Dynamic QTc interval changes observed in real-world patients with implanted insertable cardiac monitors taking class III antiarrhythmic drugs
Authors: Chu A F , Sagi V , Deus M , Rajagopal G , Landman S R , Sarkar S , Koehler J , Amin A K 
Published: October 2024

Background

QT prolongation can lead to sustained ventricular arrhythmias . Class III Antiarrhythmic drugs (AAD) are known to cause QT prolongation. Insertable cardiac monitors (ICM) have the capability to continuously monitor and detect dynamic changes in QT.

Purpose

To investigate the characteristics of QTc interval changes before and after antiarrhythmic drug loading in real-world ICM patients administered with Sotalol, Amiodarone, and Dofetilide in hospital.

Methods

The QT detection algorithm detects the T-waves and determines the QTc intervals for every beat, thus providing continuous long-term QTc trends from ICM ECG. Real-world patients from de-identified Electronic Health Record (EHR) database linked with ICM device data warehouse with implanted ICM being administered sotalol, amiodarone or dofetilide AAD for the first time in the hospital were analyzed. The patients were broken down into groups based on the AAD taken. Patients not taking AAD were selected as control. QTc intervals 7-days pre and post administered AAD are reported, and a random 14-day period was used for control patients. The paired difference in median QTc 7 days pre and post administered AAD were analyzed using the Wilcoxon signed rank test. The Wilcoxon rank-sum test was used to analyze QTc between the different groups.

Results

A total of 487 patients with ICM were included in this analysis: 56 sotalol patients (avg. age: 67±10 years, 50% male), 100 amiodarone patients (avg. age: 72±10 years, 50% male), 52 dofetilide patients (avg. age: 66±12 years, 50% male), and 248 control patients (avg. age: 70±13 years, 50% male). Sotalol, amiodarone, and dofetilide patients showed significant increase in QTc 1-7 days post AAD compared to 1-7 days pre AAD (figure 1). For sotalol (post AAD median[IQR] = 426.5[408.8,446.6] msec, pre AAD median[IQR] = 415.9[391,437.3] msec, p=0.004); Dofetilide (post median[IQR] = 432.4[413,458.7] msec; pre median[IQR] = 409.3[397.5,435.2] msec, p&lt;0.001); Amiodarone (post median[IQR] = 426.3[400.9,449] msec, pre median[IQR] = 415.5[397.5,435.2] msec, p = 0.037). The QTc 1-7 days pre AAD compared to 1-7 days post AAD for control patients was insignificant p&gt;0.05. The median change in QTc 1-7 days post AAD from 1-7 days pre AAD was 13.0, 7.5, 21.25 and -1.0 msec for sotalol, amiodarone, dofetilide, and control patients respectively (figure 2). Dofetilide patients had a significantly higher change in QTc compared to the amiodarone patients, p=0.018. QTc for all three AAD groups when compared to control group post AAD were significantly higher, p&lt;0.001. QTc was also higher pre AAD compared to control, p=0.003, p&lt;0.001, p=0.009 for sotalol, amiodarone, and dofetilide respectively.

Conclusions

There is a significant increase in QTc detected by ICM in patients receiving index drug loading of Sotalol, amiodarone and dofetilide. QTc monitoring via ICM can detect these dynamic changes in QTc allowing for early intervention.Figure 1Figure 2