小児期心疾患における201Tl Cl心筋イメージング右室圧定量的評価について

Thallium-201 myocardial imaging in children with heart disease;Quantitative assessment of right ventricular pressure

はじめに

　小児期心疾患において，右室負荷の分析は根治術の時期の決定や術後の心機能の評価に必要であるが，非侵襲的に右室負荷を知ることは困難な場合が多い。近年の心臓核医学の検査法の発達のなかで，²⁰¹Tl Cl心筋イメージングにおける右室壁の描出により定性的に右室負荷を評価する報告がみられる^1,2）が，右室圧負荷の定量的評価についての報告は少なく^3〜5），その方法も一定していない。さらに，右室負荷をきたす病態の相違により生じる右室壁の描出の差異に関した報告も少ない。

　われわれは，²⁰¹Tl Cl心筋イメージソグを用いて右室圧負荷を定量的に評価するために，左右心室壁の²⁰¹TlClの摂取カウントの比を用いる方法について検討するとともに，その方法により，疾患の相違による²⁰¹Tl Cl心筋イメージングにおける右室壁描出の差異についてもあわせて検討を行なった。

201Tl Cl myocardial imaging studies were performed to evaluate systolic pressure of rightventricle on 107 patients including 89 patients with congenital cardiac disease, patients with primary pulmonary hypertension and 13 patients with history of MCLS with the age range of 2 months to 17 years. The congenital cardiac disease group included 30 patients with tetralogy of Fa/lot, 8 patients with pulmonary stenosis (included 1 patient with double chambered right ventricle), 20 patients with ventricular septal defect, 10 patients with patent ductus arteriosus, 9 patients with atrial septa] defect and 12 patients with complete transposition of greate arteries. None of the patients with history of MCLS had coronary involvement.

50 μCi/kg of 201-TlCl was infused intravenously and after 15 minutes the images were obtained from 5 directions (anterior, LAO 30, LAO 45, LAO 60 and lateral). The angle was determined to demonstrate the intraventricular septum and ven-tricular free walls cleary separated.

The image of end-diastolic phase was obtained with ECG syncronized gated method from that direction. The ROI (region of interest) was defined as a slice line by drawing two lines perpendicular to the septum and the counts of the left and right ventricular free wall (Cl and Cr) were analized to evaluate the pressure of right ventricle.

The pressure of ventricles were obtained by cardiac catheterization performed at the same time with myocardial imaging.

The ratio of CI and Cr (Cr/Cl) had good correla-tion with the ratio of peak systolic pressure of left ventricle and right ventricle (regression equation Y=0.84X+0.08, r=0.87). In each congenital heart disease group, very good corelation was also demonstrated (Y=1.46X-0.30, r=0.96 in PS ; Y=0.70X0.20, r=0.91 in VSD ; Y=0.86X+0.15, r=0.78 in ASD and Y=0.72X+0.24, r=0.80 in PDA).

Thus 201-TlCl myocardial imaging was useful method to evaluate right ventricular pressure noninvasively in congenital cardiac disease.