[Dynamic electrocardiogram in chronic atrial fibrillation treated with digitalis].

To assess heart rate variability in chronic atrial fibrillation, 60 patients (20 men, 40 women: mean age 63 +/- 8 years: NYHA 2.0 +/- 0.5) with various cardiac conditions were investigated with 24-hour Holter monitoring during daily life. Twenty-five healthy subjects (5 men, 20 women: mean age 55 +/- 9) were considered as the control group. All patients had "controlled" heart rate (50-90 bpm) on basal ECG, normal hematological and thyroid hormone values, and took digoxin alone (mean dosage 0.22 +/- 0.05 mg). Mean digoxin plasma levels were 0.88 +/- 0.48 ng/ml. Maximum, minimum and average heart rate were quite good during the night but too high during the daytime and far higher than those observed in healthy subjects. In fact, up to 82% of patients (at 9 a.m.) had a maximum heart rate higher than 115 bpm. Pauses between 2.0 and 3.0 sec occurred in 40 out of 60 patients (66%). No patients had pauses longer than 4.0 sec. In our experience, patients in chronic atrial fibrillation "controlled" with digoxin alone showed a daytime heart rate which was often too high. We suggest 24-hour Holter monitoring to detect subgroups that may be treated successfully with digoxin associated with calcium-antagonists or beta-blockers.