Patients presenting to the hand surgeon with acute, nontraumatic causes of upper limb ischemia present diagnostic challenges, carry systemic implications, and require a multidisciplinary approach. Understanding the causes of upper limb dysvascularity will allow the hand surgeon to approach these patients in a systematic manner. An estimated 58% to 93% of acute upper extremity ischemia is attributable to cardiac embolism. We review the structural cardiac causes of upper limb ischemia and provide brief guidelines for evaluation and treatment.