Development and preliminary clinical tests of an impedance sensing VDD recording pacemaker for diagnosis and research

Episodes of serious but infrequently occurring cardiac arrhythmias can be d ifficult to detect and analyse, even with modern Holter monitoring. A previ ous diagnostic pacemaker developed by this group provided VVI pacing therap y and recorded intracardiac ECG signals but had no atrial sensing or impeda nce measuring capability. A new external diagnostic pacemaker system is des cribed that has been developed to assist in diagnosing intermittent arrhyth mias by selectively recording intracardiac signals. Unlike other ambulatory monitors, in addition to recording EGG, the device combines VDD pacing the rapy with the capability of monitoring and recording intracardiac impedance and pressure waveforms through a temporary intracardiac lead. A PCMCIA mem ory card allows storage of 48 arrhythmic events of 21 seconds each. Twelve seconds of waveform are retained before the event occurs and nine seconds a fter. Data retrieval and processing is performed with a PC which reconstruc ts each waveform for display. The ECG provides data on cardiac rhythm while cardiac function is inferred from the haemodynamic signals. During simulat ed trials, 14 event types were presented to the system. All events were suc cessfully detected and recorded. During in vivo clinical tests 83 waveform recordings were made. Impedance fluctuations with typical peak-to-peak valu es of 64 ohms were successfully recorded.