What are the causes of persistent ventricular tachycardia (V-tach) or ventricular fibrillation (V-fib)?

Causes of Persistent Ventricular Tachycardia and Ventricular Fibrillation

Persistent ventricular tachycardia (VT) or ventricular fibrillation (VF) is most commonly caused by acute myocardial ischemia, with incomplete reperfusion or recurrence of acute ischemia being the primary mechanisms requiring immediate coronary angiography. 1

Primary Cardiac Causes

Ischemic Heart Disease

• Acute myocardial infarction/ischemia - most common cause 1
• Incomplete coronary reperfusion 1
• Recurrent acute ischemia 1
• Myocardial scarring from previous infarction creating reentry circuits 2

Structural Heart Disease

• Cardiomyopathies (dilated, hypertrophic, restrictive) 1
• Severe mitral regurgitation (especially with papillary muscle rupture) 1
• Valvular heart disease 3
• Congenital heart disease 3
• Heart failure with reduced ejection fraction 4

Electrophysiological Abnormalities

• Premature ventricular complexes (PVCs) arising from injured Purkinje fibers 1
• Ventricular myocardium injured by ischemia/reperfusion 1
• Reentry circuits in scarred myocardium 2
• Abnormal automaticity in damaged cardiac tissue 5

Metabolic and Systemic Causes

Electrolyte Disturbances

• Hypokalaemia 1
• Other electrolyte abnormalities (hypomagnesemia, hypocalcemia) 3

Other Metabolic Factors

• Acid-base disturbances 1
• Hypoxia 1
• Severe anemia 3

Medication-Related Causes

Proarrhythmic Effects

• QT-prolonging medications 4
• Class I antiarrhythmic drugs (especially in structural heart disease) 4
• Excessive doses of antiarrhythmic medications 4
• Tricyclic antidepressants 4
• Certain phenothiazines 4
• Some oral macrolides 4

Autonomic Factors

• Altered autonomic tone 1
• Excessive sympathetic stimulation 6
• Catecholamine excess 6

Tachycardia-Induced Cardiomyopathy

• Persistent tachycardia leading to ventricular dysfunction 1
• Irregular ventricular rhythm causing decreased cardiac output 1
• Chronic rapid ventricular rates (>130 beats/min) 1

Management Considerations for Persistent VT/VF

Immediate Interventions

1. Electrical cardioversion/defibrillation for hemodynamically significant VT or VF 1
2. Immediate coronary angiography if ischemia is suspected 1
3. Beta-blockers for recurrent polymorphic VT/VF 1
4. Amiodarone (150-300 mg IV bolus) for acute suppression of recurrent VAs 1
5. Deep sedation to reduce episodes of VT/VF 1

For Refractory Cases

• Consider catheter ablation for recurrent VT/VF despite optimal medical therapy 1
• Evaluate for triggers such as PVCs from injured Purkinje fibers 1
• Consider low-dose esmolol for refractory VF not responding to standard measures 6

Pitfalls to Avoid

• Failing to recognize incomplete coronary reperfusion as a cause of persistent VT/VF
• Overlooking electrolyte abnormalities or acid-base disturbances
• Using Class I antiarrhythmic drugs (e.g., procainamide, propafenone, flecainide) in acute coronary syndromes, which is not recommended 1
• Confusing accelerated idioventricular rhythm (rate <120 beats/min) with true VT requiring treatment 1
• Neglecting to correct underlying causes while focusing solely on rhythm management

Early identification and correction of the underlying cause is essential for successful management of persistent VT/VF, with immediate coronary angiography being critical when ischemia is suspected.