Apparatus and methods for the treatment of atrial fibrillation are described herein where tissue to be ablated may be monitored under direct visualization for tissue parameters (e.g., temperature and impedance) prior to, during, or after ablation. The system may include a deployment catheter and an attached imaging hood deployable into an expanded configuration. The imaging hood is placed against or adjacent to the tissue to be imaged in a body lumen that is normally filled with an opaque bodily fluid such as blood. A translucent or transparent fluid can be pumped into the imaging hood until the fluid displaces any blood leaving a clear region of tissue to be imaged via an imaging element in the deployment catheter. An ablation probe and one or more interrogation needles having sensors are advanced into the tissue to be ablated and monitored. Alternatively, a combined ablation and interrogation probe may be used.