Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA; Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.
J Cardiovasc Magn Reson. 2024 Summer;26(1):101009. doi: 10.1016/j.jocmr.2024.101009. Epub 2024 Feb 10.
The 12-lead electrocardiogram (ECG) is a standard diagnostic tool for monitoring cardiac ischemia and heart rhythm during cardiac interventional procedures and stress testing. These procedures can benefit from magnetic resonance imaging (MRI) information; however, the MRI scanner magnetic field leads to ECG distortion that limits ECG interpretation. This study evaluated the potential for improved ECG interpretation in a "low field" 0.55T MRI scanner.
The 12-lead ECGs were recorded inside 0.55T, 1.5T, and 3T MRI scanners, as well as at scanner table "home" position in the fringe field and outside the scanner room (seven pigs). To assess interpretation of ischemic ECG changes in a 0.55T MRI scanner, ECGs were recorded before and after coronary artery occlusion (seven pigs). ECGs was also recorded for five healthy human volunteers in the 0.55T scanner. ECG error and variation were assessed over 2-minute recordings for ECG features relevant to clinical interpretation: the PR interval, QRS interval, J point, and ST segment.
ECG error was lower at 0.55T compared to higher field scanners. Only at 0.55T table home position, did the error approach the guideline recommended 0.025 mV ceiling for ECG distortion (median 0.03 mV). At scanner isocenter, only in the 0.55T scanner did J point error fall within the 0.1 mV threshold for detecting myocardial ischemia (median 0.03 mV in pigs and 0.06 mV in healthy volunteers). Correlation of J point deviation inside versus outside the 0.55T scanner following coronary artery occlusion was excellent at scanner table home position (r = 0.97), and strong at scanner isocenter (r = 0.92).
ECG distortion is improved in 0.55T compared to 1.5T and 3T MRI scanners. At scanner home position, ECG distortion at 0.55T is low enough that clinical interpretation appears feasible without need for more cumbersome patient repositioning. At 0.55T scanner isocenter, ST segment changes during coronary artery occlusion appear detectable but distortion is enough to obscure subtle ST segment changes that could be clinically relevant. Reduced ECG distortion in 0.55T scanners may simplify the problem of suppressing residual distortion by ECG cable positioning, averaging, and filtering and could reduce current restrictions on ECG monitoring during interventional MRI procedures.
12 导联心电图（ECG）是监测心脏介入过程和应激试验中心脏缺血和心律的标准诊断工具。这些程序可以受益于磁共振成像（MRI）信息；然而，MRI 扫描仪的磁场会导致 ECG 变形，从而限制 ECG 解读。本研究评估了在“低场”0.55T MRI 扫描仪中提高 ECG 解读能力的潜力。
在 0.55T、1.5T 和 3T MRI 扫描仪内部以及在扫描仪台“原位”的边缘场和扫描仪室外（七头猪）记录 12 导联 ECG。为了评估在 0.55T MRI 扫描仪中对缺血性 ECG 变化的解释能力，在冠状动脉闭塞前后（七头猪）记录了 ECG。还在 0.55T 扫描仪中为五名健康志愿者记录了 ECG。评估了与临床解释相关的 2 分钟记录中 ECG 特征的 ECG 误差和变化：PR 间隔、QRS 间隔、J 点和 ST 段。
与高场扫描仪相比，0.55T 处的 ECG 误差较低。只有在 0.55T 台原位，误差才接近指南推荐的 ECG 变形 0.025mV 上限（中位数 0.03mV）。在扫描仪等中心，只有在 0.55T 扫描仪中，J 点误差才落在检测心肌缺血的 0.1mV 阈值内（中位数在猪中为 0.03mV，在健康志愿者中为 0.06mV）。冠状动脉闭塞后，0.55T 扫描仪内与外 J 点偏差的相关性在扫描仪台原位非常好（r=0.97），在扫描仪等中心也很强（r=0.92）。
与 1.5T 和 3T MRI 扫描仪相比，0.55T 处的 ECG 变形得到改善。在扫描仪台原位，0.55T 处的 ECG 变形足够低，无需更繁琐的患者重新定位即可进行临床解释。在 0.55T 扫描仪等中心，冠状动脉闭塞期间的 ST 段变化似乎可以检测到，但变形足以掩盖可能具有临床意义的细微 ST 段变化。0.55T 扫描仪中 ECG 变形的减少可能通过 ECG 电缆定位、平均和滤波简化抑制残余变形的问题，并可能减少当前对介入性 MRI 过程中 ECG 监测的限制。
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