Moderate Altitude Increases Right Ventricular Pressure and Oxygen Desaturation in Adolescents with Surgically Closed Septal Defect Thomas Möller, MD,* Henrik Brun, MD, † Per M. Fredriksen, PT, PhD, ‡ Henrik Holmstrøm, MD, PhD, † Eirik Pettersen, MD, § and Erik Thaulow, MD, PhD † *Pediatric Department—Vestfold Hospital Trust, Tønsberg, Norway; † Department of Pediatric Cardiology, Pulmology and Allergy, Oslo University Hospital/Rikshospitalet, Oslo, Norway; ‡ Clinical Trials Unit—Oslo University Hospital, Oslo, Norway; § Department of Cardiology—Oslo University Hospital/Rikshospitalet, Oslo, Norway ABSTRACT Objectives. Abnormal right ventricular systolic pressure response (RVPR) during exercise has previously been demonstrated in patients with septal defects of the heart. Our study investigated whether moderate altitude affects RVPR and oxygen saturation during rest and exercise in patients with surgically closed septal defects. Design. Ten patients with surgically closed heart septal defects (six secundum atrial septal defects, four ventricular septal defects) were examined by cardiopulmonary exercise testing and by echocardiography at rest and during supine cycling at sea level. After 2 hours in a hypobaric chamber at 2500 m/8200 ft altitude, exercise echocardio- graphy was repeated. Results. During sea level exercise four patients showed abnormal RVPR (>50 mm Hg). Acute hypoxic exposure led to right ventricular systolic pressure increase above 40 mm Hg in two patients. During altitude exercise seven patients showed abnormal RVPR. Average maximal right ventricular systolic pressure was 56.5  12.7 mm Hg and average for the lowest oxygen saturation was 80.0  5.7%. Two patients had simultaneous oxygen desaturation below 80% and right ventricular systolic pressure above 50 mm Hg. Conclusions. Moderate altitude affects right ventricular systolic pressure and oxygen saturation in adolescents with surgically closed ventricular or atrial septal defects. Moderate altitude may induce or aggravate abnormal RVPR and oxygen desaturation during exercise in these patients. Key words. Congenital Heart Defects; Heart Septal Defects; Pulmonary Hypertension; Hypoxia; Exercise; Altitude Introduction C ongenital heart septal defects with left-to- right shunt, either atrial septal defect (ASD) or ventricular septal defect (VSD), cause pulmo- nary vascular volume overload and may thereby induce pulmonary vasculopathy. We have recently shown a high prevalence of right ventricular sys- tolic pressure response (RVPR) to exercise above 50 mm Hg in asymptomatic patients with isolated heart septal defects 1 which has to be interpreted as an indication of exercise-induced pulmonary hypertension in these patients. In normally trained healthy individuals 50 mm Hg can be considered the upper normal limit of exercise-induced RVPR. 2 Whether abnormal RVPR to exercise represents a static/structural or dynamic/ vasoconstrictive phenomenon in the pulmonary circulation of these patients remains unclear. RVPR during sea level exercise and RVPR due to acute hypoxic exposure has been shown to cor- relate with susceptibility to high altitude pul- monary edema (HAPE). 3–5 The prevalence of abnormal RVPR due to acute hypoxia and suscep- tibility to HAPE in healthy individuals has been demonstrated to be as low as 5–6%. 6,7 The preva- lence of abnormal RVPR in healthy individuals during sea level exercise is equally low. 2 Patent foramen ovale with a possibility of an intracardiac left-to-right shunt has been found to be four times 556 © 2010 Copyright the Authors Congenital Heart Disease © 2010 Wiley Periodicals, Inc. Congenit Heart Dis. 2010;5:556–564