Paradigm Shift for Catheter Ablation of Atypical Atrioventricular Nodal Re-Entrant Tachycardia: 3-Dimensional Mapping-Based Ablation.

BACKGROUND: In current practice, the ablation target of atypical atrioventricular nodal re-entrant tachycardia (AVNRT) is the earliest atrial activation site in the coronary sinus (CS) or conventional slow pathway region. OBJECTIVES: The purposes of this study were to map the site of earliest retrograde atrial activation using electroanatomic three-dimensional mapping during atypical AVNRT and to evaluate successful ablation sites. METHODS: A total of 42 patients with a total of 49 AVNRTs (slow/fast: 30; fast/slow: 15; slow/slow: 4) underwent electrophysiological study and ablation. Among them there were 14 patients (10 women; 60 ± 19 years of age) in whom 19 atypical AVNRT (fast/slow: 15; slow/slow: 4) were induced. RESULTS: The intracardiac electrocardiograms or three-dimensional mapping of the exit site during tachycardia revealed that 7 patients had exit sites solely inside the CS (left inferior extension [LIE]), 3 solely in the right postero-septal tricuspid annulus (TA; right inferior extension [RIE]), and 4 had both LIE and RIE exits. The distance from the CS ostium to LIE exits was 14 ± 6 mm. RIE exits were located on the TA posterior to the CS ostium (between 5 and 6 o'clock in the left anterior oblique projection). Ablation targeting these exits or conventional slow pathway succeeded in long-term elimination of AVNRT in 13 of the 14 patients (93%). There were no complications. CONCLUSIONS: Catheter ablation targeting the exit sites of LIE or RIE mapped at the CS or TA holds promise as an effective and safe alternative approach to the current targets of ablation for atypical AVNRT cases.

Orthodromic AVRT With 2 Different Wide QRS Complexes Caused by Bilateral Bystander Nodoventricular Pathways.

We present a case of orthodromic atrioventricular re-entrant tachycardia exhibiting both right and left bundle branch block pattern wide QRS morphologies caused by bilateral bystander nodoventricular (NV) accessory pathways. These wide QRS morphologies came from pre-excitation accompanied by delta waves. In the context of NV accessory pathways, left-sided manifest NV accessory pathways are rare.

Confirmation of the achievement of linear lesions using "activation vectors" based on omnipolar technology.

BACKGROUND: Although differential pacing conventionally has been used to confirm the achievement of block across linear lesion sets, high-resolution mapping demonstrates that pseudo-block is observed in 20%-30% of cases. OBJECTIVES: The purpose of this study was to examine the reliability and versatility of a method using "activation vectors" based on omnipolar technology to confirm the block line. METHODS: Linear ablation was performed during pacing, with the HD Grid catheter (Abbott) placed beside the linear lesion opposite the pacing site. The endpoint of complete linear lesion was complete inversion of the activation vectors to the opposite direction. When inversion of the activation vectors was not observed after 10 minutes of radiofrequency (RF) application, high-resolution mapping was performed to assess whether complete block was achieved. RESULTS: In 33 patients, 24 cavotricuspid isthmus lines, 11 mitral isthmus (MI) lines, 16 posterior lines, and 2 intercaval lines were performed using this method. Of the total of 53 lines, 10 (18.9%) required intermediate evaluation of the block line with high-resolution mapping because of the absence of inversion of activation vectors despite 10 minutes of RF application, resulting in incomplete block with endocardial gaps or epicardial conductions. Additional RF applications finally achieved inversion in direction of activation vectors in the 10 lines. In total, the present method can diagnose achievement of complete block line with 100% accuracy, whereas conventional differential pacing misdiagnosed incomplete block with epicardial conduction in posterior lines in 3 cases and in MI lines in 2 cases. CONCLUSION: Confirmation of complete linear lesions using "activation vectors" based on omnipolar technology is a reliable and versatile method.

Requirement of larger local impedance reduction for successful lesion formation at carinal area during pulmonary vein isolation.

PURPOSE: Local impedance (LI) measurement from an ablation catheter is useful in predicting lesion size and acute success of pulmonary vein isolation (PVI). The LI variation can be described by absolute LI drop (ΔLID) or ΔLID/initial LI (%LID). We evaluated the utility of these parameters in predicting acute lesion durability during PVI using a novel catheter capable of measuring both LI and contact force (CF). METHODS: PVI with a targeted CF, power, and duration was performed in 23 consecutive patients with paroxysmal atrial fibrillation. LI was blinded to operators during ablation. Parameters for each RF application were collected and compared for acute successful lesions and gaps. RESULTS: A total of 1633 RF applications including 97 (5.9%) gap lesions were analyzed. Successful lesions were more frequently observed at non-carinal sites and those with higher contact force, FTI, initial LI, and larger variation of LI and generator impedance (GI). Multivariate analysis demonstrated that absolute GI drop (ΔGID) [OR 1.09 (1.04-1.15), p < 0.001], ΔLID [1.12 (1.09-1.16), p < 0.001], ΔGID/initial GI (%GID) [OR 1.04 (1.01-1.07), p = 0.01], and %LID [OR 1.15 (1.12-1.28), p < 0.001] were significantly associated with successful lesions, and carinal site [OR 0.15(0.09-0.24), p < 0.001] was significantly related to gaps. Both ΔLID and %LID equally predicted the acute durability of lesions during PVI. ΔLID ≥ 24Ω and %LID ≥ 15% at the carina, and ΔLID ≥ 21Ω and %LID ≥ 14% at non-carinal sites significantly predicted acute successful lesions with negative predictive values of 93-99%. CONCLUSIONS: Both ΔLID and %LID were equally useful in predicting acute successful lesions during PVI. Larger cut-off values should be applied to carinal sites.

