Left-sided breast radiotherapy for patients with a cardiac implanted electronic device (CIED) is challenging as the achievement of an appropriate dose coverage must be combined with the lowest possible dose to the implant itself to avoid malfunction. Although the 3D technique, in principle, is the priority choice to minimize the scattered dose, this study verifies the feasibility of using the VMAT technique taking the 3D technique as benchmark. This study compares the dosimetry of VMAT and 3D-tangential field in field (TFiF) for left-sided breast treatment plans optimised in the presence of CIED.