Global Endometrial Ablation – A Comparison of Various Techniques

G D Reid, D Kowalski

University of New South Wales

Sydney, Australia

Abnormal uterine bleeding affects around 20% of women between the ages of 30 – 50 years (Fig 1). Around 10% of these will have malignant or pre-malignant pathology, 30% will have uterine myomata and another 20% will have uterine polyps. A small number will be found to have medical conditions contributing to their bleeding tendency, such as thyroid disease or various blood dyscrasias. This leaves around 40% of women who will have a normal uterine cavity with reported degrees of abnormal bleeding – or true “dysfunctional uterine bleeding”. This is a diagnosis of exclusion, and classical teaching has been to treat such women with available medical therapies.

Fig 1 – Causes of Abnormal Menstrual Bleeding

Medical therapies have not changed greatly over the last 20 years, with the exception of hormonal implants. Approaches to dysfunctional bleeding include the use of non-steroidal anti-inflammatory agents such as mefanamic acid, naproxen and ibuprofen. These have all been shown to reduce menstrual blood loss, as has the antifibrinolytic agent, tranexamic acid. Potent synthetic progestogens like danocrine have also shown to be efficacious, and parenteral administration of high dose oestrogen remains useful for acute dysfunctional bleeding. These drugs all have significant side effects, and are often not tolerated by patients.

Hormonal implants such as “Mirena” probably offer the greatest hope for management of dysfunctional uterine bleeding, as their local action on the endometrium is associated with minimal systemic side effects.

The deficiencies and disadvantages of medical therapies, however, lead many women to seek hysterectomy as a solution to their problem. 600,000 (2.4/1000) hysterectomies are performed each year in the United States, 80,000 in England and 30,400 (1.6/1000) in Australia. The cost, risks and complications of hysterectomy has led to great interest in endometrial ablation techniques that became popularised in the late 1980’s.

The development of hysteroscopy allowed accurate diagnosis of intrauterine pathology, and provided an opportunity for the delivery of potentially effective intrauterine therapies. Magos et al¹ introduced trans-cervical resection of the endometrium (TCRE) into the UK in 1989, and the procedure rapidly became popular as an alternative to hysterectomy. In Australia, the use of endometrial resection or ablation peaked in 1992. There followed general disillusionment with the outcome of the operation, and its progressive abandonment.

Why did this occur? I believe there were three main reasons. First, hysteroscopic surgery was relatively new, and many gynaecologists felt obliged to perform this new and popular procedure before their level of training and skill permitted good results. Conventional endometrial resection or ablation is a highly skill-dependent procedure, and this was poorly acknowledged. Secondly, the importance of patient selection was undervalued. Patients with large uteri, and other uterine pathology, especially adenomyosis, demonstrated poor outcomes. Thirdly, laparoscopic hysterectomy was gaining in popularity as a real alternative to the treatment of dysfunctional bleeding.

With good patient selection, and with procedures performed by skilled operators, TCRE provides around an 85% patient satisfaction rate. About half of these patients become amenorrhoeic, and the rest are hypomenorrhoeic. Patients in the older age range tended to have the highest long-term satisfaction rates.

Inevitably, complications were reported. These included intraoperative fluid overload, uterine perforation, postoperative bleeding, infection and subsequent pregnancy. Morbidity rates of around 3% were reported, and Macdonald et al² reported a mortality rate of 0.02% (1/4038), following a survey of members of the British Society for Gynaecological Endoscopy in 1992.

On July 18, 1996 the New England Journal of Medicine published an editorial stating: “it is only a matter of time before ablation is superseded by less invasive procedures such as balloon heating…” Four years before, in an editorial in Gynaecological Endoscopy, Loffer³ wrote: “It can be anticipated that in the future other simpler and more efficacious methods of applying thermal energy to the endometrial surface will become available.”

The medical technology industry responded to this call and produced a wide range of devices. The concept of less skill dependent, global ablation of the endometrium, for a common problem was addressed with enthusiasm. Many devices were introduced, and we are presently in a situation of addressing which will prove to be most effective and safe. Let us review the plethora of devices currently available.

Let us also address a major problem in evaluation of this technology. What is the end-point? Should we take amenorrhoea rates, hypomenorrhea rates, patient satisfaction rates, subsequent retreatment or hysterectomy rates, or other parameters as the measure of success? I will concentrate on amenorrhoea and patient satisfaction in my evaluation, as I believe these are measurable and significant markers.

Roller-Ball Ablation and Loop Resection of the Endometrium.

The adaptation of the urological resectoscope to operative gynaecological procedures allowed for the development of both roller-ball and resectoscopic techniques of endometrial ablation.

