Effects of hyperkalemia on the electrocardiogram of patients receiving digitalis.

In a prospective and a retrospective study, the effects of hyperkalemia on the electrocardiogram (ECG) of patients treated with customary maintenance doses of digoxin were examined and the results were compared with the effects of hyperkalemia in patients not receiving digitalis. The prospective study included 11 patients treated and 11 not treated with digitalis, and the retrospective study 27 patients treated and 61 not treated with digitalis. In all patients serum potassium concentrations (Ks) were determined within 1 hour of the recorded electrocardiogram. Serum digoxin concentrations, measured in 11 patients in the prospective and in 4 in the retrospective study, ranged from 0.7 to 5.0 ng/ml, and exceeded 2.0 ng/ml in 10 of 15 patients. Since the results of the prospective and of the retrospective study were similar, they were combined. In patients treated with digitalis, Ks ranged from 5.5 to 6.6 mEq/liter in 21 patients, from 6.7 to 7.5 mEq/liter in 17 and from 7.6 to 8.5 mEq/liter in 6; the Ks was 9.1 mEq/liter in 1 patient. The ventricular rate in patients treated with digitalis ranged from 48 to 140 beats/min, and was not significantly different from that in untreated patients within each range of Ks. Atrioventricular (AV) junctional rhythm occurred more frequently in the electrocardiograms of digitalis-treated patients (15 of 45 vs 2 of 76, p less than 0.001). The average PR intervals were longer in patients treated with digitalis who had Ks greater than 6.6 mEq/liter, but no patient in the study had greater than first-degree AV block, and no patient required a pacemaker.(ABSTRACT TRUNCATED AT 250 WORDS)