心筋梗塞量推定における99mTc-PYPおよび201Tl心筋イメージングの臨床的有用性—血清総CPK遊出量および梗塞急性期左室機能との相関

Clinical usefulness of Technetium-99m Pyrophosphate and Tl-201 myocardial imaging for the estimation of myocardial infarction

　急性心筋梗塞症では，心筋梗塞量と心室不整脈^1），左室機能不全の出現^2,3）あるいは患者の予後^4,5）との間に密接な関係が存在することが知られており，心筋梗塞量の推定は梗塞患者の治療方針の決定のために重要と考えられる。近年，RIイメージングの発達に伴い，^99mTcピロリン酸（以下PYP）心筋シンチグラフィあるいは²⁰¹Tl心筋シンチグラフィによる心筋梗塞の部位および拡がりの診断が行われるようになり，さらに心電図同期RI心血管造影による左室機能の非観血的な評価も可能となってきている。本研究の目的は，^99mTc-PYP梗塞像および²⁰¹Tl心筋像より求めた心筋梗塞量の指標と血清総CPK遊出量，および発症早期に第1回循環時法より求めた左室駆出率との相関を検討し，RIイメージングによる心筋梗塞量推定の臨床的有用性について検討することである。

A correlative study was performed between the infarct size estimated by either technetium-99 py-rophosphate (Tc-PYP) or Tl-201 myocardial imag-ing, and the cumulative total creatinine phospho-kinase activity (ΣCPK) or left ventricular ejectionfraction (LVEF) in 40 patients with acute myo-cardial infarction. Tc-PYP infarct area (TcIA) and mean Tl-201 uptake ratio (MUR) were calculated as indices of myocardial infarct size. LVEF was evaluated by first pass method using Tc-PYP in the acute phase of myocardial infraction. In 23 patients with anterior myocardial infarction, a significant correlation was shown between either TcIA or ante-rior-wall MUR and ΣCPK (r=0.81 and r=-0.69, respectively) and also between either TcIA or an-terior-wall MUR and LVEF (r=-0.84 and r=0.80, respectively). In 17 patients with inferior myocardial infarction without additional involve-ment of right ventricular wall, inferior-wall MUR correlated with ΣCPK r=-0.74). No statically significant correlation was shown between TcIA and ΣCPK, and also between either TcIA or in-ferior-wall MUR and LVEF. In conclusion, the infarct size estimated with Tc-PYP or Tl-201 myo-cardial imaging could be a useful clinical indica-tor of the severity of acute myocardial infarction especially in anterior wall.