• Images in cardiology

This ECG was obtained from a patient on VVI pacemaker with autocapture function. The ECG shows two pacemaker spikes simulating dual chamber pacing.

Pacemakers with autocapture function automatically adjust the stimulation output of the pacemaker to changes in stimulation threshold of the heart, decreasing energy consumption. It verifies every single stimulus by monitoring the evoked response signal from myocardial depolarisation; it also increases patient safety by delivering a high output backup pulse if there is a loss of capture. The ECG shown here illustrates such a phenomenon. The first stimulus was ineffective, so the pacemaker delivered a high output backup pulse, which captured the ventricle. The two pacemaker stimuli coming together simulate atrioventricular sequential pacing. Fusion or pseudo-fusion beats can result if the evoked response stimulus resulting from myocardial depolarisation is insufficient.