Cardiac Arrest in a Patient With Torsades de Pointes

Case Study

A rapid response event was initiated by the bedside nurse for a patient with sustained ventricular tachycardia. On prompt arrival of the rapid response team (RRT), it was noted that the patient was a 66-year-old female who was admitted for acute exacerbation of congestive heart failure and was being treated with intravenous diuretics. Per the nurse, the patient had been drowsy, with recurrent episodes of palpitations and dizziness. A basal metabolic panel drawn 2 h prior to the event showed a serum magnesium level of 1.1 meq/L and potassium level of 1.9 mmol/L. The patient subsequently became pulseless while the RRT was making its initial assessment.

Vital Signs

Noted before cardiopulmonary arrest:

Temperature: 98.6 °F, axillary
Blood Pressure: 80/40 mmHg
Pulse: 180 beats per min (bpm)
Respiratory Rate: 18 breaths per min
Pulse Oximetry: 85% oxygen saturation on 4 L nasal cannula

Focused Physical Examination

The pre-arrest examination showed a middle-aged female in mild distress. The patient appeared drowsy with slowed responses. Appropriate personal protective equipment was established, and the patient was examined. Her cardiac exam showed tachycardia with normal heart sounds, and no new murmurs were appreciated. Her lung exam showed decreased breath sounds bilaterally with prominent crackles at lung bases. The patient became unresponsive and lost her pulse during the exam, and cardiopulmonary resuscitation (CPR) was started.

Interventions

A cardiac monitor and defibrillator pads had already been attached when the RRT arrived at the patient’s room. Telemetry findings were consistent with Torsades de Pointes (TdP) with cyclical alterations of the QRS complex around the isoelectric line ( Fig. 16.1 ). Based on recent labs, 2 g of intravenous magnesium had already been ordered by patient’s primary team and was in the process of being administered. After the patient’s rhythm degenerated to pulseless ventricular fibrillation, CPR was initiated immediately. The airway was secured via endotracheal intubation. The patient was defibrillated at 200 J, and one ampule of 1 mg epinephrine was administered. Return of spontaneous circulation was achieved in under 2 min. Post-arrest telemetry strip showed sinus tachycardia. A 20 meq IV bolus of potassium was given, followed by an infusion rate of 20 meq/h via a central line. The patient was started on an infusion of norepinephrine for hemodynamic support and transferred to the intensive care unit for further care.

Final Diagnosis

Torsades de Pointes (TdP) because of electrolyte abnormalities.

Torsades de Pointes (TdP)

Definition and Diagnosis

Torsades or polymorphic ventricular tachycardia is defined as a ventricular rhythm that is greater than 100 bpm with alternating QRS complex morphology and/or axis. TdP usually runs between 160 and 250 bpm and can be either congenital or acquired, acquired being more common. Medications are the most common cause of acquired long QT syndrome and TdP. Other typical features include irregular RR intervals and an alternating QRS axis every 5 to 20 beats. TdP is usually self-terminating, but episodes can recur, which can degenerate into ventricular fibrillation and/or sudden cardiac death.

Risk Factors

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Medications: Drugs that prolong the QT interval directly or by slowing the metabolism of other QT-prolonging drugs by inhibiting cytochrome P450 enzymes are implicated ( Table 16.1 ).

Table 16.1

Drugs commonly associated with QT prolongation and Torsades de Pointes

Drug class	Examples
Antibiotics	Ciprofloxacin, levofloxacin, moxifloxacin, azithromycin, clarithromycin, erythromycin
Antifungals	Fluconazole, ketoconazole, pentamidine, voriconazole
Antiarrhythmics	Disopyramide, procainamide, quinidine, sotalol
Antipsychotics	Haloperidol, thioridazine, ziprasidone
Antidepressants	Citalopram, escitalopram
Antiemetics	Dolasetron, droperidol, granisetron, ondansetron
Opioids	Methadone
Diuretics	Lasix, hydrochlorothiazide