Network tools for tracing the dynamics of heart rate after cardiac transplantation

A network representation of time intervals between subsequent heart contractions is proposed as a way to qualify and quantify short-term dynamical patterns, obtained from ECG recordings. It allows the observation of the development of arrhythmia in a non-invasive and patient-oriented way. As an example, a network is constructed from the nocturnal Holter recordings of a male heart transplant patient, who had been in good overall health for 17 years after the surgery. The biatrial surgical technique applied to him led to interference between the recipient and donor pacemakers, which resulted in misleading information provided by standard heart rate variability measures. The noticeable differences in the network structure observed in the patient follow-up study serve to reveal and quantify changes in the leading mechanisms underlying the dynamics of heart contractions.