竹田 和也

ABSTRACT Background T‐wave amplitude variability (TAV), a marker of beat‐to‐beat ventricular repolarization instability, has been proposed as a potential risk marker for adverse cardiovascular outcomes, but its prognostic value remains unclear. Objectives This meta‐analysis aimed to quantitatively synthesize evidence on the association between elevated TAV and adverse cardiovascular outcomes. Methods A systematic literature search of PubMed, Embase, and the Cochrane Library was conducted. Observational studies reporting adjusted effect estimates for the association between TAV and adverse cardiovascular outcomes were included, and separate meta‐analyzes were conducted according to effect measures (hazard ratios [HRs] or odds ratios [ORs]) and exposure definition. Effect estimates were pooled using a random‐effects model. Statistical heterogeneity was assessed using the Q statistic and I ² . Results Seven studies involving 1366 patients were included. HR‐based analyzes ( n  = 3) showed that elevated TAV was significantly associated with an increased risk of adverse outcomes, including mortality and ventricular tachyarrhythmias (pooled HR 2.51, 95% CI 1.57–4.00; I ²  = 7%). In contrast, OR‐based analyzes showed no statistically significant association between TAV and ventricular tachyarrhythmias, whether evaluated as categorical (high vs. low TAV: pooled OR 3.82, 95% CI 0.87–16.84; I ²  = 75%) or continuous variable (per 1–μV increase: pooled OR 1.11, 95% CI 0.94–1.30; I ²  = 70%). Conclusion Elevated TAV is associated with an increased risk of adverse cardiovascular outcomes in HR‐based analyzes, supporting its potential utility as a marker of repolarization instability for longitudinal risk stratification. In contrast, its association with ventricular tachyarrhythmias was not significant in OR‐based analyzes, which showed substantial heterogeneity. Trial Registration: PROSPERO: CRD420251171782.

BACKGROUND: Breast magnetic resonance imaging (MRI) assesses signal intensity changes across sequential image series (kinetic curves). Motion artifacts are common and often degrade image quality. However, the optimal patient positioning to minimize motion during breast MRI remains unclear. This study aimed to identify the most effective arm-positioning method for reducing motion artifacts during breast MRI. METHODS: Six female volunteers underwent MRI at seven time points using enhanced T1 high-resolution isotropic volume excitation, a three-dimensional T1-weighted gradient-echo sequence with fat suppression. Each phase lasted 60 s and comprised seven serial images. Three arm-positions were tested: both-arms-raised, right-arm-raised, and both-arms-down. Motion was assessed using the visual evaluation score (VES) and the distance discordance metric (DDM). RESULTS: VES results were higher with both-arms-raised (2.52 ± 0.43; median: 2.60) than with arms-down (2.39 ± 0.61; median: 2.40) or the right-arm-raised (2.33 ± 0.57; median: 2.40). A significant difference in VES was observed between the both-arms-raised and right-arm-raised groups (P = .04). DDM values were lowest with both-arms-raised (1.02 ± 0.64; median: 0.85), followed by arm-down (1.89 ± 1.19; median: 1.50) and right-arm raised (1.65 ± 0.98; median: 1.56). Significant differences in DDM were observed between the both-arms-raised position and the other two positions (P < .05 and P < .001, respectively). CONCLUSION: Positioning patients with both-arms-raised effectively minimized motion-related artifacts during breast MRI. Conversely, the right-arm-raised position was associated with increased artifacts and should be avoided to maintain image quality.