PATHOPHYSIOLOGY AND NATURAL HISTORY NON-Q WAVE INFARCTION Non-Q wave perioperative myocardial infarction: assessment of the incidence and severity of regional dysfunction with quantitative two-dimensional echocardiography

Since the widespread use of hypothermic potassium cardioplegia began, marked reductions in perioperative mortality and the rate of Q wave-associated myocardial infarctions have been noted. No study to date has evaluated whether there has been an equally dramatic improvement in the incidence of postoperative myocardial infarctions unassociated with Q wave development. We used a previously validated quantitative two-dimensional echocardiographic analytic algorithm to determine the incidence and severity of regional wall motion abnormalities (RWMAs) and first-pass radionuclide ventriculography to assess deterioration in global left ventricular function in the four following groups of patients (total n = 65): (1) those with peak postoperative creatine kinase (CK)-MB levels equal to or less than the mean value for patients undergoing coronary artery bypass surgery at our institution (n = 10), (2) those with CK-MB levels between the mean and 1 SD above the mean (n = 10), (3) those with peak CK-MB levels higher than 1 SD above the mean (n = 25), and (4) those with new pathologic Q waves on the postoperative electrocardiogram (n = 20). All patients had electrocardiograms without pathologic Q waves and normal wall motion and ejection fraction by contrast ventriculography before surgery. The incidence of postoperative RWMA by two-dimensional echocardiography for groups 1 through 4 was 0%, 20%, 55%, and 89%, respectively. Percent of abnormal left ventricular segments, wall motion scores, and the deterioration in left ventricular ejection fraction as assessed by radionuclide ventriculography were similar for patients with new RWMAs whether or not new Q waves developed (p = NS for all). In summary, although the incidence of both Q wave and non-Q wave perioperative myocardial infarctions appears to have declined significantly with the use of cold potassium cardioplegia, the incidence of non-Q wave infarction remains high and in this study was calculated to be three times greater than the 4.5% incidence of Q wave infarction. Furthermore, the impact of these non-Q wave myocardial infarctions on left ventricular function is significant and equal to that of Q wave infarctions. Future evaluations of methods of myocardial preservation should include analyses of regional left ventricular function designed to identify these patients. Circulation 72, No. 4, 781-789, 1985. MYOCARDIAL PRESERVATION with hypothermic potassium cardioplegia (cold cardioplegia) has been a major factor in the decline in perioperative mortality and Q wave myocardial infarction seen since the advent of coronary artery bypass surgery (CABG). ' From the Departments of Medicine (Cardiology) and Surgery, Brockton-West Roxbury Veterans Administration Medical Center; Brigham and Women's Hospital; and Harvard Medical School, Boston. Supported by the Medical Research Service of the Veterans Administration and the David Littmann Memorial Foundation (Dr. Force). Received Jan. 30, 1985; revision accepted June 27, 1985. Address for correspondence: Thomas Force, M.D., Veterans Administration Medical Center, 1400 VFW Parkway, West Roxbury, MA 02132. Vol. 72, No. 4, October 1985 However, there may be a risk of significantly underestimating remaining problems with respect to preservation if mortality or statistics on Q wave infarction alone are examined.`4 In a study done before cold cardioplegia was used, Bulkley and Hutchinss reported that over 80% of patients with perioperative myocardial infarction did not develop pathologic Q waves on the electrocardiogram, even when transmural necrosis was seen at postmortem examination. Similarly, contrast ventriculographic studies done before cold cardioplegia was used showed new postoperative regional wall motion abnormalities (RWMAs) in 2.3 to 5.5 times as 781 by gest on A ril 1, 2017 http://ciajournals.org/ D ow nladed from