[Serum digitoxin levels in pacemaker patients].

In most cases pacemaker patients represent a diverse geriatric group in which ECG and clinical signs are of minor usefulness in diagnosing digitalis toxicity. We therefore determined serum glycoside concentrations in 200 consecutive patients attending our pacemaker clinic (with a mean maintenance dose of 0.093 mg digitoxin per day) and tried to correlate these to clinical, ECG and chemical findings. Multivariate analyses were also carried out to assess whether serum digitoxin concentrations lay in a subtherapeutic (0 to 8.99 ng/ml), therapeutic (9 to 27 ng/ml) or toxic (above 27 ng/ml) range on the basis of a combination of variables. The mean digitoxin concentration was 24.0 +/- 10.3 ng/ml (0 to 45 ng/ml) and correlated poorly with patient compliance (r = 0.36), serum potassium (r = 0.24), weight (r = 0.17) and digitoxin dose (r = 0.13), but not with ECG and subjective or clinical findings. A prediction of the three ranges of the serum digitoxin concentration was possible by means of variable compliance, body weight and digitoxin dose with a probability of up to 79%. In view of the above-mentioned problems indications for digitalis therapy in pacemaker patients must be constantly reviewed and control determination of serum digitoxin concentration should be frequently undertaken.