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Effect of low dose sotalol on the signal averaged P wave in patients with paroxysmal atrial fibrillation.
  1. P. J. Stafford,
  2. J. Cooper,
  3. D. P. de Bono,
  4. R. Vincent,
  5. C. J. Garratt
  1. Academic Department of Cardiology, Glenfield General Hospital, Leicester.

    Abstract

    OBJECTIVE--To investigate the effects of low dose sotalol on the signal averaged surface P wave in patients with paroxysmal atrial fibrillation. DESIGN--A longitudinal within patient crossover study. SETTING--Cardiac departments of a regional cardiothoracic centre and a district general hospital. PATIENTS--Sixteen patients with documented paroxysmal atrial fibrillation. The median (range) age of the patients was 65.5 (36-70) years; 11 were men. MAIN OUTCOME MEASURES--Analysis of the signal averaged P wave recorded from patients not receiving antiarrhythmic medication and after 4-6 weeks' treatment with sotalol. P wave limits were defined automatically by a computer algorithm. Filtered P wave duration and energies contained in frequency bands from 20, 30, 40, 60, and 80 to 150 Hz of the P wave spectrum expressed as absolute values (P20, P30, etc) and as ratios of high to low frequency energy (PR20, PR30, etc) were measured. RESULTS--No difference in P wave duration was observed between the groups studied (mean (SEM) 149 (4) without medication and 152 (3) ms with sotalol). Significant decreases in high frequency P wave energy (for example P60: 4.3 (0.4) v 3.3 (0.3) microV2.s, P = 0.003) and energy ratio (PR60: 5.6 (0.5) v 4.7 (0.6), P = 0.03) were observed during sotalol treatment. These changes were independent of heart rate. CONCLUSIONS--Treatment with low dose sotalol reduces high frequency P wave energy but does not change P wave duration. These results are consistent with the class III effect of the drug and suggest that signal averaging of the surface P wave may be a useful non-invasive measure of drug induced changes in atrial electrophysiology.

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