Evaluation of a real-time magnetic resonance imaging-guided electrophysiology system for structural and electrophysiological ventricular tachycardia substrate assessment.

AIMS: Potential advantages of real-time magnetic resonance imaging (MRI)-guided electrophysiology (MR-EP) include contemporaneous three-dimensional substrate assessment at the time of intervention, improved procedural guidance, and ablation lesion assessment. We evaluated a novel real-time MR-EP system to perform endocardial voltage mapping and assessment of delayed conduction in a porcine ischaemia-reperfusion model. METHODS AND RESULTS: Sites of low voltage and slow conduction identified using the system were registered and compared to regions of late gadolinium enhancement (LGE) on MRI. The Sorensen-Dice similarity coefficient (DSC) between LGE scar maps and voltage maps was computed on a nodal basis. A total of 445 electrograms were recorded in sinus rhythm (range: 30-186) using the MR-EP system including 138 electrograms from LGE regions. Pacing captured at 103 sites; 47 (45.6%) sites had a stimulus-to-QRS (S-QRS) delay of ≥40 ms. Using conventional (0.5-1.5 mV) bipolar voltage thresholds, the sensitivity and specificity of voltage mapping using the MR-EP system to identify MR-derived LGE was 57% and 96%, respectively. Voltage mapping had a better predictive ability in detecting LGE compared to S-QRS measurements using this system (area under curve: 0.907 vs. 0.840). Using an electrical threshold of 1.5 mV to define abnormal myocardium, the total DSC, scar DSC, and normal myocardium DSC between voltage maps and LGE scar maps was 79.0 ± 6.0%, 35.0 ± 10.1%, and 90.4 ± 8.6%, respectively. CONCLUSION: Low-voltage zones and regions of delayed conduction determined using a real-time MR-EP system are moderately associated with LGE areas identified on MRI.

Voltage and pace-capture mapping of linear ablation lesions overestimates chronic ablation gap size.

Aims: Conducting gaps in lesion sets are a major reason for failure of ablation procedures. Voltage mapping and pace-capture have been proposed for intra-procedural identification of gaps. We aimed to compare gap size measured acutely and chronically post-ablation to macroscopic gap size in a porcine model. Methods and results: Intercaval linear ablation was performed in eight Göttingen minipigs with a deliberate gap of ∼5 mm left in the ablation line. Gap size was measured by interpolating ablation contact force values between ablation tags and thresholding at a low force cut-off of 5 g. Bipolar voltage mapping and pace-capture mapping along the length of the line were performed immediately, and at 2 months, post-ablation. Animals were euthanized and gap sizes were measured macroscopically. Voltage thresholds to define scar were determined by receiver operating characteristic analysis as <0.56 mV (acutely) and <0.62 mV (chronically). Taking the macroscopic gap size as gold standard, error in gap measurements were determined for voltage, pace-capture, and ablation contact force maps. All modalities overestimated chronic gap size, by 1.4 ± 2.0 mm (ablation contact force map), 5.1 ± 3.4 mm (pace-capture), and 9.5 ± 3.8 mm (voltage mapping). Error on ablation contact force map gap measurements were significantly less than for voltage mapping (P = 0.003, Tukey's multiple comparisons test). Chronically, voltage mapping and pace-capture mapping overestimated macroscopic gap size by 11.9 ± 3.7 and 9.8 ± 3.5 mm, respectively. Conclusion: Bipolar voltage and pace-capture mapping overestimate the size of chronic gap formation in linear ablation lesions. The most accurate estimation of chronic gap size was achieved by analysis of catheter-myocardium contact force during ablation.

Epicardial electroanatomical mapping, radiofrequency ablation, and lesion imaging in the porcine left ventricle under real-time magnetic resonance imaging guidance-an in vivo feasibility study.

Aims: Magnetic resonance imaging (MRI) is the gold standard for defining myocardial substrate in 3D and can be used to guide ventricular tachycardia ablation. We describe the feasibility of using a prototype magnetic resonance-guided electrophysiology (MR-EP) system in a pre-clinical model to perform real-time MRI-guided epicardial mapping, ablation, and lesion imaging with active catheter tracking. Methods and results: Experiments were performed in vivo in pigs (n = 6) using an MR-EP guidance system research prototype (Siemens Healthcare) with an irrigated ablation catheter (Vision-MR, Imricor) and a dedicated electrophysiology recording system (Advantage-MR, Imricor). Following epicardial access, local activation and voltage maps were acquired, and targeted radiofrequency (RF) ablation lesions were delivered. Ablation lesions were visualized in real time during RF delivery using MR-thermometry and dosimetry. Hyper-acute and acute assessment of ablation lesions was also performed using native T1 mapping and late-gadolinium enhancement (LGE), respectively. High-quality epicardial bipolar electrograms were recorded with a signal-to-noise ratio of greater than 10:1 for a signal of 1.5 mV. During epicardial ablation, localized temperature elevation could be visualized with a maximum temperature rise of 35 °C within 2 mm of the catheter tip relative to remote myocardium. Decreased native T1 times were observed (882 ± 107 ms) in the lesion core 3-5 min after lesion delivery and relative location of lesions matched well to LGE. There was a good correlation between ablation lesion site on the iCMR platform and autopsy. Conclusion: The MR-EP system was able to successfully acquire epicardial voltage and activation maps in swine, deliver, and visualize ablation lesions, demonstrating feasibility for intraprocedural guidance and real-time assessment of ablation injury.

