Authors' objectives:

The specific aims of this technology assessment are as follows: 1. Provide a summary and description of the technology.

2. Review the peer-reviewed clinical literature on the outcomes associated with the use of: - transmyocardial laser revascularization (TMR) as a stand-alone procedure; - TMR used together with coronary artery bypass grafting (CABG); - percutaneous myocardial laser revascularization (PMR).

3. Review of available information on clinical trials underway as a horizon scan for this technology.

In addition, studies on the mechanism of action and the specific lasers used for each of the procedures were reviewed, and a description of those findings is included in this report.

Authors' recommendations: TMR has been evaluated in seven clinical trials; all seven studies report significant improvement in the frequency and/or severity of angina after TMR, with no net improvement in survival. Two trials with prolonged follow up suggest that symptomatic improvement is persistent, although other studies demonstrate a trend towards diminished relief after the first 6 months following TMR. The only benefit in survival following TMR as sole therapy compared to medical treatment has been found in a 5-year follow up of a multicenter, randomized experience. In addition to symptomatic relief, TMR was associated with an increase in exercise tolerance and quality of life. There were no consistent trends regarding the impact of TMR on admission for unstable angina, reduction in antianginal medications, cardiac events, or other complications (in particular congestive heart failure that might follow myocardial tissue damage due to therapy). Any symptomatic benefit of TMR appears to be out of proportion to demonstrable improvement in myocardial perfusion. Only one of three trials that examined myocardial perfusion demonstrated some improvement in perfusion after TMR. Only one trial assessed the benefit of TMR plus CABG; this suggested that the addition of TMR significantly reduced mortality without influencing anginal symptoms. Although both groups realized significant angina relief through 1 year, 5-year follow up indicated that CABG plus TMR provided superior angina relief compared to CABG alone. Regarding the 12-month survival benefit, it appeared to be explained entirely by the lower rate of 30-day mortality in TMR plus CABG vs. CABG alone patients (1.5 percent vs. 7.6 percent). Both clinical trials and observational studies provide information on the adverse effects of TMR. In clinical trials, 30-day mortality was variable, up to five percent. In observational studies, 30-day mortality was up to 15 percent, with 12-month mortality ranging between 13 percent and 25 percent. Risks appear to be higher in those patients with recent acute cardiac events, unstable angina, and depressed ventricular function. In addition, there are some data from observational studies regarding utilization of the procedure. Notably, TMR - a procedure intended as palliative therapy for advanced refractory coronary disease - is frequently used for less severe patients in community practice. Approximately 25 percent of patients have angina that is not severe enough to satisfy FDA labeling requirements or Medicare coverage criteria for use of TMR. Although the evidence is not as consistent, PMR trials suggest that the procedure can improve angina symptoms; this finding was reported in four of six trials. As with TMR, there is no evidence of physiological changes or increases in survival. The available studies have notable limitations. These include: - Lack of a clear definition of 'maximal medical therapy' prior to inclusion in a study and in the control arm of clinical trials. It appears that a significant proportion of patients initially referred for TMR with refractory angina can be stabilized medically. - Frequent treatment crossovers. In two major trials, Frazier and colleagues and Allen and colleagues allowed crossovers from the medical therapy group to the TMR group. In the Frazier trial, crossover was allowed as 'an incentive for patients assigned to maximal therapy to remain in the study if medical therapy failed.' - Frequent lack of blinding in outcomes assessment. This could lead to an apparent increased therapeutic effect of TMR/PMR. Though it is evidently difficult (though not impossible) to blind patients to their treatment, it is feasible to blind the individual responsible for assessing trial outcomes, as was done in blinded validations of two trials at 1 year and in the randomized long-term follow-up studies. - Presence of a placebo effect. This is likely to be a powerful factor in an intervention such as TMR or PMR, particularly in early follow up.

Authors' methods: Systematic review

Project Status: Completed

URL for project: http://www.ahrq.gov/clinic/techix.htm

Year Published: 2004

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: United States

Organisation Name: Agency for Healthcare Research and Quality

Contact Address: Center for Outcomes and Evidence Technology Assessment Program, 540 Gaither Road, Rockville, MD 20850, USA. Tel: +1 301 427 1610; Fax: +1 301 427 1639;

Contact Name: martin.erlichman@ahrq.hhs.gov

Contact Email: martin.erlichman@ahrq.hhs.gov

Copyright: Agency for Healthcare Research and Quality (AHRQ)