Antegrade slow pathway mapping of typical atrioventricular nodal reentrant tachycardia based on direct slow pathway capture

Abstract

Background: Radiofrequency (RF) ablation of typical atrioventricular nodal reentrant tachycardia (tAVNRT) is performed without revealing out the location of antegrade slow pathway (ASp). In this study, we studied a new electrophysiological method of identifying the site of ASp.

Methods: This study included 19 patients. Repeated series of very high-output single extrastimulations (VhoSESts) were delivered at the anatomical slow pathway region during tAVNRT. Tachycardia cycle length (TCL), coupling interval (CI), and return cycle (RC) were measured and the prematurity of VhoSESts [ΔPM (= TCL - CI)] and the prolongation of RCs [ΔPL (= RC - TCL)] were calculated. Pacing sites were classified into two categories: (i) ASp capture sites [DSPC(+) sites], where two different RCs were shown, and ASp non-capture sites [DSPC(-) sites], where only one RC was shown. RF ablation was performed at DSPC(+) sites and/or sites with catheter-induced mechanical trauma (CIMT) to ASp.

Results: DSPC(+) sites were shown in 13 patients (68%). RF ablation was successful in all patients without any degree of atrioventricular block nor recurrence. Total number of RF applications was 1.8 ± 1.1. Minimal distance between successful ablation sites and DSPC(+)/CIMT sites and His bundle (HB) electrogram recording sites was 1.9 ± 0.8 mm and 19.8 ± 6.1 mm, respectively. ΔPL of more than 92.5 ms, ΔPL/TCL of more than 0.286, and ΔPL/ΔPM of more than 1.565 could identify ASp with sensitivity of 100%, 91.1%, and 88.9% and specificity of 92.9%, 97.0%, and 97.6%, respectively.

Conclusions: Sites with ASp capture and CIMT were close to successful ablation sites and could be useful indicators of tAVNRT ablation.

Keywords: antegrade slow pathway; atrioventricular nodal reentrant tachycardia; extrastimulation; reset.

FIGURE 1

Schematic presentation of the hypothesized model of tAVNRT (A, B), effect of a VhoSESt during tAVNRT (C), and the order of manipulating Abl catheter (D). A: ASp conduction curve is hypothesized to be a sigmoid conduction curve. B: P1, P2, P3, P4, and P5 were located on the circuit of tAVNRT and P6 was located outside of the tAVNRT circuit. TCL was defined as the summation of the conduction time of a, b, c, d, and e. C: TCL, CI, and RC(n + 1) were measured and ΔPM and ΔPL were calculated. The electrograms drawn by the black broken line show the expected electrogram location in a case without VhoSESt. D: Abl catheter was moved sequentially from ① to ⑧ until a successful ablation was achieved. Asp, antegrade slow pathway; AFp, antegrade fast pathway; RFp, retrograde fast pathway; AVN, atrioventricular node; Abl, ablation; VhoSESt, very high‐output single extrastimulation; P1, site of RA capture by a VhoSESt delivered from Abl catheter; P2, junctional site between RA and ASp; P3, site of ASp capture by a VhoSESt delivered from Abl catheter; P4, turnaround site between ASp and RFp in AVN; P5, junctional site between RFp and RA; P6, any point in atrium and coronary sinus (CS) located away from ASp; HB, His bundle; TCL, tachycardia cycle length; CI, coupling interval, RC, return cycle; RC(n) = interval between VhoSESt and onset of QRS wave; RC(n + 1) = interval between VhoSESt and onset of A wave recorded at Abl catheter; Int(n − 1, n) = interval between the onset of QRS wave of n − 1 and n beats; Int(n, n + 1) = interval between the onset of QRS wave of n and n + 1 beats; ΔPM, prematurity of VhoSESts [= TCL − CI]; ΔPL, prolongation of return cycle [= RC(n + 1) − TCL]; TCL, tachycardia cycle length; TT, tendon of Todaro; TA, tricuspid annulus; CSos, CS ostium

