The National Institute for Clinical Excellence is examining microwave ablation 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 microwave ablation 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• The Advisory Committee will then prepare draft guidance which will be the basis for the Institute's guidance on the use of the procedure in the NHS in England, Wales and Scotland.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 microwave ablation 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 microwave energy 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.

Microwave ablation for atrial fibrillation is typically carried out in patients undergoing concomitant open heart surgery, including mitral valve replacement or repair. The procedure uses thermal damage rather than incisions to block impulse conduction. The heat generated by the flexible microwave probe coagulates the heart tissue, forming 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.

In one randomised controlled trial, patients having open heart surgery and microwave ablation were compared with those having open heart surgery alone. Immediately after the surgery, 92% (22/24) of patients who had microwave ablation were in sinus rhythm compared with 32% (6/19) of patients in the control group (p = 0.05). At 12 months, 80% (12/15) of patients having microwave ablation were in sinus rhythm compared with 33% (3/9) of control patients (p < 0.05). A non-randomised controlled trial reported that 62% (84/136) of patients treated with microwave ablation were in sinus rhythm at 12 months, compared with 10% (5/51) of patients having heart surgery without microwave ablation (p = 0.0001). A second non-randomised controlled trial comparing patients who had microwave ablation with those who had radiofrequency ablation reported no significant difference in the number of patients in sinus rhythm at 12 months; the results were 59% (13/22) for the microwave ablation group, and 57% (8/14) for the radiofrequency ablation group.

Case series reported that 61% (25/41) and 76% (32/42) of patients were in sinus rhythm immediately after surgery. In a further case series, 62% (74/119) of patients were in sinus rhythm at the 12-month follow-up. For further 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 microwave ablation.

The main complications reported were in-hospital mortality and the requirement for a permanent pacemaker. In the randomised controlled trial, the in-hospital mortality was 4% (1/24) for patients having microwave ablation and heart surgery, compared with 5% (1/19) for patients treated with heart surgery only. Four other studies reported in-hospital mortality rates, which ranged from 0% (0/42) to 4% (1/23). Four studies reported the proportion of patients who needed a permanent pacemaker; this ranged from 0% (0/41) to 23% (46/202). One study reported additional complications of bleeding in 9% of patients (2/23), the need for intra-aortic balloon pump in 4% (1/23), transient low cardiac output in 4% (1/23) and severe systemic inflammatory response syndrome in 4% (1/23). 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 microwave ablation for atrial fibrillation in association with other cardiac surgery, July 2004

Available from: www.nice.org.uk/266overview