Electrocardiography and coronary angiographic findings in patients with posterior wall myocardial infarction

Background. This study was performed to assess the electrocardiographic (ECG) manifestation of acute posterior myocardial infarction (MI) with presentation of complete right bundle branch block (CRBBB), because ECG diagnosis of acute posterior wall MI is often confused by the clinical presence of CRBBB. Methods. From December 1992 to December 1994, a total of 556 patients were admitted to our CCU with the diagnosis of acute MI. The record of each patient was reviewed for presentation of posterior, with or without lateral and/or inferior, wall MI as proved by image echocardiographic studies, Tc-99m pyrophosphate or Thallium-201 myocardial perfusion heart scan. In each posterior wall MI patient, the infarcted related artery (IRA) was defined by coronary angiogram. The findings were analyzed of 12-lead ECG, with or without the presence of CRBBB, during episodes of acute posterior wall MI. Results. A total of 11 patients of posterior wall MI, as proved by image studies, were evaluated. Among these, six with narrow QRS ECG were in Group 1; another five with CRBBB pattern were in Group 2. The ECG findings in Group 1 included 1) R/S > 1 in V1 (83%), 2) R/S > 1 in V2 (83%), 3) R wave duration > 0.04 seconds (83%), 4) ST segment depression in V1-V3 (50%), 5) ST segment elevation in V5, V6, lead 1 or aVL (50%). The specific ECG findings in Group 2 included 1) rR' configuration in V1 (100%), 2) Upwardly concave depression of ST segment in V1 or V2 (80%), 3) positive or biphasic T wave in V1-V3 (100%), 4) ST elevation in V5, V6, I, aVL (40%). Of the 11 patients, 4 had single- and 7 multi-vessel coronary artery disease. The IRA for posterior MI was apparent in 10 patients, the left circumflex artery (LCXA) in 8 and the right coronary artery (RCA) in 2, patients. There were two possible IRAs, both LCXA and RCA, in one Group 1 patient. Distribution of IRA (LCXA:RCA = 4:1) was the same in both groups. Conclusions. Different from the traditional ECG diagnostic criteria of posterior MI, the findings of the configuration of rR', an ST segment depression which sagged with upward concavity, and positive or biphasic T wave in lead V1-V2 were frequently seen in acute posterior wall MI with CRBBB pattern. The IRA seemed unrelated to the presence of CRBBB in acute posterior MI.