Techniques for determining when to deliver a pre-excitation signal to damaged cardiac tissue, e.g., infarct tissue, of a ventricle during cardiac pacing are described. A medical device detects an intrinsic or paced atrial depolarization, and then detects a subsequent mechanical event, e.g., contraction, in a ventricle. As examples, the mechanical event may be detected by measuring ventricular movement, or changes in intracardiac or systemic blood pressure. The medical device determines an interval between the atrial depolarization and the ventricular mechanical event, which may be referred to as an A-Vm interval. By subtracting a pre-excitation interval (PEI) from the A-Vm, the medical device determines an A-V interval between an atrial depolarization and delivery of the pre-excitation signal.