Effect of Experimental Congestive Heart Failure and Acetyl Strophanthidin on Myocardial Electrolyte and Water Content

Effects of chronic digoxin treatment on cardiac function, electrolytes, and sarcolemmal ATPase in the canine failing heart due to chronic mitral regurgitation

This study was designed to determine whether digoxin therapy in the canine heart failing because of mitral regurgitation (MR) provides only hemodynamic benefit and accompanying subjective improvement or if it also reverses the changes in intracellular Ca++ and sarcolemmal Na+-K+-ATPase. The dogs were divided into four groups: control, MR of 3 months' duration, MR of 6 months', and digoxin treatment for 3 months after 3 months of MR. Six months of MR produced a marked decrease in the index of myocardial contractility and function associated with a decrease in intracellular Ca++ and Na+, and an increase in intracellular K+, extracellular space, sarcolemmal Na+-K+-ATPase, and Mg++-ATPase. Digoxin treatment tended to return the changes in the index of myocardial contractility and cardiac function, intracellular Ca++, Na+, K+, extracellular space, and sarcolemmal Na+-K+-ATPase of the failing heart toward control levels. Digoxin treatment did not affect Mg++-ATPase. The right ventricle, which did not fail, also did not show any significant changes in the parameters measured. The results showed that digoxin treatment not only improved the index of myocardial contractility and cardiac function of the failing heart but also tended to return the electrolytes and sarcolemmal Na+-K+-ATPase toward control levels.

[Influence of spirolactone on the myocardial potassium balance following strophanthin in man (author's transl)]

In order to examine the question, whether improved digitalis tolerance by Spirolactone may be partially a result of antagonism on myocardial potassium balance, 6 patients without clinical signs of heart failure were given 400 mg, 3 were given 200 or 300 mg Spirolactone orally daily and 6 patients received placebo during a 5 to 7 days period. During cardiac catheterization hemodynamics and serum potassium concentrations were determined repeatedly prior to and following intravenous administration of 0,375 to 0,625 mg Strophanthin. Injection of Strophanthin resulted in a significant drop in left ventricular enddiastolic pressure and a rise in dp/dt max. In the control group a significant increase in arterial and coronary sinus potassium concentration was observed. Myocardial potassium balance was definitely negative from the third to the eighth minute. Values in the group receiving Spirolactone did not differ significantly from the placebo group. It is suggested that therapeutic doses of Strophanthin resllt in a loss of potassium from the myocardium by inhibition of the Na+, K+ membrane ATPase not influenced by pretreatment with Spirolactone.

Postmortem detection of inapparent myocardial infarction

Two methods of detecting early inapparent myocardial infarcts have been studied and their value in diagnostic practice compared. The better method proved to be the determination of the potassium to sodium ratio (ionic ratio) which falls in infarcted tissue within minutes of the onset of anoxia. The second method was nitro blue tetrazolium staining of gross sections of myocardium which revealed any infarct older than three and a half hours. As staining is dependent upon enzyme activity, the latter method is disturbed by autolysis. It was shown, on the other hand, that the ionic ratio (K(+)/Na(+)) was not affected by autolysis and was therefore well suited to forensic practice. Sixteen non-infarcted control hearts, plus the nine from cases of sudden death due to causes other than myocardial infarction, all yielded high ionic ratios (K(+)/Na(+)), average 1.4, and stained normally with tetrazolium (the normal controls). Positive control was provided by 20 histologically proven infarcts of which the ionic ratios (K(+)/Na(+)) were all low (average 0.7). Histochemical staining with tetrazolium delineated infarcted areas in each case. In a series of 29 sudden deaths, a cause of death other than myocardial infarction was found at necropsy in nine, mentioned above as normal controls. The remaining 20 hearts were not infarcted histologically, but were shown to be infarcted by examination of the ionic ratios (K(+)/Na(+)). These ratios were low (average 0.8) including three borderline ratios. Confirmatory evidence of infarction included nitro blue tetrazolium staining which revealed infarcts in 10 of the 20 cases, and clinical and necropsy observations. The ionic ratio (K(+)/Na(+)) decreases as the age of the infarct increases for at least 24 hours. Thereafter as healing proceeds, the ratio gradually reverts to normal. Thus, previous infarction and replacement fibrosis do not significantly alter the ionic ratio (K(+)/Na(+)). Nor is it changed by left ventricular hypertrophy, the presence of congestive cardiac failure, or digitalis therapy. It is suggested that macroscopic tetrazolium staining is a useful screening test for early inapparent myocardial infarcts. In cases where no infarct is delineated with that method estimation of the ionic ratio (K(+)/Na(+)) should be carried out on myocardium removed from standard areas on the anterior and posterior left ventricular walls.

Studies on digitalis. 13. A comparison of the effects of potassium on the inotropic and arrhythmia-producing actions of ouabain

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