The distribution of a group of enzymes was determined histochemically in the surgically resected auricular myocardium of 5 cases of rheumatic and 6 cases of congenital heart disease. The enzymes studied included succinic dehydrogenase, diphosphopyridine nucleotide diaphorase, adenosine triphosphatase (ATPase), glucose-6-phosphatase, alkaline and acid phosphatase, and nonspecific esterase. The only abnormality noted was the apparent marked reduction in ATPase activity in the myocardium.
Stein AA, Chang KS, Alley R. II. Histochemical Observations on Enzyme Distribution in Surgically Resected Human Myocardium. JAMA. 1962;182(5):534-537. doi:10.1001/jama.1962.03050440026008