Clinical Overview

Atrioventricular nodal reentrant tachycardia (AVNRT) is a fast, regular heart rhythm produced by a self-sustaining electrical loop confined entirely within the AV node, and it is the single most common form of paroxysmal supraventricular tachycardia (PSVT) in adults, accounting for roughly 50-60% of PSVT cases, with one source reporting over 60% (Hafeez, Ahmed, StatPearls, 2026; Hafeez, Quintanilla Rodriguez, Ahmed, Grossman, StatPearls, 2024). Where the umbrella term supraventricular tachycardia (SVT) covers any regular tachycardia arising above the ventricles — AVNRT, AVRT, focal atrial tachycardia, and automatic junctional tachycardia among them — AVNRT is one specific mechanism inside that umbrella, not a synonym for it: it is the species, not the genus. What sets AVNRT apart from its closest reentrant relative, AVRT, is where the loop lives. AVNRT’s entire circuit stays inside the AV node itself; no accessory pathway outside the AV node is involved (Hafeez, Ahmed, StatPearls, 2026).

The AV node normally conducts through a single pathway, but in patients who develop AVNRT the node contains two functionally distinct pathways: a fast pathway with a longer refractory period and a slow pathway with a shorter one. A well-timed premature atrial beat arrives while the fast pathway is still refractory, is forced down the slow pathway instead, and by the time that impulse reaches the far end the fast pathway has recovered enough to conduct it back up — closing a loop that then sustains itself (Hafeez, Ahmed, StatPearls, 2026). This slow-fast pattern is the typical, most common form of AVNRT. Atypical forms exist too: fast-slow AVNRT conducts down the fast pathway and back up the slow one, and slow-slow AVNRT uses a slow pathway in both directions; electrophysiologists distinguish these atypical patterns from one another during an EP study (Koulouris, Ahmed, StatPearls, 2023).

Clinically, AVNRT is common, usually not life-threatening, and generally carries an excellent prognosis, particularly in patients with structurally normal hearts, which most patients have (Hafeez, Ahmed, StatPearls, 2026). Episodes start and stop abruptly rather than accelerating and decelerating gradually, and at faster rates — physical-exam-documented rates above roughly 170 bpm — patients can develop presyncope or syncope from reduced ventricular filling, sometimes with cannon A waves visible in the jugular venous pulse as the atria contract against closed AV valves (Hafeez, Ahmed, StatPearls, 2026). A prolonged episode, or an episode in a patient with underlying structural heart disease, can progress to hemodynamic instability or, over time, tachycardia-induced cardiomyopathy (Hafeez, Ahmed, StatPearls, 2026).

Symptoms include sudden-onset palpitations that stop as abruptly as they start, lightheadedness, dizziness, dyspnea, and chest discomfort (Hafeez, Ahmed, StatPearls, 2026; Hafeez, Quintanilla Rodriguez, Ahmed, Grossman, StatPearls, 2024). AVNRT affects women roughly twice as often as men — about two-thirds of cases occur in women — and a 2026 retrospective emergency-department cohort found that women with SVT report a distinct, heavier symptom burden than men, including significantly higher rates of nausea and anxiety alongside palpitations; the same cohort found AVNRT itself was diagnosed more than twice as often in women as in men among ED patients presenting with SVT (12.7% vs. 5.9%) (Moser-van der Geest, Keller, Slankamenac, Frontiers in Psychiatry, 2026; Hafeez, Ahmed, StatPearls, 2026).

Most patients who develop AVNRT have structurally normal hearts. Recognized causes and risk factors include congenital variation in the AV node’s dual-pathway architecture, structural differences in the node’s transitional cells, emotional stress, stimulants such as caffeine and alcohol, shifts in autonomic tone, a suspected genetic predisposition, age-related change in conduction tissue, and female sex (Hafeez, Ahmed, StatPearls, 2026).

