RESUMO
BACKGROUND: Successful ventricular arrhythmia (VA) ablation requires identification of functionally critical sites during contact mapping. Estimation of the peak frequency (PF) component of the EGM may improve correct near field (NF) annotation to identify circuit segments on the mapped surface. In turn, assessment of near- and far field (FF) EGMs may delineate the 3-dimensional path of a VT circuit. METHODOLOGY: A proprietary NF detection algorithm was applied retrospectively to scar-related re-entry VT maps and compared to manually reviewed maps employing first deflection (FDcorr) for VT activation maps and last deflection (LD) for substrate maps. VT isthmus location and characteristics mapped with FDcorr vs. NF were compared. Omnipolar low voltage areas, late activating areas and deceleration zones in LD vs NF substrate maps were compared. On substrate maps, PF estimation was compared between isthmus and bystander-sites. Activation mapping with entrainment and/or VT termination with RF ablation confirmed critical sites. RESULTS: 18 patients with high-density VT activation and substrate maps (55.6% ischemic) were included. NF detection correctly located critical parts of the circuit in 77.7% of the cases compared to manually reviewed VT maps as reference. In substrate maps NF detection identified deceleration zones in 88.8% of cases which overlapped with FDcorr VT isthmus in 72.2% compared to 83.3% overlap of DZ assessed by LD. Applied to substrate maps, PF as a stand-alone feature did not differentiate VT isthmus-sites from low voltage bystander-sites. Omnipolar voltage was significantly higher at isthmus-sites with longer EGM durations compared to low voltage bystander-sites. CONCLUSION: The NF algorithm may enable rapid high-density activation mapping of VT circuits in the near field of the mapped surface. Integrated assessment and combined analysis of near and far field EGMs could support characterisation of 3-dimensional VT circuits with intramural segments. For scar-related substrate mapping, PF as a stand-alone EGM feature did not enable the differentiation of functionally critical sites of the dominant VT from low voltage bystander sites in this cohort.
RESUMO
PURPOSE OF REVIEW: Percutaneous radiofrequency (RF) catheter ablation is an established strategy to prevent ventricular tachycardia (VT) recurrence and ICD shocks. Yet delivery of durable lesion sets by means of traditional unipolar radiofrequency ablation remains challenging, and left ventricular transmurality is rarely achieved. Failure to ablate and eliminate functionally relevant areas is particularly common in deep intramyocardial substrates, e.g. septal VT and cardiomyopathies. Here, we aim to give a practical-orientated overview of advanced and emerging RF ablation technologies to target these complex VT substrates. We summarize recent evidence in support of these technologies and share experiences from a tertiary VT centre to highlight important "hands-on" considerations for operators new to advanced RF ablation strategies. RECENT FINDINGS: A number of innovative and modified radiofrequency ablation approaches have been proposed to increase energy delivery to the myocardium and maximize RF lesion dimensions and depth. These include measures of impedance modulation, combinations of simultaneous unipolar ablations or true bipolar ablation, intramyocardial RF delivery via wires or extendable RF needles and investigational linear or spherical catheter designs. Recent new clinical evidence for the efficacy and safety of these investigational technologies and strategies merits a re-evaluation of their role and clinic application for percutaneous VT ablations. Complexity of substrates targeted with percutaneous VT ablation is increasing and requires detailed preprocedural imaging to characterize the substrate to inform the procedural approach and selection of ablation technology. Depending on local experience, options for additional and/or complementary interventional treatments should be considered upfront in challenging substrates to improve the success rates of index procedures. Advanced RF technologies available for clinical VT ablations include impedance modulation via hypotonic irrigation or additional dispersive patches and simultaneous unipolar as well as true bipolar ablation. Promising investigational RF technologies involve an extendable needle RF catheter, intramyocardial RF delivery over intentionally perforated wires as well as a variety of innovative ablation catheter designs including multipolar linear, spherical and partially insulated ablation catheters.