Overprescription and underprescription of digitalis.

As part of a health examination of a representative sample (n = 8,000) of the adult Finnish population, cardiac state was assessed in the 747 digitalis users and the 6,329 non-users who participated in the survey. Ninety per cent of the digitalis users were in sinus rhythm and 50% were in sinus rhythm and had a normal roentgenographic heart volume. About 20% of those in sinus rhythm had a normal heart volume and a "subtherapeutic" serum digitalis concentration. The age-adjusted prevalence of digitalis therapy in the presence of sinus rhythm was 8% in men and 10% in women. The total number of these patients in Finland was estimated at 246,000 (95% confidence limits 225,000-267,000). Half of the men and two thirds of the women on digitalis received concomitant diuretic therapy. Atrial fibrillation and/or markedly enlarged heart were observed in 1.5% of the men and 0.9% of the women not receiving digitalis. Their total number in the Finnish population was estimated at 23,000 (+/- 7,000). The results suggest that questionable digitalis therapy is very common since several authors have reported successful withdrawal of maintenance digitalis therapy in at least half of the patients in sinus rhythm. On the other hand, underprescription of digitalis seems to be uncommon.