In some implementations, a method of ablating body tissue includes (a) locating an inflatable balloon portion of a cryotherapy balloon catheter at a treatment site internal to a patient's body, and inflating the inflatable balloon portion; (b) employing electrodes that are disposed on an expandable surface of the inflatable balloon portion to electrically characterize body tissue at the treatment site; (c) ablating the body tissue by supplying a cryotherapy agent to the inflatable balloon portion to cool the body tissue to a therapeutic temperature; (d) employing the electrodes to determine whether the ablating caused desired electrical changes in the body tissue; and (e) repeating (c) and (d) when it is determined that the ablating did not cause the desired electrical changes.