3.2 Factors Associated with QTc Interval
Results showed significantly different QTc intervals between patients with and without hypertension (423.7 ± 20.3 ms vs. 418.0 ± 16.8 ms, p = 0.011, respectively). No significant difference was observed between the QTc intervals between patients with and without diabetes, or male and female (Fig. 1). In addition, significantly longer QTc intervals were observed in patients with higher disease activity scores as assessed by SDAI, CDAI, DAS28-ESR, and DAS28-CRP (all p values <0.001, compared by ANOVA, see Fig. 2).
In the univariate linear correlation analysis, age, heart rate, VAS score, CDAI, SDAI, HAQ, DAS28-ESR, and DAS28-CRP were positively associated with QTc interval (Table 2). A significant association was identified between the QTc interval and ESR (p < 0.0001) and CRP (p = 0.001). Differences in QTc interval were also observed between patients with an ESR of ≥30 and <30 (418.1 ± 17.2 ms vs. 426.7 ± 21.4 ms, p = 0.004), as shown in Fig. 1.
In the multivariate linear regression analysis, age, sex, HAQ, and CRP levels were included in Model 1; SDAI and DAS28-ESR were included in Models 2 and 3, respectively (Table.2). As a result, age, male sex, and CDAI were independently associated with the QTc interval in Model 1. In Model 2, age, male sex, and SDAI were independently associated with the QTc interval, and an independent association was observed between the DAS28-ESR and QTc interval in Model 3 (p = 0.0004).