Cardiac contractility modulating (CCM) signals delivered by the OPTIMIZER System are being investigated as a treatment for medically refractory heart failure. Previous chronic studies of CCM have excluded patients with prolonged QRS and a cardiac resynchronization therapy (CRT) device. However, symptoms persist in more than 25% of these CRT patients. CCM may offer a therapeutic option for these non-responders. Here we report the first use of CCM signals in a patient who did not respond to treatment with a CRT-D device. We show that the implantation is technically feasible, that the OPTIMIZER and CRT-D devices can coexist without interference and that acute haemodynamic and clinical improvements can be observed. The results suggest that systematic investigation of CCM treatment in CRT non-responders is warranted.