Enhanced vasculotoxic metal excretion in post-myocardial infarction patients following a single edetate disodium-based infusion

Edetate Disodium-Based Chelation for Patients With a Previous Myocardial Infarction and Diabetes: TACT2 Randomized Clinical Trial

Importance

In 2013, the Trial to Assess Chelation Therapy (TACT) reported that edetate disodium (EDTA)-based chelation significantly reduced cardiovascular disease (CVD) events by 18% in 1708 patients with a prior myocardial infarction (MI).

Objective

To replicate the finding of TACT in individuals with diabetes and previous MI.

Design, Setting, and Participants

A 2 × 2 factorial, double-masked, placebo-controlled, multicenter trial at 88 sites in the US and Canada, involving participants who were 50 years or older, had diabetes, and had experienced an MI at least 6 weeks before recruitment compared the effect of EDTA-based chelation vs placebo infusions on CVD events and compared the effect of high doses of oral multivitamins and minerals with oral placebo. This article reports on the chelation vs placebo infusion comparisons.

Interventions

Eligible participants were randomly assigned to 40 weekly infusions of an EDTA-based chelation solution or matching placebo and to twice daily oral, high-dose multivitamin and mineral supplements or matching placebo for 60 months. This article addresses the chelation study.

Main Outcomes and Measures

The primary end point was the composite of all-cause mortality, MI, stroke, coronary revascularization, or hospitalization for unstable angina. Median follow-up was 48 months. Primary comparisons were made from patients who received at least 1 assigned infusion.

Results

Of the 959 participants (median age, 67 years [IQR, 60-72 years]; 27% females; 78% White, 10% Black, and 20% Hispanic), 483 received at least 1 chelation infusion and 476 at least 1 placebo infusion. A primary end point event occurred in 172 participants (35.6%) in the chelation group and in 170 (35.7%) in the placebo group (adjusted hazard ratio [HR], 0.93; 95% CI, 0.76-1.16; P = .53). The 5-year primary event cumulative incidence rates were 45.8% for the chelation group and 46.5% for the placebo group. CV death, MI, or stroke events occurred in 89 participants (18.4%) in the chelation group and in 94 (19.7%) in the placebo group (adjusted HR, 0.89; 95% CI, 0.66-1.19). Death from any cause occurred in 84 participants (17.4%) in the chelation group and in 84 (17.6%) in the placebo group (adjusted HR, 0.96; 95% CI, 0.71-1.30). Chelation reduced median blood lead levels from 9.03 μg/L at baseline to 3.46 μg/L at infusion 40 (P < .001). Corresponding levels in the placebo group were 9.3 μg/L and 8.7 μg/L, respectively.

Conclusions and Relevance

Despite effectively reducing blood lead levels, EDTA chelation was not effective in reducing cardiovascular events in stable patients with coronary artery disease who have diabetes and a history of MI.

Trial Registration

ClinicalTrials.gov Identifier: NCT02733185.

Global health burden and cost of lead exposure in children and adults: a health impact and economic modelling analysis

BACKGROUND

Lead exposure is a worldwide health risk despite substantial declines in blood lead levels following the leaded gasoline phase-out. For the first time, to our knowledge, we aimed to estimate the global burden and cost of intelligence quotient (IQ) loss and cardiovascular disease mortality from lead exposure.

METHODS

In this modelling study, we used country blood lead level estimates from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019. We estimated IQ loss (presented as estimated loss in IQ points with 95% CIs) in the global population of children younger than 5 years using the blood lead level-IQ loss function from an international pooled analysis. We estimated the cost of IQ loss, which was calculated only for the proportion of children expected to enter the labour force, as the present value of loss in lifetime income from the IQ loss (presented as cost in US dollars and percentage of gross domestic product with a range). We estimated cardiovascular deaths (with 95% CIs) due to lead exposure among people aged 25 years or older using a health impact model that captures the effect of lead exposure on cardiovascular disease mortality that is mediated through mechanisms other than hypertension. Finally, we used values of statistical life to estimate the welfare cost of premature mortality (presented as cost in US dollars and percentage of GDP). All estimates were calculated by World Bank income classification and region (for low-income and middle-income countries [LMICs] only) for 2019.

