INTRODUCTION

Electrocardiogram (ECG) is the most commonly used diagnostic tool for recognizing and triaging of patients with symptoms suggestive of acute myocardial infarction (AMI) [1]. ST  levation (STE) represents common electric sign of acute transmural ischemia caused by an occlusion of an epicardial coronary artery by a blood clot. Especially in pre hospital care and without other investigations, urgent therapy for patients with chest pain and STE must be considered to reanalyze the occluded artery by percutaneous coronary intervention or  brinolysis when cat lab is unavailable or far away. However, many patients presenting with typical symptoms have elevation of the ST segment due to non ischemic etiologies (NISTE) [2]. We report here a case of hypertrophic cardiomyopathy mimicking a ST elevation myocardial infarction (STEMI) in patient with chest pain in pre hospital care.

CASE REPORT

A 37-year-old male patient presented to emergency room in primary centre, complaining of chest pain, acute coronary syndrome was suspected. Our emergency medical system
received call for this patient and activated pre hospital emergency team for transfer.

Without any medical history, the patient su!ered from a continuous angina chest pain one hour before our intervention. "The patient was not on any regular medication. "The patient
vital signs included the following: blood pressure was 150/80 mmHg, heart rate 70 beats/min, respiratory rate was breaths/min, oxygen saturation was 97% and temperature was 37°c. Cardiac auscultation was normal.

"There were no congested neck veins. Neither lower limb edema nor signs of pulmonary congestion was observed. "The initial ECG showed a sinus rhythm, undetermined QRS axis in both frontal and precordial leads, a Q wave with concave STE was observed in D2 D3 AVF, in V6 V7 V8 V9 and in V3R V4R with reciprocal changes in leads D1 and AVL, as well as inverted biphasic T wave in anterior leads. "The initial diagnosis of STEMI was established. After initiating treatment by Aspirin (250 mg), Clopidogrel (300 mg) and intravenous heparin, the patient was transferred to cat lab. Coronary angiography performed thirty minutes later, however showed normal coronary arteries without signicant stenosis. Transthoracic echocardiography concluded to hypertrophic cardiomyopathy with normal left ventricle systolic function, and no resting wall motion abnormalities.

DISCUSSION

Today, the ECG still has a major role in diagnosing and triage of patients presenting with chest pain [3]. "The current American college of cardiology/ American heart association (ACC/AHA) guidelines for STEMI recommend that patients with suggestive symptoms of myocardial ischemia who have STE at the J point in (2 contiguous leads or more of 0.2 mV or more in males or 0.15 mV or more in women in leads V2 V3 and/o of 0.1 mV or more in all other leads in threshold) should undergo immediate reperfusion therapy [2].

In Emergency department, STE ins seen in approximately 20 % of patients presenting with chest pain, but only minority of them have a true Acute coronary syndrome (ACS) [4]. Otto Found that 63 among 123 (59%) with chest pain and STE in pre hospital care had diagnosis rather than AMI [5]. In another study, Brady found that 157 among 212 (74%) patients presenting with chest pain had NISTE [6]. NISTE is very common in emergency department (ED): in up to 29% of ECG [5]. "This condition is challenging for emergency physicians and even cardiologists. Jason found a rate of 3 to 29 % of false positive STEMI with expert ECG reader (cardiologist), whereas the false negative rate was between 0 and 50 % [4]. "The differential diagnosis of elevation of the ST segment is wide including conditions with secondary of the myocardium (for example dissection of aortic wall), pre existing STE without  acute ischemia and instances with new ST with chest pain and without evidence of ischemia (for example myocarditis or pericarditis, pulmonary embolism, electrolyte imbalance, rate related repolarization changes etc.) [1]. Wang described twelve conditions of mimicking STEMI, and highlighted the electrocardiographic clues that can be used to di!erentiate them from AMI [7]. Some criteria can be useful to di!erentiate STEMI from NISTE.

"The most sensitive is reciprocal changes, it support the diagnosis of AMI with a positive predictive value more than 90 %. Reciprocal changes were present in our case and it induced diagnosis error. "Therefore over diagnosis STEMI STEM caused false activation of PCI protocol and also unnecessary indeed unsafe administration of brinolytic therapy. Another criterion was also studied: concavity versus convexity. Brady and all reported 77 % sensitivity, 97 % specicity, 94% PPV and 88% NPV for a non concave STE morphology in acute MI diagnosis [8]. But the most specific distinguishing criterion is changes in time of ischemic electrical signs [6].

Previous papers reported similar cases of HCM mimicking AMI [9,10,11,12,13,14] and from those cases, many instructive keys should be emphasized. First HCM can mimic AMI in all points. Chest pain is common particularly in young patients [15]. "This symptom may be caused by cardiac ischemia secondary to imbalance between oxygen supply and demand in the thickened ventricle or by compromised coronary arteries filling during diastole. "Then, ECG in HCM shows frequently “pseudo ischemic” signs. "The most common abnormality is High QRS voltage in precordial leads due to left ventricular hypertrophy. Our case is the first report with biventricular hypertrophy and consequent T wave changes. Deep and narrow Q wave in inferior and lateral leads are also common in HCM [9]. In the other side, ECG of our patient showed wide Q waves particularly in D2 D3 and AVF mimicking myocardial necrosis. Moreover, reciprocal changes were present and were in favor of STEMI diagnosis. Several abnormalities should alert physicians on the hypothesis of HCM. They include: high QRS voltage, concave morphology of STE, absence of reciprocal changes and non modication of electrical signs. Echocardiography must be performed before any therapy and coronary angiography should be considered early when patient present continuous chest pain. 

CONCLUSION

Emergency physician must be aware of the importance to differentiate between STEMI and NISTE in patients presenting with symptoms suggestive of MI in order to avoid unsafe treatment. Chest pain is common in HCM and a sensible ECG analyze can detect specic signs and indicate echocardiography in order to conrm diagnosis.