Comparison of two catheters measuring local impedance: local impedance variation vs lesion characteristics and steam pops.

PURPOSE: The size of the distal electrode and the method of measuring local impedance (LI) are different between the IntellaNav MiFi-OI™ (MiFi-OI) and IntellaNav STABLE POINT™ (SP) catheters. We investigated the impact of these differences on LI, efficacy, and safety of radiofrequency (RF) applications. METHODS: RF applications at a range of powers (30 W, 40 W, and 50 W), contact forces (10 g and 20 g), and durations (10-120 s) were performed in excised porcine hearts (N = 48). LI variation was defined by δLI-drop (= initial LI - post-RF LI) and %LI-drop (= δLI-drop/initial LI) × 100, and the relationship between lesion characteristics and LI variation was compared. RESULTS: A total of 576 lesions were examined. Although absolute δLI-drop during RF applications was significantly larger for the SP than MiFi-OI catheter (47[31-65]ohm for SP vs 37[24-51]ohm for MiFi-OI, p < 0.0001), %LI-drop was similar (23.3 [15.5-30.6]% in SP vs 24.9[17.3-32.5]% in MiFi-OI, p = 0.10). Although lesions produced by both catheters were similarly correlated with LI variation, the SP catheter produced generally larger lesions (depth; 5.0 [3.7-6.1]mm vs 4.7 [3.3-6.0]mm, p = 0.06; surface areas, 46.9 [36.8-58.8]mm2 vs 44.7 [34.3-55.5]mm2, p = 0.02; volume, 321 [165-533]mm3 vs 265[141-471]mm3, p = 0.02). Steam pops were similarly observed with both catheters. In both catheters, %LI-drop was superior to δLI-drop in correlation to lesion size (p < 0.0001) and in predicting steam pops (p < 0.01). CONCLUSIONS: Although no difference in safety profile is observed between MiFi-OI and SP catheters, the SP catheter produces larger lesions. %LI-drop is superior to δLI-drop in correlation to lesion size and in predicting steam pops as well as in normalizing the difference between catheters.

Impact of a formula combining local impedance and conventional parameters on lesion size prediction.

BACKGROUND: Although ablation energy (AE) and force-time integral (FTI) are well-known active predictors of lesion characteristics, these parameters do not reflect passive tissue reactions during ablation, which may instead be represented by drops in local impedance (LI). This study aimed to investigate if additional LI data improves predicting lesion characteristics and steam pops. METHODS: RF applications at a range of powers (30 W, 40 W, and 50 W), contact forces (8 g, 15 g, 25 g, and 35 g), and durations (10-180 s) using perpendicular/parallel catheter orientations were performed in excised porcine hearts (N = 30). The correlation between AE, FTI, and lesion characteristics was examined, and the impact of LI (%LI drop (%LID) defined by the ΔLI divided by the initial LI) was additionally assessed. RESULTS: Three hundred seventy-five lesions without steam pops were examined. Ablation energy (W × s) and FTI (g × s) showed a positive correlation with lesion depth (ρ = 0.824:P < 0.0001 and ρ = 0.708:P < 0.0001), surface area (ρ = 0.507:P < 0.0001 and ρ = 0.562:P < 0.0001), and volume (ρ = 0.807:P < 0.0001 and ρ = 0.685:P < 0.0001). %LID also showed a positive correlation individually with lesion depth (ρ = 0.643:P < 0.0001), surface area (ρ = 0.547:P < 0.0001), and volume (ρ = 0.733:P < 0.0001). However, the combined indices of AE × %LID (AE multiplied by %LID) and FTI × %LID (FTI multiplied by %LID) provided significantly stronger correlation with lesion depth (ρ = 0.834:P < 0.0001 and ρ = 0.809:P < 0.0001), surface area (ρ = 0.529:P < 0.0001 and ρ = 0.656:P < 0.0001), and volume (ρ = 0.864:P < 0.0001 and ρ = 0.838:P < 0.0001). This tendency was observed regardless of the catheter placement (parallel/perpendicular). AE (P = 0.02) and %LID (P = 0.002) independently remained as significant predictors to predict steam pops (N = 27). However, the AE × %LID did not increase the predictive power of steam pops compared to the AE alone. CONCLUSION: LI, when combined with conventional parameters (AE and FTI), may provide stronger correlation with lesion characteristics.