Explanation

This patient with pericarditis will most likely have diffuse ST segment elevation (except for aVR and V1 which will show reciprocal ST depression and PR elevation). Pericarditis is an inflammation of the pericardial sac. The pericardium is composed of a visceral layer, which forms the epicardium, and the parietal layer. These layers are separated by a space that normally contains 15-50 mL of serous fluid. During acute pericarditis, changes in the ECG reflect inflammation of the epicardium, since the parietal layer of the pericardium is electrically inert. The ECG evolves through as many as four stages during acute pericarditis. Lasting hours to days, stage 1 involves generalized ST segment elevations and PR segment depression. ST and PR segments normalize during stage 2. Stage 3 development is variable in some patients. Stage 3 is characterized by diffuse T wave inversions. Stage 4 represents normalization of the ECG. However, not all causes of pericarditis cause alterations in the ECG. Uremic pericarditis rarely causes epicardium inflammation and therefore, the ECG will show none of the changes described above. Chest pain is the most consistent finding associated with pericarditis. The pain is typically described as sharp and pleuritic. The tendency for the pain to decrease in intensity when the patient leans forward is a distinctive characteristic. Sitting up and leaning forward reduces the pressure on the parietal pericardium and allows for diaphragm splinting. In addition to an ECG, echocardiography should be performed to evaluate for pericardial effusions and to rule out cardiac tamponade. Unless contraindicated, nonsteroidal anti-inflammatory drugs (NSAIDs) are considered first line treatment for acute pericarditis. NSAIDs should not be used to treat pericarditis after myocardial infarction or uremic pericarditis.

The typical ECG of Wolff-Parkinson-White syndrome ECG has a shortened PR segment and slurring of the initial QRS segment (A). Wolff-Parkinson-White syndrome is a congenital condition, characterized by abnormal conduction pathways between the atria and ventricles. ST segment depression in leads V2-V4 (B) is characteristic of myocardial ischemia. While both myocardial infarction and pericarditis can cause ST segment elevation, pericarditis differs from myocardial infarction in several ways. The morphology of the ST segment in pericarditis usually remains concave. The ST segment seen with an MI is typically convex. Additionally, ST segments in MI are limited to the corresponding affected artery, and reciprocal changes are usually noted in opposite leads. Pericarditis produces generalized ST segment elevation. Q waves may also be noted in MI. Pericarditis does not result in Q waves unless there is concomitant myocarditis. U waves and flattened T waves (D) are caused by hypokalemia. In severe hypokalemia, the T wave becomes completely flat. Prolonged vomiting and diarrhea, eating disorders, drugs, hyperaldosteronism, and renal disease are potential causes of hypokalemia.