Europace Advance Access originally published online on October 30, 2008
Europace 2008 10(12):1458; doi:10.1093/europace/eun291
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LETTERS TO THE EDITOR
Homocysteine and heavy metal interactions in atrial fibrillation and ablation treatments
Department of Medical and Molecular
Bio-Sciences, University of Technology
Sydney, New South Wales, Australia
Department of Radiology, St Vincent's Hospital,
Melbourne, Australia
Department of Medical and Molecular
Bio-Sciences, University of Technology Sydney,
New South Wales, Australia
Department of Cardiovascular Medicine,
St Vincent's Hospital, Melbourne, Australia
Tel: +61 0414 242 294 E-mail address: reperfusion{at}hotmail.com
We read with interest the study by Shimano et al.1
whereby the investigators show a significant association between high basal homocysteine levels and persistent AF. We would like to propose a possibility for the involvement of heavy metals in explaining the association between persistent atrial fibrillation and high plasma homocystine levels post-radiofrequency ablation.
It is well known that heavy metals can cause overmethylation of biomolecules in the body. With regard to homocysteine, this process is linked to bio-converting cysteine into homocysteine. Because cysteine and homocysteine contain sulfur groups they can attract heavy metals, which bind to them irreversibly, this therefore inhibits the homocysteine molecule binding at its native binding site, causing homcysteine to remain free in the blood and accumulate at greater levels.2,3
Interestingly, we also note that the study by Shimano et al.1 was conducted at Nagoya University, <600 km from Minamata Bay which is the site of the world's worst industrial mercury contamination in 1956 (52 years ago). The mercury contamination was methymercury that bioaccumulates in marine creatures in the surrounding waters.4 Considering Japanese consume large amounts of seafood in their diets, persistent AF patients may have had high levels of mercury and other heavy metals that in turn contributed to higher levels of homocysteine.
Heavy metal tissue accumulation could also theoretically occur during RF ablation for atrial fibrillation, for example, the long exposure to ionizing radiation during the radiofrequency catheter ablation procedure may induce ionization of heavy metals5 and redistribute these to local cardiac structures and/or the circulation. Pre- and postablation treatment with chelating agents such as dimercaptosuccinic acid or dimercaptopropanesulfonic acid could reduce the risk of persistent or recurrent AF after ablation and or increased homocysteine levels because the free ions created by the procedure would be chelated and eliminated via renal excretion.6
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[1] Shimano M, Inden Y, Tsuji Y, Kamiya H, Uchikawa T, Shibata R, et al. Circulating homocysteine levels in patients with radiofrequency catheter ablation for atrial fibrillation. Europace (2008) 10:961–6.
[2] Chia SE, Ali SM, Lee BL, Lim GH, Jin S, Dong NV, et al. Association of blood lead and homocysteine levels among lead exposed subjects in Vietnam and Singapore. Occup Environ Med (2007) 64:688–93.
[3] Guallar E, Silbergeld EK, Navas-Acien A, Malhotra S, Astor BC, Sharrett AR, et al. Confounding of the relation between homocysteine and peripheral arterial disease by lead, cadmium, and renal function. Am J Epidemiol (2006) 163:700–8.
[4] Tomiyasu T, Nagano A, Yonehara N, Sakamoto H, Rifardi, Oki K, et al. Mercury contamination in the Yatsushiro Sea, south-western Japan: spatial variations of mercury in sediment. Sci Total Environ (2000) 257:121–32.[CrossRef][Medline]
[5] Michel C, Balla I. Interaction between radiation and cadmium or mercury in mouse embryos during organogenesis. Int J Radiat Biol (1987) 51:1007–12.[CrossRef][Web of Science]
[6] Lippard LJ, Berg JM. Principles of Bioinorganic Chemistry. (1994) Mill Valley, CA: University Science Books.
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