Outcomes of adjuvant chemoradiotherapy after a radical gastrectomy and a D2 node dissection for gastric adenocarcinoma.

PURPOSE: Intergroup 0116 (INT-0116) established adjuvant chemoradiation as the standard of care for resected high-risk adenocarcinoma of the stomach in the United States. However, adjuvant chemoradiation remains controversial in many parts of Asia and Europe, where patients tend to undergo a more thorough D2 dissection. In INT-0116, 90% of patients had a limited or inadequate node dissection (D0 or D1). Also, 17% of patients in the chemoradiation arm had to discontinue treatment because of toxicities. The objectives of this retrospective study are to report the clinical outcomes of a cohort of patients who were mostly treated with a D2 node dissection and received adjuvant chemoradiation as per INT-0116, and the toxicities of chemoradiation in the context of more aggressive surgery. METHODS: After the results of INT-0116 became apparent, we adopted an institutional policy whereby patients who would otherwise fit the inclusion criteria of INT-0116 received adjuvant chemoradiation. Between March 1999 and November 2004, 70 consecutive patients with pathologic stage T3, T4, or node-positive disease were treated according to the chemoradiation arm of INT-0116. Patients received intravenous 5-fluorouracil 425 mg/m and leucovorin 20 mg/m in cycles 1, 3, and 4. Concurrent chemoradiation was given in cycle 2 and consisted of bolus 5-fluorouracil and leucovorin and radiotherapy (45 Gy over 25 fractions in 5 weeks). All patients were operated on by dedicated Japan-trained Surgical Oncologists. RESULTS: Sixty-seven patients (96%) had a D2 nodal dissection. Sixty-five patients (93%) had negative pathologic margins (R0 resection) and 5 (7%) had microscopically involved margins (R1 resection). The median follow-up was 27 months (range, 10.1-60.3). The 3-year overall survival, disease-free survival, and local control were 60.6%, 54.1%, and 84.3%, respectively. Of the 30 patients who relapsed, 5 (17%) had isolated locoregional recurrences only. The National Cancer Institute--Common Terminology Criteria version 3.0 acute grade 3 or 4 gastrointestinal and hematological toxicity rates were 15.7% and 4.3%, respectively. Toxicities led to chemotherapy dose-reductions in 18 patients and dose-delay in 19 patients. Including chemotherapy dose-reductions and delays, 66 patients (94%) completed the entire chemoradiation regimen. There were no toxicity-related deaths. CONCLUSION: In our cohort of 70 patients who had a more thorough D2 node dissection, adjuvant chemoradiation was well tolerated with acceptable toxicities and reasonable tumor control.

Efficacy of an integrated continuing medical education (CME) and quality improvement (QI) program on radiation oncologist (RO) clinical practice.

PURPOSE: There has been little radiation oncologist (RO)-specific research in continuing medical education (CME) or quality improvement (QI) program efficacy. Our aim was to evaluate a CME/QI program for changes in RO behavior, performance, and adherence to department protocols/studies over the first 12 months of the program. METHODS AND MATERIALS: The CME/QI program combined chart audit with feedback (C-AWF), simulation review AWF (SR-AWF), reminder checklists, and targeted CME tutorials. Between April 2003 and March 2004, management of 75 patients was evaluated by chart audit with feedback (C-AWF) and 178 patients via simulation review audit (SR-AWF) using a validated instrument. Scores were presented, and case management was discussed with individualized educational feedback. RO behavior and performance was compared over the first year of the program. RESULTS: Comparing the first and second 6 months, there was a significant improvement in mean behavior (12.7-13.6 of 14, p = 0.0005) and RO performance (7.6-7.9 of 8, p = 0.018) scores. Protocol/study adherence significantly improved from 90.3% to 96.6% (p = 0.005). A total of 50 actions were generated, including the identification of learning needs to direct CME tutorials, the systematic change of suboptimal RO practice, and the alteration of deficient management of 3% of patients audited during the program. CONCLUSION: An integrated CME/QI program combining C-AWF, SR-AWF, QI reminders, and targeted CME tutorials effectively improved targeted RO behavior and performance over a 12-month period. There was a corresponding increase in departmental protocol and study adherence.