A 77-year-old female is brought in by ambulance for a syncopal episode today in the kitchen, witnessed by her daughter. Her past medical history includes hypertension and recently diagnosed pneumonia. She takes hydrochlorothiazide regularly and is almost finished with her levofloxacin. Vital signs are BP 131/78 mmHg, P 72 bpm, RR 16 bpm, O2sat 98% room air, T98.4F (36.9C). The patient reports feeling palpitations and lightheadedness immediately before losing consciousness. Currently, the patient denies chest pain, fever, shortness of breath, vomiting or abdominal pain. ECG is shown. What should be the next step in management of this patient?
A. Calcium gluconate
B. Magnesium sulfate
C. Sodium bicarbonate
D. Transvenous pacing
B) Magnesium sulfate is correct
A. Calcium gluconate
Calcium gluconate is typically administered in the setting of hyperkalemia and widened QRS – it is not indicated in this case.
B. Magnesium sulfate
This EKG demonstrates prolonged QT, which predisposes the patient to arrhythmia, classically ventricular tachycardia. Classic medications that are associated with QT prolongation include: fluoroquinolines, macrolides, antipsychotics, antiemetics, procainamide (and other antiarrhythmics), among others. There are congenital prolonged QT syndromes as well, although a medication induced cause is more likely in this patient.
Patients with acquired prolonged QT interval should be assessed for risk of developing torsades de pointes. The first measure is to discontinue offending medications and to assess serum potassium/magnesium levels. These should be repleted as needed to minimize further exacerbation of QT prolongation. Patients with concerning symptoms, especially syncope, and/or ECG instability (e.g. PVCs, AV block, QRS widening) should be admitted for monitoring. In unstable patients with torsades de pointes, immediate unsynchronized electrical defibrillation is indicated.
Magnesium sulfate IV is considered first-line medical therapy in torsades de pointes. Although its mechanism of action is not exactly unknown and it does not significantly shorten the QT interval, magnesium sulfate has been shown to be effective in suppressing short-term recurrences of torsades de pointes. In this patient, who had a syncopal episode, potentially from a brief episode of torsades de pointes that spontaneously converted, magnesium sulfate would be indicated to prevent short-term recurrence of another episode of torsades.
References:
Pourmand A, Mazer-Amirshahi M, Chistov S, et al. Emergency department approach to QTc prolongation. Am J Emerg Med. 2017;35(12):1928-1933. https://www.ncbi.nlm.nih.gov/pubmed/28855066
Li M, Ramos LG. Drug-induced QT prolongation and Torsades de Pointes. P T. 2017;42(7):473-477. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5481298/
C. Sodium bicarbonate
Sodium bicarbonate is typically administered in widened QRS for tricyclic overdose. This ECG demonstrates prolonged QT, not widened QRS.
D. Transvenous pacing
Transvenous pacing would be indicated in 3rd degree AV block – this ECG demonstrates prolonged QT, not AV block.3% choose this answer
