Monophasic vs. biphasic stimulation of single cardiomyocite cell: A simulation study

Mechanisms involved in the initiation of fibrillation and defibrillation are complex and still not totally understood. This paper computationally investigated the effect of monophasic, biphasic and reversed biphasic stimuli on single cardiomyocyte, with a modified Ten Tusscher model of human ventricular action potential (AP) and calcium dynamics. Three different S1-S2 protocols with variable duration were used: monophasic, biphasic and reversed biphasic. Results were expressed in terms of total response duration (TRD), defined as the interval between the S1 onset and the response generated by S2. TRD was focused both on AP (V_m-TRD) and on Calcium transient (Ca-TRD). Simulations confirmed previous results obtained with the Beeler-Reuter model pointing to the role of I_Na in prolonging the refractory period when using a biphasic stimulus. No differential effects of biphasic vs monophasic stimulation when Ca-TRDs are compared instead of V_m-TRDs were found.