The leadless multichamber pacemaker offers significant advantages in treating arrhythmias and enhancing cardiac function. Intracardiac communication is essential for ensuring coordinated pacing of multi-chamber pacemakers that do not have leadless technology. However, the dynamic changes in the intracardiac channel present a significant challenge. Hence, mastering the dynamic characteristics of intracardiac channels and accurately modeling them is crucial. In this paper, we introduce a validated intracardiac channel equivalent circuit model that accounts for the electrical characteristics of cardiac tissue and the volume fluctuations in cardiac chambers. The results demonstrate that the agreement coefficient between the circuit model and the in vitro pig heart model reached 80.7% in the time domain. The proposed equivalent circuit model demonstrates high accuracy and stability in addressing the challenge of dynamic changes in intracardiac channels and simplifying in vivo or in vitro experiments.