 20% in some adult series) should be performed in centers with significant experience.9
The ability of a pre-tricuspid (atrial) shunt to provide symptomatic relief in a child with PH depends upon having right atrial pressures high enough to force blood to flow from the right atrium to the left. Assuming a competent tricuspid valve, right atrial pressure is directly reflective of right ventricular end diastolic pressure (RVEDP). Consequently, for an atrial shunt to benefit a PH patient, the RVEDP must be abnormally elevated to generate right-to-left atrial flow. This elevation of RVEDP can happen acutely, as with exercise, or as the result of progressive right ventricular failure with decreasing systolic function and concomitantly rising RVEDP. Thus, a child with PH who improves from an AS is often one whose right ventricular failure is relatively advanced, perhaps suggesting why children who have had an AS may still require additional PH medications and where survival outcomes may not be obviously improved.10,12,13 This relatively “end stage” benefit of an AS contrasts with the potential advantage that a post-tricuspid shunt has to intervene much earlier in a child’s disease course.