Chronic arsenic exposure and cardiac repolarization abnormalities with QT interval prolongation in a population-based study

Abstract

Background: Chronic arsenic exposure is associated with cardiovascular abnormalities. Prolongation of the QT (time between initial deflection of QRS complex to the end of T wave) interval and profound repolarization changes on electrocardiogram (ECG) have been reported in patients with acute promyelocytic leukemia treated with arsenic trioxide. This acquired form of long QT syndrome can result in life-threatening arrhythmias.

Objective: The objective of this study was to assess the cardiac effects of arsenic by investigating QT interval alterations in a human population chronically exposed to arsenic.

Methods: Residents in Ba Men, Inner Mongolia, have been chronically exposed to arsenic via consumption of water from artesian wells. A total of 313 Ba Men residents with the mean arsenic exposure of 15 years were divided into three arsenic exposure groups: low (< or = 21 microg/L), medium (100-300 microg/L), and high (430-690 microg/L). ECGs were obtained on all study subjects. The normal range for QTc (corrected QT) interval is 0.33-0.44 sec, and QTc > or = 0.45 sec was considered to be prolonged.

Results: The prevalence rates of QT prolongation and water arsenic concentrations showed a dose-dependent relationship (p = 0.001). The prevalence rates of QTc prolongation were 3.9, 11.1, 20.6% for low, medium, and high arsenic exposure, respectively. QTc prolongation was also associated with sex (p < 0.0001) but not age (p = 0.486) or smoking (p = 0.1018). Females were more susceptible to QT prolongation than males.

Conclusions: We found significant association between chronic arsenic exposure and QT interval prolongation in a human population. QT interval may potentially be useful in the detection of early cardiac arsenic toxicity.

Figure 1

Map of three counties in Ba Men where residents have been chronically exposed to arsenic via drinking water and arsenicosis has been reported. The study sites are located in Long Sheng of Lin He County (1, low exposure), Gu Cheng of Lin He County and Yong Li of Wu Yuan County (2, 3, medium exposure), and Fen Zi Di of Lin He County (4, high exposure).

Figure 2

Effects of arsenic exposure (A; p = 0.001) and age (B; p = 0.486), sex (C; p = 0.0001), and smoking (D; p = 0.1018) on QTc interval using chi-square tests. The y-axis shows percent subjects with QTc interval ≥ 0.45 sec. The numbers above each bar are numerator for the number of subjects with QTc ≥ 0.45 sec and denominator for total number of subjects in this group. p-Values are from chi-square tests.