Interventional procedure consultation document

Percutaneous closure of patent foramen ovale for the secondary prevention of recurrent paradoxical embolism in divers

The foramen ovale is a hole in the wall that divides the two upper chambers of the heart at the level of the atria. The hole is present in the heart of a developing fetus, but normally closes up soon after the baby is born. If it fails to close it is known as a patent foramen ovale (PFO) and in most people causes no problems. However, some studies have shown that a PFO can increase the chance of substances (e.g. gas bubbles or blood clots) crossing from the right side into the left side of the heart, and from there into the arterial circulation where they may block blood vessels and cause serious problems such as a stroke. In divers resurfacing too quickly from a dive, bubbles of gas can form in the veins and cross into the arterial circulation causing permanent damage with stroke-like symptoms.

This procedure involves passing a device through a large vessel in the groin up into the heart and closing/blocking the hole in the wall. The aim is to lower the chances of substances crossing the heart and causing serious problems.

The National Institute for Health and Clinical Excellence (NICE) is examining percutaneous closure of patent foramen ovale for the secondary prevention of recurrent paradoxical embolism in divers and will publish guidance on its safety and efficacy to the NHS in England, Wales, Scotland and Northern Ireland. NICE’s Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisers, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about percutaneous closure of patent foramen ovale for the secondary prevention of recurrent paradoxical embolism in divers.

This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

• comments on the provisional recommendations
• the identification of factual inaccuracies
• additional relevant evidence, with bibliographic references where possible.

Note that this document is not NICE’s formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that NICE will follow after the consultation period ends is as follows.

• The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.
• The Advisory Committee will then prepare draft guidance which will be the basis for NICE’s guidance on the use of the procedure in the NHS in England, Wales, Scotland and Northern Ireland.

For further details, see the Interventional Procedures Programme manual, which is available from the NICE website (www.nice.org.uk/ipprogrammemanual).

NICE is committed to promoting through its guidance race and disability equality and equality between men and women, and to eliminating all forms of discrimination. One of the ways we do this is by trying to involve as wide a range of people and interest groups as possible in the development of our guidance on interventional procedures. In particular, we aim to encourage people and organisations from groups in the population who might not normally comment on our guidance to do so. We also ask consultees to highlight any ways in which draft guidance fails to promote equality or tackle discrimination and give suggestions for how it might be improved. NICE reserves the right to summarise and edit comments received during consultations, or not to publish them at all, where in the reasonable opinion of NICE, the comments are voluminous, publication would be unlawful or publication would otherwise be inappropriate.

Closing date for comments: 24 August

Target date for publication of guidance: December 2010

1   Provisional recommendations

1.1  Current evidence on the efficacy of percutaneous closure of patent foramen ovale (PFO) for the secondary prevention of recurrent paradoxical embolism in divers is inadequate in quality and quantity, and the evidence on safety shows that there is a possibility of serious complications. Therefore this procedure should only be used with special arrangements for clinical governance, consent and audit or research.

1.2  Clinicians wishing to undertake percutaneous closure of PFO for the secondary prevention of recurrent paradoxical embolism in divers should take the following actions.

• Inform the clinical governance leads in their Trusts.
• Ensure that patients understand the uncertainty about the procedure’s efficacy and the possibility of complications, and that they understand alternative options which may include modifying their diving practice to reduce the risk of gas bubble formation. Clinicians should provide patients with clear written information. In addition, the use of NICE’s information for patients (‘Understanding NICE guidance’) is recommended (available from www.nice.org.uk/IPGXXXpublicinfo). [[details to be completed at publication]]

1.3  Patient selection for this procedure should only be carried out by clinicians with specific expertise in decompression sickness, in liaison with an interventional cardiologist.

1.4  The procedure should only be carried out in units where there are arrangements for emergency cardiac surgical support in the event of complications.

1.5  Data on all patients having this procedure should be submitted to the UK Central Cardiac Audit Database (www.ccad.org.uk).

1.6  NICE encourages further research into this procedure. Studies should document the recurrence of neurological decompression sickness in patients treated by this procedure compared with recurrence among those in whom the PFO is not closed. Outcomes should include details of the depth and duration profile of dives undertaken.

