A junctional escape rhythm is when a ventricular contraction originates from an ectopic pacemaker site within the atrial ventricular junction. This can occur when the AV junction fires prematurely, or when the intrinsic rhythm fired by the SA node fails to meet the AV junction on time.
Junctional Escape Rhythm ECG
Heart Rate: 40-60 bpm
Rhythm: irregular in single junctional escape complexes, but regular in junctional escape rhythm.
P waves: depends on the site of the ectopic foci. P waves will usually be inverted, and may appear before or after the QRS complex, or they may be absent, hidden by the QRS complex. This is because the P wave represents the depolarization of the SA node, which is occuring just before or just after the AV Junction depolarizes, meaning that the P wave “appears” very close to the QRS complex or even after it and is inverted.
P-R interval: if the P wave occurs before the QRS complex, the interval will be shorter than normal (less than 0.12 seconds).
QRS Complex: Uuually normal in duration and morphology (less than 0.12 seconds).
Junctional Escape Rhythm Signs and Symptoms
The patient will commonly be unaware of their underlying heart rhythm until the rate becomes low enough to become symptomatic. At a rate of 50/minute the person my find it slightly harder to exercise, but will often be unaware of any changes. As the rate lowers towards 40/minute the patient will become poorly perfused, with signs such as cool, pale, clammy skin. They may feel symptoms such as dizziness, mild palpitations, chest pain, chest tightness, and generaly weakness.