Performance and safety of temperature- and flow-controlled radiofrequency ablation for ventricular arrhythmia

Abstract

Aims: High-power ablation is effective for ventricular arrhythmia ablation; however, it increases the risk of steam pops. The aim of this study was to define the safety and efficacy of QMODE ablation in the ventricle and the risk of steam pop.

Methods and results: Consecutive patients undergoing ventricular ablation using QDOT were included in a prospective single-centre registry. Procedural data, complications, and follow-up were systematically analysed and compared with a historical ventricular tachycardia (VT) and premature ventricular complexes (PVC) cohort ablated using STSF. QMODE (≤50 W) ablation was performed in 107 patients [age 62 ± 13 years; 76% male; VT (n = 41); PVC (n = 66)]. A total of 2456 applications were analysed [power: 45.9 ± 5.0 W with minimal power titration (90% > 95% max power); duration 26 ± 8 s; impedance drop 9.4 ± 4.7 Ω; ablation index: 569 ± 163; mean-max temperature 44.3 ± 2.6°C]. Ventricular tachycardia ablation was associated with shorter radiofrequency (RF) time and a trend towards shorter procedure times using QDOT (QDOT vs. STSF: 20.1 ± 14.7 vs. 31 ± 17 min; P = 0.002, 151 ± 59 vs. 172 ± 48 min; P = 0.06). Complications, VT recurrence, and mortality rates were comparable (QDOT vs. STSF: 2% vs. 2%; P = 0.9, 24% vs. 27%; P = 0.82, and 2% vs. 4%; P = 0.67). Five audible steam pops (0.02%) occurred. Premature ventricular complex ablation was associated with comparable RF and procedure times (QDOT vs. STSF: 4.8 ± 4.6 vs. 3.9 ± 3.1 min; P = 0.25 and 96.1 ± 31.9 vs. 94.6 ± 24.7 min; P = 0.75). Complication and PVC recurrence were also comparable (QDOT vs. STSF: 0% vs. 3%; P = 0.17 and 19% vs. 22%; P = 0.71).

Conclusion: Ventricular ablation using QMODE ≤ 50 W is safe and effective for both VT and PVC ablation and is associated with a low risk for steam pop.

Keywords: Micro-EGM; Steam pop; Temperature guided; Ventricular arrhythmia.

Graphical Abstract

Figure 1

Para-Hisian PVC strategy using micro-His cloud avoidance strategy. Adapted from Berte et al., Heart Rhythm 2022 ‘High-resolution para-Hisian mapping and ablation using micro-electrode embedded ablation catheters’ with permission from the author. Left: Micro-His EGM with clear His EGM on both conventional electrodes and micro-electrodes (arrows). Middle: Light blue, micro-His cloud that should be avoided during ablation to avoid AV block; yellow, macro-only His cloud where prudent ablation is possible. Right: Absence of a His signal on the micro-electrodes. Presence of His signals on the conventional electrodes.

Figure 2

Steam pop analysis. From left to right and top to bottom. Upper left: Example of a steam pop using the Navistar 4 mm catheter during AVNRT. The impedance spike is not visible on the graph due to a lower impedance sampling rate of the generator. Retrospective analysis of the raw data impedance did demonstrate a clear typical fast and high impedance rise during the steam pop. No gradual impedance rise was seen before the pop. Low left: analysis of all RF application for impedance drop, impedance plateau phase, and application duration. Upper right: Five steam pops (0.3% of VT applications and 11% of VT procedures) during QMODE 50 W ablation with the QDOT catheter. (1) Superior glass mode view of inHEART model during VT ablation of anterolateral scar. Papillary muscles are in green. Red tag is application that resulted in steam pop. Vizigo sheath, DECANAV, and QDOT catheter visible. (2) Right anterior oblique view of a patient after inferior infarction with post-ischaemic posterior papillary muscle (in green on inHEART model). Red tag is application that resulted in steam pop. Vizigo sheath, DECANAV, and QDOT catheter visible. (3) Ventricular tachychardia ablation due to electrical storm. Patient after large inferior myocardial infarction. Bipolar voltage map (0.5–1.5 mV) of a large inferior substrate after myocardial infarction. Steam pop point is highlighted with orange halo around visitag, curved catheter below the mitral valve. DECANAV, PentaRay, and QDOT catheters (all Biosense Webster) are visible. (4) Arrhythmogenic right ventricular cardiomyopathy ablation below the lower part of the tricuspid valve. inHEART model in Glassmode in AP view with fibrofatty replacement substrate in brown. Red dot = ablation tag that resulted in steam pop. (5) Right anterior oblique view of a patient after inferior infarction with post-ischaemic posterior papillary muscle (in green on inHEART model). Red tag is application that resulted in steam pop. Vizigo sheath, PentaRay catheter, and QDOT catheter visible. Right side: Graphs during corresponding applications. Power in yellow, impedance in green, maximal thermocouple temperature in orange, and contact force in blue. In none of the graphs, there was a gradual impedance rise before the pop. (1) Absence of prior power titration. Absence of impedance spike during steam pop, due to lower sampling rate as described above. (2) Power titration (yellow arrow) due to insufficient cooling after increased irrigation. Impedance spike (green arrow) during steam pop and temperature drop. (3) Absence of prior power titration. Impedance spike (green arrow) during steam pop and temperature drop (orange arrow). (4) Power titration (yellow arrow) due to insufficient cooling after increased irrigation. Impedance spike (green arrow) during steam pop and temperature drop. (5) Power titration (yellow arrow) due to insufficient cooling after increased irrigation. Impedance spike (green arrow) during steam pop and temperature drop.

Figure 3

Micro-EGM signal quality during PVC, VT, and VF ablation. From left to right and top to bottom. Upper left: Posteroanterior view of activation map (CARTO) during the ablation of a posteroseptal RVOT PVC. QDOT demonstrates very nice fragmentation on micro-EGM (yellow arrow). Earliest activation was manually readapted towards first peak of micro-EGM activation. Premature ventricular complex was gone after 2.7 s QMODE 50 W ablation. Upper right: Posteroanterior view of inHEART model with inferior scar and clear CT channel. Within the CT channel, LAVA activity was found. At exactly the same location, similar EGM was found of the PentaRay catheter and the micro-electrodes of the QDOT catheter (yellow arrows). Lower panel: Trigger ablation for ventricular fibrillation. Upper ECG: dynamic LVOT PVC coupling as a sign of ischaemia. Middle telemetry: documented ventricular fibrillation due to early PVC within the vulnerable phase of the T-wave. Lower ECG: Absence of PVC, sinus rhythm. The earliest activity was first mapped using the OctaRay catheter (Biosense Webster) with good differentiation between sharp near-field activity (yellow arrow) and blunt far-field activity. Earliest activity was found in the left coronary cusp (LCC) and LVOT region. At the ablation site, subtle early fragmentation was seen during PVC and late fragmentation during sinus rhythm on the micro-electrodes.