FINDINGS

We estimated that children younger than 5 years lost 765 million (95% CI 443-1098) IQ points and that 5 545 000 (2 305 000-8 271 000) adults died from cardiovascular disease in 2019 due to lead exposure. 729 million of the IQ points lost (95·3% of the total global IQ loss) and 5 004 000 (90·2% of total) cardiovascular disease deaths due to lead exposure occurred in LMICs. IQ loss in LMICs was nearly 80% higher than a previous estimate. Cardiovascular disease deaths were six times higher than the GBD 2019 estimate. The global cost of lead exposure was US$6·0 trillion (range 2·6-9·0) in 2019, which was equivalent to 6·9% (3·1-10·4) of the global gross domestic product. 77% (range 70-78) of the cost was the welfare cost of cardiovascular disease mortality, and 23% (22-30) was the present value of future income losses from IQ loss.

INTERPRETATION

Our findings suggest that global lead exposure has health and economic costs at par with PM2·5 air pollution. However, much work remains to improve the quality of blood lead level measurement data, especially in LMICs.

FUNDING

The Korea Green Growth Trust Fund and the World Bank's Pollution Management and Environmental Health Program.

A State-of-the-Science Review on Metal Biomarkers

PURPOSE OF REVIEW

Biomarkers are commonly used in epidemiological studies to assess metals and metalloid exposure and estimate internal dose, as they integrate multiple sources and routes of exposure. Researchers are increasingly using multi-metal panels and innovative statistical methods to understand how exposure to real-world metal mixtures affects human health. Metals have both common and unique sources and routes of exposure, as well as biotransformation and elimination pathways. The development of multi-element analytical technology allows researchers to examine a broad spectrum of metals in their studies; however, their interpretation is complex as they can reflect different windows of exposure and several biomarkers have critical limitations. This review elaborates on more than 500 scientific publications to discuss major sources of exposure, biotransformation and elimination, and biomarkers of exposure and internal dose for 12 metals/metalloids, including 8 non-essential elements (arsenic, barium, cadmium, lead, mercury, nickel, tin, uranium) and 4 essential elements (manganese, molybdenum, selenium, and zinc) commonly used in multi-element analyses.

RECENT FINDINGS

We conclude that not all metal biomarkers are adequate measures of exposure and that understanding the metabolic biotransformation and elimination of metals is key to metal biomarker interpretation. For example, whole blood is a good biomarker of exposure to arsenic, cadmium, lead, mercury, and tin, but it is not a good indicator for barium, nickel, and uranium. For some essential metals, the interpretation of whole blood biomarkers is unclear. Urine is the most commonly used biomarker of exposure across metals but it should not be used to assess lead exposure. Essential metals such as zinc and manganese are tightly regulated by homeostatic processes; thus, elevated levels in urine may reflect body loss and metabolic processes rather than excess exposure. Total urinary arsenic may reflect exposure to both organic and inorganic arsenic, thus, arsenic speciation and adjustment for arsebonetaine are needed in populations with dietary seafood consumption. Hair and nails primarily reflect exposure to organic mercury, except in populations exposed to high levels of inorganic mercury such as in occupational and environmental settings. When selecting biomarkers, it is also critical to consider the exposure window of interest. Most populations are chronically exposed to metals in the low-to-moderate range, yet many biomarkers reflect recent exposures. Toenails are emerging biomarkers in this regard. They are reliable biomarkers of long-term exposure for arsenic, mercury, manganese, and selenium. However, more research is needed to understand the role of nails as a biomarker of exposure to other metals. Similarly, teeth are increasingly used to assess lifelong exposures to several essential and non-essential metals such as lead, including during the prenatal window. As metals epidemiology moves towards embracing a multi-metal/mixtures approach and expanding metal panels to include less commonly studied metals, it is important for researchers to have a strong knowledge base about the metal biomarkers included in their research. This review aims to aid metals researchers in their analysis planning, facilitate sound analytical decision-making, as well as appropriate understanding and interpretation of results.

