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D. Are There Alternative Catastrophic Diagnoses?

OBJECTIVE

Identify patients with life-threatening conditions that may mimic an AMI and may also require immediate medical attention.

ANNOTATION

Patients may present with chest pain syndromes that mimic AMI symptoms and signs, including ECG changes typical of an AMI. The focused history and physical examination should help make the appropriate diagnosis. It is important to diagnose such conditions rapidly, as most of them are life-threatening and may be worsened by standard AMI therapies. Potential catastrophic mimics include pericarditis, pericardial tamponade, thoracic aortic dissection, pneumothorax, pulmonary embolus, and pancreatitis.

Table 4. Clinical Findings for Alternative Catastrophic Diagnoses
Diagnoses Clinical Findings
Pericarditis
  • Pain that is more severe in a supine position
  • Friction rub may be present
  • ECG with diffuse ST-elevation
Pericardial tamponade
  • Jugular venous distension
  • Pulsus paradoxus
  • ECG with low voltage/electrical alternans
Thoracic aortic dissection
  • Very severe midline pain, maximal at onset
  • Pain often radiates to the back
  • Unequal pulses or blood pressure difference in arms
Pneumothorax
  • Associated with trauma, COPD, or mechanical ventilation
  • Unilateral diminished breath sounds
  • Normal or increased resonance to percussion
Pulmonary embolus
  • Pleuritic chest pain
  • Shortness of breath, without evidence of CHF
Pancreatitis
  • History of gall bladder disease or alcoholism
  • Abdominal tenderness
  • Nausea and vomiting


DISCUSSION

Pericarditis: This condition is frequently characterized by chest, neck, or shoulder pain that is more severe in the supine position. Physical examination may reveal a rub. The electrocardiogram may show diffuse ST-segment elevation, PR-depression, or T-wave inversion. Associated elevation of cardiac enzymatic markers suggests coexisting myocarditis.

Pericardial tamponade: Patients who have pericardial tamponade classically present with hypotension, tachycardia, and jugular venous distention; however, none of these signs is required for a positive diagnosis. Importantly, patients will have an increased pulsus paradoxus (i.e., a fall in systolic blood pressure of 12 mm Hg or more during inspiration). The chest X-ray may show an increased cardiac silhouette. The ECG may show evidence of pericarditis, low voltage, and/or electrical alternans. The most common cause of pericardial tamponade in the United States is malignancy. Other etiologies include infection (e.g., tuberculosis or viral myocarditis), collagen vascular diseases, renal failure, and trauma.

Thoracic aortic dissection: This is a catastrophic event with high mortality, if it is not addressed immediately. Presentation may be characterized by severe back or chest pain, reduced or absent peripheral pulses, CHF, cardiac tamponade, and/or aortic regurgitation. The ECG may show focal ST-segment elevation consistent with an infarction, if the dissection plane extends into a coronary artery. The chest X-ray may show a widened mediastinum.

Pneumothorax: Patients presenting with pneumothorax may complain of shortness of breath or chest pain and a physical examination may reveal absent or diminished breathe sounds, on one side. A chest X-ray is diagnostic.

Pancreatitis: Patients presenting with acute pancreatitis may experience severe epigastric discomfort and nausea. There are reports of associated ECG changes in which ST-segment elevation mimics the elevation typical of an AMI, although this is uncommon.

Pulmonary Embolus: Patients presenting with an acute pulmonary embolus may experience chest pain, which may be pleuritic, as well as shortness of breath. The ECG may show sinus tachycardia or atrial dysrhythmias, such as atrial fibrillation or flutter. It may also show an S1Q3 pattern, S1Q3T3 pattern, right axis deviation, complete or incomplete right bundle branch pattern or T-wave inversion in the right precordial leads. These ECG findings may be transient. The chest X-ray may be unremarkable or show subsegmental atelectasis, segmental hyperlucency from oligemia, or small pleural effusions.

EVIDENCE

Table 5. Evaluation of Patient for Non-AMI Chest Pain Syndromes that Mimic AMI Symptoms
  Recommended Actions Sources of Evidence QE   R
1 Assess for pericarditis. ACC/AHA AMI, 1996 III   A
2 Assess for pericardial tamponade. III   A
3 Assess for thoracic aortic dissection.                                         III   A
4 Assess for pneumothorax. III   A
5 Assess for pulmonary embolus. III   A
6 Assess for pancreatitis. Khoury et al., 1996
Cohen et al., 1971 		III   A
QE = Quality of Evidence; R = Recommendation (See Introduction.) *Note: This link will take you out of Module A.