多段階トレッドミル運動負荷試験による酸素輸送系機能の評価に関する研究—健常群と冠動脈性心疾患群との比較

Studies on evaluation of the oxygen transport system function with multistage treadmill stress testing:Comparison between normal control subjects and patients with coronary heart disease

　酸素輸送系の機能障害は，従来Bruceらの示すFunc—tional Aerobic Impairment（FAI）で表され，これは左室機能障害（Left Ventricular Impairment：LVI）と末梢機能障害（Peripheral Circulatory Impairment：PCI）の和として定義される^1）。日常の臨床においては多段階運動負荷試験による症候限界性最大運動負荷試験が行われ，それによって得られた最大酸素摂取量（V_O2max），最大心拍数（HR_max），そして，最大二重積（PRP_max）より酸素輸送系機能が評価されるが^1,2），わが国においては，これまでそれらの基準となる健常者の成績が示されていないので，本研究では健常成人男性についてFAI，LVI，そして，PCIの諸値を求め，これらの基準に対して冠動脈性心疾患（CHD）における機能障害を，その重症度とA-C Bypass術後について比較検討した。

　CHDに見られる酸素輸送系機能障害には疾患による機能低下の他に，年齢による機能低下も加味されており，またCHDの障害血管数に対する重症度は，この評価法によって適切に表現されるとともに，A-C Bypass術後の治療効果についても正当に評価し得る基準となることが知られた。

　The oxygen transport system (OTS) function was evaluated with multistage treadmill stress testing on 171 normal control subjects and 80 patients with coronay heart disease (CHD). After Bruce's definition, OTS function was expressed with functional aerobic impairment (FAI), left ventricular impairment (LVI) or myocardial aerobic impairment (MAI), heart rate impairment (HRI) or chronotropic reserve impairment (CRI) and peripheral circulatory impairment (PCI). All subjects were monitored on heart rate, blood pressure, electrocardiogram and endtidal O₂ and CO₂ before and every one minute during the symptom limited maximal stress testing. Seventy three of 80 coronary patients were sujected to the coronary arteriography and were classified into four groups ; 31 with single vessel disease (SVD), 20 with double vessel disease (DVD), 15 with tripple vessel disease (TVD) and 7 with A-C bypass surgery. Comparison between normal control subjects and the CHD patients with regard to the relation of age and Vo₂max derived from the linear regression analysis disclosed the identical age-related decrease in Vo₂maa in both groups. The age corrected Vo₂max in the CHD patients, however, was 2. 2 METS less than that of normal control subjects. Therefore, the level of Vo₂max in CHD patients was determined not only by disease, but also by ageing process itself. Comparisons among three CHD groups with regard to FAI, LVI, HRI and PCI clearly demonstrated different functional impairments paralleling to the severity of the disease process. On the other hand, the patients with A-C bypass surgery revealed almost identical functional impairment to the patients with SVD. In conclusion, these simple and noninvasive evaluations of the oxygen transport system could give us valuable informations reasonably differntiating the clinical status of the patients with CHD.