特发性扩张型心肌病合并甲状腺功能减退加重心肌损伤的影像学评价

Myocardial injury aggravated by hypothyroidism in patients with idiopathic dilated cardiomyopathy： the evidence based on ^99Tc^m-MIBI SPECT/^18F-FDG PET imaging and cardiac MRI

目的通过^99Tcm-MIBI心肌灌注SPECT／^18F—FDG心肌代谢PET显像和心脏MRI延迟增强成像（cMRI—LGE），探讨特发性扩张型心肌病（IDC）合并甲状腺功能减退（简称甲减）与心肌损伤的关系。方法2010年10月至2012年12月诊断为IDC的连续病例63例[男42例，女21例，平均年龄（52±11）岁]入选，患者均进行血浆TT3、TT4、FT3、FT4和TSH全自动化学发光免疫法测定、^99Tcm-MIBI心肌灌注SPECT／^18F—FDG心肌代谢PET显像和cMRI—LGE。利用标准17节段模型进行心肌节段分析，灌注／代谢图像分成4种类型：正常灌注／代谢、灌注／代谢不匹配、灌注／代谢轻中度匹配、灌注／代谢完全匹配；cMRI-LGE图像分为无延迟强化、壁间强化和透壁强化。通过x^2检验进行分组数据的比较。结果根据所测血浆激素水平，患者被分成甲状腺功能（简称甲功）正常组（53例）和甲减组（10例）。甲功正常组正常灌注／代谢的心肌节段数所占的比例明显高于甲减组：71.8％（647／901）和57．6％（98／170）,x^2=13．50，P〈0．001；而灌注／代谢不匹配的心肌节段比例则低于甲减组：17．8％（160／901）和31．2％（53／170）x^2=16．20，P〈0．001。甲功正常组cMRI—LGE无延迟强化的心肌节段比例明显高于甲减组，分别为88．0％（793／901）和69．4％（118／170），x^2=35．70，P〈0．001；但壁间强化的心肌节段比例则低于甲减组，分别为4．8％（43／901）和24．1％（41／170），x^2=74．70，P〈0．001。结论^99Tc^m-MIBI心肌灌注SPECT／^18F—FDG心肌代谢PET显像和cMRI—LGE证实甲减能够加重IDC患者的心肌损伤。SPECT／PET可以检测出更多的慢性缺血／存活心肌，而cMRI-LGE可以检测出更多的心肌纤维化病变，两者结合能提供更全面的心肌损伤信息。

Objective To explore the relationship between hypothyroidism and myocardial injury in patients with idiopathic dilated cardiomyopathy （IDC） by ^99Tcm-MIBI SPECT/^18F-FDG PET and late-gadolinium enhancement cardiac magnetic resonance imaging （cMRI-LGE）. Methods Sixty-three consecutive patients （42 males and 21 females, （52±11） years） with IDC were enrolled from October 2010 to December 2012. Serum TT3, TF4, FT3, FT4 and TSH were determined using a fully automated chemiluminescence immunoassay. All patients underwent ^99Tcm-MIBI myocardial perfusion SPECT/^18F-FDG myocardial metabolism PET imaging and cMRI-LGE. Seventeen segments model was used for segmental analysis. Patterns ofperfusion/metabolism were classified as normal, mismatch, mild-to-moderate match and complete match. cMRI-LGE was classified into 3 categories （non-LGE, mid-wall LGE and transmural LGE）. x^2 test was used for data analysis. Results All patients were divided into euthyroid group （n = 53） and hypothyroidism group （n= 10） according to the levels of serum thyroid hormones. The percentage of normal perfusion/metabolism segments in the euthyroid group was apparently higher than that in the hypothyroidism group： 71.8% （647/901） vs 57.6% （98/170）, x^2= 13.50, P〈0.001 ; whereas the percentage of perfusion/metabolism mismatch segments in the euthyroid group was significantly lower than that in the hypothyroidism group： 17.8%（160/901） vs 31.2%（53/170）, x^2= 16.20, P〈0.001. The euthyroid group had a higher percentage of non-LGE segments （88.0% （793/901） vs 69.4% （ 118/170）, x^2 = 35.70, P〈0.001 ） and a lower percentage of mid-wall LGE segments （4.8% （43/901） vs 24.1% （41/170）, x^2 = 74.70, P〈0.001 ） compared to hypothyroidism group. Conclusions Hypothyroidism has a detrimental effect on myocardium. ^99Tcm-MIBI SPECT/^18F-FDG PET imaging is sensitive in detecting viable/isehemia myocardium, and cMRI-LGE is good at detecting moderate fibrosis. Combining SPECT/PET imaging and cMRI-LGE for assessing myocardial iniury would provide more comprehensive information.