2   The procedure

2.1  Indications and current treatments

2.1.1  A patent foramen ovale (PFO) is the persistence of an opening (the foramen ovale) in the septum between the right atrium and left atrium of the heart. In the fetus, the foramen ovale allows blood to bypass the lungs, directly from the venous to the arterial side of the circulation, supplying blood to the brain and body before it returns to the placenta to be oxygenated. After birth the foramen ovale normally closes but in approximately 25% of people it remains either fully or partially patent into adulthood. Usually a PFO causes no symptoms, although a “shunt” or movement of blood from the right to left side of the heart may be demonstrable using specialist tests.

2.1.2  During ascent from a deep dive (decompression), nitrogen which has accumulated in the blood and tissues during the dive is normally  removed through the lungs. If decompression is rapid, gas bubbles may form in the venous circulation and pass across the PFO into the arterial circulation. This may cause neurological damage (symptoms of which may resemble a stroke and are termed “neurological decompression sickness”).

2.1.3  The  pathophysiology of divers with a PFO who have a history of neurological decompression sickness is not fully understood and it has been described in divers with no demonstrable PFO.  There is currently no consensus on the optimal management of divers with a PFO and a history of neurological decompression sickness.

2.2   Outline of the procedure

2.2.1  The procedure is carried out with the patient under local anaesthesia and intravenous sedation, or general anaesthesia. A small incision is made in the groin and a guidewire and delivery sheath are introduced via the femoral vein into the heart and across the PFO. A closure device is then inserted through the opening via the delivery sheath and released, closing the PFO.

2.2.2  A range of different devices are available for this procedure.

Sections 2.3 and 2.4 describe efficacy and safety outcomes from the published literature that the Committee considered as part of the evidence about this procedure. For more detailed information on the evidence, see the overview, available at www.nice.org.uk/IP853overview

2.3   Efficacy

2.3.1  In a case series of 185 patients (undergoing atrial septal defect or PFO closure for several indications), residual shunt was seen in 5% (10/185) at 6-month follow-up echocardiogram (not otherwise described).

2.3.2  A case series of 29 divers treated by percutaneous closure of PFO for neurological decompression sickness reported that 79% (23/29) had returned to diving (3 only had closure recently and 3 had not returned to diving for other unrelated reasons). In the 23 who returned to diving, no recurrences of decompression sickness were reported.

2.3.3  The Specialist Advisers stated that a key efficacy outcome is adequate closure of the PFO assessed by a suitable technique (such as bubble contrast echocardiography, transcranial Doppler or transoesophageal echocardiography).

2.4   Safety

2.4.1  Pericardial tamponade requiring pericardiocentesis occurred in 1 patient in each of a case series of 825 and the case series of 185 patients (of whom 51 and 44 respectively were divers).

2.4.2  Retroperitoneal haematoma requiring blood transfusion was reported in 1 patient in the case series of 185 patients.

2.4.3  Erosion of the device and creation of a small atrial septal defect (successfully closed with another occluder) was reported in 2 patients (detected on TOE in 1 patient after 2 years and in 1 after 6 months) in the case series of 825 patients.

2.4.4  Periprocedural transient ischaemic attack with visual symptoms (1 patient), and air embolism with transient symptoms (4 patients) were reported in the case series of 825 patients undergoing PFO closure (51 of whom were divers).

2.4.5  Periprocedural embolisation of the device or parts of the device was reported in 5 patients in the case series of 825 patients (all were removed percutaneously).

2.4.6  Transient inferior ST elevation during the procedure occurred in 1 patient in the case series of 185 patients.

2.4.7  The Specialist Advisers listed anecdotal adverse events as transient increase in migraine and transient palpitations (not requiring treatment). They considered theoretical adverse events to include device erosion in the long term resulting in tamponade and late thrombosis on the device (both being related to type and size of device used).

2.5   Other comments

2.5.1  The Committee noted that an episode of neurological decompression sickness might influence subsequent diving activity whether a PFO is present or not. This could confound evaluation of the effect of PFO closure.

3   Further information

3.1  For related NICE guidance see www.nice.org.uk

Bruce Campbell

Chairman, Interventional Procedures Advisory Committee

July 2010

NICE is also consulting on this procedure for:

IP237/2 – Percutaneous closure of patent foramen ovale for the secondary prevention of recurrent paradoxical embolism

IP812 - Percutaneous closure of patent foramen ovale for recurrent migraine

_{Personal data will not be posted on the NICE website. In accordance with the Data Protection Act names will be anonymised, other than in circumstances where explicit permission has been given.}

 _{It is the responsibility of consultees to accurately cite academic work in order that they can be validated.}