A system, operatively connectable both to a cardiac-rhythm-management (CRM) subject, and to a CRM device associated with that subject, and an associated method, operable, in relation to received-and-processed, real-time, CRM-subject-specific, simultaneous ECG and heart-sound information, and other information including measurement time markers where available, for blocking, under all circumstances during the ventricular relative refractory period lying within each of successive CRM-subject cardiac cycles occupying a span of such cycles, the ventricular pacing activity of the subject-associated CRM device—the beginning and ending of such blocking in each cardiac cycle being system-defined to lie preferably, and respectively, (a) within the real-time, ventricular depolarization window in the cycle, and (b) at the time of the real-time, S2 heart-sound, plus or minus any user-defined time-delta.