房间隔缺损等效圆转换在封堵器选择中的初步应用

Preliminary application of equivalent circle conversion in selection of atrial septal defect occluder

目的比较房间隔缺损长径CT血管造影术(CTA)测量值及等效圆直径(ECD)理论值与房间隔缺损参考标准之间的差异及相关性,探讨以等效圆转换解决房间隔缺损形状影响封堵器选择问题的可行性。方法前瞻性研究96例成功施行房间隔缺损封堵术患者,患者均于术前行冠状动脉CTA检查以除外冠心病,将患者冠状动脉CTA资料进行三维容积重建,采用CT横断序列辅助测量技术(CTAS)测量房间隔缺损的长径a(ASDa,a)与短径b(ASDb,b),运用Zanchetta转换公式ECDz=(b4/a2+a2-b2)^(1/2),计算ECD理论值,参考回归方程Y(ASO)=1.03X(ECDz)-0.45±1(mm)指导封堵器的选择。于术后第2日拍摄正、侧位胸片,在侧位胸片上测量封堵术后封堵器的腰部直径(POS),以此作为房间隔缺损直径的参考标准。再分别运用等面积转换公式ECDs=(ab)^(1/2)、等周长转换公式ECDc=b+2(a-b)/π、以及等周长转换公式的简化公式ECDcs=b+2(a-b)/3计算各自的等效圆直径理论值。首先将各等效圆直径及ASDa分别与ASO型号相比较,筛查差值≥0 mm的病例数,并进行χ2检验;其次比较房间隔缺损三种等效圆直径理论值及ASDa与参考标准值间的差异,进一步分析各值与参考标准值及与术中选择使用的封堵器型号之间的相关性。结果 ASDa与ASO之差>0 mm者共8例,ECDz与ASO之差>0 mm者1例,Fisher' Exact Test示P=0.017,差异有统计学意义;ECDs、ECDc及其简化形式ECDcs之差均>0 mm。各等效圆直径及ASDa与POS相比,ECDz标准差最大,为2.29 mm;ECDc标准差最小,为2.05 mm;ECDz与POS相关性良好(Y=1.10X+2.42;R2=0.89,P<0.05),ASDa与POS的相关性与之相近(Y=0.98X+2.54;R2=0.89,P<0.05),ECDc与POS的相关性最强(Y=1.06X+2.38;R2=0.91,P<0.05)。结论房间隔缺损等效圆转换能克服参考最大径选择封堵器的局限性,且等周长转换与金标准有更好的相关性,是指导封堵器选择的理想工具。

Objective To compare Equivalent Circle Dimension （ECD） with atrial septal defect major dimension and gold standard, and assess the use of the Equivalent Circle Conversion in selection of atrial septal defect occluder. Methods Prospective assessment of 96 consecutive patients who underwent ASD closure successfully. Cardiac CT was performed before planned transcatheter ASD closure for detection of coronary artery disease, followed by 3D reconstruction of ASD for determination of the defect size in the GE-workstation, and axial sequence assisted volumetric measurement（ CTAS ） were used for calculating the major axis a （ ASDa, a） and the minor axis b（ ASDb, b） of the ASD respectively. We derived the dimensions of the Equivalent Circle that circumference and area are equal to the elliptic ASD according to the formulation （ D=√b4/a2＋a2-b2 ）. The Atrial septal defect occlude （ASO） was chosen on the basis of the formula of Y（ASO） = 1. 03X（ECDx） - 0. 45 ± 1 mm. Postoperative chest radiograph was performed in both posteroanterior and lateral view, the ASDs occluder dimension was measured in the lateral chest radiograph, and this postoperative occluder-waist size （POS） value was regarded as the gold standard for the measurement of ASD. Then the other forms of Equivalent Circle Conversion were performed according to the Equal-area conversion formulation ECDs√ab, the Equal-circumference conversion formulation ECDc = b ＋ 2 （ a - b）/ 7, And its Simplified form ECDcs = b ＋2（a -b）/3 respectively. To compare ASDa and the ECD with ASO size for screening out the cases whose ASD~ or ECD is larger than ASO size, and χ2 Tests were performed; then to compare ECD and POS, and the correlation were evaluated between the ECD and POS. Results The ASDa were larger than ASO size in 8 cases, and the ECDz was larger than ASO size in 1 case. No case with larger ECDs and ECDc, Fisher＇ Exact Test shows the significant difference （ P = 0. 007 ）. Compared with POS, the biggest standard deviation of 2. 29 mm occurred in ECDz, and the least of 2. 05 mm occurred in ECDc. The correlation between ECDz and POS was excellent（ Y = 1.10X ＋ 2. 42, R2 = 0. 89 ,P 〈 0. 05 ）, and the correlation between ASDa and POS was similar to it（Y = 0. 98X ＋ 2. 54 ;R2 = 0. 89 ,P 〈 0. 05 ）. The strongest correlation was found between ECDc and POS （ Y = 1.06X ＋ 2. 38, R2 = 0. 91, P 〈 0. 05 ）. Conclusions Equivalent Circle Conversion can overcome the limitation of ASD major dimension as a tool of selection ASO, and the ECDc can be an optimal alternative approach for its better correlation with conference standard.