Contents

AvnrtEdit

Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common form of paroxysmal supraventricular tachycardia, arising from a reentrant circuit within the atrioventricular node that briefly disrupts normal heart rhythm. In clinical practice, AVNRT typically presents as sudden-onset, short-lived episodes of a rapid heart rate in otherwise healthy individuals, most often in young to middle-aged adults. The condition is usually benign, and many patients experience symptom relief after targeted treatments, though episodes can be disruptive to daily life and sleep.

AVNRT is driven by the presence of dual pathways within the AV node—a slow pathway and a fast pathway—that enable a self-perpetuating reentrant loop. This anatomical setup allows a premature impulse to propagate down one pathway while returning via the other, creating a rapid, narrow-complex tachycardia. The result is a transient increase in heart rate that commonly ranges from 150 to 250 beats per minute and can fluctuate with activity, stress, or caffeine intake. Because the electrical activity remains above the ventricles, the QRS complexes are typically narrow on the electrocardiogram during an episode.

Pathophysiology

AVNRT is rooted in the existence of two pathways within the AV node: a slow pathway with longer conduction time and a fast pathway with shorter conduction time. During an episode, antegrade conduction often travels down the slow pathway, while retrograde conduction uses the fast pathway, creating a loop that sustains the tachycardia. In some patients, this dual-pathway physiology is present but clinically silent until unmasked by a trigger such as a premature atrial beat or heightened sympathetic tone. The result is a sudden-onset arrhythmia with abrupt termination, often well into the episode or after a spontaneous reset.

Clinical features

  • Sudden onset of a rapid heartbeat with a sense of palpitations, dizziness, or shortness of breath.
  • Episodes commonly last from minutes to hours but can resolve spontaneously.
  • Between episodes, patients usually feel well and have normal resting ECGs and heart structure.

Diagnosis

  • Diagnostic confirmation is typically achieved during an episode with a narrow-complex tachycardia on the electrocardiogram and a regular rhythm.
  • Termination with vagal maneuvers or pharmacologic agents such as adenosine is characteristic, though not exclusive.
  • After an episode terminates, tracing the patient’s history and prior ECGs helps distinguish AVNRT from other forms of SVT, including atrial fibrillation or atrial flutter.
  • Electrophysiology studies, when performed, map the dual-pathway physiology within the AV node and can confirm the mechanism.

Management

  • Acute management during an episode often relies on noninvasive measures first (vagal maneuvers) and pharmacologic termination with adenosine when needed.
  • Long-term strategies focus on reducing recurrence and improving quality of life.
    • Catheter ablation of the slow pathway within the AV node is highly effective, with success rates commonly exceeding 95% and a low risk of major complications in experienced centers. This approach can be curative for many patients and eliminates the need for daily medications.
    • Medical therapy uses rate-controlling drugs such as non-dihydropyridine calcium channel blockers (for example, diltiazem) or beta blockers to reduce tachycardia episodes, though these are not curative and require ongoing adherence.
    • In selected cases, patients may be managed with lifestyle modifications and selective use of antiarrhythmic agents, though these options are generally reserved for those who are not candidates for, or decline, ablation.
  • Potential risks of ablation include rare but significant complications such as AV block requiring a pacemaker, or, less commonly, vascular injury or pericardial effusion. The risk profile is highly dependent on operator experience and the structure of the patient’s conduction system.

Prognosis

  • With appropriate treatment, the prognosis for AVNRT is excellent. Most patients experience substantial improvement in symptoms after ablation or long-term medical therapy.
  • Recurrence after ablation is uncommon but possible; follow-up care emphasizes monitoring for any new episodes and evaluating the need for additional interventions.

Epidemiology

  • AVNRT accounts for a substantial proportion of paroxysmal supraventricular tachycardia cases and is more frequent in people without structural heart disease.
  • It most commonly presents in late adolescence through middle age, with a slight female predominance in some populations.
  • The condition is a leading cause of palpitations in otherwise healthy individuals and often prompts evaluation by primary care physicians or cardiologists.

Controversies and debates

  • Timing and choice of intervention: Proponents of early ablation argue that a definitive procedure reduces the burden of episodes, avoids chronic medication use, and can be cost-effective over time. Critics worry about upfront procedural costs, the rarity of complications, and whether all patients with infrequent episodes require invasive treatment.
  • Prevention versus cure: Some clinicians favor a “start with medication” approach for infrequent, mild episodes, preserving ablation for those with persistent symptoms or a clear impact on quality of life. Others emphasize a patient-centered model where the option of a one-time ablation is discussed early to provide a potential cure.
  • Access and equity: Availability of experienced electrophysiology services varies by region. In settings with limited access, patients may rely on noninvasive management and delayed intervention, which can influence outcomes and satisfaction.
  • Overdiagnosis concerns: Since AVNRT can present with intermittent and variable symptoms, there is ongoing discussion about when to pursue invasive testing, particularly in patients with atypical presentations or multiple potential etiologies for palpitations.

See also