Interpretation Guide

Key Features:

• Rate: typically 140-250 bpm (Hafeez, Ahmed, StatPearls, 2026), consistent with the broader 150-250 bpm range reported for paroxysmal SVT generally (Hafeez, Quintanilla Rodriguez, Ahmed, Grossman, StatPearls, 2024). Atypical forms can present at more variable rates.
• Rhythm: regular, narrow-complex, and paroxysmal — onset and termination are abrupt rather than gradual, unlike a rhythm that speeds up and slows down with activity or fever (Hafeez, Ahmed, StatPearls, 2026; Hafeez, Quintanilla Rodriguez, Ahmed, Grossman, StatPearls, 2024).
• P waves: in typical (slow-fast) AVNRT, the retrograde P wave is buried in or immediately around the QRS, producing a very short RP interval — a pseudo-R’ deflection at the terminal QRS in lead V1, and a pseudo-S deflection notching the terminal QRS in the inferior leads (II, III, aVF) (Hafeez, Ahmed, StatPearls, 2026). In atypical AVNRT (fast-slow or slow-slow), the P wave is visible after the QRS with a long RP interval instead (Koulouris, Ahmed, StatPearls, 2023).
• PR interval: not usually measurable in typical AVNRT, since there is no discrete P wave preceding the QRS to measure from; where a retrograde P wave is visible after the QRS in an atypical form, the RP interval is the meaningful measurement instead.
• QRS complex: narrow, under 120 ms, consistent with conduction proceeding down the normal His-Purkinje system rather than an accessory pathway (Hafeez, Ahmed, StatPearls, 2026; Hafeez, Quintanilla Rodriguez, Ahmed, Grossman, StatPearls, 2024).
• ST segment: not a defining or diagnostic feature of AVNRT; assess on a post-conversion tracing rather than at rate.
• T waves: not a defining feature, but at these rates the T wave can obscure a retrograde P wave, which is part of why the pseudo-R’/pseudo-S pattern in V1 and the inferior leads is the more reliable clue.
• QT interval: not a diagnostic feature of AVNRT; a reliable measurement generally has to wait until after the rhythm converts, since the T wave and following P wave overlap at rate.
• Other findings: cannon A waves may be visible on jugular venous pulse exam during the tachycardia (Hafeez, Ahmed, StatPearls, 2026). After successful slow-pathway ablation, a spontaneous regular narrow-complex rhythm can appear that mimics recurrent AVNRT but is actually a junctional rhythm; this distinction is confirmed on an EP study rather than by surface ECG alone (Haroun, Kabunga, Cureus, 2025).

Key Leads

• V1 — the highest-yield lead for typical AVNRT. Look for a small terminal positive deflection at the end of the QRS: that pseudo-R’ is the buried retrograde P wave (Hafeez, Ahmed, StatPearls, 2026).
• Leads II, III, and aVF — the inferior leads, where the same buried retrograde P wave instead produces a pseudo-S wave notching the terminal QRS (Hafeez, Ahmed, StatPearls, 2026).
• Any lead with a clean, high-amplitude baseline — used to judge regularity and the abruptness of onset and offset, neither of which is lead-specific.

This condition is not lead-agnostic: V1 and the inferior leads carry disproportionate diagnostic weight, because they are where the defining pseudo-R’/pseudo-S pattern is visible.

