Entrainment in modulated parasystole

A computer model of modulated parasystole is described in which the sinus-node cycle length is sinusoidally varied with three different amplitudes and periods, to mimic low-frequency fluctuations in the heart rate. The model has been programmed in MS-Fortran V4.0 and has 15 parameters, all represented as 4-byte integer numbers, which can be divided into three groups: parameters regarding the sinus node, parameters regarding the ectopic pacemaker, and pacemakers regarding refractoriness. Each simulation run consists of the computation of 1000 pacemaker firings, irrespective of their nature (sinus node or ectopic) or their effectiveness (hidden or manifest). Eventual convergence to an entrained state is assumed to happen within the first 400 firings. The simulations suggest that entrainment on the pacemaker-firing level is to be expected in cases of varying sinus rhythm. However, this entrainment does not directly become manifest in the ECG. The model shows that various forms of concealed entrainment may be expected in the real world