3 The technologies

3 The technologies

3.1 Second-generation EA techniques have been introduced with the aim of providing simpler, quicker and more effective treatment options for HMB compared with first-generation EA techniques and hysterectomy. These techniques are less operator-dependent than the first-generation techniques, but they rely heavily on the devices themselves to ensure safety and efficacy. Second-generation EA techniques include fluid-filled thermal balloon EA (TBEA), radiofrequency (thermoregulated) balloon EA, hydrothermal EA, 3D bipolar radiofrequency EA, microwave EA (MEA), diode laser hyperthermy, cryoablation and photodynamic therapy. The most frequently used second-generation EA techniques in UK clinical practice, and the focus of this appraisal, are fluidfilled TBEA and MEA. These techniques do not require direct visualisation of the uterine cavity, and can be carried out under either local or general anaesthesia.

3.2 TBEA destroys the inner layers of the uterus by transferring heat from heated liquid within a balloon inserted into the uterine cavity. The two devices available in the UK, Cavaterm and Thermachoice, both involve an electronic controller, a single-use latex or silicone balloon catheter housing a heating element and two thermocouples, and an umbilical cable. TBEA cannot be used on women with large or irregular uterine cavities because the balloon must be in direct contact with the uterine wall to cause ablation. Cavaterm is contraindicated for women whose uterine cavity is more than 10 cm long (from the internal os to the fundus), and Thermachoice for women whose uterine cavity is more than 12 cm long, and for those who have a latex allergy. TBEA is also contraindicated if classical caesarean section (vertical midline incision in the upper segment of the uterus) has been performed, or if other uterine surgery has left a scar where the uterine wall is less than 8 mm thick. The use of endometrial thinning agents before TBEA is not recommended.

3.3 The MEA technique uses microwaves (at a fixed frequency of 9.2 GHz) to destroy the uterine glandular lining, using a hand-held applicator (microwave probe) that is inserted into the uterine cavity. The Microsulis MEA system consists of a system console that houses a control module with an embedded computer, a microwave generator, and a power supply. Additional components are a hand-held applicator, a pneumatic footswitch, coaxial and data cables, a printer (optional), a power cord and a portable trolley.

3.4 The MEA applicator must be cleaned and sterilised before each use. MEA can be used in women whose uterine cavity is irregular in shape as a result of mild to moderate fibroids, polyps or congenital abnormalities. MEA is contraindicated if classical caesarean section (vertical midline incision in the upper segment of the uterus) has been performed, or if other uterine surgery has left a scar where the uterine wall is less than 8 mm thick. The use of endometrial thinning agents before MEA is recommended.

3.5 Although equipment failures for MEA and TBEA were reported in early usage, the devices have been improved and these failures are now much less common. Adverse events with second-generation EA techniques include uterine infection, perforation, visceral burn, bleeding, haematometra, laceration, intra-abdominal injury and cyclical pain. Women who do not respond to initial EA may require further ablations or, eventually, hysterectomy.

3.6 The outcome of EA is dependent on selecting the most appropriate technique for the individual patients' needs.

3.7 The Cavaterm and Thermachoice control unit/generators cost £3990 and £6000 respectively, and the disposable balloon catheters cost £280 and £350. The Microsulis MEA system costs around £40,000 (with an additional £5000 per annum for the maintenance contract). However, most centres in the UK have a 'placement arrangement' with manufacturers, under which centres pay a fixed fee per treatment (about £280 per treatment with no capital cost for MEA).