Water and electrolyte content of cardiac and skeletal muscle in heart failure and myocardial infarction.

Abstract The water and electrolyte content of cardiac and skeletal muscle from patients dying of congestive failure or recent myocardial infarction was compared with the composition of specimens from patients dying of noncardiac causes. Myocardial blocks from four standard sites in the left ventricle were analyzed for water, sodium, potassium, chloride, magnesium, and phosphorus in twenty-nine cases and for water, sodium, and potassium in eighteen additional cases; blocks from the pectoralis major were analyzed for all six substances in twenty-five cases and for water, sodium, and potassium in four additional cases. The control group comprised sixteen patients with normal hearts at autopsy and no evidence of a metabolic disorder. Myocardial analyses yielded averages of 78.8 Gm. of water, 4.96 meq. of sodium, 8.32 meq. of potassium, 4.04 meq. of chloride, 0.445 meq. of magnesium, and 3.88 meq. of phosphorus per 100 Gm. of wet tissue. Estimates of the partition of water between the extracellular and intracellular compartments and of the concentrations of base within the cells were made according to the method of Newburgh. Skeletal muscle from the same patients was comparable to myocardium in total water content, but showed a relatively smaller extracellular and larger intracellular volume. The concentration of total base in the cells was essentially the same as that in myocardium, but sodium level was slightly higher and potassium and magnesium levels were slightly lower. Uncomplicated left ventricular hypertrophy was found in fourteen patients who showed no evidence of congestive failure during hospitalization and died of noncardiac causes. The average content of water and each electrolyte in the myocardium was almost identical with that in the normal control group. Congestive failure, complicating left ventricular hypertrophy, was present during hospitalization and at autopsy in eight patients. Analyses of cardiac and skeletal muscle showed significant reduction in potassium below the control values, but no significant change in content of water, sodium, chloride, magnesium, or phosphorus. The estimated partition of water in both cardiac and skeletal muscle was similar to that in the controls. The estimated intracellular concentration of total base was reduced to a similar level in cardiac and skeletal muscle, largely from potassium loss. The significance of these observations is discussed. Recent myocardial infarction was responsible for the death of seven patients. Separate analyses were made of blocks from infarcted areas and of blocks from distant areas that appeared uninfarcted to gross examination. Infarcted myocardium showed a marked but proportionate increase in sodium and chloride, reflecting a severe interstitial edema, and an even more marked reduction in potassium, magnesium, and phosphorus, reflecting primarily losses from dead and dying cells. The analyses of distant blocks that were not grossly infarcted gave results for all five electrolytes that were intermediate between the values obtained from infarcted segments and those from normal controls. The abnormalities in chemical composition of myocardium well beyond the boundaries of a recent infarct were attributed to ischemia. Analysis of skeletal muscle from these patients did not deviate significantly from the normal.