Among patients with diabetes mellitus, there in the composite endpoint for the chelation-treated patients relative to the placebo-treated patients (P=0.02 for interaction). Despite these positive findings, the TACT investigators did not recommend the routine use of chelation therapy to reduce symptoms or cardiovascular complications for all patients with SIHD, given the modest overall benefit, high proportion of patient withdrawals (18% lost to follow-up), absence of adequate scientific basis for the therapy, and possibility of a false positive outcome. The large proportion of withdrawals was especially concerning given that 50% more patients withdrew from chelation therapy than from placebo, which raised important concerns about unmasking of treatment assignments that could have influenced key outcomes (eg, revascularization or hospitalization for angina). In addition, chelation therapy is not risk free. Disodium EDTA, particularly when infused too rapidly, may cause hypocalcemia, renal failure, and death.45,46 Although disodium EDTA is approved by the US Food and Drug Administration for specific indications, such as iron overload and lead poisoning, it is not approved for use in preventing or treating cardiovascular disease. Accordingly, the writing group finds that the usefulness of chelation therapy in cardiac disease is highly questionable. 4.4.4. Alternative Therapies for Relief of Symptoms in Patients With Refractory Angina: Recommendation See Table 3 for the recommendation on enhanced external counterpulsation (EECP) and Online Data Supplement 3 for evidence supporting the recommendation. 4.4.4.1. Enhanced External Counterpulsation Although EECP was carefully reviewed in the 2012 SIHD comments received after the guideline s publication prompted a re-examination of the existing literature, even though no truly new data have become available. 