From the Guidelines
Yes, someone with Atrioventricular Nodal Reentrant Tachycardia (AVNRT) can have a completely normal electrocardiogram (EKG) when they are not experiencing an episode of tachycardia. AVNRT is a paroxysmal condition, meaning it occurs in episodes rather than continuously. Between these episodes, the heart's electrical conduction system functions normally, resulting in a normal EKG reading. This is why AVNRT can sometimes be challenging to diagnose, as patients may show no abnormalities during routine EKG testing if they are not actively experiencing symptoms 1.
Key Points to Consider
- The diagnosis of AVNRT often requires capturing an EKG during an actual tachycardia episode, which typically shows a narrow-complex tachycardia with a regular rhythm and heart rates between 140-250 beats per minute, often with retrograde P waves hidden within or just after the QRS complex.
- For patients with suspected AVNRT who have normal resting EKGs, physicians may recommend ambulatory monitoring (like Holter monitors or event recorders), or in some cases, electrophysiology studies where the arrhythmia is deliberately triggered in a controlled setting to confirm the diagnosis.
- According to the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia, a 12-lead ECG obtained during tachycardia and during sinus rhythm may reveal the etiology of tachycardia 1.
Clinical Implications
- A normal EKG does not rule out the possibility of AVNRT, and further diagnostic testing may be necessary to confirm the diagnosis.
- The use of beta blockers, diltiazem, flecainide, procainamide, propafenone, and verapamil may be considered for the treatment of junctional tachycardia, although the efficacy of these treatments for AVNRT specifically may vary 1.
- It is essential to consider the clinical context and patient symptoms when interpreting EKG results and making diagnostic decisions.
From the Research
AVNRT and Normal EKG
- AVNRT (Atrioventricular Nodal Reentrant Tachycardia) is a type of supraventricular tachycardia that can occur in individuals with structurally normal hearts 2.
- The condition is characterized by rapid rhythms that originate and are sustained in atrial or atrioventricular node tissue above the bundle of His.
- Physical examination and electrocardiography findings may be normal in individuals with AVNRT, making diagnosis challenging 2.
Diagnostic Challenges
- A normal Electrocardiogram (EKG) does not rule out the possibility of AVNRT, as the condition may only be apparent during episodes of tachycardia 3.
- A Holter monitor or event recorder may be needed to confirm the diagnosis of AVNRT, as these devices can capture episodes of tachycardia that may not be present during a standard EKG 2.
- The transesophageal ventriculo-atrial interval can be used to diagnose AVNRT, with a cutoff of ≤80 ms having high diagnostic accuracy 3.
Treatment and Management
- AVNRT can be treated with vagal maneuvers, adenosine, calcium channel blockers, beta blockers, and class Ic antiarrhythmics 2, 4.
- Catheter ablation is a highly effective treatment for AVNRT, with a success rate of 95% and a recurrence rate of less than 5% 4, 5.
- Radiofrequency ablation of the slow pathway is a common treatment approach for AVNRT, and can be guided by electrophysiologic mapping 5, 6.