From the Heart Hospital Imaging Centre, University College London, 16-18 Westmoreland St, London W1G 8PH, England (C.M., A.S.H., G.C., J.C.M.); Multidisciplinary Cardiovascular Research Centre and Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds, England (D.P.R., S.P., J.P.G.); Department of Medicine (T.C.W., E.B.S.) and UPMC Cardiovascular Magnetic Resonance Center (E.B.S.), University of Pittsburgh School of Medicine, Pittsburgh, Pa; NIHR Cardiovascular Biomedical Research Unit, Barts Health NHS Trust and Queen Mary University of London, London, England (S.E.P.); and Wessex Cardiothoracic Unit, Southampton University Hospitals NHS Trust, Southampton, England (C.P.).
Radiology. 2015 Sep;276(3):732-40. doi: 10.1148/radiol.2015142059. Epub 2015 Apr 29.
To investigate the pharmacology and potential clinical utility of splenic switch-off to identify understress in adenosine perfusion cardiac magnetic resonance (MR) imaging.
Splenic switch-off was assessed in perfusion cardiac MR examinations from 100 patients (mean age, 62 years [age range, 18-87 years]) by using three stress agents (adenosine, dobutamine, and regadenoson) in three different institutions, with appropriate ethical permissions. In addition, 100 negative adenosine images from the Clinical Evaluation of MR Imaging in Coronary Heart Disease (CE-MARC) trial (35 false and 65 true negative; mean age, 59 years [age range, 40-73 years]) were assessed to ascertain the clinical utility of the sign to detect likely pharmacologic understress. Differences in splenic perfusion were compared by using Wilcoxon signed rank or Wilcoxon rank sum tests, and true-negative and false-negative findings in CE-MARC groups were compared by using the Fisher exact test.
The spleen was visible in 99% (198 of 200) of examinations and interobserver agreement in the visual grading of splenic switch-off was excellent (κ = 0.92). Visually, splenic switch-off occurred in 90% of adenosine studies, but never in dobutamine or regadenoson studies. Semiquantitative assessments supported these observations: peak signal intensity was 78% less with adenosine than at rest (P < .001), but unchanged with regadenoson (4% reduction; P = .08). Calculated peak splenic divided by myocardial signal intensity (peak splenic/myocardial signal intensity) differed between stress agents (adenosine median, 0.34; dobutamine median, 1.34; regadenoson median, 1.13; P < .001). Failed splenic switch-off was significantly more common in CE-MARC patients with false-negative findings than with true-negative findings (34% vs 9%, P < .005).
Failed splenic switch-off with adenosine is a new, simple observation that identifies understressed patients who are at risk for false-negative findings on perfusion MR images. These data suggest that almost 10% of all patients may be understressed, and that repeat examination of individuals with failed splenic switch-off may significantly improve test sensitivity.
通过腺苷灌注心脏磁共振成像（MR）研究中脾关闭来识别应激状态，以探讨其药理学和潜在的临床应用价值。
该研究经三个机构的伦理批准，对 100 例患者（平均年龄 62 岁[年龄范围：18-87 岁]）的 100 例灌注心脏 MR 检查（分别使用三种应激药物：腺苷、多巴酚丁胺和雷卡地诺生）进行脾关闭评估。另外，还评估了来自临床评估心脏磁共振成像在冠心病中的应用（CE-MARC）试验的 100 例阴性腺苷图像（35 例假阴性和 65 例真阴性；平均年龄 59 岁[年龄范围：40-73 岁]），以确定该征象在检测可能的药物应激不足方面的临床应用价值。采用 Wilcoxon 符号秩或 Wilcoxon 秩和检验比较脾脏灌注差异，采用 Fisher 确切检验比较 CE-MARC 组中的真阴性和假阴性结果。
脾脏在 99%（200 例中的 198 例）的检查中可见，脾关闭的视觉分级观察者间一致性极好（κ=0.92）。视觉上，90%的腺苷研究中发生了脾关闭，但多巴酚丁胺或雷卡地诺生研究中从未发生过。半定量评估结果支持这些观察结果：与静息时相比，腺苷时的峰值信号强度降低了 78%（P<0.001），但雷卡地诺生时没有变化（减少 4%；P=0.08）。不同的应激药物之间，峰值脾脏与心肌信号强度比（peak splenic/myocardial signal intensity）也不同（腺苷中位数为 0.34，多巴酚丁胺中位数为 1.34，雷卡地诺生中位数为 1.13；P<0.001）。CE-MARC 中假阴性发现的患者脾关闭失败的发生率显著高于真阴性发现的患者（34%比 9%，P<0.005）。
腺苷灌注时脾关闭失败是一种新的简单观察指标，可以识别应激不足的患者，这些患者在灌注 MR 图像上有发生假阴性发现的风险。这些数据表明，近 10%的患者可能存在应激不足，对脾关闭失败的患者进行重复检查可能会显著提高检测的敏感性。