Differential Diagnosis

• Supraventricular Tachycardia — the broad umbrella AVNRT sits inside, alongside AVRT, focal atrial tachycardia, and automatic junctional tachycardia. Distinguishing clue: a record or strip labeled simply “SVT” tells you the tachycardia is supraventricular in origin, not which mechanism produced it; AVNRT is identified specifically by the pseudo-R’ in V1 and pseudo-S in the inferior leads produced by a retrograde P wave buried in or immediately around the QRS.
• Atrioventricular Reentrant Tachycardia (AVRT) — the closest reentrant relative, and the differential that matters most for locating the circuit. Distinguishing clue: AVRT’s loop uses an accessory pathway outside the AV node as one limb; AVNRT’s loop stays entirely within the AV node itself, with no accessory pathway involved at all (Hafeez, Ahmed, StatPearls, 2026).
• Atrial Tachycardia — a focal, ectopic-driven rhythm rather than an AV-nodal reentrant one. Distinguishing clue: discrete, organized non-sinus P waves of a single consistent morphology precede each QRS with a visible isoelectric segment, rather than being buried in or immediately around the QRS the way AVNRT’s retrograde P wave is.
• Junctional Tachycardia — arises from enhanced automaticity or triggered activity in the AV junction rather than from a reentrant circuit (Schiedat, Kloppe, Herzschrittmachertherapie & Elektrophysiologie, 2026). Distinguishing clue: an automatic junctional rhythm does not depend on a well-timed premature beat to start or a critically-timed block to stop, so it lacks AVNRT’s sharply paroxysmal onset and offset; this distinction matters most right after AVNRT ablation, where a junctional rhythm can otherwise be mistaken for AVNRT recurrence (Haroun, Kabunga, Cureus, 2025).

Treatment Brief

• Assess hemodynamic stability first — blood pressure, level of consciousness, chest pain, signs of poor perfusion. Stability, not the rate number, drives the treatment path (Hafeez, Ahmed, StatPearls, 2026).
• For a hemodynamically stable patient, vagal maneuvers (Valsalva, carotid sinus massage) come first, though they succeed in fewer than 30% of episodes; if vagal maneuvers fail, IV adenosine is the first-line pharmacologic therapy, terminating AV-node-dependent PSVT in 75-95% of patients (Hafeez, Quintanilla Rodriguez, Ahmed, Grossman, StatPearls, 2024). Non-dihydropyridine calcium channel blockers (verapamil, diltiazem) or beta-blockers are alternatives (Hafeez, Ahmed, StatPearls, 2026).
• For a hemodynamically unstable patient, immediate synchronized cardioversion is the treatment (Hafeez, Ahmed, StatPearls, 2026).
• Confirm lead placement and rule out artifact before escalating, and capture a strip during the episode when possible — the pseudo-R’/pseudo-S pattern and the abruptness of onset and offset are diagnostic information that is easy to lose once the rhythm converts.
• For recurrent, symptomatic AVNRT, catheter ablation of the slow pathway is the guideline-preferred, first-line long-term treatment, with a long-term success rate reported as high as 95-97% and a recurrence rate as low as 1.5% in some series (Hafeez, Quintanilla Rodriguez, Ahmed, Grossman, StatPearls, 2024; Koulouris, Ahmed, StatPearls, 2023). A 28-year, single-center follow-up of 1,290 slow-pathway ablation procedures (mean follow-up 12.6 years) found 97% of patients achieved long-term rhythm control, with late AV block requiring a pacemaker in only 0.58 per 1,000 patient-years — a rate the authors did not find clearly higher than the spontaneous background rate of AV block (Yaakop et al., Journal of Cardiovascular Electrophysiology, 2026). Immediate post-procedure AV block after slow-pathway ablation is reported at 1-2.3% of cases (Koulouris, Ahmed, StatPearls, 2023).
• Pulsed field ablation, a newer non-thermal technique, has shown a high acute procedural success rate for AVNRT specifically (99.8%) in early systematic-review data, but the same review reported transient AV block in 19.3% of AVNRT slow-pathway PFA cases, with most resolving within 24 hours, and the evidence base is still smaller than for conventional radiofrequency ablation with longer-term outcome data still accumulating [CLINICAL REVIEW NEEDED: treat pulsed-field-ablation success and complication figures as preliminary rather than as an established alternative to radiofrequency slow-pathway ablation] (Sawalha et al., Trends in Cardiovascular Medicine, 2026).
• After conversion or ablation, keep the patient on the monitor. A regular narrow-complex rhythm appearing shortly after successful ablation is not necessarily recurrence — it can be a junctional rhythm that only resembles AVNRT, and treating it as one without careful reassessment risks an unnecessary repeat procedure (Haroun, Kabunga, Cureus, 2025).