The techniques used for the performance of these procedures have been well described elsewhere. In addition there has been much published data to report amenorrhoea occurring in 20% to 50% of patients and patient satisfaction with the procedure to occur in approximately 85% of subjects. A requirement for retreatment or hysterectomy has generally been reported in approximately 5% to 10% of patients⁴.

Uterine Thermal Balloons

This was the initial global approach to the endometrium. Two balloons have been developed – Thermachoice (USA) and Caviterm (Switzerland).

The Thermachoice device involves a handpiece with a catheter, and controller. The catheter is 16 cm long and 4.5 mm in diameter. On the end of the catheter is a latex balloon. The catheter is inserted blindly through the cervical canal to the level of the uterine fundus. The balloon is then inflated to a pressure of 180 mm Hg (90-190 mm Hg) with 5% dextrose in water. The control unit is then activated, heating the fluid to 87° ± 5° for 8 minutes. The activated cycle will terminate if the pressure drops to 45 mm Hg. This protects against inadvertent balloon rupture, or perforation of the uterus.

Because the balloon pressure compresses the endometrium, pre-treatment for endometrial thinning is not required, although the parent company recommends that this be done.

Fig 2 – The Thermachoice System

	Fig 3 - The Caveterm System

We undertook some studies with the Thermachoice device and found it particularly easy to use, and very suitable for high-risk patients, such as those on high-dose anti-coagulation. However we found rather sub-optimal depth of thermal coagulation in patients with larger uterine size, or those with deep cornual horns. Inconsistent temperature fall-off from the central heating element led the parent company to explore balloons with circulation devices, but to date these are not available in Australia.

Neuwirth⁵ conducted the initial laboratory development and peri-hysterectomy studies of this device in 1988, having previously described the use of the urological resectoscope for classical endometrial resection in 1983. Pilot clinical studies were conducted by Singer and Neuwirth in 1990, and pressure studies by Haber and Vilos in 1994. An international multicentre study was established in 1994, to gather data for FDA approval. 541 cases had been entered on this study by 1996. The first 300 of these patients followed up at 3 and/or 6 and/or 12 months was published by Amso et al⁶ in 1998. At 12 months 163 patients were available for follow-up. 15% were amenorrhoeic, 48% were hypomenorrhoeic and 25% were eumenorrhoeic. Twelve percent reported menorrhagia. There were no intraoperative complications, and postoperatively there was one case of cystitis, six patients with febrile morbidity (presumed endometritis) and two patients who developed hematometra. No major complications were reported.

Potential problems with this device include conformity to the uterine cavity, and in particular accommodation to deep cornual horns. Degradation of temperature from the heating element to the surface of the endometrium has been alluded to, and may account for Amso et al’s⁶ findings that treatment outcomes are improved in patients with a smaller uterine cavity.

The second thermal balloon device available at present is the Cavaterm (Wallsten Medical, Switzerland) system. It operates at a considerably lower temperature than the Thermachoice device and for a significantly longer treatment cycle. It also differs from the Thermachoice device in having an adjustable balloon length, as well as a circulation system for the contained fluid. A series of 32 patients with 18-28 months of follow-up was reported by Friberg B, Persson BR et al⁷ in 1998. They reported amenorrhoea rates of 31%, hypomenorrhoea rates of 41%, eumenorrhoea rates of 19% and failure rates of 9%. Again, no complications were reported.

Radiofrequency Thermal Balloons

Valleylab, USA developed this device. It was a balloon with 12 electrodes attached to the surface of a silastic balloon. Once inflated, an electrosurgical generator delivered 45W of current to the electrodes.

Treatment cycle time was 4 minutes, and was computer controlled.

Development of this device was ceased in 2000, and it is no longer available commercially.

Hydrothermal Ablation

The Hydrotherm Ablation (HTA) device was developed by BEI Medical Systems, New Jersey, USA. This device allows the application of thermo-destructive energy to the endometrium by free circulating saline heated to 90° C, for a treatment time of 10 minutes. The fluid flows into the uterine cavity through an insulated sheath surrounding a 3mm (rather than the usual 4 mm) hysteroscope. It requires dilatation of

Fig 4 – The Hydrotherm Ablation System

the cervical canal to 8 mm, and a Gimpleson (4 – pronged) clamp applied to the cervix to create a watertight seal around the apparatus.

A computerised controller monitors the treatment cycle. Fluid is instilled under adjustable pole-height pressure and actively scavenged from the uterus to create circulation. Pole height adjustment allows for intrauterine operating pressures of 40 – 50 mm Hg, below the tubal opening pressure of 70 – 75 mm Hg. Therefore heated fluid is not lost through the fallopian tube, nor from the sealed cervix.

