Can Atrial Fibrillation with RVR Lead to Ventricular Fibrillation?
Atrial fibrillation with rapid ventricular response does not typically progress to ventricular fibrillation in most patients, but it can trigger ventricular fibrillation and sudden death specifically in patients with Wolff-Parkinson-White (WPW) syndrome when atrial impulses conduct rapidly down an accessory pathway. 1
The Critical Exception: WPW Syndrome
In patients with WPW syndrome, atrial fibrillation may induce ventricular fibrillation and sudden death when atrial impulses are conducted antegrade across a bypass tract. 1 This occurs because:
- Accessory pathways are muscle connections between the atrium and ventricle that have the capacity to conduct rapidly, potentially resulting in a very rapid and fatal ventricular response 1
- Patients at highest risk are those with short antegrade bypass tract refractory periods (less than 250 ms) and short R-R intervals during preexcited AF 1
- There is also a higher incidence of multiple pathways in patients prone to ventricular fibrillation 1
Incidence and Risk Stratification
The actual incidence of sudden death in WPW patients ranges from 0 to 0.6% per year, making this complication feared but infrequent. 1 A large population-based study in Olmsted County, Minnesota found only two sudden deaths over 1,338 patient-years of follow-up among patients with WPW. 1
Management of AF with RVR in WPW Patients
Patients with WPW in whom AF occurs with a rapid ventricular response associated with hemodynamic instability should be cardioverted immediately because of the high risk of developing ventricular fibrillation. 1
Critical Medication Contraindications
It is critically important to avoid agents with the potential to increase the refractoriness of the AV node, which could encourage preferential conduction over the accessory pathway. 1 Specifically:
- Intravenous administration of beta-blocking agents, digitalis glycosides, diltiazem, or verapamil is contraindicated in patients with WPW syndrome who have preexcited ventricular activation in AF 1, 2
- These drugs do not block conduction over the accessory pathway and can even enhance conduction, resulting in hypotension, cardiac arrest, or acceleration of ventricular rate leading to ventricular fibrillation 1, 2
Appropriate Treatment Options
For hemodynamically stable patients with WPW and AF with RVR:
- Intravenous procainamide or ibutilide should be administered in an attempt to restore sinus rhythm in patients with a wide QRS complex (≥120 ms duration) 1
- Catheter ablation of the accessory pathway is recommended for symptomatic patients with WPW, particularly those who have had documented AF or syncope suggesting rapid heart rate 1
AF with RVR in Patients Without WPW
In patients without accessory pathways, AF with RVR does not lead to ventricular fibrillation. 1 Instead, the primary concerns are:
- Hemodynamic compromise from loss of synchronous atrial mechanical activity and inappropriately rapid heart rate 1
- Risk of tachycardia-induced cardiomyopathy with persistently elevated ventricular rates (≥130 bpm) 1
- Increased thromboembolic risk 3
The AV node ordinarily limits conduction during AF, preventing the extremely rapid ventricular rates that could theoretically trigger ventricular arrhythmias. 1
Key Clinical Pitfall
The critical pitfall is administering AV nodal blocking agents (beta-blockers, calcium channel blockers, digoxin) to patients with WPW and pre-excited AF, as this can precipitate ventricular fibrillation. 1, 2 Extremely rapid rates (over 200 bpm) during AF should raise suspicion for the presence of an accessory pathway and require urgent cardiology referral. 4, 2