C43-12 A Case of Pectus Excavatum Resulting in Cardiac Limitation on Cardiopulmonary Exercise Testing

Abstract Pectus excavatum (PE) is the most common congenital chest wall deformity, characterized by a concave depression of the chest wall. The severity is classified by the Haller Index (HI), or the Pectus Index, a ratio of the transverse diameter and the anterior-posterior diameter of the chest. Anatomic severity typically correlates with the degree of functional impairment. The use of cardiopulmonary exercise testing (CPET) as an assessment tool has been controversial. A 31 year-old male with history of PE developed worsening exertional dyspnea despite a HI of 3.2 on computed tomography (CT) and no anatomic evidence of severe cardiac displacement. A maximal, symptom-limited CPET was performed on a cycle ergometer using a 25-watt ramp protocol. Results showed a low heart rate reserve, moderately reduced VO2 max of 59% predicted, a reduced anaerobic threshold of 31%, a reduced O2 pulse (VO2/HR) of 62% predicted with an attenuated trajectory, an elevated chronotropic index of 1.7, and a reduced VO2/Work rate slope of 7.9. There was no ventilatory limitation or gas exchange abnormality. The findings were suggestive of a primary cardiac limitation in the setting of mild to moderate PE by HI. The misshaping of the thoracic cavity in PE causes mechanical compression of the heart and displacement of its chambers within the chest cavity, particularly the right ventricle, causing exercise intolerance due to low stroke volume index and cardiac index at peak exercise. This CPET demonstrates a more severe functional impairment than would be predicted by anatomic measurements alone, namely a HI of less than 3.25. The typical criteria for correction is HI greater than 3.25 plus either psychosocial distress or functional impairment. CPET has been utilized to measure the physiologic limitations in PE, with conflicting results when compared to HI or other tests, such as cardiac MRI or echocardiography. This patient highlights potential discordance between functional and anatomic determinants of severity. Dynamic physiologic effects may manifest to different degrees during maximal exercise even in milder deformities, particularly in adults, demonstrating the potential value of CPET in the evaluation of patients with PE. PE requires careful assessment of cardiopulmonary dysfunction and limitations of exercise capacity. While the Haller index exists as an anatomic guideline primarily in children and teens, more research needs to be conducted in the adult population regarding the role of protocolized symptom-limited exercise testing due to possible underestimation of functional impairment in HI less than 3.25. This abstract is funded by: None