In WPW, atrial fibrillation can conduct rapidly over the accessory pathway. What is this dangerous ECG pattern?

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Multiple Choice

In WPW, atrial fibrillation can conduct rapidly over the accessory pathway. What is this dangerous ECG pattern?

In WPW, an accessory pathway lets impulses bypass the AV node. If atrial fibrillation occurs, the atrial impulses can conduct very rapidly down that pathway to the ventricles, because the AV node’s normal rate-limiting delay doesn’t control these impulses. The result is atrial fibrillation with pre-excitation, an ECG pattern that shows an irregularly irregular rhythm with a very fast ventricular rate and wide QRS complexes due to ventricular pre-excitation. The QRS morphologies can vary beat to beat as some beats are pre-excited and others are not, and the overall rhythm can degenerate toward ventricular fibrillation because the pathway may have a short refractory period. This is the dangerous pattern because the ventricular response during AF can become extremely rapid via the accessory pathway, far exceeding what the AV node alone would limit. Other arrhythmias described—like atrial flutter with variable block, AV nodal reentrant tachycardia, or sinus tachycardia with aberrancy—do not involve rapid conduction of chaotic atrial impulses through an accessory pathway to produce the same high-risk, irregular, pre-excited ventricular activation.

In WPW, an accessory pathway lets impulses bypass the AV node. If atrial fibrillation occurs, the atrial impulses can conduct very rapidly down that pathway to the ventricles, because the AV node’s normal rate-limiting delay doesn’t control these impulses. The result is atrial fibrillation with pre-excitation, an ECG pattern that shows an irregularly irregular rhythm with a very fast ventricular rate and wide QRS complexes due to ventricular pre-excitation. The QRS morphologies can vary beat to beat as some beats are pre-excited and others are not, and the overall rhythm can degenerate toward ventricular fibrillation because the pathway may have a short refractory period.

This is the dangerous pattern because the ventricular response during AF can become extremely rapid via the accessory pathway, far exceeding what the AV node alone would limit. Other arrhythmias described—like atrial flutter with variable block, AV nodal reentrant tachycardia, or sinus tachycardia with aberrancy—do not involve rapid conduction of chaotic atrial impulses through an accessory pathway to produce the same high-risk, irregular, pre-excited ventricular activation.

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