Introduction: Differentiation between AVNRT and AVRT can be sometimes challenging. Apical right ventricular (RV) entrainment can help in differentiation, however it has some fallacies. We thought to compare the accuracy of basal RV entrainment to RV apical entrainment in identifying the mechanism of SVT.
Methods: 42 consecutive patients with SVT undergoing catheter ablation were prospectively studied. Apical RV entrainment was performed 20 ms faster than tachycardia cycle length (TCL) initially followed by basal entrainment from the anteroseptal basal RV avoiding His or atrial capture. Postpacing interval (PPI), PPI-TCL, corrected PPI-TCL and Stim-A minus VA were measured.
Results: Entrainment was achieved from both sites of RV in 34 patients (10 men; mean age: 42±15 years), 20 with typical AVNRT, 1 with atypical AVNRT, and 13 with AVRT (8 left sided, 4 right sided, and 1 septal APs). PPI-TCL, cPPI-TCL and SA-VA were significantly longer with basal entrainment in AVNRT (171±30 vs 153±22 ms (p=0.003), 148±21 vs 131±20 ms (p=0.002) and 145±17 vs 136±15 ms (p=0.005) respectively). Receiver Operator Charecteristic (ROC) curves showed higher AUC for the above parameters with basal entrainment compared to apical entrainment. Basal PPI-TCL>110 ms had a sensitivity of 100% and a specificity of 84% for diagnosis of AVNRT. Basal cPPI-TCL>95 ms had a sensitivity of 100% and a specificity of 93% for diagnosis of AVNRT. Basal SA-VA>105 ms had a sensitivity of 100% and a specificity of 93% for diagnosis of AVNRT.
Conclusions: Entrainment from the anteroseptal basal RV is a simple maneuver that is superior to apical ventricular entrainment in identifying the mechanism of SVT.