1 九州大学病院ハートセンターHeart Center, Kyushu University Hospital
2 九州大学病院循環器内科Department of Cardiovascular Medicine, Kyushu University Hospital
目的：経胸壁心エコー検査（TTE）による重症大動脈弁狭窄症（AS）における二尖弁（BAV）の診断は困難な症例が存在する．今回，TTEによる弁尖数の診断能力を検証しBAVを三尖弁（TAV）と診断する要因を明らかにするとともに，BAVの診断能力を向上させる因子について検討した．
対象と方法：2010～2015年までのAS術前患者227例（男性126例，女性101例，平均年齢76.0±9.5歳）を対象とした．1）弁尖数は手術所見もしくはCT等より最終判断し，TTEによる診断能力を算出するとともに，TAVと誤診断されたBAV症例においては，その原因検索を行った．2）患者背景およびTTE計測データについてBAV群とTAV群の比較を行った．
結果と考察：1）対象227例のうちBAVは46例であった．TTEによるBAV診断能力について，感度35%，特異度99%，正診率86%と感度が極めて低い値であった．BAVをTAVと診断した10例では，縫線（raphe）や交連部の石灰化等によるアーチファクトが散見された．2）多変量解析にて年齢，左房径，上行大動脈径がBAVの独立した予測因子であった．ROC曲線にて，年齢72歳以下もしくは最大大動脈径40 mm以上のいずれかによるBAVの診断能力は，感度89%，特異度77%，正診率80%と感度を改善させることができた．
結論：TTEによるBAVの診断感度は低いが，複数断面からの観察によるrapheおよびアーチファクトの判別に加え，年齢や大動脈径という弁以外の指標を併用することにより，BAVの診断感度を向上させうると考えられた．
Purpose: The standard test for identifying the number of aortic leaflets is transthoracic echocardiography (TTE); however, it is well-known that the diagnostic accuracy of TTE in patients with severe aortic valve stenosis (AS) is limited. The aim of this study was to investigate the diagnostic accuracy of TTE for identifying the number of aortic leaflets.
Subjects and Methods: We enrolled 227 patients (126 men and 101 women; mean age, 76.0±9.5 years) diagnosed with severe AS and who were scheduled to undergo aortic valve replacement or transcatheter aortic valve implantation. 1) We determined the number of aortic valves based on surgery records or computed tomography (CT) findings and analyzed the diagnostic accuracy, such as sensitivity and specificity. Furthermore, we tried to determine the cause of misidentification in patients whose bicuspid aortic valve (BAV) had been diagnosed as a tricuspid aortic valve (TAV). 2) According to the final diagnosis, we divided the patients into two groups, namely, the TAV and BAV groups and compared background and TTE measurement data.
Results and Discussion: 1) Of the 227 patients, BAV was found in 46 patients. The sensitivity of TTE for diagnosing BAV was only 35%. CT findings indicated the presence of echocardiographic specific artifacts, such as acoustic shadows and multiple reflections which originated from heavily calcified valves, commissures, and raphe, as causes of the misidentification of the leaflet numbers. 2) A multivariable logistic analysis indicated age [OR, 0.86; 95% confidence interval (CI), 0.80–0.91; p＜0.001), left atrial dimension (OR, 0.88; 95% CI, 0.81–0.94; p＜0.001), and ascending aorta (OR, 1.40; 95% CI, 1.25–1.61; p＜0.001) to be independent predictive parameters of BAV. Optimum cut-off points for age and the maximum aortic diameter were 72 years and 40 mm, respectively, for predicting diagnostic accuracy with a receiver operating curve (specificity 77%, sensitivity 89%, and accuracy 80%).
Conclusions: The sensitivity of TTE for identifying BAV was not high because of the presence of severe calcification and artifacts. Multiple windows, including right parasternal, suprasternal, and subcostal approaches, should, therefore, be employed for improving the sensitivity of TTE.
Key words: aortic valve stenosis; bicuspid aortic valve; tricuspid aortic valve; diagnostic accuracy; transthoracic echocardiography
© 2018 一般社団法人日本超音波検査学会© 2018 Japanese Society of Sonographers
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