The FDA approved EDTA for its metal-binding ability but has since issued the following warning: “The two EDTA drugs have established names that are easily confused and both are referred to in clinical practice as "EDTA."  This confusion has resulted in medication errors in which some patients have received the wrong drug, which has been fatal in some cases or caused serious adverse reactions in others. The error is especially dangerous when edetate disodium is erroneously given to a patient who is supposed to receive edetate calcium disodium. 
The two EDTA drugs have different approved uses and significantly different effects. Risks are low when infusion protocols are followed.  

• Gerber M. Thirty Years of Progress in Cardiovascular Health, Townsend Newsletter. Feb/Mar 2006
• BELKNAP EL. EDTA in the treatment of lead poisoning. Ind Med Surg. 1952 Jun;21(6):305–306.
• FDA - Drug Safety Information for Patient and Providers - 37k - 2009-06-03

Summary of the response to Dr. Michael Gerber's article "Thirty Years of Progress in Cardiovascular Heath", Townsend Newsl Oct 2011: view

• Studies indicate NaMgEDTA is successful in treating atherosclerotic disease.
• EDTA is not a suitable chelating substance for mercury
• In its oral form, EDTA only detoxifies the digestive tract
• As a suppository, EDTA detoxifies the colon.
• EDTA, provided orally or as a suppository, does not cause clinically or statistically significant metal binding within the blood stream.

L. Terry Chappel MD¹ & John F. Stahl PhD². The Correlation between EDTA Chelation Therapy and Improvement in Cardiovascular Function: A Meta-Analysis. J of Advancements in Med. vol 6, #3, 1993 

A thorough literature search identified 40 articles on the subject. Nineteen studies met the criteria for inclusion with data on 22765 patients. The meta-analysis revealed a correlation of 0.88, which indicates a high positive relationship between NaMgEDTA therapy and improved cardiovascular function. Eighty-seven per cent of the patients included in the meta-analysis demonstrated clinical improvement by objective testing.

¹ Assistant professor at Wright State School of Medicine. ²Prof. of Electrical Engineering and Director of Cooperative Education at Ohio Northern University College of Engineering.

Na2EDTA is referred to as Ethylene diamine tetraacetic acid disodium salt or in short Sodium EDTA. It easily binds with calcium, hence its use in the treatment of hypercalcemia and of atherosclerotic disease. It must be noted that administering a Na2EDTAinfusion in too short of time can potentially cause a state of hypocalcemia. Na2EDTA should not be used in children or patients suffering from parathyroid disease.

CaEDTA is the calcium salt of Ethylene diamine tetraacetic acid, also referred to as Calcium ethylenediamine tetra-acetic acid. Since it is bound to calcium, it will not be effective in removing calcium. It can potentially induce a state of hypercalcemia and should not be used in children or patients suffering from parathyroid disease. Bolus injections are not recommended.