Does any correlation exist between a high plasma digoxin level and an electrocardiogram in older and younger patients?

In a group of 171 patients aged 65 to 92 years and 58 patients aged 35 to 64 years, plasma digoxin level measuring 2.5-6.2 nmol/l correlated with the clinical symptoms and the electrocardiogram. Conduction disturbances and arrhythmias as well as the P-R interval, P-T-Q index, and corrected Q-T interval in the ECG were analyzed. Clinical symptoms of hypersaturation with digitalis were present in 55.5% of the elderly and 34.4% of the younger patients. Conduction disturbances were found in 43.2% of the elderly and 20.6% of the younger patients, while arrhythmias appeared in 40.3% of the elderly and 29.3% of the younger patients: 16.3% of the elderly and 50.1% of the younger patients were without these changes. A correlation between the P-R interval and high plasma digoxin level in the elderly (p < 0.01) and younger patients (p < 0.05), as well as between the P-T-Q index and high plasma digoxin level in the elderly (p < 0.01), was found. There was no correlation between the corrected Q-T interval and high plasma digoxin level in both groups. No correlation was found between the high plasma digoxin level and serum creatinine level in both groups, or between the high plasma digoxin level and serum potassium level in both groups, although many patients had chronic renal failure. The effect of digitalis has not been shown to be a cause of specific changes in an electrocardiogram either in the elderly or in younger patients. However, the association between prolonged P-R interval, as well as changes in the P-T-Q index, and high plasma digoxin level has been found more often in the elderly than in younger patients.