A 42-year-old woman is brought to the hospital after losing consciousness. She was at an outdoor graduation ceremony when her daughter’s name was called and she stood up with excitement. After she stood up, she felt lightheaded, nauseous, and started to develop tunnel vision. She tried to sit down but forgets what happened at this point. She awoke seconds later and was alert. She has a history of diabetes and GERD and takes metformin and omeprazole. There is no family history of heart disease or seizures. She is currently comfortable with no abnormalities on physical examination. Her blood pressure is normal and it does not change after going from a seated to a standing position.
Which of the following is the most likely diagnosis?
A. ArrhythmiaVasovagal syncope. Syncope is defined as loss of consciousness that results from cerebral hypoperfusion. The most common cause of syncope is neurocardiogenic (vasovagal) syncope, which is caused by a sudden surge of sympathetic activity that transiently increases the contractility of the left ventricle. Mechanoreceptors in the left ventricle sense this increased contractility and cause an excessive vagal response, which lowers heart rate and contractility. This transiently drops the blood pressure and causes syncope. These patients typically have symptoms of lightheadedness, nausea, and narrowing vision prior to losing consciousness and can usually brace their fall somewhat. Diagnosis can be made with the tilt table test
(A) Cardiovascular causes of syncope include arrhythmias, mechanical heart disease (e.g., aortic stenosis and hypertrophic cardiomyopathy), pulmonary embolism, aortic dissection, and cardiac tamponade. Patients with sudden onset syncope and trauma to the face (indicating an inability to brace the fall) should increase the reader’s suspicion for a cardiac etiology. (B) Orthostatic hypotension usually occurs in the presence of hypovolemia, dysautonomia, and/or certain medications (e.g., diuretics and β-blockers). Diagnosis can be made if systolic blood pressure decreases by ≥20 mmHg or diastolic blood pressure decreases by ≥10 mmHg when going from a sitting to a standing position, which was not seen in this patient. (C) Seizures technically do not meet the definition of syncope, since they are not caused by a disruption in cerebral blood flow. History that would indicate a seizure include a preceding aura, tonic–clonic movements during the episode, and a postictal state (confusion with gradual improvement in neurologic function).