Myocardial Metabolism in Cyanotic Congenital Heart Disease

Abstract

Eight normal subjects and 7 cyanotic patients, 5 with tetralogy of Fallot, and 2 with Eisenmenger’s syndrome, were studied with coronary sinus catheterization. In the resting state mean coronary flows were lower and myocardial oxygen extractions higher in cyanotic patients so that myocardial oxygen consumption was the same in the 2 groups. Coronary flows appeared to be inversely related to hematocrit in the cyanotic group. Myocardial lactate balance was similar in the 2 groups, but coronary sinus lactate/ pyruvate ratios were frequently higher than arterial ratios in the cyanotic group. The subjects were stressed with supine leg exercise or with an isoproterenol infusion. In cyanotic subjects exercise caused a fall in arterial oxygen and myocardial oxygen extraction so that oxygen delivery tended to be more dependent upon coronary flow. Myocardial oxygen delivery appeared adequate during stress in cyanotic patients and lactate and pyruvate analysis failed to show evidence of myocardial hypoxia. Between the 3rd and 8th min of exercise, cyanotic patients continued to have falling arterial oxygen values and rising arterial lactate and lactate/pyruvate ratios indicating that they had not reached steady metabolic state. Myocardial glucose and free fatty acid uptake were similar in the 2 groups. These results indicate that although the mechanisms of oxygen delivery to the myocardium may differ in normals and some patients with cyanotic congenital heart disease, left ventricular myocardial oxidative metabolism is intact even in the presence of hypoxemia.

Regulation of Sympathetic Activity in Children with Various Congenital Heart Diseases

“…In congenital heart diseases, cyanosis has been associated with various alterations in cardiac sympathetic activity (1)(2)(3)(4)(5)(6). In acute hypoxemia, for example, stimulation of the sympathetic activity results in increased heart rate and cardiac output as a compensatory mechanism to maintain adequate oxygen supply (7,8), whereas in chronic situations, such as in cyanotic congenital heart disease, several complex events probably contribute toward the mechanism(s) to sustain adequate oxygen supply (9).…”

Myocardial perfusion reserve in adults with cyanotic congenital heart disease

“…This suggests that increases in myocardial oxygen demand need to be accompanied by nearly parallel increases in perfusion to sustain aerobic metabolism. Measurements of myocardial perfusion have previously been made in a small number of CCHD patients during cardiac catheterization, using clearance rates of inert gases or iodine-131 iodoantipyrine (51,53). These early studies were limited by the methodology used to measure the tracer clearance rates and were further confounded by the need to normalize blood flows to derived estimates of ventricular mass.…”

Myocardial Metabolic Changes in Chronic Hypoxia

“…Comparative data from other chronic hypoxic conditions [5,9,10,12,29,[37][38][39][40][41] are shown in table I. Arterial saturation is similar in all groups except for patients with chronic cor pulmonale studied by R u dolph [38][39][40], It should be noted that the age of the subjects in the various studies is different: young in the groups living at high altitude or having congenital heart disease, older in the other groups. Coronary blood flow in the first two groups is lower than in the control group, but it seems to be well adapted to the myocardial oxygen requirements.…”