CHARACTERISTICS OF PATIENTS AT RISK FOR PERIOPERATIVE MYOCARDIAL-INFARCTION AFTER INFRAINGUINAL BYPASS-SURGERY - AN EXPLORATORY-STUDY

Patients requiring infrainguinal bypass surgery often have diffuse ath erosclerotic disease, and perioperative myocardial infarction (MI) is a potentially lethal complication that is not uncommon in these patien ts. To establish additional clinical characteristics that might be use ful in identifying patients who require more extensive cardiac evaluat ion, we conducted an exploratory case-control study comparing 22 patie nts who had a perioperative MI following elective infrainguinal bypass surgery with 191 control subjects whose bypasses were uneventful. In addition to previously recognized risk factors (e.g., history of angin a or prior MI), we examined the association of perioperative MI with ( 1) results of common preoperative laboratory tests and ECG, (2) preope rative use of certain medications, and (3) intraoperative factors that might be anticipated prior to surgery (e.g., duration of surgery or t ype of anesthesia). Perioperative MI was associated not only with a hi story of angina, prior MI, or coronary artery disease but also with th e need for certain cardiac medications, higher white blood cell (WBC) counts, ST-segment depression, left bundle branch block, and lengthy s urgical procedures. Multiple logistic regression analysis identified t he following factors as being independently associated with perioperat ive MI: preoperative antiarrhythmic agents (odds ratio [OR] = 26.4, p = 0.006), nitrates (OR = 8.4, p = 0.006), calcium channel blockers (OR = 5.5, p = 0.04), and aspirin (OR = 6.8, p < 0.01) and ST-segment dep ression (OR = 11.8, p = 0.01), WBC count (OR = 1.27/1000, p = 0.005), and duration of surgery (OR = 2.2/hr, p = 0.0001). In patients undergo ing infrainguinal bypass surgery, perioperative MI is associated not o nly with a history of previous cardiac events and ECG evidence of isch emia but also with regular use of certain cardiac medications, higher WBC counts, and longer surgical procedures. Incorporation of these var iables into current methods of risk assessment might improve their pre dictive value sufficiently to provide an objective, inexpensive means of distinguishing patients who warrant extensive preoperative cardiac evaluation from those who do not.