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This Article Accepted manuscript (PDF) All Versions of this Article: JOE-08-0140v1 198/1/253    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by van Noord, C. Articles by Stricker, B. PubMed PubMed Citation Articles by van Noord, C. Articles by Stricker, B.

C van Noord, Epidemiology & Biostatistics, Erasmus MC, Rotterdam, 3015 GE, Netherlands
W van der Deure, Internal Medicine, Erasmus MC, Rotterdam, Netherlands
M Sturkenboom, Epidemiology & Biostatistics, Erasmus MC, Rotterdam, Netherlands
S Straus, Epidemiology & Biostatistics, Erasmus MC, Rotterdam, Netherlands
A Hofman, Epidemiology & Biostatistics, Erasmus MC, Rotterdam, Netherlands
T Visser, Internal Medicine, Erasmus MC, Rotterdam, Netherlands
J Kors, Medical Informatics, Erasmus MC, Rotterdam, Netherlands
J Witteman, Epidemiology & Biostatistics, Erasmus MC, Rotterdam, Netherlands
B Stricker, Epidemiology & Biostatistics, Erasmus MC, Rotterdam, Netherlands

Correspondence: Charlotte van Noord, Email: c.vannoord{at}erasmusmc.nl

Abstract

Background:

The literature on the effect of excess thyroid hormone on ventricular repolarization is controversial. Our aim was to examine whether free T4 and TSH are associated with QTc prolongation.

Methods:

Setting: A population-based cohort study.

Participants: 365 men and 574 women, >55 years from the Rotterdam Study with an electrocardiogram who were randomly sampled for assessment of thyroid status (free T4/TSH) at baseline, after exclusion of participants with hypothyroidism, use of antithyroid drugs, thyroid hormones or digoxin, LVH and bundle branch blocks.

Endpoints: Length of QTc interval and risk of borderline QTc prolongation.

Analysis: Multivariate linear and logistic regression analysis.

Results:

Overall, there was no significant association between TSH and QTc interval (0.8 msec [95%CI-3.5;5.2] in the first quintile compared to the fifth quintile). Subjects in the fifth quintile of free T4 did not have an increased QTc interval (3.2 msec[95%CI-1.1;7.6]); stratification on gender showed an increment of 10.9 msec(95%CI 3.4;18.3) in the fifth quintile in men and 1.1 msec(95%CI-4.2;6.3) in the fifth quintile of free T4 in women. Compared to subjects in the first quintile, male subjects in the fifth quintile of free T4 had a significantly increased risk of a borderline QTc interval and QTc prolongation (OR2.40[95%CI1.20;4.80]).

Conclusions:

High levels of free T4 are associated with substantial QTc prolongation in men of up to 10 msec. The fact that free T4 is also associated with a significantly increased risk of borderline and prolonged QTc values with its risk of sudden cardiac death, endorses the clinical importance of our findings.