Correlation between electrocardiographic changes, serum digoxin, and total body digoxin content.

Serial electrocardiograms and serum digoxin levels were obtained in four healthy volunteers receiving daily doses of digoxin, 0.25 mg for the first two weeks and 0.5 mg for two more weeks. We found a linear relationship between serum digoxin levels and the "PTQ index" (a function of the PR-interval, corrected QT-time, and T-wave depression). In 3 of the 4 subjects the correlation was statistically significant. The degree of linear correlation was improved when PTQ was correlated with the computer-calculated total body burden of digoxin.