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BackgroundAlthough ablation energy (AE) and force-time integral (FTI) are well-known active predictors of lesion characteristics, these parameters do not reflect passive tissue reactions during ablation, which may instead be represented by drops in local impedance (LI). This study aimed to investigate if additional LI data improves predicting lesion characteristics and steam pops.MethodsRF applications at a range of powers (30 W, 40 W, and 50 W), contact forces (8 g, 15 g, 25 g, and 35 g), and durations (10–180 s) using perpendicular/parallel catheter orientations were performed in excised porcine hearts (N = 30). The correlation between AE, FTI, and lesion characteristics was examined, and the impact of LI (%LI drop (%LID) defined by the ΔLI divided by the initial LI) was additionally assessed.ResultsThree hundred seventy-five lesions without steam pops were examined. Ablation energy (W × s) and FTI (g × s) showed a positive correlation with lesion depth (ρ = 0.824:P < 0.0001 and ρ = 0.708:P < 0.0001), surface area (ρ = 0.507:P < 0.0001 and ρ = 0.562:P < 0.0001), and volume (ρ = 0.807:P < 0.0001 and ρ = 0.685:P < 0.0001). %LID also showed a positive correlation individually with lesion depth (ρ = 0.643:P < 0.0001), surface area (ρ = 0.547:P < 0.0001), and volume (ρ = 0.733:P < 0.0001). However, the combined indices of AE × %LID (AE multiplied by %LID) and FTI × %LID (FTI multiplied by %LID) provided significantly stronger correlation with lesion depth (ρ = 0.834:P < 0.0001 and ρ = 0.809:P < 0.0001), surface area (ρ = 0.529:P < 0.0001 and ρ = 0.656:P < 0.0001), and volume (ρ = 0.864:P < 0.0001 and ρ = 0.838:P < 0.0001). This tendency was observed regardless of the catheter placement (parallel/perpendicular). AE (P = 0.02) and %LID (P = 0.002) independently remained as significant predictors to predict steam pops (N = 27). However, the AE × %LID did not increase the predictive power of steam pops compared to the AE alone.ConclusionLI, when combined with conventional parameters (AE and FTI), may provide stronger correlation with lesion characteristics.

Abstract PurposeThe size of the distal electrode and the method of measuring local impedance (LI) are different between the IntellaNav MiFi-OI™ (MiFi-OI) and IntellaNav STABLE POINT™ (SP) catheters. We investigated the impact of these differences on LI, efficacy, and safety of radiofrequency (RF) applications.MethodsRF applications at a range of powers (30 W, 40 W, and 50 W), contact forces (10 g and 20 g), and durations (10–120 s) were performed in excised porcine hearts (N = 48). LI variation was defined by δLI-drop (= initial LI − post-RF LI) and %LI-drop (= δLI-drop/initial LI) × 100, and the relationship between lesion characteristics and LI variation was compared.Results A total of 576 lesions were examined. Although absolute δLI-drop during RF applications was significantly larger for the SP than MiFi-OI catheter (47[31–65]ohm for SP vs 37[24–51]ohm for MiFi-OI, p < 0.0001), %LI-drop was similar (23.3 [15.5–30.6]% in SP vs 24.9[17.3–32.5]% in MiFi-OI, p = 0.10). Although lesions produced by both catheters were similarly correlated with LI variation, the SP catheter produced generally larger lesions (depth; 5.0 [3.7–6.1]mm vs 4.7 [3.3–6.0]mm, p = 0.06; surface areas, 46.9 [36.8–58.8]mm2 vs 44.7 [34.3–55.5]mm2, p = 0.02; volume, 321 [165–533]mm3 vs 265[141–471]mm3, p = 0.02). Steam pops were similarly observed with both catheters. In both catheters, %LI-drop was superior to δLI-drop in correlation to lesion size (p < 0.0001) and in predicting steam pops (p < 0.01).ConclusionsAlthough no difference in safety profile is observed between MiFi-OI and SP catheters, the SP catheter produces larger lesions. %LI-drop is superior to δLI-drop in correlation to lesion size and in predicting steam pops as well as in normalizing the difference between catheters.

