EEM Rewind The 3 Types of V Tach

Ventricular tachycardia is not one rhythm problem but three clinically distinct entities: monomorphic VT, polymorphic VT with a normal QTc, and torsades de pointes with a prolonged QTc. Correct classification changes the drug choice, the role of cardioversion, and which common antiarrhythmics can make the rhythm worse.

Three Types of Ventricular Tachycardia

• Monomorphic VT pattern: Sustained monomorphic VT usually reflects scar-mediated reentry from prior MI or other structural heart disease, making electricity plus procainamide the core treatment approach.
• Polymorphic VT with normal QT: Generic polymorphic VT is usually an ischemia or Brugada problem rather than a torsades problem, so management pivots toward shock, ACS treatment, and cause-specific follow-up.
• Torsades definition: Torsades de pointes requires polymorphic VT plus a prolonged QTc on a baseline or peri-event ECG; a rhythm strip alone cannot make the diagnosis. That distinction is worth hearing in the episode.
• Baseline ECG importance: The key diagnostic move is to find the QTc before or just after the run, because the bedside appearance of twisting complexes does not reliably separate torsades from other polymorphic VT.
• Wrong drug hazard: Amiodarone and procainamide are useful in other VT syndromes but can worsen torsades by lengthening repolarization further, a high-stakes treatment error in the unstable patient.

Cause-Specific Treatment Pearls

• Monomorphic VT therapy: For persistent monomorphic VT, shock remains first-line and procainamide is the most successful antiarrhythmic, while amiodarone can be especially useful in electrical storm because of beta-blocking effects.
• Ischemic polymorphic VT approach: Polymorphic VT with a normal QTc should trigger a search for acute coronary syndrome and consideration of the cath lab, not reflex treatment as torsades.
• Brugada syndrome clue: A normal-QTc polymorphic VT pattern can point to Brugada syndrome, where electrophysiology referral and defibrillator evaluation matter more than routine antiarrhythmic thinking.
• Magnesium for torsades: Magnesium is first-line therapy for torsades when shock alone is not enough, followed by strategies that shorten repolarization and prevent recurrence. We walk through the pacing logic in the chapter.
• Electrolyte correction goals: Torsades often rides on hypokalemia, hypomagnesemia, or hypocalcemia, so treatment includes aggressive correction after conversion with potassium and magnesium targets kept deliberately high.

References:

1. Thomas, Simon HL, and Elijah R. Behr. "Pharmacological treatment of acquired QT prolongation and torsades de pointes." British journal of clinical pharmacology 81.3 (2016): 420-427.
2. Trinkley, Katy E., et al. "QT interval prolongation and the risk of torsades de pointes: essentials for clinicians." Current medical research and opinion 29.12 (2013): 1719-1726.
3. Choy, Anna Maria, et al. "Normalization of acquired QT prolongation in humans by intravenous potassium." Circulation 96.7 (1997): 2149-2154.
4. Tzivoni, Dan, et al. "Treatment of torsade de pointes with magnesium sulfate." Circulation 77.2 (1988): 392-397.
5. Etienne, Y., et al. "Antiarrhythmic effects of intravenous magnesium sulfate in torsade de pointes. Apropos of 6 cases." Archives des Maladies du Coeur et des Vaisseaux 79.3 (1986): 362-367.