[Environment and cardiovascular health: causes, consequences and opportunities in prevention and treatment]

The environment is a strong determinant of cardiovascular health. Environmental cardiology studies the contribution of environmental exposures with the aim of minimizing the harmful influences of pollution and promoting cardiovascular health through specific preventive or therapeutic strategies. The present review focuses on particulate matter and metals, which are the pollutants with the strongest level of scientific evidence, and includes possible interventions. Legislation, mitigation and control of pollutants in air, water and food, as well as environmental policies for heart-healthy spaces, are key measures for cardiovascular health. Individual strategies include the chelation of divalent metals such as lead and cadmium, metals that can only be removed from the body via chelation. The TACT (Trial to Assess Chelation Therapy, NCT00044213) clinical trial demonstrated cardiovascular benefit in patients with a previous myocardial infarction, especially in those with diabetes. Currently, the TACT2 trial (NCT02733185) is replicating the TACT results in people with diabetes. Data from the United States and Argentina have also shown the potential usefulness of chelation in severe peripheral arterial disease. More research and action in environmental cardiology could substantially help to improve the prevention and treatment of cardiovascular disease.

Environment and cardiovascular health: causes, consequences and opportunities in prevention and treatment

The environment is a strong determinant of cardiovascular health. Environmental cardiology studies the contribution of environmental exposures with the aim of minimizing the harmful influences of pollution and promoting cardiovascular health through specific preventive or therapeutic strategies. The present review focuses on particulate matter and metals, which are the pollutants with the strongest level of scientific evidence, and includes possible interventions. Legislation, mitigation and control of pollutants in air, water and food, as well as environmental policies for heart-healthy spaces, are key measures for cardiovascular health. Individual strategies include the chelation of divalent metals such as lead and cadmium, metals that can only be removed from the body via chelation. The TACT (Trial to Assess Chelation Therapy, NCT00044213) clinical trial demonstrated cardiovascular benefit in patients with a previous myocardial infarction, especially in those with diabetes. Currently, the TACT2 trial (NCT02733185) is replicating the TACT results in people with diabetes. Data from the United States and Argentina have also shown the potential usefulness of chelation in severe peripheral arterial disease. More research and action in environmental cardiology could substantially help to improve the prevention and treatment of cardiovascular disease.

The trial to assess chelation therapy 2 (TACT2): Rationale and design

BACKGROUND

Intravenous edetate disodium-based infusions reduced cardiovascular events in a prior clinical trial. The Trial to Assess Chelation Therapy 2 (TACT2) will replicate the initial study design.

METHODS

TACT2 is an NIH-sponsored, randomized, 2x2 factorial, double masked, placebo-controlled, multicenter clinical trial testing 40 weekly infusions of a multi-component edetate disodium (disodium ethylenediamine tetra-acetic acid, or Na2EDTA)-based chelation solution and twice daily oral, high-dose multivitamin and mineral supplements in patients with diabetes and a prior myocardial infarction (MI). TACT2 completed enrollment of 1000 subjects in December 2020, and infusions in December 2021. Subjects are followed for 2.5 to 5 years. The primary endpoint is time to first occurrence of all-cause mortality, MI, stroke, coronary revascularization, or hospitalization for unstable angina. The trial has >;85% power to detect a 30% relative reduction in the primary endpoint. TACT2 also includes a Trace Metals and Biorepository Core Lab, to test whether benefits of treatment, if present, are due to chelation of lead and cadmium from patients. Design features of TACT2 were chosen to replicate selected features of the first TACT, which demonstrated a significant reduction in cardiovascular outcomes in the EDTA chelation arm compared with placebo among patients with a prior MI, with the largest effect in patients with diabetes.

RESULTS

Results are expected in 2024.

CONCLUSION

TACT2 may provide definitive evidence of the benefit of edetate disodiumbased chelation on cardiovascular outcomes, as well as the clinical importance of longitudinal changes in toxic metal levels of participants.

Heavy Metal Toxicity in Chronic Renal Failure and Cardiovascular Disease: Possible Role for Chelation Therapy

Exposure to heavy metals is common. This exposure is related to environmental contamination of air, water and soil, occupational exposure, accumulation in food, tobacco, and other factors. Cadmium and lead are notable for their widespread contamination, long-lasting effects in the body, and renal as well as cardiovascular toxicity. Acute toxicity due to high-level exposure, as well as chronic low-level exposure are now well-established pathogenic entities. Both chronic renal failure and ischemic heart disease patients have been treated separately in recent studies with ethylenediaminetetraacetic acid (EDTA) chelation therapy. In patients with chronic kidney disease (serum creatinine: 1.5-4.0 mg/dL) and increased body lead burden, weekly low-dose chelation with calcium EDTA slowed the rate of decline in renal function in patients with diabetes and in non-diabetic patients. In patients with a history of myocardial infarction, the Trial to Assess Chelation Therapy study showed that EDTA chelation decreased the likelihood of cardiovascular events, particularly in patients with diabetes. However, heavy metal levels were not measured in this study. It is clear that more research is needed in this area. There is also a need to more frequently consider and test for the possibility of cadmium and lead toxicity in patients with increased risk, such as those with hypertension, diabetes mellitus, and chronic renal disease.

