Management of severe pulmonary hypertension continues to be a difficult task .Medical therapy is not definitive, in-spite of the new prostocyclins, endothelin antagonists and sildenafil analogues.Natural history depends mainly on the presence of any treatable cause ( Especially ,connective tissue disorders) , supportive management along with anticoagulation.
Ultimate strategy would involve a plan for a “Lung “or “Heart -Lung”transplantation , if feasible. Last decade saw an innovative modality of creating an artificial inter atrial shunt to decompress the right heart .This had varied response in the real world , still most showed some benefit .In fact , in 1998 the world symposium on PHT , formulated guidelines for BAS (Balloon atrial septostomy)
Principle of Balloon atrial septostomy (BAS) and mechanism of benefit
The symptomatology of pulmonary HT is largely determined by mean RA pressure .
Puncturing the IAS and diverting blood flow into left atrium would decompress the RA ( or even the RV ) and reduce the Mean RAP.
The resultant right to left to shunt can increase the cardiac output only slightly , still good enough to provide relief from the fatigue.(Though at the cost of desaturation.)
What is the risk involved in the BAS.
Procedural risk of a cath study in a sick patient with hypertensive lungs (Can be really high !)
In some patients even a small fall in systemic oxygen saturation can be counter productive.
What is the balloon used ?
Mansfield or Tyshak balloons are good choices .
Balloon diameters are between 5 -14 mm
Technique
Involves standard Brockenborough needle /Mullin sheath /Guide wire in pulmonary vein.
Atrial anatomy to be well analysed prior to BAS . (Please note even though it is similar to PTMC , anatomically we encounter a large right atrium rather than left atrium .)
Fluroscopy with TEE guide optimal
Pulmonary angiogram might help.
Intra-cardiac Echo may be ideal.
Blade septostomy may be preferred if hardware is available
The endpoint of procedure
- Size of ASD > 5mm
- Fall of arterial saturation < 80 %
- Sustained atrial fibrillation with hypotension
- Any disabling complication
Hemodynamic impact
- Cardiac output increase by 750 ml to 1 liter
- It is expected , RA mean pressure would fall at least 5mmhg from the baseline value.
- PA pressure , no significant impact expected.
- Tricuspid regurgitation regresses.
- RA,RV size marginal reduction observed.
Follow up and outcome
- Greatest relief is from syncope.
- Functional class improvement in >50% .
- One year survival benefit is substantial (75-90%) .Beats the natural history (40%) convincingly.
- Late deterioration can occur as ASD gets closed in few.
When BAS is contraindicated ?
- Critical RV failure
- Patient in class 4
- Mean RA pressure > 20mmhg
- Pulmonary vascular resistance index> 55 Wood units / sq.meter
* BAV should not be considered as a live saving procedure in any dying patient with PAH. It needs to be selected early and carefully .In fact, the very high procedural complication rate is related to late selection of patients.
Natural foramen PFO better than BAV ?
We do not know yet.It is highly possible natural opening up of PFO is good thing to happen for patients with severe pulmonary hypertension.
Reference
1 . SS Kothari et all Indian heart journal 2002
2. http://content.onlinejacc.org/cgi/reprint/32/2/297.pdf
3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC484602/pdf/heart00028-0066.pdf
4. http://erj.ersjournals.com/content/early/2011/02/24/09031936.00072210.abstract
Dr.S.Venkatesan MD 