How do you work up patients who present with elevated myoglobin in the setting of normal creatinine kinase and exercise intolerance?

Myoglobin may originate either from cardiac or skeletal muscle; therefore, I would first try pinpointing the origin with troponins and CK fractions. I would work up the exercise intolerance with a non-ischemic forearm test to determine whether a flat lactate curve is present. In that case, I’d typic...