FIGURE 2

Schematic presentation of RC(n + 1) in the cases of ASp non‐capture with a ΔPM of x (A), of ASp non‐capture with a ΔPM of x + ε (B), and of ASp capture with a ΔPM of x (C). A: RCNC(x) = TCL + α and ΔPLNC(x) = α. B: RCNC(x + ε) = TCL + β and ΔPLNC(x + ε) = β. C: RCC(x) = TCL + β – ε = RCNC(x + ε) – ε and ΔPLNC(x) = β – ε = ΔPLNC(x + ε) – ε. RCNC(x) and RCNC(x + ε) = RC in the cases of ASp non‐capture with a ΔPM of x and x + ε, respectively; ΔPLNC(x) and ΔPLNC(x + ε) = ΔPL in the cases of ASp non‐capture with a ΔPM of x and x + ε, respectively; RCC(x) and ΔPLC(x) = RC and ΔPL in case of ASp capture with a ΔPM of x. The other abbreviations are the same as those given in Figure 1

FIGURE 3

Schematic presentation of the relationship between ASp capture and ASp non‐capture in the sigmoid conduction curve of ΔPLNC in the ΔPM‐ΔPL coordinate system (A) and the relationship of the anatomical location of the pacing site of ASp, ΔPM, and ΔDSPC in response to a VhoSESt delivered between n − 1 and n beats (B). A: ΔPLC(x) (point C) was created by shifting ΔPLNC(x + ε) (point B) leftward then downward by the same amount of ε. B: The area between n − 1 and n beats was divided into nine areas based on the pacing site along the ASp, ΔPM, and ERP of RA and ASp. The effects of VhoSESts in each area were shown below. A positive value of ΔDSPC(n + 1) with a prolongation of Int(n, n + 1) was only shown in area ⑧ and was mostly confined to dASp. This area was the target of this study. The blue circle in area ⑧ showed the maximum positive value of ΔDSPC(n + 1). The pink star in area ② was the estimated pacing site in the previous study. †: the change in RC(n + 1) and ΔDSPC(n + 1) depended on the change in Int(n − 1, n). ‡: the change in RC(n + 1) and ΔDSPC(n + 1) depended on the change in Int(n − 1, n). §: the change of Int(n, n + 1) depended on the change in Int(n − 1, n). pASp, mASp, and dASp, proximal, middle, and distal part of the ASp, respectively; ERP, effective refractory period; RA‐ASp‐J, junctional site between the RA and ASp; Term, termination of tAVNRT; ΔDSPC(n) = Int(n − 1, n)C(x) − Int(n − 1, n)NC(x); ΔDSPC(n + 1) = RCC(x) − RCNC(x) = ΔPLC(x) − ΔPLNC(x) = Int(n, n + 1)C(x) − Int(n, n + 1)NC(x) (except for area ⑤). U, unchanged; S, shortening; P, prolongation; NA = not assessed; N, no; Y, yes. The other abbreviations are the same as those given in Figures 1 and 2

FIGURE 4

Receiver operating characteristic (ROC) curves for the detection of ASp displaying the diagnostic performance of a ΔPL > 92.5 ms, ΔPL/TCL > 0.286, and ΔPL/ΔPM > 1.565. All indicators showed a good discrimination. The other abbreviations are the same as those given in Figures 1, 2, and 3

FIGURE 5

Case presentation of patient 3. A: Conduction curve of ΔPLNC (green) and ΔPLC (blue) on the ΔPM‐ΔPL coordinate system. Two discrete values of ΔPL were shown at DSPC(+) sites (ΔPLNC and ΔPLC). In the case of ASp non‐capture, tAVNRT was terminated in response to a ΔPM of more than 60 ms Blocking site was estimated to be located at RA‐ASp‐J. B: Location of DSPC(+) sites, DSPC(‐) sites, Abl sites, and HB electrogram recording sites on the 3D map. First RF application ¹ was delivered 2.6 mm blow DSPC(+) site, and JR occurred, but resulted in F2. Second RF application ² at DSPC(+) site was successful (Sn). C: Intracardiac electrograms in a case of ASp non‐capture. ΔPLNC was 62 ms in response to a ΔPM of 41 ms D: Intracardiac electrograms in a case of ASp capture at the same pacing site as C. ΔPLC was 158 ms in response to a ΔPM of 39 ms and ΔDSPC(n + 1) was 96 ms Notice that HB was antegradely activated by ASp(n), not by VhoSESt retrogradely. The other abbreviations are the same as those given in Figures 1, 2, and 3