冠静脈血中酸素飽和度連続記録ならびに心筋乳酸代謝からみた症候性および無症候性心筋虚血

Symptomatic and Asymptomatic Myocardial Ischemia Estimated by Continuous Measurement of Coronary Sinus Oxygen Saturation and Myocardial Lactate Metabolism

　症候性および無症候性心筋虚血を頻回心房ペーシング負荷（RAP）時の冠静脈血中酸素飽和度（CSO₂-Sat）連続記録と心筋乳酸摂取率（MLER）から検討した．左前下行枝に有意狭窄所見を有する12例のうち，RAPでは狭心痛と虚血性心電変化が認められたのは6例（A群），狭心痛も虚血性心電図変化も認められなかったのは4例（B群），狭心痛はないが虚血性心電図変化が認められたのは2例（C群）であった．RAPによりA群ではCSO₂-Sat（41.3±3.0％→32.3±2.5％）とMLER（33.3±3.2％→3.6±8.1％）の低下がみられ，B群ではいずれの指標にも有意の変化はなかった．C群の2例ではいずれの症例でもCSO₂-Sat（44％→25％，40％→28％）とMLER（32％→−2％，25％→−10％）の低下が明らかであった．以上から，無症候性であってもその虚血重症度は必ずしも症候性心筋虚血を下回るものではなく，無症候性心筋虚血の発現には痛覚閾値の上昇が関連していると推察された．

We investigated symptomatic and asymptomatic myocardial ischemia on rapid atrial pacing (RAP) loading in terms of changes in coronary sinus oxygen saturation (CSO₂^-Sat) which was recorded continuous-ly, and myocardial lactate extraction ratio (MLER). In 12 patients with significant stenosis in the left anterior descending coronary artery, 6 had both ischemic ECG changes and anginal pain (group A), 4 had neither ischemic ECG changes nor anginal pain (group B), and 2 had ischemic ECG changes and no anginal pain (group C) during RAP intervention. In group A, both CSO₂^- Sat and MLER significantly decreased from 41.3±3.0% to 32.3±2.5% and from 33.3±3.2% to 3.6±8.1%. respec-tively, during RAP. These remained almost constant in group B. Decreases in CSO₂^-Sat (44% to 25%, 40% to 28%) and MLER (32% to -2%, 25% to -10%) were also remarkable in group C. These results imply that asymptomatic myocardial ischemia doesn't necessarily-mean less severe ischemia is associated with the ele-vated pain threshold, resulting in disappearance of angina.