Iodine Excess, Thyroid Dysfunction, Cardiovascular Outcomes, and Mortality Among U.S. Veterans

Va Greater Los Angeles Healthcare System, Los Angeles CA

Investigators

Abstract

Background and Innovation The focus of this project is to rigorously add to our understanding of how the use of iodinated contrast media, a common requirement of many radiologic procedures, is associated with thyroid dysfunction and cardiovascular risks. In U.S. adults, the recommended dietary allowance (RDA) of iodine is 150 mcg/day. Exposure to excessive iodine can induce thyroid dysfunction due to two well-established physiologic principles: the failure to escape from the acute Wolff-Chaikoff effect (resulting in hypothyroidism) and the Jod-Basedow phenomenon (resulting in hyperthyroidism). The iodine content of radiologic iodinated contrast agents can be up to several hundred-fold higher than the U.S. RDA for iodine. In susceptible individuals, thyroid dysfunction (hyperthyroidism or hypothyroidism) can occur even after only a single exposure to an iodine-rich substance. Thyroid status is important for several cardiac parameters, including systolic contraction, cardiac output, preload, coronary arteriolar angiogenesis, coronary vascular resistance, vascular tone, and cardiac hypertrophy. Significance and Impact to Veterans Healthcare: Iodinated contrast media is commonly required for routine radiologic and other interventional procedures among patients who receive care from the Veterans Health Administration. Our published work of the national VHA electronic health records database thus far shows that iodinated contrast administration is associated with an increased risk of thyroid dysfunction (hypothyroidism and hyperthyroidism) and of incident long-term adverse cardiovascular outcomes (heart failure and atrial fibrillation/flutter). This project will build upon our analyses of the existing VHA dataset we have constructed to robustly refine the understanding of these important associations. The goals of this project will be to: 1) employ advanced statistical tools to specifically delineate the key factors driving these relationships, and 2) develop a dynamic relative risk calculator that can be used in real-time to apply the observed associations into routine clinical practice. This work directly addresses VA/ORD research priorities 2 and 3, to increase the substantial real-world impact of VA research and put VA data to work for Veterans, respectively. Path to Translation/Implementation: As use of iodinated contrast in medical settings continues to increase, the real-world applications of the established risks of iodinated contrast use have not been studied thus far, yet are urgently needed. The findings of this project, including the creation of a risk stratification tool/calculator, would directly guide the care of Veterans who commonly receive iodine contrast dye through routine radiologic studies, such as computed tomography (CT) scans used in anatomical imaging and angiograms required for cardiac catheterization procedures in centers across the VHA.