Quan H, Ghali WA, Verhoef MJ, Norris CM, Galbraith PD, and Knudtson ML. Use of chelation therapy after coronary angiography. Am J Med 2001 Dec15;111(9):686-691.

Purpose: Among patients who had undergone coronary angiography, we sought to determine the proportion of chelation therapy users, their sociodemographic and clinical characteristics, and the association of chelation therapy with subsequent revascularization.

Methods: We studied all patients who underwent coronary angiography in the province of Alberta, Canada, during 1995 and 1996. The cohort was followed for up to 6 years to determine subsequent revascularization status. Use of chelation therapy was determined by a mailed survey 1 year after angiography.

Results: Among the 5854 patients who responded to the mail survey (70% response rate), 210 (3.6%) reported current use of chelation therapy and 252 (4.3%) reported past use. Current use of chelation therapy was associated with extensive coronary artery disease (adjusted odds ratio [OR]=3.3; 95% confidence interval [CI]: 1.9 to 5.7 for 3-vessel disease; and OR = 2.7; 95% CI: 1.2 to 6.0 for left main disease, as compared with those with normal anatomy) and the absence of diabetes (OR= 0.6; 95% CI: 0.4 to 0.9). Current users were less likely to have undergone percutaneous transluminal coronary angioplasty (OR=0.7; 95% CI: 0.5 to 0.9) and coronary artery bypass graft (CABG) surgery (OR = 0.3; 95% CI: 0.2 to 0.5) in the first year after angiography, but were as likely as nonusers of chelation therapy to have undergone CABG surgery in the subsequent 3-to 5-year period (adjusted hazard ratio [HR]=1.1; 95% CI: 0.7 to 1.9). Past use of chelation therapy was associated with a history of CABG surgery before coronary angiography (OR=1.6; 95% CI: 1.1 to 2.3) and extensive coronary artery disease. Past users were also more likely to have undergone CABG surgery in the follow-up period (HR = 1.7; 95% CI: 1.1 to 2.6).

Conclusions: About 8% of patients who underwent cardiac catheterization for coronary artery disease were using or had previously tried chelation therapy. Users may have foregone revascularization in favor of this less invasive yet unproven treatment, with some users subsequently undergoing conventional treatment after chelation. Alternatively, some patients may have turned to chelation as a “last resort” after having been judged unsuitable for revascularization.

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