Removal of AC interference from the electrocardiogram.

A method is described for the removal of AC interference from the electrocardiogram in monitors which do not have isolated inputs. The patient's leads are connected to an isolation amplifier which provides isolation between the input and the output and has a high common mode rejection ratio. The output from the isolation amplifier is taken to the electrocardiographic monitor. The isolation amplifier not only provides additional patient safety but also reduces the level of AC interference without interfering with any frequency components in the electrocardiogram.