What does "escape rhythm" refer to?

An escape rhythm refers to a backup pacemaker that takes over when the primary pacemaker of the heart, typically the sinoatrial (SA) node, fails to initiate electrical impulses sufficiently or at all. This situation often occurs when there is a disruption in the normal rhythm of the heart, such as in bradycardia where the heart rate is too slow. The inherent pacing mechanism of the heart can involve other pacemaker cells located in the atrioventricular (AV) node or the ventricles, which can generate impulses at a slower rate than the SA node, effectively "escaping" to maintain some level of cardiac rhythm and function.

This mechanism is crucial because it provides a safety net for the heart, ensuring that heart function can continue even in the presence of underlying issues with the primary pacemaker. In contrast, the other responses either describe different types of arrhythmias or heart rate changes that do not specifically define the concept of an escape rhythm.