An implantable cardiac stimulation device is configured to generate multiphasic stimulation pulse waveforms. These multiphasic stimulation pulse waveforms are configured such that they can be substantially rejected within the intracardiac signal sensing circuitry. In certain implementations this allows for simultaneous stimulation therapy and sensing and analysis of intracardiac signals. In other implementations, the blanking interval associated with the intracardiac signal sensing circuitry may be reduced or eliminated. Furthermore, the fast recharge period may be reduced or eliminated, and/or the polarization at lead-tissue interface may be reduced or effectively eliminated by using multiphasic stimulation pulse waveforms. Such cardiac stimulation techniques are particularly useful in providing antitachycardia pacing (ATP) therapy, wherein pacing during a T wave can lead to fibrillation being triggered.