Can atrial fibrillation cause ventricular fibrillation?

Atrial fibrillation is the commonest sustained arrhythmia. In which situation is atrial fibrillation likely to cause ventricular fibrillation? 1. When associated with hyperthyroidism 2. When associated with hypothyroidism 3. When associated with WPW syndrome 4. When associated with mitral stenosis Correct answer: 3. When associated with WPW syndrome In Wolff-Parkinson-White (WPW) syndrome, atrial fibrillation gets conducted to the ventricles both through the normal atrioventricular (AV) conduction system and the accessory pathway. The normal AV conduction system has decremental properties and the refractory period increases as the number of impulses reaching it increases. Hence the normal AV conduction system does not allow too many impulses from the atrium to reach the ventricles. At the same time accessory pathway refractory period decreases as the rate increases and it can transmit large number of impulses to the ventricle from the atrium. As the the atrial rate is very high in atrial fibrillation, the presence of accessory pathway in WPW syndrome allows large number of atrial impulses to be conducted the ventricles leading to fast ventricular response. The rate may become so high that it leads to hemodynamic compromise and the ventricular rhythm can degenerate into ventricular fibrillation. In all the other conditions listed above, as long as the AV conduction system is intact and there is no accessory pathway, large number of atrial signals are blocked from reaching th...
Source: Cardiophile MD - Category: Cardiology Authors: Tags: Cardiology MCQ DM / DNB Cardiology Entrance Source Type: blogs