Early and long-term outcomes after manual and remote magnetic navigation-guided catheter ablation for ventricular tachycardia.

Aims: Remote magnetic navigation (RMN) is a safe and effective means of performing ventricular tachycardia (VT) ablation. It may have advantages over manual catheter ablation due to ease of manoeuvrability and catheter stability. We sought to compare the safety and efficacy of RMN vs. manual VT ablation. Methods and results: Retrospective study of procedural outcomes of 139 consecutive VT ablation procedures (69 RMN, 70 manual ablation) in 113 patients between 2009 and 2015 was performed. Remote magnetic navigation was associated with overall higher acute procedural success (80% vs. 60%, P = 0.01), with a trend to fewer major complications (3% vs. 9% P = 0.09). Seventy-nine patients were followed up for a median of 17.0 [interquartile range (IQR) 3.0-41.0] months for the RMN group and 15.5 (IQR 6.5-30.0) months for manual ablation group. In the ischaemic cardiomyopathy subgroup, RMN was associated with longer survival from the composite endpoint of VT recurrence leading to defibrillator shock, re-hospitalization or repeat catheter ablation and all-cause mortality; single-procedure adjusted hazard ratio (HR) 0.240 (95% CI 0.070-0.821) P = 0.023, multi-procedure HR 0.170 (95% CI 0.046-0.632) P = 0.002. In patients with implanted defibrillators, multi-procedure VT-free survival was superior with RMN, HR 0.199 (95% CI 0.060-0.657) P = 0.003. Conclusion: Remote magnetic navigation may improve clinical outcomes after catheter ablation of VT in patients with ischaemic cardiomyopathy. Further prospective clinical studies are required to confirm these findings.

Five seconds of 50-60 W radio frequency atrial ablations were transmural and safe: an in vitro mechanistic assessment and force-controlled in vivo validation.

AIMS: Longer procedural time is associated with complications in radiofrequency atrial fibrillation ablation. We sought to reduce ablation time and thereby potentially reduce complications. The aim was to compare the dimensions and complications of 40 W/30 s setting to that of high-power ablations (50-80 W) for 5 s in the in vitro and in vivo models. METHODS AND RESULTS: In vitro ablations-40 W/30 s were compared with 40-80 W powers for 5 s. In vivo ablations-40 W/30 s were compared with 50-80 W powers for 5 s. All in vivo ablations were performed with 10 g contact force and 30 mL/min irrigation rate. Steam pops and depth of lung lesions identified post-mortem were noted as complications. A total of 72 lesions on the non-trabeculated part of right atrium were performed in 10 Ovine. All in vitro ablations except for the 40 W/5 s setting achieved the critical lesion depth of 2 mm. For in vivo ablations, all lesions were transmural, and the lesion depths for the settings of 40 W/30 s, 50 W/5 s, 60 W/5 s, 70 W/5 s, and 80 W/5 s were 2.2 ± 0.5, 2.3 ± 0.5, 2.1 ± 0.4, 2.0 ± 0.3, and 2.3 ± 0.7 mm, respectively. The lesion depths of short-duration ablations were similar to that of the conventional ablation. Steam pops occurred in the ablation settings of 40 W/30 s and 80 W/5 s in 8 and 11% of ablations, respectively. Complications were absent in short-duration ablations of 50 and 60 W. CONCLUSION: High-power, short-duration atrial ablation was as safe and effective as the conventional ablation. Compared with the conventional 40 W/30 s setting, 50 and 60 W ablation for 5 s achieved transmurality and had fewer complications.

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.

Influence of BMI on inducible ventricular tachycardia and mortality in patients with myocardial infarction and left ventricular dysfunction: The obesity paradox.

BACKGROUND: There is little known about the influence of obesity on ventricular electrical remodelling after myocardial infarction. The aim of our study was to assess the relationship between body mass index (BMI) and the primary outcome of inducible-VT and the secondary outcome of all-cause mortality in consecutive patients who presented with ST elevation myocardial infarction (STEMI) and LV-dysfunction (LVEF ≤ 40%). METHODS AND RESULTS: Consecutive patients (n = 380) with STEMI and LV-dysfunction (LVEF ≤ 40%) underwent electrophysiological (EP) studies for risk-stratification. Inducible-VT ≥200 ms cycle-length (CL) with one to four extra-stimuli (ES) was considered abnormal. Patients were classified according their body mass index (BMI) to be normal (18.5-24.9), overweight (25-29.9) or obese (>30). The primary outcome of inducible-VT occurred in 42.7%, 21.5% and 21% of normal weight, overweight and obese patients respectively (p < 0.001). When adjusting for ejection-fraction, hypertension and triple-vessel-disease, normal BMI remained a significant predictor for inducible-VT. All-cause mortality was higher in patients with normal weight (12.8%) when compared to overweight (3.2%) and obese (3.8%) patients (p = 0.002) and was mainly driven by increased cardiac-death (6.8%, 1.9% and 1.9% in normal, overweight and obese patients respectively, p = 0.05). After adjusting for age, EF, and hypertension, normal BMI remained a significant predictor of mortality. CONCLUSION: In patients presenting with STEMI and LV-dysfunction, BMI appears to be a significant predictor of inducible-VT and all-cause mortality, with worse outcomes for those with normal weight, when compared to overweight or obese individuals. These findings are consistent with the obesity-paradox.

Influence of Intramyocardial Adipose Tissue on the Accuracy of Endocardial Contact Mapping of the Chronic Myocardial Infarction Substrate.

BACKGROUND: Recent studies have demonstrated that intramyocardial adipose tissue (IMAT) may contribute to ventricular electrophysiological remodeling in patients with chronic myocardial infarction. Using an ovine model of myocardial infarction, we aimed to determine the influence of IMAT on scar tissue identification during endocardial contact mapping and optimal voltage-based mapping criteria for defining IMAT dense regions. METHOD AND RESULTS: In 7 sheep, left ventricular endocardial and transmural mapping was performed 84 weeks (15-111 weeks) post-myocardial infarction. Spearman rank correlation coefficient was used to assess the relationship between endocardial contact electrogram amplitude and histological composition of myocardium. Receiver operator characteristic curves were used to derive optimal electrogram thresholds for IMAT delineation during endocardial mapping and to describe the use of endocardial mapping for delineation of IMAT dense regions within scar. Endocardial electrogram amplitude correlated significantly with IMAT (unipolar r=-0.48±0.12, P<0.001; bipolar r=-0.45±0.22, P=0.04) but not collagen (unipolar r=-0.36±0.24, P=0.13; bipolar r=-0.43±0.31, P=0.16). IMAT dense regions of myocardium reliably identified using endocardial mapping with thresholds of <3.7 and <0.6 mV, respectively, for unipolar, bipolar, and combined modalities (single modality area under the curve=0.80, P<0.001; combined modality area under the curve=0.84, P<0.001). Unipolar mapping using optimal thresholding remained significantly reliable (area under the curve=0.76, P<0.001) during mapping of IMAT, confined to putative scar border zones (bipolar amplitude, 0.5-1.5 mV). CONCLUSIONS: These novel findings enhance our understanding of the confounding influence of IMAT on endocardial scar mapping. Combined bipolar and unipolar voltage mapping using optimal thresholds may be useful for delineating IMAT dense regions of myocardium, in postinfarct cardiomyopathy.