Impact of different patterns of invasive care on quality of life outcomes in patients with non-ST elevation acute coronary syndrome: results from the GUSTO-IIb Canada-United States substudy.

Background: Comparing American and Canadian practice patterns and outcomes offers a natural experiment to examine the relative benefits of aggressive versus conservative management of coronary artery disease. In a prospective substudy of the Global Use of Strategies to Open Occluded Coronary Arteries IIb (GUSTO-IIb) trial, differences in the management of non-ST elevation acute coronary syndrome, and the associated impact on quality of life (QOL) outcomes, were examined in the two countries.

Methods And Results: The patient population, selected randomly from the parent trial population, comprised 390 Canadian and 1122 American patients for whom both baseline and one-year data were available. Validated instruments were used to assess QOL, including the Duke Activity Status Index (DASI) and scales from the SF-36 questionnaire. At baseline, American patients had significantly higher cardiac catheterization rates (83% versus 45%), percutaneous coronary intervention rates (39% versus 24%) and coronary bypass surgery rates (19% versus 12%) than did Canadian patients, respectively. However, at one year, Canadian coronary bypass surgery rates were at par with those in the United States (24% versus 26%, respectively). At baseline, the mean DASI score was 24.6 among Canadian patients and 23.4 among American patients (P=0.14). At one year, neither cohort reported any significant change in functional scores and there was no intercountry difference in DASI scores, even after accounting for baseline risk. Canadian patients had significantly worse mental health scores than American patients at baseline (mean score 71.6 versus 75.4, respectively; P=0.02), but by one year, Canadian patients had better scores (mean score 80.1 versus 76.2, respectively; P=0.01). After adjusting for baseline characteristics, Canadian patients continued to report better mental health status scores than did American patients (4 points higher, P<0.01). When asked to rate their health state on a scale from 0 to 100, both cohorts reported similar values at baseline. However, after adjusting for baseline characteristics, American patients' perception of their health state was better than that reported by Canadians (3 points higher, P<0.01).

Conclusion: Despite higher rates of invasive procedures in the American cohort, one-year QOL outcomes in the cohort were similar to those in the more conservatively managed Canadian cohort. These results suggest that routine cardiac catheterization and increased procedure use may be associated with diminishing marginal returns with respect to improving QOL outcomes among patients with non-ST elevation acute coronary syndromes.