So, why is this situation not arisen? The details are explored below but the basic presumptions that a patient will simultaneously contact the mains, with a catheter inserted, using equipment that grounds the catheter, is very, very unlikely. Also most electrical connections made in or around a patients heart will be those of medical electrical equipment. Medical electrical equipment, which have such applied parts, are constructed to strict standards that limit the allowable currents flowing via such connections (applied parts). This ensures the safety of the patient.