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. 2023 Dec 15;40(1):131–142. doi: 10.1002/joa3.12976

FIGURE 2.

FIGURE 2

Patient 1. Intracardiac electrograms of (A–E) fast–slow AVNRT with a bystander cNVP connected to the slow pathway (SP) and (F) slow–fast AVNRT. (A) The PVC delivered during His‐refractoriness delays the tachycardia, with with a delay of the atrium preceding the His delay, indicating presence of an AP (Step 1). (B) The reset phenomenon disappears after the early PVC, which captures the His antidromically (rH). The observation indicates that both the AP and His‐bundle are outside the tachycardia circuit, which is diagnostic of fast–slow AVNRT with a bystander cNVP connected to the SP and excludes ORT (Step 2). (C) The tachycardia sustains despite occurrence of atrioHisian block, which indicates that His‐bundle is not involved in the tachycardia circuit and rules out ORT (Step 2). (D) Right ventricular overdrive pacing (D) delays the atrial electrograms during the transition zone and (E) results in a post‐pacing interval − tachycardia cycle length of 140 ms, which also supports the diagnosis. (F) The His‐refractory PVC fails to uncover the presence of an AP during the slow‐fast AVNRT, possibly due to the SP ERP. A, atrium; AP, accessory pathway; AVN, atrioventricular node; cNVP, concealed nodoventricular pathway; CS, coronary sinus; d, distal; ERP, effective refractory period; FP, fast pathway; H, His; HB, His bundle; HRA, high right atrium; ORT, orthodromic reciprocating tachycardia; p, proximal; PVC, premature ventricular contraction; RVA, right ventricular apex; S, stimulus; SP, slow pathway; V, ventricle.