The Case For Cadmium and Lead Heavy Metal Screening

Exposure to cadmium and lead is widespread, and is related to environmental contamination, occupational sources, food, tobacco and other consumer products. Lower socioeconomic status increases the risk of heavy metal exposure and the diseases associated with cadmium and lead toxicity. Concurrent toxicity with both cadmium and lead is likely but has not often been assessed. There is now substantial evidence linking cadmium and lead to many diseases including hypertension, diabetes mellitus, obesity, cancer, coronary artery disease, chronic kidney disease (CKD) and lung disease. Both chronic renal failure and ischemic heart disease patients have been treated separately in recent studies with calcium disodium ethylenediaminetetraacetic acid (Ca EDTA) chelation therapy. In patients with CKD, serum creatinine 1.5-4.0 mg/dL, and increased body lead burden, weekly low dose chelation with Ca EDTA slowed the rate of decline in renal function in diabetics and non-diabetics. In patients with a history of myocardial infarction, the Trial to Assess Chelation Therapy (TACT) study showed that Ca EDTA chelation decreased the likelihood of cardiovascular events, particularly in diabetics. Ca EDTA chelation administered carefully at lower dosage (<50 mg/kg per week) is generally safe. In the past, acute renal failure associated with much higher dosage was reported. We suggest that the preponderance of the evidence favors a more activist approach towards diagnosis and possible intervention in heavy metal toxicity.

Low-Level Metal Contamination and Chelation in Cardiovascular Disease-A Ripe Area for Toxicology Research

Cardiovascular disease remains the leading cause of death worldwide. In spite of cardiovascular prevention, there is residual risk not explicable by traditional risk factors. Metal contamination even at levels previously considered safe in humans may be a potential risk factor for atherosclerosis. This review examines evidence that 2 metals, lead, and cadmium, demonstrate sufficient toxicological and epidemiologic evidence to attribute causality for atherosclerotic disease. Basic science suggests that both metals have profound adverse effects on the human cardiovascular system, resulting in endothelial dysfunction, an increase in inflammatory markers, and reactive oxygen species, all of which are proatherosclerotic. Epidemiological studies have shown both metals to have an association with cardiovascular disease, such as peripheral arterial disease, ischemic heart disease, and cardiovascular mortality. This review also examines edetate disodium-based chelation as a possible pharmacotherapy to reduce metal burden in patients with a history of cardiovascular disease and thus potentially reduce cardiovascular events.

Urinary Metal Levels after Repeated Edetate Disodium Infusions: Preliminary Findings

Environmentally acquired lead and cadmium are associated with increased cardiovascular disease risk. In the Trial to Assess Chelation Therapy, up to 40 infusions with edetate disodium over an approximately one-year period lowered the cardiovascular disease risk in patients with a prior myocardial infarction. We assessed whether a reduction in surrogate measures of total body lead and cadmium, post-edetate disodium urine lead and pre-edetate urine cadmium, could be detected after repeated edetate disodium-based infusions compared to the baseline. Fourteen patients with coronary artery disease received multiple open-label edetate disodium infusions. The urine metals pre- and post-edetate infusion, normalized for urine creatinine, were compared to urine levels pre and post final infusion by a paired t-test. Compared with the pre-edetate values, post-edetate urine lead and cadmium increased by 3581% and 802%, respectively, after the first infusion. Compared to baseline, post-edetate lead decreased by 36% (p = 0.0004). A reduction in post-edetate urine lead was observed in 84% of the patients after the final infusion. Pre-edetate lead decreased by 60% (p = 0.003). Pre-edetate lead excretion became undetectable in nearly 40% of patients. This study suggests that edetate disodium-based infusions may decrease the total body burden of lead. However, our data suggest no significant reduction in the body burden of cadmium.

