What might indicate the presence of an AV bypass tract in atrial fibrillation?

The presence of an AV bypass tract in atrial fibrillation is often indicated by a very rapid ventricular response, particularly when the QRS duration exceeds 120 milliseconds. This abnormal conduction can occur in patients with accessory pathways, such as those seen in Wolff-Parkinson-White syndrome. The rapid ventricular response can be attributed to the presence of an abnormal electrical pathway connecting the atria and ventricles, allowing for faster conduction of impulses, which results in a wider QRS complex on the ECG.

While other options may relate to different aspects of atrial fibrillation or general arrhythmias, they do not specifically denote the presence of an AV bypass tract. For instance, a wavy baseline may indicate atrial fibrillation itself rather than the presence of an accessory pathway, a prolonged QT interval suggests different underlying issues, and a regularly regular heart rhythm is associated with other types of rhythm disorders. Thus, the rapid ventricular response with a widened QRS is a key feature signaling the potential presence of an AV bypass tract.