[Circadian pattern features of paroxysmal atrial fibrillation in elderly patients with ischemic heart disease].

Forty-eight elderly patients with IHD and paroxysmal atrial fibrillation were studied to determine circadian pattern of arrhythmia onset. The data were obtained by detailed interview and analysis of medical documents. The found variations were fitted to cosinusoidal function with a period of 24 hours Y = 9.75 + 3.5cos(2 pi t/24 + 0.2) (R2 = 0.69; F = 10.2; P < 0.01; two first coefficients of equation are significant by t-test, P < 0.01), the peak of arrhythmia onset was observed about midnight. 59.8% of overall number of episodes developed at dark period of day (P < 0.05). Findings testify that time periods of arrhythmia onset increase in number with disease evolution. It may be an additional criterion of paroxysmal atrial fibrillation transformation into its permanent form.