Differentiating AV Nodal vs Orthodromic AV Reentrant Tachycardia

Aim: To evaluate the usefulness of interpretation of 12-lead ECGs recorded during tachycardia and history taking to differentiate AV nodal reentrant tachycardia (AVNRT) from AV reentrant tachycardia (AVRT). Knowledge of tachycardia mechanism is crucial for counselling patients before ablation about success rates and complications.
Methods: Part one: three cardiologists on different training levels assessed
49 ECGs recorded during tachycardia in a blinded mode. Diagnosis of AVNRT or AVRT was given based solely on the ECG without knowledge of clinical setting. Part two: 55 patients filled out a questionnaire with 10 questions related to trigger factors, relief and concomitant symptoms of attacks, frequency of occurrence and familial clustering. Single questions and combinations were analysed for their ability to predict AVNRT or AVRT.
Results: Overall, 59% of the ECGs were correctly assigned. AVNRT was more often identified than AVRT (76% versus 28%, p-value <0.05). There was no significant difference between the three physicians. Questions pertaining to termination by means of the Valsalva manoeuvre or to occurrence of syncope were significantly predictive for AVNRT and AVRT, respectively, but both questions were answered positively by fewer than 50%. However, a combination of negative answers to three specific questions (no coincidence with psychic stress, no fainting and no “frog sign”) was significant and clinically meaningful for diagnosis (69% for AVRT, 33% for AVNRT, p-value 0.03).
Conclusion: Detailed analysis of an ECG registered during tachycardia and specific history taking can help to differentiate between AVNRT and AVRT, but the obtained reliability was only moderate.