Differential Outcomes With Edetate Disodium-Based Treatment Among Stable Post Anterior vs. Non-Anterior Myocardial Infarction Patients

BACKGROUND

The Trial to Assess Chelation Therapy (TACT) found that chelation therapy significantly reduced clinical events in patients with a history of myocardial infarction (MI). The initial report of TACT included the observation of an interaction between edetate disodium infusions and MI location, as well as diabetes. Thus, we examined in greater detail the effect of edetate disodium chelation therapy as a function of MI location and diabetes.

METHODS

Patients (n = 1708) at least 6 weeks post-MI and age ≥ 50 were randomized to receive 40 infusions of a 500 mL chelation solution or placebo (median follow-up 55 months). The effect of edetate disodium on the primary outcome (all-cause mortality, MI, stroke, hospitalization for angina, or coronary revascularization) was assessed as a function of MI location using log-rank test and Cox regression model, adjusting for other prognostic variables.

RESULTS

Among patients with post anterior MI (n = 674), chelation was associated with a lower risk of the primary endpoint (HR 0.63, 95% CI 0.47-0.86, p = 0.003) among anterior MI patients, but not in post non-anterior MI (n = 1034) patients (HR 0.96, 95% CI 0.77-1.20, p = 0.702) (p-for-interaction = 0.032). The point estimates for each component of the primary endpoint favored chelation therapy. The differing treatment effect in patients with post anterior vs. non-anterior MI was consistent among patients with or without diabetes and remained significant after adjusting for other prognostic variables (p < 0.01).

CONCLUSIONS

Edetate disodium infusions reduced the risk of cardiovascular events among patients with a prior anterior MI. Future studies should focus on replicating these results and understanding the mechanisms of benefit.

Limb Preservation Using Edetate Disodium-based Chelation in Patients with Diabetes and Critical Limb Ischemia: An Open-label Pilot Study

Background In 2015, there were 30.3 million patients with diabetes in the US, including 25.2% of people ages 65 or older and 108,000 hospitalizations for non-traumatic amputations. Severe diabetic limb disease includes critical limb ischemia (CLI ) due to an infrapopliteal disease with foot pain and ischemic ulcerations including gangrene. Environmentally acquired toxic metals, such as lead and cadmium, have been associated with cardiovascular disease. Thus, we designed the present unblinded pilot study to determine whether there was a signal of benefit for edetate disodium-based infusions in patients with critical limb ischemia. Methods This was an open-label pilot study in 10 patients with diabetes and critical limb ischemia. Each patient received up to 50 edetate disodium-based infusions and was assessed for safety, clinical efficacy, metal excretion, and quality of life. The primary endpoint was to assess the effect of edetate disodium-based therapy plus vitamins in patients with diabetes and infra-popliteal peripheral artery disease presenting with severe CLI and determine if there were improvements in vascular flow parameters. Results We enrolled 10 (60% male) predominantly Caucasian (90%) subjects. The mean age was 75.3 (8.0) years. Smoking was reported by 30%. There were 70% with coronary artery disease (30% had prior coronary artery bypass grafting) and 50% had a prior lower-extremity amputation, three having previous minor amputations and two major amputations. There were no major adverse cardiovascular events during the infusion phase through the one-year follow-up. Patients completing 40 infusions demonstrated complete wound healing and improvement in the quality of life. Conclusion Patients with diabetes and CLI treated with a regimen of edetate disodium-based infusions demonstrated a potential signal of benefit and preliminary evidence of safety. The Trial to Assess Chelation Therapy in Critical Limb Ischemia (TACT3a), a randomized double-blind, placebo-controlled clinical trial now in progress, will further test these findings.

Edetate Disodium-based Treatment in a Woman with Diabetes and Critical Limb Ischemia Scheduled for Lower Extremity Amputation

Historically, it is underappreciated that women undergoing amputation for critical limb ischemia (CLI) are older, more severely ill, and have a poorer prognosis than men. Epidemiological studies have shown an association between environmentally acquired vasculotoxic metals, coronary events, and peripheral artery disease. In this paper, we describe an elderly woman with CLI referred for primary amputation underwent edetate disodium-based treatment, known to reduce toxic metal burden, as a final option for limb salvage.

