The dominant left coronary system occlusion: An ECG dilemma for Emergency physicians

Abstract

Introduction/Objective Acute chest pain is the main clinical manifestation of acute coronary syndrome. A posterior myocardial infarction (MI) most commonly occurs as a complication or extension of an inferior MI because of the overlapping coronary vascularization. We are presenting a case in which the patient exhibited mild anginal symptoms and an ECG pattern which did not correlate with a devastating infarction. Case report: The Emergency Medical Team (EMT) was dispatched at 5 am to help a 62-year-old patient, who had been woken from his sleep by a feeling of tightness in his chest and weakness in both arms. Upon examination, the patient was hypertensive (160/90 mmHg) and moderately bradycardic (58-62/min), with normal oxygen saturation on room air (SaO2 98%). His prehospital ECG findings were as follows: sinus rhythm, horizontal ST depression in V1-V3 1 to 2mm, ST elevation ≤1mm in lead V6, subtle ST depression in D1 and aVL <1mm, ST elevation in D3 and aVF <1mm. After attaching additional posterior leads, the modified ECG recording showed an ST elevation of 1 to 2 mm in V7-V9. Continuous laboratory monitoring of cardiac enzyme markers showed elevated and increasing values: Troponin T -2377, 3756 ng/l; CK -1572, 1564 U/l. Coronary angiography: The LCA system was dominant. The RCA was nondominant with a 70-80% stenosis, and a complete Occlusion Myocardial Infarction (OMI) distally. Using the most accurate LCxc/RCA occlusion algorithms, the ECG finding suggested an occlusion in the right dominant coronary system, which does not correlate with the coronary angiography report. Conclusion: Excellent knowledge of recording, analysis, and interpretation of ECG tracings, facilitates adequate pre-hospital care and precise planning for further processing of patients with chest pain. It is recommended to record posterior and right unipolar leads in all patients with inferior and suspicion of posterior myocardial infarctions and to include the ST-elevation myocardial infarction equivalent into the STEMI network. Given the physiological differences in left ventricular vascularization and the possible predominance of the left coronary system over the right, future studies must focus on establishing more precise algorithms for assessing RCA/LCx occlusion.