QT prolongation and subsequent torsades de pointes

(A) ECG showing sinus rhythm at 96 beats per minute and occasional PVCs. The QT interval is 454 ms, and, using Bazett's correction, the QTc is 573 ms. This patient had pneumonia that was treated with azithromycin and presented with stress (takotsubo) cardiomyopathy and hypokalemia. Prior to this presentation, the baseline ECG demonstrated a QTc 470 to 520 ms.