Adenosine primarily converts certain types of supraventricular tachycardias (SVTs), specifically those involving the atrioventricular (AV) node in a re-entrant circuit, into a normal sinus rhythm.
Understanding Adenosine's Action
Adenosine is a medication often used in emergency settings due to its rapid and transient effects on the heart. Its main mechanism of action involves producing a brief, but effective, block in the AV node.
- Mechanism: When administered as an intravenous bolus, adenosine slows down the electrical conduction through the atrioventricular node. This transient atrioventricular nodal block interrupts re-entrant electrical pathways that are often responsible for supraventricular tachycardias.
- Target Rhythms: Adenosine is particularly effective for paroxysmal supraventricular tachycardias (PSVTs), which are characterized by a rapid heart rate originating above the ventricles, frequently involving the AV node in their underlying mechanism.
The Conversion Process
The goal of adenosine administration is to reset the heart's electrical activity back to its natural pace, which is the sinus rhythm.
| Condition Before Adenosine | Adenosine's Therapeutic Action | Resulting Rhythm After Conversion |
|---|---|---|
| Paroxysmal Supraventricular Tachycardia (PSVT) | Induces transient atrioventricular nodal block, interrupting re-entrant circuits | Normal Sinus Rhythm |
This conversion to sinus rhythm is crucial for stabilizing patients experiencing these rapid heart rhythms, restoring proper cardiac function.
Clinical Significance
Beyond its therapeutic role, adenosine also has diagnostic value. If a narrow-complex tachycardia converts to sinus rhythm following adenosine administration, it strongly suggests that the tachycardia was a type of supraventricular tachycardia dependent on AV nodal conduction. If it doesn't convert but merely slows down, it can help reveal underlying atrial activity (like atrial flutter or fibrillation).
It's important to note that adenosine is not effective for all types of rapid heart rhythms. For instance, ventricular tachycardias or atrial fibrillation/flutter without AV nodal involvement are typically not converted to sinus rhythm by adenosine.