Abstract PurposeLocal impedance (LI) measurement from an ablation catheter is useful in predicting lesion size and acute success of pulmonary vein isolation (PVI). The LI variation can be described by absolute LI drop (ΔLID) or ΔLID/initial LI (%LID). We evaluated the utility of these parameters in predicting acute lesion durability during PVI using a novel catheter capable of measuring both LI and contact force (CF).MethodsPVI with a targeted CF, power, and duration was performed in 23 consecutive patients with paroxysmal atrial fibrillation. LI was blinded to operators during ablation. Parameters for each RF application were collected and compared for acute successful lesions and gaps.ResultsA total of 1633 RF applications including 97 (5.9%) gap lesions were analyzed. Successful lesions were more frequently observed at non-carinal sites and those with higher contact force, FTI, initial LI, and larger variation of LI and generator impedance (GI). Multivariate analysis demonstrated that absolute GI drop (ΔGID) [OR 1.09 (1.04–1.15), p < 0.001], ΔLID [1.12 (1.09–1.16), p < 0.001], ΔGID/initial GI (%GID) [OR 1.04 (1.01–1.07), p = 0.01], and %LID [OR 1.15 (1.12–1.28), p < 0.001] were significantly associated with successful lesions, and carinal site [OR 0.15(0.09–0.24), p < 0.001] was significantly related to gaps. Both ΔLID and %LID equally predicted the acute durability of lesions during PVI. ΔLID ≥ 24Ω and %LID ≥ 15% at the carina, and ΔLID ≥ 21Ω and %LID ≥ 14% at non-carinal sites significantly predicted acute successful lesions with negative predictive values of 93–99%.ConclusionsBoth ΔLID and %LID were equally useful in predicting acute successful lesions during PVI. Larger cut-off values should be applied to carinal sites.

INTRODUCTION: Myelolipoma is a benign tumor composed of mature adipose tissue and hematopoietic elements that typically arises in the adrenal glands, and involvement of the anterior abdominal region is extremely uncommon. We report a rare case of myelolipoma arising in the subxiphoid preperitoneal region adjacent to the site where a sternum-lifting device had been placed during previous surgery.CASE PRESENTATION: A 62-year-old man had undergone extended thymectomy for thymoma associated with myasthenia gravis at the age of 39. The procedure was performed via bilateral video-assisted thoracoscopic surgery using a sternum-lifting technique. The tumor was classified as Masaoka stage III, and postoperative radiotherapy was administered. No recurrence was observed during 13 years of follow-up. Ten years after completion of follow-up, CT performed for an unrelated condition incidentally revealed a slowly enlarging 65 × 40-mm mass in the preperitoneal space, adjacent to the previous surgical site where a sternum-lifting device had been placed. MRI demonstrated a fat-containing component within the lesion, and the differential diagnosis included liposarcoma and teratoma. Complete surgical resection was therefore planned. A midline incision extending caudally from the xiphoid process was made, and en bloc resection of the tumor with the involved peritoneum was performed via laparotomy. Histopathological examination revealed mature adipose tissue admixed with hematopoietic elements, confirming the diagnosis of myelolipoma.CONCLUSIONS: This unique case of extra-adrenal myelolipoma highlights the importance of MRI-based qualitative assessment for tumors arising at unusual sites and underscores the need to include extra-adrenal myelolipoma in the differential diagnosis of fat-containing lesions occurring at previous surgical sites.

Background The optimal extent of lymph node dissection (LND) in early‐stage non–small cell lung cancer (NSCLC) remains controversial. This study aimed to compare perioperative and oncological outcomes between lobe‐specific LND (LSD) and systematic LND (SND) in patients with clinical stage I NSCLC based on the 8th edition of the TNM classification. Methods We retrospectively analyzed 390 patients with clinical stage I NSCLC who underwent lobectomy with LND between 2010 and 2020. Patients with tumors in the right middle lobe or left lingular segment were excluded. Propensity score matching (PSM; 1:1 nearest‐neighbor matching) was performed using clinical and radiological covariates, yielding 140 matched patients in each group. Perioperative outcomes, postoperative complications (Clavien–Dindo grade ≥ II, with postoperative pneumonitis assessed according to CTCAE version 5.0), overall survival (OS), relapse‐free survival (RFS), and recurrence patterns were compared. Results After PSM, the LSD group had significantly shorter operative time, less blood loss, and shorter durations of chest tube placement and postoperative hospital stay than the SND group (all p < 0.05). Postoperative supraventricular tachyarrhythmia occurred more frequently in the SND group (0.7% vs. 7.1%, p = 0.006), whereas other complications were comparable. There were no significant differences in OS or RFS before or after PSM. Recurrence rates and patterns, including ipsilateral lymph node recurrence, were comparable. Conclusions LSD appears to be an oncologically valid and less invasive alternative to SND in patients with clinical stage I NSCLC. LSD may reduce surgical invasiveness and postoperative morbidity without compromising survival or increasing the risk of recurrence. In this propensity score‐matched study of clinical stage I non‐small cell lung cancer, lobe‐specific lymph node dissection achieved comparable overall and relapse‐free survival to systematic lymph node dissection while reducing operative invasiveness and postoperative supraventricular tachyarrhythmia.