NEW ECG CRITERIA FOR IMMEDIATE DIAGNOSIS OF MYOCARDIAL INFARCTION IN THE PRESENCE OF LEFT BUNDLE BRANCH BLOCK

It is a common Knowledge that the ECG diagnosis of myocardial infarction in the presence of left bundle ­branch block (LBBB) is extremely difficult and often impossible. Physicians frequenlly recommend that patients with chest pain in the presence of LBBB receive thrombolytic therapy or urgent coronary arteriography assuming that acute injury and ischemia cannot be interpreted in the presence of LBBB.
In this study we retrospectively examined the electrocardiograms of 64 patients with complete LBBB and acute chest pain and reviewed twelve electrocardiographic criterias of acute ischemia. All, 24 cases had acute myocardial infarction confirmed by enzyme studies.
The criteria of ST segment configuration (the j point depression and horizontaly or upward convexity of ST segment) that was concordant with QRS-complex had an accuracy of 82.81% and included 23 of 24 (94.8%) acute myocardial infarction patients. The absence of this criteria and terminal S wave that had positive QRS-complex had highest accuracy (90.6%) to rule out myocardical infarction.