Fluid volumes are constantly monitored, and the system will shut down if it detects a 10 ml fluid loss, either through the fallopian tube, the cervix or a uterine perforation. This is the only global ablation system to employ real-time hysteroscopic visualization, and I believe this is a major advantage in its favour. Furthermore, ablation is possible in septate and bicornuate uteri, as well as in the presence of sessile polyps and myomata. The use of this system in one case of a pedunculated myoma demonstrated severe limitation of free saline circulation, so it is not recommended in this situation.

Thinning of the endometrium prior to treatment is essential with this device, as there is no endometrial compressive effect during treatment. This may be achieved with either danocrine or a GnRH analogue. Pre-treatment curettage is not sufficient, as induced bleeding interferes with the treatment procedure.

FDA efficacy and safety data requirements led to the establishment of an international multi-centre study to assess HTA. 650 patients were enrolled from 16 treatment centres. At 12 months this data produced an amenorrhoea rate of 44.4%, a hypomenorrhoea rate of 37.5% and a eumenorrhoea rate of 13.8%. HTA results were then published in a number of individual series, such as Romer and Muller⁸ who reported amenorrhoea rates of 50%, hypomenorrhoea rates of 39% and eumenorrhoea rates of 5.5%. Botacini das Dores and Richart et al⁹ reported results on 26 women undergoing the HTA procedure. 87.5% of women were amenorrhoeic or hypomenorrhoeic at 12 months.

Three-Dimensional Bipolar Ablation

The Novasure system consists of a disposable handpiece and a computerised generator. The handpiece incorporates a catheter which carries an expandable skeleton over which is draped a metallic membrane, electrically isolated into 4 quadrants. The generator delivers power at up to 180 W, establishing a swirl of energy around the expanded membrane. The generator automatically calculates the required power from uterine length and width measurement.

This system is novel, in that the generator appliers suction to draw the endometrium into contact with the electrode. This also removes steam and moisture from the tissue, allowing efficient desiccation. The procedure is terminated when a preset impedance of 50W is reached, indicating an adequate depth of endometrial destruction. Treatment times range from 40 to 120 seconds, making this the fastest global ablation system available.

Fig 5 – The Novasure System

Cooper et al¹⁰ have published an amenorrhoea rate of 41% using this system in 175 patients followed for 12 months.

Microwave Endometrial Ablation

While this is not a true global ablation system, microwave endometrial ablation (MEA) was introduced by Microsulis, Waterloo, UK, and has become popular. It uses a microwave frequency of 9.2GHz at 30W to achieve tissue penetration not exceeding 6mm¹¹.

The energy is delivered through an 8mm intra-uterine probe, controlled via a footswitch. Intrauterine temperatures are monitored by thermocouples on the external surface of the probe, guiding movement of the probe by the surgeon, with reference to a display on a video monitor.

Fig 6. The Microwave Endometrial Ablation System

Endometrial temperatures of greater than 95° C are achieved within seconds of activation, with total treatment times ranging from 1 – 4 minutes (Mean 2 minutes, 12 seconds).

Initial reports from the UK in more than 500 patients treated indicate an amenorrhoea rate of 37.2%, and patient satisfaction rates of 83.7% at 3 years¹².

This is expensive technology. Apart from this it has been promoted as a simple but blind procedure. There have already been a number of bowel injuries reported in Australia – resulting from unrecognised uterine perforations. Without doubt, this is very effective technology, with uniform and deep endometrial destruction, but where it sits in the treatment of dysfunctional uterine bleeding remains to be determined – from a risk vs. benefit viewpoint.

Laser Interstitial Hyperthermy

Laser Interstitial Hyperthermy, ELITT, was introduced by Gynelase, Needham, USA, and uses fiberoptic technology to deliver Nd:YAG laser energy to the endometrium.

This is a blind treatment procedure of approximately 7 minutes, during which temperatures within the uterine cavity reach 102° C, but temperatures within 6 – 7 mm of the device do not exceed 60°C¹³

In initial studies in limited numbers of patients amenorrhoea rates of 86% at 6 months and 91% at 12 months have been reported¹⁴

General Overview

There have been many reports comparing various global systems against classical ablation (by skilled operators), showing comparable results. Parkin¹⁵ highlighted the importance of such studies in his editorial report in 2000. There is evidence that the outcome of global systems compare favourably with conventional resection / ablation.

There are considerable capital costs involved in the installation of these systems, and considerable disposable costs. Many companies will amortize the cost of controller devices against the costs of disposables, but ultimately all the equipment must be paid for by one means or another.

