In the initial management of stable, regular, monomorphic wide-complex tachycardia, which agent is indicated?

In the initial management of stable, regular, monomorphic wide-complex tachycardia, which agent is indicated?

• A. Lidocaine
• B. Adenosine
• C. Amiodarone
• D. Metoprolol

Answer: (B)

In this scenario, you’re evaluating a patient with a stable, regular, monomorphic wide-complex tachycardia. The key idea is that wide-complex tachycardia can be either tachycardia that’s VT or SVT with aberrant conduction. Adenosine is useful here because it transiently blocks AV nodal conduction, which can terminate AV-nodal dependent tachycardias such as AVNRT or AVRT and, in many cases, reveal SVT with aberrancy as the rhythm becomes more regular or returns to sinus rhythm. Using adenosine as an initial diagnostic/therapeutic trial helps distinguish SVT with aberrancy from VT: if the tachycardia terminates or converts to a regular rhythm, SVT with aberrancy is favored; if there is no effect, VT becomes more likely and you’d shift to antiarrhythmic therapy appropriate for VT (eg, amiodarone or lidocaine) and avoid AV-nodal blockers that could worsen VT. Adenosine is given as a rapid IV push (start with 6 mg, can give 12 mg if no response after 1–2 minutes) with continuous monitoring. It’s particularly appropriate when SVT with aberrancy is plausible and the patient is stable. If the rhythm does not respond, or if VT is strongly suspected (such as in the presence of structural heart disease, missed signs of ischemia, or nonresponse to adenosine), proceed with agents more specific for VT, like amiodarone or lidocaine, and avoid beta-blockers or calcium channel blockers as first-line in this setting.

In this scenario, you’re evaluating a patient with a stable, regular, monomorphic wide-complex tachycardia. The key idea is that wide-complex tachycardia can be either tachycardia that’s VT or SVT with aberrant conduction. Adenosine is useful here because it transiently blocks AV nodal conduction, which can terminate AV-nodal dependent tachycardias such as AVNRT or AVRT and, in many cases, reveal SVT with aberrancy as the rhythm becomes more regular or returns to sinus rhythm. Using adenosine as an initial diagnostic/therapeutic trial helps distinguish SVT with aberrancy from VT: if the tachycardia terminates or converts to a regular rhythm, SVT with aberrancy is favored; if there is no effect, VT becomes more likely and you’d shift to antiarrhythmic therapy appropriate for VT (eg, amiodarone or lidocaine) and avoid AV-nodal blockers that could worsen VT.

Adenosine is given as a rapid IV push (start with 6 mg, can give 12 mg if no response after 1–2 minutes) with continuous monitoring. It’s particularly appropriate when SVT with aberrancy is plausible and the patient is stable. If the rhythm does not respond, or if VT is strongly suspected (such as in the presence of structural heart disease, missed signs of ischemia, or nonresponse to adenosine), proceed with agents more specific for VT, like amiodarone or lidocaine, and avoid beta-blockers or calcium channel blockers as first-line in this setting.