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Large Trial Reaffirms Intervention Benefit For Unstable Angina

Rates of angina could be halved if interventions such as balloon angioplasty or coronary artery bypass surgery are undertaken soon after identification of patients at moderate risk of myocardial infarction.

The multi-center British Heart Foundation Randomised Intervention Trial of Unstable Angina (RITA) shows, like previous trials, that "the hazards of intervention seem to be more than counterbalanced by the subsequent reduction in risk of heart attack," declares lead author Dr Keith Fox of the University of Edinburgh.

The most appropriate revascularisation strategy after presentation with unstable angina or non-ST-segment-elevation myocardial infarction remains contentious for patients at moderate risk, the researchers point out: "The American Heart Association/American College of Cardiology (AHA/ACC) guidelines recommend an invasive strategy for patients at high risk, but specify that either an invasive strategy or a conservative strategy is appropriate for patients at moderate or low risk."

However, in large-scale international registries, only 25 to 28 percent of patients with non-ST-elevation myocardial infarction and 18 percent of those with unstable angina undergo percutaneous coronary intervention (PCI) during the initial hospital admission. Rates vary between 38 percent in the United States, 29 percent in Europe; 24 percent in Argentina and Brazil; and 16 percent in Australia, New Zealand, and Canada.

The researchers carried out a randomised trial among 1,810 patients at moderate risk of an MI. Patients were assigned to either an intervention or conservative treatment group.

The 895 patients assigned to intervention were given angiography and, if necessary, revascularisation. Conservative treatment among 915 patients was a wait-and-see strategy with subsequent intervention if needed.

The antithrombin agent enoxaparin was used among both treatment groups.

At four months, 9.6 percent of patients in the intervention group had died, had an MI, or had angina, compared with 14.5 percent of patients in the conservative group. The differences were mainly due to a halving of refractory angina in the intervention group. Rates of death and MI were similar between the two groups at one year follow-up: 7.6 percent in the intervention group and 8.3 percent in the conservative treatment group.

Around a quarter of patients given conservative treatment subsequently required surgery for coronary revascularisation within one year.

Dr Fox and colleagues conclude: "Our study has shown that, among patients with unstable coronary syndromes, the combined endpoint of death, non-fatal heart attack, or severe angina is significantly reduced in patients assigned intervention, and that the main effect was on severe angina. Conclusive evidence for the effect on prognosis (death or myocardial infarction) will require completion of the planned five year follow-up."
http://image.thelancet.com/extras/02art8090web.pdf

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