Abstract: HISTORY: An 18 y/o female collegiate rower lost consciousness during a 3000 meter ergometer test. The athlete was eight minutes into the piece when she developed shortness of breath and tingling of her hands and mouth. The athlete then collapsed off the ergometer, unconscious. She was breathing and had a pulse but took about 40 minutes to "come around." The athletic trainer called 911, and the athlete was taken to emergency room. A CBC, CMP, TSH, 12-lead ECG were normal. She was diagnosed with hyperventilation. On follow-up in training room with the team physician the athlete reported having three prior episodes of loss of consciousness with exertion. The athlete's mother witnessed one of these past episodes and reported that her daughter was "almost post-ictal" after the event. The athlete had no family history of sudden death. She did not take any medications nor use drugs. PHYSICAL EXAMINATION: Vital signs: supine blood pressure 120/65, heart rate 70, standing blood pressure 125/60, heart rate 75. Height 5'6", Weight 140#. Non-Marfanoid body habitus. Cardiovascular: RRR, no m/r/g in seated and supine positions. Neurologic: Alert and oriented × 3, cranial nerves II-XII intact, upper and lower extremity strength 5/5, reflexes upper and lower extremities 2+ bilaterally, normal finger to nose testing. DIFFERENTIAL DIAGNOSIS: Cardiovascular Arrhythmia Hypertrophic cardiomyopathy Anomalous coronary artery Arrhythmogenic right ventricular dysplasia Neurologic Seizure TIA/stroke Vasovagal TEST AND RESULTS: The athlete was restricted from play until completion of a cardiovascular work-up. ECG, transthoracic echo, and stress echo were all normal. Holter monitor normal. Upon ruling out cardiovascular causes for the exertional syncope, neurology was consulted. MRI and MRA: normal. EEG: abnormalities during stage II of sleep concerning for epileptiform activity. FINAL WORKING DIAGNOSIS: Complex partial seizure disorder, triggered by hyperventilation TREATMENT AND OUTCOMES: Lamotrigine was started with a goal dose of 100mg daily. The athlete was cleared for training on land. Once she was taking the full dose of lamotrigine and tolerating high intensity ergometer, the athlete was cleared for competing on the water. She successfully completed the spring racing season with no further episodes.