肥大型心筋症における胸痛，労作時ST下降の機序—ペーシング負荷試験，冠攣縮誘発試験，心筋生検からの検討

Mechanisms of Chest Pain and ST-segment Depression in Patients with Hypertrophic Carcliomyopathy: A study from atrial Pacing, provocation of spasm and myocardial biopsy

　肥大型心筋症（HCM）における胸痛や労作時ST下降の機序について，心房ペーシング負荷試験（AP），冠攣縮誘発試験，心筋生検所見から検討した．対象は，HCM患者20例で，AP，アセチルコリン負荷試験（ACh），エルゴノビン負荷試験（Ergo）を施行後両室生検を施行し，小動脈，毛細血管を中心に光顕，電顕観察を行った．APにより13例（65％）で著明なST下降がみられた．組織学的には，ST下降のみられた11例中8例（72％）で中膜肥厚を中心とする小動脈硬化所見を認め，毛細血管では内皮細胞の軽度腫大と基底膜の著明な肥厚を認めた．冠攣縮誘発率は，AChで33％，Ergoで27％であった．HCMにおける胸痛や労作時ST下降の発現には，心筋肥大による心筋酸索需要の増大のみならず中膜成分を中心とする小動脈硬化が関連し，毛細血管異常も冠微小循環障害を助長していると推測された．また，一部の症例では，心外膜側の冠攣縮が胸痛や心電図変化に関連していることも考えられた．

It has been reported that chest pain and ST segment depression on ECG have been recognized in patients with hypertrophic cardiomyopathy (HCM), but the mechanisms have not been made clear. To understand the mechanisms, we examined right atrial pacing and endomyocardial biopsy in 20 patients with HCM. Acetylcholine test (ACh) was performed in 12, and ergonovine test (Ergo) in 11 out of 20 patients to provoke coronary artery spasm. We further examined the degree of severity in sclerosis of small arteries by light microscope, and measured the degree of cytoplas-mic swelling of endothelial cells and the degree of thickening of the basal lamina in the capillary by electron microscope. A wide range of ST segment depression was recognized in 13 out of 20 (65%) by the pacing. Then, sclerosis of the small arteries could be confirmed in 8 out of 11 (72%) who showed ST-segment depression and contained small arteries in the biopsied specimen. In capillaries, the degree of cytoplasmic swelling of endothelial cells was 0.31±0.08 in patients with HCM compared with that of 0.20±0.06 in the control group (p＜0.001), and the degree of thickening of the basal lamina was 0.80±0.20 in patients with HCM compared with that of 0.12±0.05 in the control group (p＜0.001). On the other hand, 4 out of 12 (33%) in ACh and 3 out of 11 (27%) in Ergo showed positive according to our criteria for the spasm. It is suggested that chest pain and ST segment depression in patients with HCM should be related to disturbed coronary microcirculation due to sclerosis of small arteries and capillary abnormalities in addition to increased myocar-dial oxygen demand due to myocardial hypertrophy. Moreover, coronary artery spasm may also be related in some patients with HCM to ischemic manifestations.