A system for diagnosis or treatment of tissue in a body is provided. The system includes an ablation catheter having a deformable, elongate shaft having proximal and distal ends. The catheter further includes an ablation delivery member disposed proximate the distal end of the shaft and configured to deliver ablation energy to ablate the tissue. In one embodiment, the ablation delivery member comprises an ablation electrode and may also be configured to generate a signal indicative of electrical activity in the tissue. The catheter further includes one or more sensing electrodes disposed proximate the ablation delivery member. The sensing electrodes are configured to generate signals indicative of electrical activity in the tissue. The system further includes an electronic control unit configured to control delivery of ablation energy from the ablation delivery member responsive to one or more of the generated signals indicative of electrical activity in the tissue.