What is a junctional rhythm on an ECG?

As a medical professional with expertise in cardiology, I can explain that a junctional rhythm on an ECG, also known as a junctional escape rhythm, occurs when the electrical impulses that control the heartbeat originate from the atrioventricular (AV) junction, rather than the normal pacemaker, which is the sinoatrial (SA) node located in the right atrium. Under normal circumstances, the SA node sends electrical signals that travel through the heart, causing it to contract and pump blood. However, if the SA node's rate is too slow or if there is a block in the conduction of these signals, the heart has backup pacemakers that can take over. The AV junction is one of these backup pacemakers. When the AV junction becomes the primary pacemaker, it can produce a regular rhythm, but at a slower rate than the SA node, typically between 40 and 60 beats per minute. On an ECG, a junctional rhythm is characterized by inverted P waves (since the electrical impulse is traveling in the opposite direction of normal), followed by normal QRS complexes and a regular rate. This rhythm is often a compensatory mechanism when the heart's primary pacemaker is not functioning properly. It's important to note that while a junctional rhythm can be a normal response to certain conditions, it can also be associated with various heart diseases or electrolyte imbalances. It requires further evaluation by a healthcare professional to determine the underlying cause and appropriate treatment.

A junctional rhythm occurs when the electrical activation of the heart originates near or within the atrioventricular node, rather than from the sinoatrial node. Because the normal ventricular conduction system (His-Purkinje) is used, the QRS complex is frequently narrow.