Background: Atrial fibrillation (AF) is the most common form of cardiac arrhythmia. A number of studies have demonstrated that heart rate control is the first line therapy for patients with AF. However, the correct ventricular rate and the parameters to be assessed are still open to question. The aim of the study was to evaluate whether mean heart rate (mHR) in 24-hour ECG Holter monitoring (HM) is useful parameter for the assessment of ventricular rhythm control in patients with AF. Additionally, we investigated whether other parameters such as episodes of tachy AF, irregularity of rhythm and the patient’s awareness of "palpitations" play an important role in controlling ventricular rate in AF.
Methods: Patients with chronic brady-tachy AF who had undergone VVI pacemaker implantation between 2 and 9 days earlier (a mean of 5.6 days previously) with optimal pharmacotherapy and mHR below 90 bpm were enrolled in this study. The studied parameters included mHR and the coefficient of irregularity (CI), based on HM and the percentage of fast ventricular rates (tachy AF episodes defined as a heart rate of > 120 bpm) derived from the pacemaker memory data. Symptoms such as "palpitations" were marked with a "+" over a period of 24 hours.
Results: Forty two patients (18 male, 24 female) with a mean age of 70.2 ± 8 years were included in the study. Their mHR in HM ranged from 48 bpm to 79 bpm, with a mean of 64.8 ± 7.5 bpm. Despite of a correct mHR, in 21 patients (50%) tachy AF episodes were observed. accounting for 1% to 8% beats, with a mean of 2.7 ± 2.02%. CI in HM varied from 0.9 to 0.33 with a mean of 0.23 ± 0.06. Significant irregularity, a CI above 0.2, together with a correct mHR was found in 73% patients. In the majority of patients with a low CI of < 0.2 (10 out of 11) there were no tachy AF episodes. A significant CI (> 0.2) was found in 10 out of 18 patients (56%) with a correct mHR and without tachy AF episodes. Palpitations were noted in 16 out of 21 patients with the correct mHR who had tachy AF episodes and 9 out of 10, also with the correct mHR, in whom no such episodes were recorded. All these patients had a significant ventricular rate irregularity with a CI of > 0.2.
Conclusions: The parameter of mHR derived from HM is not sufficient for controlling ventricular rate in the majority of patients with brady-tachy AF. It seems that evaluating tachyAF episodes, rhythm irregularity and symptoms experienced by the patient are also necessary for establishing for correct control of the heart rate in patients with AF. The CI could be superior to other parameters for the assessment of patients with AF who have correct mean heart rate.