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Intercostal retractions occur when the muscles between the ribs pull inward. The movement is most often a sign that the person has a breathing problem. Intercostal retractions are a medical emergency.
Less common causes of ST segment elevation. 1  Pulmonary embolism and acute cor pulmonale (usually in lead III) 2  Acute aortic dissection (classically causes inferior STEMI due to RCA dissection) 3  J-waves (hypothermia, hypercalcaemia) 4  Hyperkalaemia. 5  Sodium-channel blocking drugs (secondary to QRS widening) 6  Following electrical cardioversion.