**6.6 Exercise and stress testing**

Cardiopulmonary exercise testing by treadmill is an important adjunct for ccTGA patient evaluation and management. In those patients able to perform treadmill tests, exercise capacity is determined through minute ventilation, carbon dioxide production, and oxygen consumption. Impaired exercise capacity in ccTGA patients has been shown to correlate with diastolic dysfunction in the form of increased RV filling pressures as measured by tissue Doppler imaging (Tay et al., 2011). Cardiopulmonary exercise testing in combination with gadolinium-enhanced MRI has been utilized to demonstrate RV myocardial fibrosis hypothesized to be responsible for RV dysfunction (Giardini et al., 2006). Systemic RV function can also be evaluated by dobutamine stress testing, in which MRI is performed at baseline and with dobutamine infusion. Objectively defining the capacity of the systemic RV to respond to stress may guide treatment on both initial and follow-up evaluations (Dodge-Khatami et al., 2002; Fratz et al., 2008). Sequential testing, performed either by exercise testing or by dobutamine stress test, is useful to assess overall cardiopulmonary function and response to medical or surgical therapy.
