心室頻拍を伴う肥大型心筋症の運動負荷201Tl心筋SPECT像

Exercise stress thallium-201 myocardial imaging in hypertrophic cardiomyopathy with ventricular tachycardia

　肥大型心筋症（HCM）における心室頻拍（VT）は，突然死の有力な原因として注目されている^1〜3）。Tanakaらの報告によれば，突然死したHCMの剖検例では心疾患以外で死亡したHCMに比し心筋組織における線維化がより強く，線維化の程度が予後を決める重要な因子であることを示唆している^4）。運動負荷²⁰¹Tl心筋SPECT像（Single photon emission computed tomo—graphy）を用いれば，心筋組織における線維化の強い部分を欠損像として描出することが可能である^5）。今回，我我はVTを伴うHCMの運動負荷²⁰¹Tl心筋SPECT像の特徴をVT非出現例と比較し，その臨床的意義を検討したので，若干の文献的考察を加え報告する。

Exercise stress Thallium-201 emission computed tomogram in hypertrophic cardiomyopathy (HCM) with ventricular tachycardia (VT) was assessed. Twenty-four hour amburatory electrocardiographic monitoring was performed in 26 patients with HCM. VT was detected during monitoring in 8 patients (VT group) and not detected in 18 patients (Non VT group). Every 26 patients exercised on ergo-meter (graded multi-stage protocol) until they de-veloped chest pain, breathlessness or fatigue. At peak exercise 3 mCi of thallium was injected. Scan-ning was begun at 10 minutes after the administra-tion of thallium (initial image), and scans were re-peated 4 hours later (delayed image). After SPECT image was divided into 6 segments, the presence of perfusion defect (both initial and delayed images) and redistribution in each segments was assessed. The prevalence of perfusion defect was not signi-fiicantly different between VT group (5 of 8 [63%]) and Non VT group (7 of 18 [39%]), and the pre-valence of redistribution was not significantry dif-ferent between VT group (4 of 8 [50%]( and Non VT group (9 of 18 [50%]).

The prevalence of perfusion defect more than two segments was significantly higher in VT group (4 of 8 [50%]) than in Non VT group (1 of 18 [6%]) (v..:0. 05). But the prevalence of redistribution more than two segments was not significantly different between VT group (2 of 8 [25%]) and Non VT group (7 of 18 [39%]). Coronary arteriography was performed in 17 patients and showed no significant luminal stenosis greater than 75%.

In summary, the prevalence of perfusion defect more than two segments was significantly higher in VT group than in Non VT group.