The effect of EDTA-based chelation on patients with diabetes and peripheral artery disease in the Trial to Assess Chelation Therapy (TACT)

OBJECTIVE

Approximately 1 in 7 US adults have diabetes; and over 60% of deaths in patients with diabetes have cardiac disease as a principal or contributing cause. Both coronary and peripheral artery disease (PAD) identify high-risk cohorts among patients with diabetes. We have previously demonstrated improved cardiovascular outcomes with edetate disodium-based chelation in post-MI patients with diabetes, enrolled in the Trial to Assess Chelation Therapy (TACT). In these analyses we further studied the effect size of patients with diabetes and severe disease in 2 vascular beds; coronaries, and lower extremity arteries. We questioned whether greater atherosclerotic burden would attenuate the observed beneficial effect of edetate disodium infusions.

RESEARCH DESIGN AND METHODS

The multicenter TACT used a double blind, placebo controlled, 2 × 2 factorial design with 1708 participants, randomly assigned to receive edetate disodium-based chelation, or placebo and high dose oral vitamins or placebo. There were 162 (9.5% of 1708) post-MI patients with a diagnosis of diabetes mellitus and PAD for this post hoc analysis. Patients received up to 40 double-blind intravenous infusions of edetate disodium-based chelation, or placebo. The composite primary endpoint of TACT consisted of death from any cause, myocardial infarction, stroke, coronary revascularization and hospitalization for angina.

RESULTS

The median age was 66 years, 15% female, 5% non-Caucasian, and BMI was 31. Insulin was used by 32% of patients. Active infusions significantly reduced the primary endpoint compared with placebo infusions (HR, 0.52; 95% CI, 0.30-0.92; P = 0.0069), with a 30% absolute risk reduction in the primary endpoint. There was a marked reduction in total mortality from 24% to 11%, although of borderline significance (P = 0.052).

CONCLUSION

Atherosclerotic disease in multiple vascular beds did not attenuate the beneficial effect of edetate disodium infusions in post MI patients with diabetes. Studies now in progress will prospectively test this post hoc finding.

Potential Role of Metal Chelation to Prevent the Cardiovascular Complications of Diabetes

CONTEXT

For decades, there has been epidemiologic evidence linking chronic toxic metal exposure with cardiovascular disease, suggesting a therapeutic role for metal chelation. Given the lack of compelling scientific evidence, however, the indications for metal chelation were never clearly defined. To determine the safety and efficacy of chelation therapy, the National Institutes of Health funded the Trial to Assess Chelation Therapy (TACT). TACT was the first double-blind, randomized, controlled trial to demonstrate an improvement in cardiovascular outcomes with edetate disodium therapy in patients with prior myocardial infarction. The therapeutic benefit was striking among the prespecified subgroup of patients with diabetes.

DESIGN

We review the published literature focusing on the atherogenic nature of diabetes, as well as available evidence from clinical trials, complete and in progress, of metal chelation with edetate disodium therapy in patients with diabetes.

RESULTS

The TACT results support the concept that ubiquitous toxic metals such as lead and cadmium may be modifiable risk factors for cardiovascular disease, particularly in patients with diabetes.

CONCLUSIONS

The purpose of this review is to discuss the potential mechanisms unifying the pathogenesis of atherogenic factors in diabetes with toxic metal exposure, and the potential role of metal chelation.

Chelation therapy to treat atherosclerosis, particularly in diabetes: is it time to reconsider?

INTRODUCTION

Case reports and case series have suggested a possible beneficial effect of chelation therapy in patients with atherosclerotic disease. Small randomized trials conducted in patients with angina or peripheral artery disease, however, were not sufficiently powered to provide conclusive evidence on clinical outcomes.

AREAS COVERED

The Trial to Assess Chelation Therapy (TACT) was the first randomized trial adequately powered to detect the effects of chelation therapy on clinical endpoints. We discuss results and future research. Expert commentary: Chelation reduced adverse cardiovascular events in a post myocardial infarction (MI) population. Patients with diabetes demonstrated even greater benefit, with a number needed to treat of 6.5 patients to prevent a cardiac event over 5 years, with a 41% relative reduction in risk of a cardiac event (p = 0.0002). These results led to the revision of the ACC/AHA guideline recommendations for chelation therapy, changing its classification from class III to class IIb. TACT2, a replicative trial, will assess the effects of chelation therapy on cardiovascular outcomes in diabetic patients with a prior myocardial infarction. We are seeking participating sites for TACT2.