Ventricular fusion mimicking acute inferior myocardial infarction in a patient with a dual-chamber pacemaker.

Abstract: Background and purpose: Early diagnosis of acute myocardial infarction is based on 12-lead electrocardiography (ECG), however this interpretation could be difficult in patients with ventricular-paced rhythm. Subject: We describe the clinical case of a 44-year-old man already implanted with a dual-chamber closed loop stimulation (CLS) pacemaker (PM) and admitted to our department with an ECG showing ST elevation in the inferior leads. All examinations were negative and showed no abnormalities. After CLS-PM was reprogrammed in order to allow the appearance of spontaneous atrioventricular conduction, we found a complete normalization of ST segment. Conclusion: After a careful analysis of admission ECG, ST elevation was interpreted as ventricular fusion due to the presence of a ventricular pacing artifact and the QRS complex being a hybrid of spontaneous and totally paced beats. Intermittent ST elevation, evident only during ventricular fusion should suggest secondary ventricular repolarization and not myocardial injury. [Copyright &y& Elsevier]