Intracardiac　wireless　communication　is　crucial　for　the　development　of　multi-chamber　leadless　cardiac　pacemakers　(LCP).　However,　the　time-varying　characteristics　of　intracardiac　channel　pose　major　challenges.　As　such,　mastering　the　dynamic　conduction　properties　of　the　intracardiac　channel　and　modeling　the　equivalent　time-varying　channel　are　imperative　for　realizing　LCP　multi-chamber　pacing.　In　this　paper,　we　present　a　limiting　volume　variational　approach　based　on　the　electrical　properties　of　cardiac　tissues　and　trends　in　chamber　volume　variation.　This　approach　was　used　to　establish　a　quasi-static　and　a　continuous　time-varying　equivalent　circuit　model　of　an　intracardiac　channel.　An　equivalence　analysis　was　conducted　on　the　model,　and　a　discrete　time-varying　equivalent　circuit　phantom　grounded　on　the　cardiac　cycle　was　subsequently　established.　Moreover,　an　ex　vivo　cardiac　experimental　platform　was　developed　for　verification.　Results　indicate　that　in　the　frequency　domain,　the　congruence　between　phantom　and　ex　vivo　experimental　outcomes　is　as　high　as　94.3%,　affirming　the　reliability　of　the　equivalent　circuit　model.　In　the　time　domain,　the　correlation　is　up　to　75.3%,　corroborating　its　effectiveness.　The　proposed　time-varying　equivalent　circuit　model　exhibits　stable　and　standardized　dynamic　attributes,　serving　as　a　powerful　tool　for　addressing　time-varying　challenges　and　simplifying　in　vivo　or　ex　vivo　experiments.　IEEE