A method for invasive cardiac treatment, including inserting a catheter via a transvascular route into a beating heart of a patient who is anesthetically paralyzed and intubated for ventilation, and, after inserting the catheter, temporarily halting ventilation of the patient. The method includes moving the catheter between a plurality of locations of myocardial tissue of the heart while the ventilation is halted; and ablating the myocardial tissue of the heart at the plurality of locations while the ventilation is halted.