<p>In this paper, we present a novel Matlab platform for pacemaker algorithm assessment based on anatomically detailed closed-loop computer modeling of cardiac electrophysiology. Our platform couples whole-heart cardiac electrophysiology monodomain models based on patient-specific geometries with a pacemaker emulator to enable closed-loop simulations of cardiac pacing. A custom-designed graphical user interface, developed as an integral part of our platform, drives the user through the setup process, from model generation to pacing algorithm definition and simulation execution. Our platform offers a high degree of flexibility and provides a powerful tool for in-silico testing and assessment of pacemaker algorithms. Indeed, we tested its functioning in three different scenarios, including healthy activation, endless-loop tachycardia induction by ectopic ventricular activation in a first-degree atrioventricular block condition, and endless-loop tachycardia induced by a ventricular pacing minimization strategy. In particular, we exploited our platform to characterize the induction of endless-loop tachycardia due to atrioventricular delay hysteresis algorithms as a function of pacemaker parameters and intrinsic conduction properties of the patient. This in-silico study provides an example of how our platform could identify safer pacemaker configurations depending on the electrophysiological heart condition. Thus, the proposed approach enables the investigation of complex pacemaker-heart interactions in anatomically detailed cardiac models, providing valuable insights into pacing algorithm performance and safety. We believe our platform could also be easily employed by users without any experience in computer modeling to enhance pacemaker configuration, assess clinical performance, and support the development of new algorithms.</p>