2025 – PAGE 122 – CARDIOLOGY

AV NODE REENTRANT TACHYCARDIA (AVNRT)

In AV node reentrant tachycardia, the tachycardia originates at or near the node itself and is due to a fast and a slow conduction pathway around or in the AV node. In typical AVNRT, a “slow fast” AVNRT results in which there is conduction down the slow pathway and up the fast pathway. EKG findings (look at V1) may include retrograde P waves fused towards the end of QRS complexes, or a small R’ that is similar to that of a right bundle branch block (but with a normal QRS duration of < 120ms). AVNRT as a cause of supraventricular tachycardia (SVT) is common and will respond to vagal maneuvers and adenosine.

• NAME ALERT: The name alert is for AV REENTRANT TACHYCARDIA (AVRT) without “NODE.”

ADENOSINE AND VAGAL MANEUVERS

Adenosine and vagal maneuvers increase the refractory period, or temporarily block, the AV node (AVN).

ATRIAL TACHYCARDIAS

Atrial tachycardias do NOT respond to adenosine or vagal maneuvers. This includes atrial fibrillation and atrial flutter.

MNEMONIC: If signals from the atria are firing away on their own, they will continue to do so even if a signal that is further down the pathway (AVN) is blocked.

ATRIAL FIBRILLATION & ATRIAL FLUTTER

Atrial fibrillation and atrial flutter are most commonly seen in children with repaired structural heart disease, not in normal children. Also look for a cause of atrial dilation or tachycardia (e.g., hyperthyroidism). You may use adenosine to slow the rate for diagnostic purposes, but not for treatment. Treatment options include beta blockade, calcium channel blockers, digoxin, cardioversion, and ablation. These do not slow the atrial rate, but they do slow the ventricular rate by AVN blockade. See the caution above about atrial fibrillation and flutter in patients with WPW.

VENTRICULAR TACHYCARDIA (VT OR VTACH)

Etiologies of ventricular tachycardia include digoxin toxicity, hyperkalemia, and prolonged QT interval. In the absence of prolonged QT, treat with amiodarone. You may also use lidocaine or cardioversion.