Techniques are described for delivering inotropic electrical therapy to myocardial tissue using an implantable cardiac stimulation device such as a pacemaker. In one example, electrical stimulation is applied by a pacemaker to the heart of a patient while taking into account dynamic trans-cardiac impedance waveforms measured within the patient. In another example, a series of subthreshold inotropic stimulation pulses are delivered just prior to delivery of a suprathreshold depolarizing pulse that triggers systole. Additional subthreshold inotropic stimulation pulses can also be delivered following the suprathreshold pulse. Preferably, the magnitudes of the inotropic pulses are incrementally increased prior to systole then decremented thereafter, thereby gradually recruiting myocardium that has differing thresholds for depolarization. Both techniques seek to improve myocardial contractility of diseased tissue by improving calcium flux. Both techniques may additionally exploit the use of “multidimensional forced fusion”, described herein.