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.