Report:

Pacemaker rhythm 70/min 2

Somatic tremor 4

Pacemaker inhibition by myopotentials 4

Comment:

Unipolar pacemakers are more likely to be inhibited by myopotentials than bipolar ones. Muscle inhibition is rarely seen in modern pacemakers (this one is from 1976). In a totally pacemaker-dependent patient, the simplest therapy is to convert the demand unit to fixed-rate (asynchronous) mode. In this case, the patient was just advised to avoid straining his pectorals. Fortunately, he was not a body-builder.

It is important to ensure the patient’s safety from falls when performing this test. I did, but the patient refused to repeat the exercise, saying: “Now we know, fair enough”. He must have sensed I was after another recording for my own benefit.

Fig 69. 49 year old woman with large basal infarction and documented Möbitz 2 AV block requiring pacing. Following multiple arrests the pacemaker threshold rose from 1.0 to 6.0 mAmps and the tracing shown below was obtained. What are the conduction abnormalities observed? What is the likely position of the pacemaker tip?