Most Common Cause of Ventricular Fibrillation
Ischemic heart disease is the most common cause of ventricular fibrillation in adults, accounting for the majority of sudden cardiac arrest cases. 1
Primary Etiology
- Acute myocardial ischemia and infarction represent the predominant trigger for VF, with coronary artery disease underlying most adult sudden cardiac arrests 1
- VF is the most common primary arrhythmia in adult cardiac arrest, often preceded by a brief period of ventricular tachycardia that deteriorates into VF 1
- The majority of individuals who die from acute coronary syndrome do so before reaching the hospital, with VF as the terminal rhythm 1
Mechanism in Ischemic Disease
- Myocardial ischemia creates electrical instability through heterogeneous conduction, creating the substrate for reentrant circuits and rapid focal discharge 2, 3
- The capacity to fibrillate is inherent in ventricular muscle because electrophysiological properties of different ventricular segments are not uniform, and ischemia enhances this electrical asynchrony 3
- Anterior myocardial infarction carries higher risk for primary VF compared to other locations (OR 1.52) 4
Additional Risk Factors During Acute MI
When VF occurs during first myocardial infarction, specific modifiable factors increase risk:
- Hypokalemia (K+ <3.5 mEq/L) doubles the risk of primary VF (OR 2.28), even when measured before VF occurs 4
- Low systolic blood pressure at presentation independently predicts VF (OR 0.982 per mm Hg decrease) 4
- Physical inactivity increases VF risk (OR 1.73) 4
- Family history of sudden death increases risk (OR 1.80) 4
Other Cardiac Causes
Beyond ischemia, structural heart disease accounts for additional VF cases:
- Tachycardia-induced cardiomyopathy from atrial fibrillation can lead to ventricular dysfunction that predisposes to VF 1
- Hypertrophic cardiomyopathy, dilated cardiomyopathy, and restrictive cardiomyopathies create arrhythmogenic substrates 5
- Valvular heart disease, particularly when causing ventricular dysfunction 5
Non-Ischemic Triggers
- Inherited ion channelopathies (long QT syndrome, Brugada syndrome) cause VF in structurally normal hearts, though these represent a minority of cases 2
- Acute conditions including pulmonary embolism, myocarditis, and pericarditis can trigger VF 5
- Metabolic derangements, particularly electrolyte abnormalities and hyperthyroidism 5
Critical Clinical Pitfalls
- Do not assume VF is purely electrical—always search for underlying acute coronary syndrome, as this is the most common reversible cause requiring immediate revascularization 1
- Check potassium levels immediately in any patient with VF, as hypokalemia is both common and correctable 4
- In prolonged VF (>7.5 minutes), immediate countershock alone has poor outcomes; brief CPR with high-dose epinephrine before defibrillation improves myocardial perfusion and resuscitation success 6
- The chances of successful defibrillation decline by 2-7% per minute of delay, making rapid defibrillation the priority once VF is identified 1