Torsades de pointes

Vignette says a 55 year old female with a history of depression presents to the emergency department after experiencing a sudden episode of syncope; She reports of feeling lightheaded and palpitations before suddenly losing consciousness for a few seconds, and spontaneously regained her consciousness; She was diagnosed with urinary tract infection 5 days back and has been taking ciprofloxacin twice daily since then; She has a history of depression and takes citalopram; She doesn’t smoke and drink alcohol; Examination findings are normal; Vital signs show blood pressure of 100/60 mm of Hg, pulse rate of 55 bpm, respiratory rate of 18 breaths/min, oxygen saturation of 98% in RA and temperature of 97.9 F; ECG shows long QT interval (i.e. QTc > 500ms) and polymorphic ventricular tachycardia with a characteristic twisting of the QRS complexes around an isoelectric line; Diagnosis?

Diagnosis is Torsades de pointes.

Torsades de pointes (i.e. twisting of the QRS complexes around an isoelectric line) is a polymorphic ventricular tachycardia associated with congenital or acquired long QT interval (i.e. long QT interval >0.45 in male and >0.47 in female); Tdp can progress to ventricular fibrillation; "R-on-T phenomenon" (i.e. ventricular depolarization coincides with vulnerable period of ventricular repolarization).

Pathogenesis:- Long QT interval → inhibition of the delayed rectifier potassium current → early after depolarization → polymorphic ventricular tachycardia.

Etiologies:- Drugs, hypokalemia, hypocalcemia, hypomagnesemia, and congenital long QT interval syndrome (e.g. Romano-Ward syndrome and Jervell and Lange Nielsen syndrome).

Drugs are ABCDE:-
1. AntiArrhythmic (e.g. Class IA, Class III)
2. AntiBiotics (e.g. macrolides, fluoroquinolones)
3. Antipsychotics (e.g. haloperidol)
4. AntiDepressants (e.g. TCA)
5. AntiEmetics (e.g. ondansetron)

Presents with dizziness, palpitations, syncope, and sudden cardiac death.

ECG shows long QT interval and polymorphic ventricular tachycardia.

Management:-
1. Stop the offending agents.
2. Immedicated DC cardioversion in hemodynamically unstable patients.
3. Intravenous magnesium (2 g IV) is the 1st line therapy for hemodynamically stable patients.
4. Isoproterenol (Beta agonist) is used in Torsades de Pointes with prolonged QT that is refractory to magnesium by increasing heart rate; It is contraindicated in congenital QT prolongation syndrome.
5. Overdrive pacing.
6. Consider implantable cardioverter defibrillator (ICD) in high risk patients.