Pulmonary embolism presenting as non-ST elevation myocardial infarction: a case report
© licensee BioMed Central Ltd. 2009
Received: 3 March 2009
Accepted: 24 July 2009
Published: 11 August 2009
We describe a case which highlights the difficulties in diagnosing pulmonary embolism as it can mimic other conditions. In a patient with chest pain with raised troponin, a diagnosis of pulmonary embolism should also be considered as well if the clinical picture does not fit with myocardial infarction. Otherwise, the diagnosis of pulmonary embolism can be easily missed and patients may not receive appropriate treatment resulting in increased mortality.
The patient was initially diagnosed with myocardial infarction based on the nature of his chest pain and raised Troponin-T which is a very sensitive cardiac marker of injury. The diagnosis seemed so convincing that he had an urgent inpatient angiogram that was normal. The nature of the pain was different in the second admission, which was subsequently confirmed as due to the pulmonary emboli. It is likely that the Troponin rise in the first admission was due to the extensive PE which was discovered in the second admission. To suspect PE in his case was very difficult as he was remarkably fit for his age and had no apparent risk factors. Patients who have undergone significant operations (for example on the hip or abdomen) which predispose them to immobility are known to be at risk for PE . Could a trivial day case nasal polyp operation (one week before the first admission) have been the predisposing risk factor in his case? Some coagulation disorders can increase the risk of thrombosis for e.g. factor Leyden mutation. The patient has to be off warfarin for at least three months before accurate thrombophilia testing can be done and our patient is waiting to undergo testing after his anticoagulation treatment is finished. This case highlights the difficulties in diagnosing PE as it can mimic other conditions. It underlines the need to keep a high index of suspicion even if a PE seems an unlikely possibility. Cardiac Troponins can be positive in both cases (acute myocardial infarct and pulmonary embolism), so one should be cautious in interpreting them if it does not fit with the overall clinical picture. Pruszczyk et al. in their study showed that 50% of their confirmed PE patients in the cohort had elevations in the Troponin level which was associated with an adverse prognosis . To add to the diagnostic difficulty; sometimes both conditions (MI & PE) can show similar changes on the ECG in the form of T wave inversions. In such cases an echocardiogram can be useful as it can demonstrate a high RV:LV (ratio of end-diastolic dimension of the right and left ventricular chambers) which is a well recognized consequence of acute pulmonary arterial obstruction . Treating our patient for myocardial infarction initially was probably the most prudent and appropriate thing to do given the history and elevated cardiac enzymes. But one important take-home message for doctors in training is that a patient with chest pain and an elevated cardiac Troponin should not be discharged home before eliminating the diagnosis of PE when an angiography has been found normal.
The other important learning point from this case for junior doctors is that when pulse oximetry appears deceptively normal in somebody complaining of shortness of breath it is advisable to perform a blood gas to confirm the presence of hypoxia and assess pulmonary shunting. Since respiratory alkalosis can left-shift the Haemoglobin-O2 dissociation curve, the SpO2 can wrongly be seen as normal. One should be aware that all the classical signs or risk factors might not be present in some patients with pulmonary embolism. Around 97% of patients with PE present complaining of at least one of the following: dyspnoea, tachypnoea or pleuritic chest pain. D-dimer test is useful in ruling out PE only in low probability cases and patients should undergo scan if they are deemed to be of high probability for having PE .
Clinical prediction scores for PE: the revised Geneva score and the Wells score
Revised Geneva score
Previous DVT or PE
Previous DVT or PE
Surgery or fracture Within 1 month
Unilateral lower limb pain
Heart rate >100/min
Clinical signs of DVT
Alternative diagnosis less than PE
Pain on lower limb deep vein at palpation and unilateral oedema
Clinical probability ( 2 levels)
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
arterial blood gas
computed tomography pulmonary angiogram
European Society of Cardiology
Non-ST elevated myocardial infarction
partial pressure of oxygen
Partial pressure of carbon dioxide
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