From the Guidelines
Procainamide is contraindicated in polymorphic ventricular tachycardia (VT) due to its potential to worsen the arrhythmia. According to the 2015 ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1, the use of other anti-arrhythmic drugs in acute coronary syndrome (ACS), such as procainamide, is not recommended. This is because procainamide, as a Class IA antiarrhythmic drug, can prolong the QT interval by blocking sodium channels and delaying cardiac repolarization, which can exacerbate the underlying electrical instability in polymorphic VT.
Key considerations in managing polymorphic VT include:
- Correcting underlying causes such as electrolyte abnormalities (particularly potassium and magnesium)
- Discontinuing QT-prolonging medications
- Administering magnesium sulfate (1-2g IV over 5-15 minutes) for Torsades de Pointes
- Increasing the heart rate with isoproterenol (2-10 mcg/min) or temporary pacing (at 90-110 beats per minute) for Torsades de Pointes
- Using beta-blockers, amiodarone, or lidocaine as alternative treatments for polymorphic VT with normal QT interval, along with addressing any underlying ischemia or structural heart disease.
The 2015 ESC guidelines 1 suggest that recurrent polymorphic VT degenerating into VF may respond to beta-blockers, and amiodarone (150–300 mg i.v. bolus) can be considered to acutely suppress recurrent haemodynamically relevant ventricular arrhythmias. However, procainamide is not a recommended treatment option due to its potential to worsen the arrhythmia.
From the FDA Drug Label
In the unusual ventricular arrhythmia called "les torsades de pointes" (twistings of the points), characterized by alternation of one or more ventricular premature beats in the directions of the QRS complexes on ECG in persons with prolonged Q-T and often enhanced U waves, Group 1A antiarrhythmic drugs are contraindicated Administration of PA in such cases may aggravate this special type of ventricular extrasystole or tachycardia instead of suppressing it. Procainamide is bad for polymorphic ventricular tachycardia (VT), specifically Torsades de Pointes, because it may aggravate this type of arrhythmia instead of suppressing it, as it is a Group 1A antiarrhythmic drug 2.
From the Research
Procainamide and Polymorphic Ventricular Tachycardia
- Procainamide can induce polymorphous ventricular tachycardia, as demonstrated in a study published in 1981 3.
- This study presented seven cases of procainamide-induced polymorphous ventricular tachycardia, with four patients experiencing the arrhythmia after intravenous administration of procainamide.
- The arrhythmia was associated with Q-T prolongation and recurrent syncope in three patients who received oral procainamide for treatment of chronic premature ventricular contractions or atrial flutter.
Mechanism and Risk Factors
- Procainamide can produce an acquired prolonged Q-T syndrome with polymorphous ventricular tachycardia, as noted in the 1981 study 3.
- The risk of procainamide-induced polymorphous ventricular tachycardia is increased in patients with underlying heart disease or those taking other medications that prolong the Q-T interval.
- Monitoring of Q-T interval is recommended when initiating procainamide therapy to prevent drug toxicity, as suggested in a 1993 study 4.
Comparison with Other Antiarrhythmic Agents
- A 2017 study compared the safety and efficacy of intravenous procainamide and amiodarone for the acute treatment of tolerated wide QRS tachycardia, finding that procainamide was associated with fewer major cardiac adverse events and a higher proportion of tachycardia termination within 40 minutes 5.
- However, the choice between procainamide and other antiarrhythmic agents, such as amiodarone, depends on various factors, including the patient's underlying condition and the specific arrhythmia being treated.
Clinical Considerations
- Torsade de pointes, a form of polymorphic ventricular tachycardia, can be induced by procainamide and other antiarrhythmic agents, as discussed in a 2004 study 6.
- Clinical considerations and management of torsade de pointes are crucial, and distinguishing between congenital and acquired forms of long QT syndrome is important for proper treatment.