QT‐Related Rate‐Responsive Pacing During Acute Myocardial Infarction

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Abstract
We studied the findings in a patient who had a TX 915 pacemaker and who was suffering from an acute inferior myocardial infarction. On admission, we observed pacing at the upper rate limit due to excessive adrenergic tone. Shortly thereafter a strong vagal reaction occurred, and the pacing rate fell back to the lower rate limit. This condition was improved with atropine. (1) In the described condition the TX pacemaker behaved in a very "physiological" fashion; (2) Sudden strong cholinergic activity lengthened the QT interval; (3) Programming of a steep slope must be avoided in coronary artery disease; (4) Stimulus-T-wave intervals at maximal adrenergic and cholinergic stimulation should be taken into account when programming the slope and the T-wave sensing window.