A comprehensive analysis of myocardial infarction due to left circumflex artery occlusion: Comparison with infarction due to right coronary artery and left anterior descending artery occlusion

Abstract

Forty consecutive patients with creatine kinase-MB confirmed myocardial infarction due to circumflex artery occlusion (Group 1) were prospectively evaluated and compared with 107 patients with infarction due to right coronary artery occlusion (Group 2) and 94 with left anterior descending artery occlusion (Group 3). All 241 patients underwent exercise thallium-201 scintigraphy, radionuclide ventriculography, 24 h Holter etectrocardiographic (ECG) monitoring and coronary arteriography before hospital discharge and were followed up for 39 ± 18 months. There were no significant differences among the three infarct groups in age, gender, number of risk factors, prevalence and type of prior infarction, Norris index, Killip class and frequency of in-hospital complications. Acute ST segment elevation was present in only 48% of patients in Group 1 versus 71 and 72% in Groups 2 and 3, respectively (p = 0.012), and 38% of patients with a circumflex artery-related infarct had no significant ST changes (that is, elevation or depression) on admission (versus 21 and 20% for patients in Groups 2 and 3, respectively) (p = 0.001). Abnormal R waves in lead V1were more common in Group 1 than in Group 2 (p < 0.003) as was ST elevation in leads I, aVL and V4to V6(p ≤ 0.048). These differences in ECG findings between Group 1 and 2 patients correlated with a significantly higher prevalence of posterior and lateral wall asynergy in the group with a circumflex artery-related infarct. Infarct size based on peak creatine kinase levels and multiple radionuclide variables was intermediate in Group 1 compared with that in Group 2 (smallest) and Group 3 (largest). During long-term follow-up, the probability of recurrent cardiac events was similar in the three infarct groups.When patients with a circumflex artery-related infarct were stratified according to the presence or absence of abnormal R waves in lead V1or V2, the abnormal R wave group had more admission ST elevation (p = 0.025), a larger infarct (p < 0.05) and more extensive coronary artery disease (p = 0.027). In fact, all patients with a circumflex artery-related infarct and an abnormal R wave in lead V1had multivessel disease. An abnormal R wave in lead V1had a 96% specificity for circumflex versus right coronary artery-related infarction but a sensitivity of only 21%. Discriminate function analysis of all admission historical and ECG variables identified inferior and lateral ST elevation as independent predictors of circumflex artery-related infarction.It is concluded that 1) the clinical characteristics and prognosis after circumflex artery-related infarction are no different from those occurring after right coronary or left anterior descending artery-related infarction; 2) circumflex artery-related infarction is less likely to result in acute ECG changes because of its posterior location; 3) in patients with admission ST elevation, only ST elevation in the lateral lead is helpful in distinguishing circumflex from right coronary artery-related infarction; and 4) an abnormal R wave in lead V1on serial ECG is a specific but insensitive marker for circumflex artery-related infarction. In addition, this finding indicates a large infarction and correlates with more extensive coronary artery disease.