7.8.10 Junctional escape beats
A junctional escape beat is a protective mechanism that occurs when there has been no supraventricular stimulus to the ventricles to initiate systole. It is assowith failure of stimulus formation in the SA node (SA arrest) or conduction through the AV node, although the delay must be very marked for an escape beat to occur unless the junctional rate is raised (see below). On auscultation, a long diastolic pause is followed by a loud S1. An arrhythmia will be appreciated. When a junctional escape beat is present, the ECG shows a slow heart rate with a long pause followed by a normal or nearly normal QRS complex. Retrograde P waves may be seen just before, or coincident with the QRS complex.