Mayen's sign is a medical sign used to diagnose aortic insufficiency. To detect the sign, the patient's blood pressure must be measured whilst they are in a recumant position with their arms by their side. The patient's arm is then raised 90° to the body and the blood pressure measured a second time. If there is a difference in diastolic pressures of > 15 mmHg between the two readings then the sign is present.