MYOCARDIAL LACTATE METABOLISM IN HEALTH AND DISEASE, STUDIES BY CORONARY SINUS CATHETERIZATION

Abstract

The coronary sinus catheterization was carried out on ninetyeight human subjects, including twenty-two normal subjects, fourty patients with cardiac failure, thirteen patients with coronary sclerosis, six cases of hypertension, six cases of anemia, ten patients with hyperthyroidism, and one patient with beri-beri. In these subjects, the myocardial lactate metabolism was investigated in the recumbent rest, in the exercise test, and in the 10% oxygen hypoxia test, as well as during the intravenous administration of Lanatoside C or Vitamin B1. The results thus obtained were as follows.
1. In the healthy individuals with the mean arterial lactate concentration of 7.79±1.30mg per dl the coronary venous lactate concentration averaged 3.80±0.60mg per dl, the coronary arterio-venous lactate difference 3.99±0.79mg per dl, and the myocardial lactate O₂ extraction ratio 30.5±6.4 per cent. The relationship of the coronary arterio-venous lactate difference (ΔL) plotted against arterial lactate concentration (La) follows the next formula, and the rising arterial lactate concentration upon the exercise test resulted in increased coronary arterio-venous lactate difference according to the same formula.
La=0.116 ΔL²+0.608 ΔL+3.15
Consequently, in this report, the problems of the myocardial lactate extraction were discussed on the basis of the myocardial lactate extraction coefficient ratio (ΔL/ΔLn):ΔLn is the normal value of the coronary arterio-venous lactate difference, corresponding to a particular arterial lactate level in the formula. In the resting state as well as upon the exercise test, the increases in the arterial lactate concentration were accompanied with a rise in the myocardial lactate O₂ extraction ratio, and at the arterial lactate concentration of 30mg per dl the ratio reached approximately to 90 per cent.
2. In the moderate and severe cardiac failure the coronary venous lactate concentration was significantly elevated, and in the severe cardiac failure both the coronary arterio-venous lactate difference and the myocardial lactate O₂ extraction ratio were significantly reduced. In cardiac failure as well as in coronary sclerosis or hypertension, the myocardial lactate extraction was significantly lowered, resulting in lowered myocardial lactate O₂ extraction ratio as compared with that of the normal at a comparable arterial level. It was noteworthy that in cardiac failure these decreases were in parallel with the grade of its severity. In addition, the decreases in these heart diseases became more evident by the exercise test and the hypoxia test. The data described above suggests that the myocardial lactate metabolic abnormality is not due to the secondary effect of the cardiac failure but precedes it.
3. In the cases of thyrotoxicosis and anemia the coronary venous lactate concentration was significantly elevated, and both the coronary arterio-venous lactate difference and the myocardial lactate extraction were significantly lowered. One patient with beri-beri showed also a remarkable reduction in the myocardial lactate extraction. Additionally, in thyrotoxicosis the myocardial lactate O₂ extraction ratio was significantly lowered, and in severe anemia and in beri-beri the ratios were lowered as compared with that of the normal at the same arterial level. Moreovere, these abnormalities became conspicuous by the exercise test.
4. After the administration of Lanatoside C to the cases of cardiac failure the myocardial lactate extraction was significantly improved in contrast with the control patients.
5. The myocardial lactate usage was determined in eight healthy individuals and nineteen patients with heart diseases. The normal value was distributed widely between 0.47 and 3.75mg per dl per 100 grams per minute (Mean value:1.88±0.88).