Pacemaker Failure to Capture

The pacemaker in this recording is not sensing, as the sensing circuit has been disabled by placing the magnet over the pacemaker and converting it to VOO pacing.

Note the following:

• the second (as well as other) pacer spike does not capture the ventricle
• the first pacer spike captures the ventricle and resets the sinus node too, as the next sinus beat is slower than the patient's intrinsic rate of about 70/min
• that the pacer spikes that fall near to the T wave tend to capture while those away from the T wave not to capture. This is some what like supranormal conduction, and is seen with pacers where a preceding beat can lower the pacing threshold.
• This is either a lead failure or a pacer that was programmed to too low an output.

Dr. M. Rosengarten