Effect of pentaphasic pulse sequence as an impedance sensor on standard electrocardiographic recordings

Two advances in cardiac pacing have resulted in an internal conflict in some pacemakers. One is the development of a standard lead physiological sensor and the other is protection from electromagnetic interference (EMI). One popular type of standard lead sensor uses subthreshold pulses to measure intracardiac and intrathoracic impedance changes, i.e., minute ventilation. Recent clinical observations and extensive in vitro testing have verified that digital cellular phones can be troublesome. Large feedthrough capacitors (FCs), effective in blocking the EMI, will preclude sensing of the standard impedance-based signals. A variety of pulse configurations were studied that might be effective for a sensor-based impedance signal while allowing the pacemaker to continue to use large FCs protecting them from environmental EMI. In comparison to both monophasic and biphasic pulse sequences, a pentaphasic pulse sequence was effective as an impedance sensor, still allows large FCs to function as an effective filter for environmental EMI, and would not produce artifacts on surface ECG.