Acute Myocardial Ischemia During Pacemaker Implantation: Implication for Threshold Determinations and Potential Complications

The onset of acute myocardial ischemia during pacemaker implantation may strikingly alter measured threshold values so that unnecessarily high generator output parameters are programmed. In addition, ischemia muscle is more vulnerable to malignant arrhythmias if the stimulating electrode is in an ischemic area. Two patients are presented whose threshold values rose sharply during an ischemic attack and returned to baseline after the angina subsided. Relief of angina is a clinically useful determinant of the safety necessary to proceed with implantation and threshold measurements