Non ST Elevation Myocardial Infarction: Diagnosis
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History and Symptoms
A person with unstable angina (UA) will have a history of angina that has increased in frequency or intensity at the same level of exertion. Anginal pain can manifest in many forms ranging from chest pain to chest pressure to shortness of breath to epigastric pain. As mentioned above, UA is in the spectrum of ACS and requires immediate assessment by a qualified physician. The history and symptoms described by a patient with NSTEMI can be identical to those of the patient presenting with a STEMI and thus it is most useful to describe the classic history and symptoms suggestive of ACS.
According to the ACC/AHA UA/NSTEMI guidelines, most important factors on the initial history are
1) the nature of the anginal symptoms,
2) prior history of CAD (e.g., prior myocardial infarction (MI), angina, cardiac catheterization, coronary artery bipass grafting (CABG)),
3) male gender,
4) older age
5) an increasing number of traditional risk factors. andersonref1 Other pertinent medical history which will help with risk-stratification should also be obtained rapidly, including cardiac risk factors (i.e., family history of premature coronary artery disease in a first degree relative < 60 yrs old, elevated cholesterol, hypertension, diabetes mellitus, smoking history past or present), current medications and allergies.giblerref1
The most common history given by a patient with ACS is that of chest discomfort, described as crushing, left-sided substernal chest pain or pressure that radiates to the neck or left arm. Indeed, sometimes it is described as the sensation of "an elephant is sitting on the chest." However, in reality the history can be quite variable. The pain is sometimes located solely in the epigastric region, the right side of the chest, the jaw, neck, arm, shoulder or back and a history of nausea, dyspnea or diaphoresis is not infrequent. andersonref1 It is important to note that certain patient populations may be even less likely to present with classic symptoms. These groups include women, older patients and patients with renal failure and diabetes. giblerref1 Pleuritic pain (sharp pain on inspiration or from a cough), mid/lower abdominal pain, pain reproducible with palpation or movement, very brief episodes of pain (e.g., seconds) and pain that radiates to the lower extremities are all traits that are less likely to be from - although they do not exclude - ACS. Similarly, a history that nitroglycerine does not relieve the pain or a history that a "GI coctail" does relieve the pain is less suggestive of ACS, although ACS still cannot be excluded on this basis. andersonref1
A thorough history of present illness (HPI) obtained by the physician will include the time of onset, duration, location, radiation, quality, intensity, aggravating and relieving factors (i.e., deep breathing, position, exertion), associated symptoms (i.e., diaphoresis, nausea, vomiting, dyspnea, dizziness), any history of prior similar symptoms along with a comparison of the pain to any previously diagnosed angina.giblerref1
Laboratory Findings
Electrolyte and Biomarker Studies
If there is an elevation of a marker of myocardial necrosis (CK-MB or troponin), then the patient does not have unstable angina, but instead has a syndrome of either ST elevation MI or Non ST elevation MI depending upon the EKG changes.
Electrocardiogram
The resting electrocardiogram may show either
- No changes
- Flipped T waves
- ST Depression as shown to the right. ST depression carries the poorest prognosis.
Chest X Ray
A Chest X Ray is critical to aid in the exclusion of aortic dissection.
A mediastinal mass consistent with a cancer may be present, but it is unlikely to present with a syndrome of accelerating chest pain.
Differential Diagnosis of Chest Pain
Cardiovascular
- Acute Aortic Dissection
- Acute Coronary Syndrome
- Angina
- Aortic Aneurysm
- Aortic Stenosis
- Arryhthmias
- Bland-White-Garland Syndrome
- Cardiac tamponade
- Cor pulmonale
- Coronary Heart Disease
- Dressler's syndrome (postpericardiotomy)
- Functional cardiac problems
- Hypertrophic Cardiomyopathy
- Mitral valve prolapse
- Myocarditis
- Non ST Elevation Myocardial Infarction
- Pericardial tamponade
- Pericarditis
- ST Elevation Myocardial Infarction
References
- PMID 16046952
- PMID 17692756
- Bickley, LS (2003). Bates' Guide to Physical Examination and History Taking. Lippincott: Philadelphia, PA. ISBN 0781735114