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The following is a summary of “Continuous QTc monitoring for patients intoxicated with QTc prolonging medication in the ED: a proof of principle.,” published in the November 2024 issue of Emergency Medicine by Bot et al. 

Determining safe discharge timing for patients with overdoses of QT-interval prolonging drugs is challenging, mainly when intoxication time and substance(s) are unknown.  

Researchers conducted a retrospective study to determine if continuous QTc interval analysis could establish optimal observation durations for patients with QTc-prolonging medication intoxication.  

They pre-processed ECG signals sampled at 500 Hz from individuals in the emergency department (ED) presenting with intoxication from QT-interval prolonging drugs. The average heart rate-corrected QT interval (QTc) was calculated every 5 minutes and plotted over time. A third-order polynomial was fitted to the data to visualize the point of peak QTc (electrophysiological T_max) and the observed T_max was then compared to the predicted T_max based on the pharmacokinetic characteristics of the ingested drugs.  

The results showed 22 ED visits involving 15 individuals, for 17 out of 22 visits, an electrophysiological time to maximum QT interval (T_max) was calculable. In the remaining 5 cases, 4 individuals arrived well after the electrophysiological T_max had passed, and 1 was admitted to the ward before reaching the T_max. The mean (SD) difference between the T_max estimated based on drug pharmacokinetics and the calculated electrophysiological T_max was 18 (133) minutes, ranging from -158 to 296 minutes. Despite the broad variability, a significant correlation was observed between the calculated electrophysiological T_max and the estimated T_max (r=0.67, P =0.012).  

Investigators concluded that continuous electrophysiological monitoring can be used as an adjunct to determine the toxicokinetic T_max for patients with intoxication, mainly when ingestion time or substance is unknown. 

Source: jem-journal.com/article/S0736-4679(24)00359-7/fulltext