背景 三氧化二砷近年來廣泛被用於復發之急性前髓性白血病，療效甚佳。最近文獻報告三氧化二砷具心臟毒性，會引起QT間期延長而導致心律不整。本研究即在探討三氧化二砷對心電圖其他波形及間期之影響。方法 以鼻胃管灌食成年天竺鼠（400-600克重）三氧化二砷（10 mg/Kg，30 mg/Kg，50 mg/Kg）。灌食前，灌食後每30分鐘直到3小時後仔細觀察記錄心電圖，測量P波，PR間期及QRS波，另以靜脈注射三氧化二砷（0.15mg/Kg，0.45 mg/Kg及1.5 mg/Kg）仔細觀察並記錄心電圖兩小時，每分鐘測量P波，PR間期及QRS波。結果 灌食或靜脈注射三氧化二砷均可延長P波，PR間期及QRS波，尤其PR間期的延長最明顯，甚至有房室傳導阻斷產生。而對這些心電圖波形及間期之延長和劑量及時間有關。當觀察時間越久，或劑量越大，則延長越明顯。結論 灌食或靜脈注射三氧化二砷可廷長P波，PR間期及QRS波之延長，甚至造成房室傳導阻斷。因此病人接受三氧化二砷治療時，尤其原來即有P波延長或PR間期延長或支束傳導阻斷者，或原已服用鈉離子通道阻斷者，必須常常監測心電圖。

Background: Arsenic trioxide had recently been found to be very effective for relapsed acute promyelocytic leukemia. Several articles reported prolongation of QT interval or ventricular arrhythmias in patients receiving arsenic trioxide. However, the effects on other electrocardiogram (ECG) have not been determined. Methods: Three-channel ECG (leads II, V1 and V5) was recorded from adult Hartley guinea pigs (400-600gm). The P wave, PR interval and QRS duration were measured at baseline condition just before the administration of various doses (10 mg/Kg, 30 mg/Kg, and 50 mg/Kg) of arsenic trioxide or water (control group) via nasogastric tube, and every 30 minutes until 3 hours. The effect of intravenous arsenic trioxide was also tested. Arsenic trioxide, 0.15 mg/Kg, 0.45 mg/Kg, and 1.5 mg/Kg, were infused for duration of 2 hours. The control group received equivalent volume of saline. The ECG parameters were measured immediately before infusion, at 10 minutes after, and every 30 minutes after infusion for a total of 2 hours. Results: Both oral and intravenous arsenic trioxide increased P wave, PR interval and QRS duration in guinea pigs. The percent increase was dose-dependent, and time-dependent, and was more prominent in PR interval compared with those in the P wave and QRS duration. There was no change in the control group. Atrioventricular block was observed in high-dose group. Conclusions: We have demonstrated that oral and intravenous arsenic trioxide prolonged P wave, PR interval and QRS duration. Routine regular ECG follow-up in patients receiving arsenic trioxide therapy may be indicated, especially in patients who already have prolongation of P wave, PR interval, or bundle branch block, or receiving concomitant administration of sodium channel blockers.