A59-15 Prolonged Exertional Syncope in an Adolescent With Exercise-induced Laryngeal Obstruction and Dysfunctional Breathing

Background Syncope during exercise is considered a red flag for cardiac pathology. In contrast, post-exertional syncope is more often caused by non-cardiac mechanisms. Emerging evidence has challenged the reliability of timing alone as a predictor of etiology, emphasizing the importance of comprehensive evaluation. This case describes an adolescent with repeated and prolonged loss of consciousness (LOC) at peak exertion with a normal cardiac evaluation at baseline and during exertional syncope. Case Presentation A 14-year-old previously healthy adolescent athlete presented with multiple episodes of exertional syncope while running, some episodes of LOC lasted approximately 30 minutes before full recovery. Cardiac evaluation including electrocardiogram, echocardiogram, and laboratory studies was unremarkable. A cardiac stress test triggered syncope with no abnormalities of cardiac rate or rhythm, nor systemic blood pressure. A combined continuous laryngoscopy during exercise and cardiopulmonary exercise test (CLE-CPET) was performed on a treadmill. The patient experienced exertional syncope at 14.5 km/h running without incline. She exhibited a peak oxygen consumption of 47.1 ml/kg/min (103% of predicted), peak heart rate of 184 (92% of predicted), and peak respiratory exchange ratio of 1.03. No significant abnormalities of cardiac rate, rhythm or systemic blood pressure were detected. Blood glucose, electrolytes, and partial pressure of end-tidal carbon dioxide were normal. The CPET revealed a chaotic relationship of tidal volume and respiratory rate to minute ventilation without hyperventilation throughout exercise. This is consistent with exercise-induced dysfunctional breathing (EIDB). CLE revealed Grade 2 mixed-type exercise-induced laryngeal obstruction (EILO), i.e., obstruction at the glottic and supraglottic level just prior to exertional syncope. The patient underwent three sessions of speech therapy for EILO and four sessions of physical therapy for EIDB, completing at-home exercises to augment treatment. She has had resolution of exertional syncope and shortness of breath during exertion for five months following completion of treatment for these respiratory conditions. Figure 1. A) Continuous Laryngoscopy during Exercise showing normal anatomy and function of the larynx during inspiration at rest. B) Grade 2 mixed exercise-induced laryngeal obstruction with vocal cords adducting and arytenoids collapsing into the airway during inspiration at peak exercise intensity. The top images (1) show the original screen capture from the laryngoscope. The bottom images (2) show a markup highlighting the positions of the vocal cords (straight lines) and the arytenoids (curved lines). Discussion This case highlights the diagnostic importance of considering non-cardiac etiologies in exertional syncope, with a multidisciplinary evaluation that includes CPET and CLE.