Slow Pathway Radiofrequency Ablation Using Magnetic Navigation: A Description of Technique and Retrospective Case Analysis.

BACKGROUND: The Magnetic Navigation System (MNS) catheter was shown to be stable in the presence of significant cardiac wall motion and delivered more effective lesions compared to manual control. This stability could potentially make AV junctional re-entrant tachycardia (AVNRT) ablation safer. The aim of this study is to describe the method of mapping and ablation of AVNRT with MNS and 3-D electro-anatomical mapping system (CARTO, Biosense Webster, Diamond bar, CA, USA) anatomical mapping, with a view to improve the safety of ablation. METHODS: The method of precise mapping and ablation with MNS is described. Consecutive AVNRT cases (n=30) from 2012 January to 2015 November, in which magnetic navigation was used, are analysed. RESULTS: Ablation was successful in 27 (90%) out of 30 patients. In three cases, ablation was abandoned due to the proximity of the three-dimensional His image to the potential ablation site. No complications, including AV nodal injury, occurred. The distance from the nearest His position to successful ablation site in both LAO and RAO projections of CARTO images was 26.4±8.8 and 27±7.7mm respectively. Only in two (9%) patients, ablation needed to be extended superior to the plane of coronary sinus ostium, towards the His bundle region, to achieve slow pathway modification. CONCLUSION: AVNRT ablation with MNS allows for accurate mapping of the AV node and stable ablation at a safe distance, which could help avoid AV nodal injury. We recommend this modality for younger patients with AVNRT.

Ninety Seconds Could be the Optimal Duration for Ventricular Radiofrequency Ablation - Results From a Myocardial Phantom Model.

BACKGROUND: Shallow lesions could be the predominant factor affecting the efficacy of ventricular radiofrequency (RF) ablations. The objective of this study was to assess lesion dimensions and overheating in extended RF ablations up to 180seconds and compare with that of conventional 30seconds ablations. METHODS: The Navistar Thermocool irrigated catheter (Biosense Webster, CA, USA) was used in a previously validated myocardial phantom. Ablations were performed with 20W, 30W, 40W and 50W powers for 180seconds. The volume of lesion and overheating were measured at 530C and 800C isotherms respectively. RESULTS: A total of 110 RF lesions were analysed. The lesion depth increment when ablation was extended from the conventional 30seconds to 90seconds were 31.2±0.2, 33.6±0.6, 36.3±1.8% of that at 30seconds, respectively for powers 30W, 40W and 50W. During 30W ablations, at 90seconds the lesion width and depth were 95.4±1.2%, 91.8±1.6% respectively of the final dimensions at 180seconds. Similar proportions were observed for 40W and 50W. During 40W ablations, the volume of overheating was 113±6% and 184±11% higher at 90seconds and 180seconds respectively compared to that at 30seconds and was 142±9% and 194±9% for 50W ablations. CONCLUSION: Extending RF ablations up to 90seconds significantly increased the lesion depth (30-40%), however, overheating was present at 40W and 50W powers. Ablations beyond 90seconds provided little incremental value.

MELD3.0 is superior to MELDNa and MELD for prediction of mortality in patients with cirrhosis: An external validation in a multi-ethnic population.

Background and Aim: The model for end-stage liver disease (MELD) was updated to MELDNa and recently to MELD3.0 to predict survival of cirrhotic patients. We validated the prognostic performance of MELD3.0 and compared with MELDNa and MELD amongst cirrhotic inpatients. Methods: Demographical, clinical, biochemical, and survival data of cirrhotic inpatients in Singapore General Hospital (SGH) from 01 January 2018 to 31 December 2018, were studied retrospectively. Patients were followed up from first admission in 2018 until death or until 01 April 2023. Area under the receiver operating characteristic curves (AUROC) were computed for the discriminative effects of MELD3.0, MELDNa, and MELD to predict 30-, 90-, and 365-day mortalities. AUROC was compared with DeLong's test. The cutoff MELD3.0 score for patients at high risk of 30-day mortality was determined using Youden's Index. Survival curves of patients with MELD3.0 score above and below the cutoff were estimated with Kaplan-Meier method and compared with log-rank analysis. Results: Totally 862 patients were included (median age 71.0 years [interquartile range, IQR: 64.0-79.0], 65.4% males, 75.8% Chinese). Proportion of patients with Child-Turcotte-Pugh classes A/B/C were 55.5%/35.5%/9.0%. Median MELD3.0/MELDNa/MELD scores were 12.2 (IQR: 8.7-18.3)/11.0 (IQR: 8.0-17.5)/10.3 (IQR: 7.8-15.0). Median time of follow-up was 51.9 months (IQR: 8.5-59.6). The proportion of 30-/90-/365-day mortalities was 5.7%/13.2%/26.9%. AUROC of MELD3.0/MELDNa/MELD in predicting 30-, 90-, and 365-day mortalities, respectively, were 0.823/0.793/0.783, 0.754/0.724/0.707, 0.682/0.654/0.644 (P < 0.05). Optimal cutoff to predict 30-day mortality was MELD3.0 > 19 (sensitivity = 67.4%, specificity = 82.4%). Patients with MELD3.0 > 19, compared with patients with MELD3.0 ≤ 19, had shorter median time to death (98.0 days [IQR: 28.8-398.0] vs 390.0 days [IQR: 134.3-927.5]), and higher proportion of 30-day mortality (68.8% vs 43.0%) (P < 0.001). Conclusion: MELD3.0 performs better than MELDNa and MELD in predicting mortality in cirrhotic inpatients. MELD3.0 > 19 predicts higher 30-day mortality.