The National Institute for Clinical Excellence is examining cryoablation for atrial fibrillation in association with other cardiac surgery and will publish guidance on its safety and efficacy to the NHS in England, Wales and Scotland. The Institute's Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisors, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about cryoablation for atrial fibrillation in association with other cardiac surgery.

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 preliminary recommendation
• the identification of factual inaccuracies
• additional relevant evidence.

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

The process that the Institute 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• The Advisory Committee will then prepare draft guidance which will be the basis for the Institute's guidance on the use of the procedure in the NHS in England, Wales and Scotland.

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

Closing date for comments: 26 January 2005

Target date for publication of guidance: 27 April 2005

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

Current evidence on the safety and efficacy of cryoablation for atrial fibrillation in association with other cardiac surgery appears adequate to support the use of this procedure provided that the normal arrangements are in place for consent, audit and clinical governance.

Patient selection and follow-up should be carried out by a multidisciplinary team. Cardiac surgeons wishing to use this procedure should be specifically trained in the use of cryoablation equipment.

Atrial fibrillation is the irregular and rapid beating of the upper two chambers of the heart (the atria). It may be classified as paroxysmal, persistent or permanent. It is the most common type of arrhythmia and the incidence increases markedly with age. Patients with atrial fibrillation may be asymptomatic or they may have symptoms such as palpitations, dizziness and breathlessness. They also have an increased risk of stroke as a result of blood clots forming in the left atrium and then embolising to the brain.

Although atrial fibrillation may occur in the absence of other heart disease, it is particularly common in patients with mitral valve disease.

Cryoablation for atrial fibrillation is typically carried out in patients undergoing concomitant open heart surgery, including mitral valve replacement or repair. A cryoprobe is used to freeze tissue. The damaged tissue forms linear scars or lesions that disrupt the transmission of the abnormal electrical impulses. The procedure may be carried out on both atria or on the left atrium only. It can be performed from within or outside the atrium.

One non-randomised trial compared patients who had mitral valve surgery and cryoablation with patients who had mitral valve surgery and the conventional surgical maze procedure. Of patients treated with cryoablation, 85% (94/110) were in sinus rhythm at discharge, compared with 86% (95/110) of patients treated with the conventional maze surgery (p = 0.84). The survival rate at 3 years was 92% for the cryotherapy group and 98% for the conventional maze group (p = 0.32).

Two non-randomised trials compared patients having cryoablation and concomitant heart valve surgery with patients having heart valve surgery only. In the cryoablation groups, 100% (36/36) and 78% (25/32) of patients were in sinus rhythm immediately after surgery, compared with 33% (5/15) and 22% (4/18) of patients in the control groups. In one of these trials, 90% (26/29) of patients treated with cryoablation were in sinus rhythm at 9 months, compared with 25% (4/16) of patients in the control group. In the other trial, 78% (28/36) of patients treated with cryoablation and 20% (3/15) of patients in the control group were in sinus rhythm at 6 months. For more details, refer to the sources of evidence.

The Specialist Advisors considered this procedure to be a variation on the Cox maze technique.

As this procedure is performed during open heart surgery, it is difficult to differentiate the complications that relate specifically to cryoablation.

Three studies reported in-hospital mortality, which ranged from 0% (0/28) to 3% (3/95, 1/32). In four studies, 3% (1/32) to 14% (4/28) of patients required a pacemaker following surgery. Other complications included re-operation, delayed cardiac tamponade, mediastinitis, low cardiac output, the need for intra-aortic balloon pump, dialysis, and transient ischaemic attack. For more details, refer to the sources of evidence.

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

Interventional procedure overview of cryoablation for atrial fibrillation as an associated surgery with other cardiac surgery, July 2004

Available from: www.nice.org.uk/271overview