Institutions need comparative efficacy data to assist in selection of systems, but this data is limited by variable length of follow-up, variable patient populations and variable criteria for reporting results and adverse outcomes. This led Morris Wortman¹⁶ to say that the time had come to set standards for comparison of these technologies. He summarised some available published data, but no clear conclusions could be drawn regarding the superiority of one system over another (Table 2).

Nevertheless, with his stringent requirements for ammenorrhoea as an endpoint, Thermachoice provided a 20.6% and 15.2% incidence in the two papers studied. Vestablate provided a 31.8% rate and HTA a 50% rate. This compared with a 25-40% rate for classical resection or ablation. None of this was statistically significant.

Kremer and Duffy¹⁷ considered these issues at length in a British Journal of Obstetrics and Gynaecology editorial in December 2000. They assessed all the current generation methods of endometrial ablation. They were critical that insufficient data were available to assess global endometrial ablation. They acknowledged that these global ablation systems seemed safe, and called for an assessment of cost effectiveness.

I believe there are three conclusions that can be drawn from all this:

1. Global ablation systems have been compared with classical endometrial ablation / resection, and the clinical results in the short term are not statistically different.

2. The various global ablation systems available show no statistically significant difference in their short-term outcomes, with a trend for Thermachoice to show a lower ammenorrhoea rate than the other systems.

3. All the global systems have a low morbidity rate.

Cost must be considered in these comparisons. This is a difficult analysis, as most of the companies producing global ablation systems are willing to amortize the cost of computers and controllers, against a guaranteed rate of disposable utilization. The cost of pre-treatment and disposables must then be compared with outcomes of endometrial ablation by conventional means.

There is no doubt that properly selected women have good outcomes from classical endometrial ablation or resection or both, when performed by trained and skilled operators. We commonly perform endometrial ablation and resection, and seldom have failures in terms of requirement for retreatment or poor patient satisfaction.

We are meticulous about patient selection. They must:

1. Be over the age of 35 (preferably >40).

2. Have a uterine cavity less than 12cm.

3. Have no other pelvic or uterine pathology (especially adenomyosis).

We are also meticulous about technique:

1. Roller-Ball ablation to the cornua and uterine fundus.

2. Resection of the body of the uterus

3. Roller-Ball to the resected uterine body

4. Maximum duration of surgery – 45 min.

5. Maximum fluid (Glycine) loss – 800 ml.¹⁸

The uterus will accept a huge amount of energy, without significant serosal temperature rise. I believe that that this fear of transmitted energy held us back from appropriate ablative techniques during the early years. If appropriate energy is used to destroy the endometrial lining, patient satisfaction and outcomes are particularly good, with simple and relatively inexpensive equipment. Global ablation systems attempt to match these results – at a cost. They have not demonstrated clear superiority in efficacy.

Could we suggest that both in Australia and India, a relatively small number of doctors could gain a large amount of experience in classical ablative techniques, providing very cost-effective management of a common problem? This concept is quite different from that proposed by the companies promoting global ablation systems – that a large number of doctors gain a small amount of experience in apparently simplistic surgery.

We need to return to training doctors to perform endometrial ablation / resection on well-chosen patients with good indications. Perhaps we will then impact on the cost of treating dysfunctional uterine bleeding.

Table 1. Comparison of Various Endometrial Destruction Techniques
DEVICE				HYSTEROSCOPY			DIAMETER	TREAT (min)
Ablation/resection	Optional			Yes			8 – 10mm	-
Thermachoice	Optional			No			4.5mm	8
HTA	Essential			Yes			8mm	10
Novasure	Optional			No			7mm	2
Microwave	Recommended			No			8mm	1 – 6
ELITT	Recommended			No			6mm	7
Table 2. Outcomes following Endometrial Destruction Techniques
TECHNIQUE		NO.	FU		AMEN (%)	RETREAT (%)			HYST (%)
Endometrial Ablation - hysteroscopic
Roller-Ball		128^19	NA		25.0	8.5			8.5
		200^20	30		40.0	4.0			5.0
		65^21	12		55.4	NA			NA
Resection		113^22	12		25.0	7.0			4.0
		363^23	3-4		NA	7.5			6.8
Endometrial Ablation - Global
Thermachoice		68^24	12		20.6	20.6			4.2
		125^25	12		15.2	NA			1.6
Cavaterm		32^7	18		31.0	NA			NA
Vestablate		132^26	12		31.8	NA			NA
HTA		18^8	12		50.0	NA			NA
Novasure		175^10	12		41.0	2.3			1.7
Endometrial Ablation – Blind, Non-Global
MEA		43^12	36		37.2	6.9			9.3

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