Correct!
4. Overdrive pacing
Overdrive pacing, either electrical or chemical (e.g., with a beta agonist such as isoproterenol), has been shown to be the most effective therapy in a case series of patients with loperamide toxicity (2,3). Loperamide toxicity can lead to prolongation of both the QRS and QT. While sodium channel blockade is frequently cited as a cause of wide QRS, it is more likely that wide QRS is caused by gap junction inhibition in the setting of loperamide toxicity. Unlike sodium channel blockade, gap junction inhibition does not typically respond to administration of sodium bicarbonate or hypertonic saline solutions. It may still be prudent to trial administration of sodium bicarbonate and assess QRS response, however the risk of hypokalemia with repeated administration may outweigh the benefit. Magnesium sulfate should nearly always be administered to a patient with polymorphic ventricular tachycardia to stabilize the cardiac membrane, however in a patient with refractory TdP magnesium will likely not be adequate. Calcium gluconate is used to stabilize the cardiac membrane in patients with critical hyperkalemia and EKG changes, however it would likely not be useful in loperamide toxicity.
After stabilizing, she had a recurrence of her ventricular tachycardia. The fluoroscope which had been used to place the pacing catheter was still at her bedside and an image was obtained (Figure 2).
Figure 2. Image from the fluoroscope taken shortly after recurrence of the ventricular tachycardia.
What does the chest x-ray show? (Click on the correct answer to be directed to the sixth of seven pages)