Pulmonary embolism mimicking acute myocardial infarction: a case report and review of literature

The diagnosis of pulmonary thromboembolism (PTE) with changes shown by electrocardiography (ECG) is a challenge in the clinical practice due to rare pathognomonic findings. We report the case of a 37-year old woman managed in out of hospital sitting for a chest pain. Electrocardiogram was suggestive of antero-septal acute myocardial infarction (AMI). Catheterization revealed non occlusive coronary disease. Transthoracic echocardiography showed an elevated pulmonary and right heart pressures. Computed tomography pulmonary angiography confirmed the diagnosis of bilateral pulmonary embolism. PTE with ECG changes should be considered in the differential diagnosis of AMI, particularly in young patients with chest pain and ST segment elevation suggestive of acute coronary syndrome.


Introduction
The ST segment elevation 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 ST elevation must be considered to reanalyze the occluded artery by percutaneous coronary intervention or fibrinolysis when cat lab is unavailable or far away. Symptoms of pulmonary thromboembolism (PTE) and acute myocardial infarction (AMI) can be similar, including acute dyspnea, chest pain, syncope and palpitations. Physical examination is nonspecific and cannot reliably distinguish these two diagnoses. Electrocardiogram (ECG) may be helpful for the diagnosis of PE but its limited by his sensitivity and specificity [1][2][3]. Although several ECG changes can be observed in the acute phase of PTE, ST segment elevation is a rare finding [4][5][6]. We report a case of woman who had dynamic ST segment elevation suggestive of antero-septal AMI that proved to be bilateral PTE.

Patient and observation
A 37-year-old woman, without past medical history, presented to emergency room in primary center, 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. The patient suffered from continuous acute two hours before our intervention. She doesn't have previous history of similar episode. No previous history of coronary artery disease, peripheral vascular disease, stroke, malignancy, or venous thromboembolism was reported. There was no family history of thromboembolic disease. Physical examination revealed: a regular pulse rate 110 beats/min, blood pressure was 100/65mmHg, respiratory rate wa 20 breaths/min, oxygen saturation was 95% at room air and 99% with 2l/min oxygen via nasal canula and temperature was 37°C. Cardiac auscultation was normal. There were no congestive neck veins. An initial ECG showed a sinus rhythm, an ST segment elevation of 2 mm in V2 and V3 without other anomalies ( Figure 1). The initial diagnosis of antero-septal AMI was established.
After initiating treatment by Aspirin (250 mg), Clopidogrel (300 mg) and intravenous heparin, the patient was transferred to cat lab.

Discussion
The ECG still has a major role in diagnosing and triage of patients  (Table 1) and highlighted the electrocardiographic clues that can be used to differentiated them from AMI [11]. Some criteria can be useful to differentiate STEMI from the elevation of ST due to non ischemic etiologies (NISTE). The most sensitive is reciprocal changes, it support the diagnosis of AMI with a positive predictive value more than 90%.
Reciprocal changes were not present in our case. Due to the presence of atypical ECG changes for acute PTE in our patient, AMI was considered initially in the differential diagnosis and a coronary angiogram was performed before other non invasive tests. Other evaluations like echocardiography could be helpful in this case. TTE is a readily available bedside test that can be performed in the emergency department on admission and is helpful to differentiate massive PTE and anteroseptal AMI. The ST segment changes in the ECG of this case were similar to those of previous report [12].
However, ST segment elevation is not among the usual findings associated with PE. It probably occurs due to acute right ventricular strain and elevated pressures resulting from a sub massive or massive PE [13]. Chia et al. [14] described ECG findings of ST segment elevation and a qs or qr pattern in 3 patients with PE in the right precordial leads those abnormalities were mostly normalized within 6 weeks due to the transient nature of ECG abnormalities.

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 PE and a sensible ECG analyze can detect specific signs.