HPSD RF applications resulted in similar lesion volumes but significantly different lesion geometries when compared with standard setting RF applications.

This novel catheter gives reproducible recordings of local impedance, which are dependent on scar level. Absolute LI drop, and also percentage drop, on ablation may give an indication of tissue contact and subsequent effective lesion formation.

BACKGROUND Activation mapping using noninvasive electrocardiographic imaging (ECGi) has recently been used to describe the physiology of different cardiac abnormalities. These descriptions differ from prior invasive studies, and both methods have not been thoroughly confronted in a clinical setting.OBJECTIVE The goal of the present study was to provide validation of noninvasive activation mapping in a clinical setting through direct confrontation with invasive epicardial contact measures.METHODS Fifty-nine maps were obtained in 55 patients and aligned on a common geometry. Nearest-neighbor interpolation was used to avoid map smoothing. Quantitative comparison was performed by computing between-map correlation coefficients and absolute activation time errors. RESULTSThe mean activation time error was 20.4 6 8.6 ms, and the between-map correlation was poor (0.03 6 0.43). The results suggested high interpatient variability (correlation 20.68 to 0.82), wide QRS patterns, and paced rhythms demonstrating significantly better mean correlation (0.68 6 0.17). Errors were greater in scarred regions (21.9 6 10.8 ms vs 17.5 6 6.7 ms; P , .01). Fewer epicardial breakthroughs were imaged using noninvasive mapping (1.3 6 0.5 vs 2.3 6 0.7; P , .01). Primary breakthrough locations were imaged 75.7 6 38.1 mm apart. Lines of conduction block (jumps of 50 ms between contiguous points) due to structural anomalies were recorded in 27 of 59 contact maps and were not visualized at these same sites noninvasively. Instead, artificial lines appeared in 33 of 59 noninvasive maps in regions of reduced bipolar voltage amplitudes (P 5 .03). An in silico model confirms these artificial constructs.CONCLUSION Overall, agreement of ECGi activation mapping and contact mapping is poor and heterogeneous. The between-map correlation is good for wide QRS patterns. Lines of block and epicardial breakthrough sites imaged using ECGi are inaccurate. Further work is required to improve the accuracy of the technique.

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Background - Achieving bidirectional mitral isthmus (MI) block using radiofrequency catheter ablation (RFCA) alone is challenging, and MI reconnection is common. Adjunctive vein of Marshall (VOM) ethanol infusion (VOM-Et) can facilitate acute MI block. However, little is known regarding its long-term success. This study sought to evaluate the impact of adjunctive VOM-Et on MI block achievement and durability compared to RFCA alone. Methods - Patients undergoing a first attempt of posterior MI ablation were grouped according to their MI block index strategy: adjunctive VOM-Et and RFCA alone. Rates of acute MI block and MI reconnection observed during repeat procedures were compared between the two groups. Results - The VOM-Et group consisted of 152 patients (63.8 ± 9.4 years) undergoing adjunctive VOM-Et for MI block. The RFCA group consisted of 110 patients (60.9 ± 9.2 years) undergoing MI ablation using RFCA alone. Acute MI block was more frequently achieved in the VOM-Et group (98.7% [150/152] vs. 63.6% [70/110]; p < 0.001) with shorter RFCA duration (5.00 [3.00-7.00] vs. 19.0 [13.6-22.0] mins; p < 0.001). Of the 220 patients with MI block achieved during the index procedure, 81 underwent a repeat procedure during follow-up (VOM-Et group: 23.3% [35/150] vs. RFCA group: 65.7% [46/70], respectively; p < 0.001). A significantly greater number of patients exhibited durable MI block in the VOM-Et group (62.9% [22/35] vs. 32.6% [15/46], respectively; p = 0.008). Conclusions - Beyond facilitating acute MI block, VOM-Et is associated with greater lesion durability as evidenced by higher rates of MI block during repeat procedures.

Background Ventricular tachycardia with structural heart disease is dependent on re-entry within scar regions. We set out to assess the VT circuit in greater detail than has hitherto been possible, using ultra highdensity mapping. Methods All ultra high-density mapping guided ventricular tachycardia ablation cases from six high-volume European centres were assessed. Maps were analysed offline to generate activation maps of tachycardia circuits. Topography, conduction velocity and voltage of the VT circuit were analyzed in complete maps. Results Thirty-six tachycardias in 31 patients were identified, 29 male and 27 ischaemic. VT circuits and isthmuses were complex, eleven were single-loop and 25 double-loop; three had two entrances, five had two exits and 15 had dead ends of activation. Isthmuses were defined by barriers which included anatomical obstacles, lines of complete block and slow conduction (in 27/36 isthmuses). Median conduction velocity was 0.08m/s in entrance zones, 0.29m/s in isthmus regions (p<0.001), and 0.11m/s in exit regions (p=0.002). Median local voltage in the isthmus was 0.12mV during tachycardia and 0.06mV in paced/sinus rhythm. Two circuits were identifiable in five patients. The median timing of activation was 16% of diastole in entrances, 47% in the mid isthmus, and 77% in exits. Conclusions VT circuits identified were complex, some of them having multiple entrances, exits and dead ends. The barriers to conduction in the isthmus appear to be partly functional in 75% of circuits. 3 Conduction velocity in the VT isthmus slowed at isthmus entrances and exits, when compared with the mid isthmus. Isthmus voltage is often higher in VT than in sinus or paced rhythms.

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Aims Extra-atrial injury can cause complications after catheter ablation for atrial fibrillation (AF). Pulsed field ablation (PFA) has generated preclinical data suggesting that it selectively targets the myocardium. We sought to characterize extra-atrial injuries after pulmonary vein isolation (PVI) between PFA and thermal ablation methods. Methods and results Cardiac magnetic resonance (CMR) imaging was performed before, acutely (&lt;3 h) and 3 months post-ablation in 41 paroxysmal AF patients undergoing PVI with PFA (N = 18, Farapulse) or thermal methods (N = 23, 16 radiofrequency, 7 cryoballoon). Oesophageal and aortic injuries were assessed by using late gadolinium-enhanced (LGE) imaging. Phrenic nerve injuries were assessed from diaphragmatic motion on intra-procedural fluoroscopy. Baseline CMR showed no abnormality on the oesophagus or aorta. During ablation procedures, no patient showed phrenic palsy. Acutely, thermal methods induced high rates of oesophageal lesions (43%), all observed in patients showing direct contact between the oesophagus and the ablation sites. In contrast, oesophageal lesions were observed in no patient ablated with PFA (0%, P &lt; 0.001 vs. thermal methods), despite similar rates of direct contact between the oesophagus and the ablation sites (P = 0.41). Acute lesions were detected on CMR on the descending aorta in 10/23 (43%) after thermal ablation, and in 6/18 (33%) after PFA (P = 0.52). CMR at 3 months showed a complete resolution of oesophageal and aortic LGE in all patients. No patient showed clinical complications. Conclusion PFA does not induce any signs of oesophageal injury on CMR after PVI. Due to its tissue selectivity, PFA may improve safety for catheter ablation of AF.