Accelerated junctional rhythm (AJR) is a heart rhythm originating from a specific area of the heart. It beats faster than a typical junctional rhythm but not as fast as some other rapid heart rhythms. This condition involves the heart’s electrical system, which functions as its natural pacemaker.
The Heart’s Electrical Symphony
The heart’s rhythm begins with an electrical impulse generated by the sinoatrial (SA) node, often called the heart’s natural pacemaker. Located in the upper right atrium, the SA node sends out electrical signals at a rate of 60 to 100 beats per minute. These impulses then spread across the atria, causing them to contract and pump blood into the ventricles.
The electrical signal then arrives at the atrioventricular (AV) node, near the heart’s center. The AV node acts as a “gatekeeper,” briefly delaying the impulse to allow the atria to fully empty their blood into the ventricles before ventricular contraction begins. After this brief delay, the signal travels through the bundle of His, bundle branches, and Purkinje fibers, rapidly spreading the impulse throughout the ventricles, causing them to contract and pump blood to the body. If the SA node is not functioning correctly or is too slow, the AV node can take over as a backup pacemaker, producing a junctional rhythm at a slower rate of 40 to 60 beats per minute.
Unpacking Accelerated Junctional Rhythm
Accelerated junctional rhythm (AJR) occurs when the AV node, or the surrounding junctional tissue, generates electrical impulses at a rate faster than its usual escape rhythm but not as fast as a true tachycardia originating from this area. Specifically, AJR is characterized by a heart rate ranging from 60 to 100 beats per minute. This rate falls between a junctional escape rhythm (40-60 bpm) and junctional tachycardia (over 100 bpm).
On an electrocardiogram (ECG), AJR presents with distinct features. The QRS complex, representing ventricular electrical activity, is narrow. The P wave, indicating atrial activity, is a key characteristic; in AJR, P waves may be absent, inverted, appear after the QRS complex, or be hidden within the QRS complex itself. This occurs because the electrical impulse originates in the AV junction and can sometimes travel backward into the atria.
While some individuals with AJR might not experience symptoms, others may. These symptoms can include palpitations, fatigue, dizziness, or shortness of breath.
Common Triggers and When to Be Aware
Accelerated junctional rhythm can stem from various underlying causes. A common trigger is digitalis toxicity, a side effect of certain heart medications. Other causes include conditions that inflame the heart muscle, such as myocarditis, or damage to heart tissue from a myocardial infarction, also known as a heart attack. Electrolyte imbalances, with an atypical concentration of essential minerals in the body, can also contribute to this rhythm.
Cardiac surgery, particularly open-heart procedures or valve replacements, can lead to AJR due to inflammation or direct trauma to the heart’s electrical pathways. The appearance of AJR post-surgery may indicate a combination of accelerated junctional activity and a slowed sinus node discharge. While AJR is a benign and temporary condition that may resolve without specific treatment, it can signal a more significant underlying heart issue. If symptoms are present or if AJR is persistent, medical evaluation is important to identify and manage the root cause, as it can lead to issues like low blood pressure.