Although single-node leadless pacemakers eliminate several complications associated with subcutaneous pockets and leads, they have the significant limitation of only being able to perform single-chamber pacing. Multi-nodal pacing can outperform single-chamber pacing by providing a closer approximation of sinus rhythm but requires energy-efficient wireless communication to preserve synchrony. In this work, we propose a novel biocompatible communication concept wherein the pacemaker node located in the sinoatrial (SA) node stimulates the right atrium and simultaneously sends a synchronization message, encoded into the pacing time, to all other pacemaker nodes located at different sites in the heart. We refer to this concept as the Pace Time Modulation (PTM) method and assess its performance in terms of symbol error rate and achievable information rate. The analyses and numerical simulations indicate that PTM can be applicable in realistic scenarios, without deviating the heart rate from its normal range.