Answer : I guess all mechanisms contribute.Though E appears unlikely, its backed by evidence (Ref 5)
Balloon pericardiotomy is done as a drainage procedure in recurrent pericardial effusion. It is actually a replication of surgical pericardial window by Interventional cardiologist.The window not only drains the effusion , it also act as a continuous drain. Though the benefits are real (Pericardial fluid is shunted away from the pericardial space) the exact mechanism of its benefit is not clear .
By concept , the catheter and balloon should not cross the pleural space , (As pneumothorax may ensue) but still pleural effusion is a common consequence of this procedure .How is this possible ? One probable explanation is, the pleural space has some hidden communication with pericardial space .The other possibility is that, balloon creates virtual tissue channels in the para-cardiac spaces of mediastinum .The extra-cardiac lymphatics does the drainage job without true shunting pericardial space into the pleural space..
There is an article from Annals of thoracic surgery which specifically looked into the mechanism of benefit of surgical pericardial window and came to a surprise conclusion, ie, it is not the continuous drainage that keeps the space dry , rather it is likely the window somehow obliterates the pericardial space permanently.(Sugimoto 1990,Annals of thoracic surgery )
Future Innovation : A technical add-on to balloon pericarditomy could be , delivering a covered stent across the pericardial space into peritoneal space like a VP shunt done by Neurosurgeons.(If no body has done this , Can I claim the patency for this !)
The procedure
Image used from Daniel A. Jones & Ajay K. Jain, Journal of thoracic Oncology , 2011
Risk of procedure
The procedure carries a definite risk especially if done in an emergency fashion. The aim of procedure is two fold one to drain pericardial effusion second to prevent recurrence of effusion .Since procedure carries considerable risk its to be performed only in malignant effusion that are documented to be recurrent.
Surgical vs Balloon window and other alternatives
Surgical window creation is well known procedure , ever since Palacios (Ref 1) in 1991 described this per cutaneous approach as an alternative to surgery has become less popular. The risk of anesthesia and co-morbidity makes balloon pericardiotomy attractive. But surgical window creation still may have a role. A video assisted pericardiotomy by thoracoscopy is also possible .Another option is injecting sclerosing agents into pericardial space .This time tested simple modality probably requires more attention.
Need for subsequent pleural tapping
It should be realised this procedure may just shift the fluid from pericardium to pleural space. Some of them become significant effusion that requires pleural space drainage.
Concern of risk of dissemination of malignancy
Its a real issue , there has been instances of accelerated death after the procedure. Hence this procedure is a trade-of between patient comfort and quality of life with a potential risk of dissemination impacting the longevity of life .
Dr.S.Venkatesan MD 