Phenotyping the patient with a systemic right ventricle

Patients with ‘transposition of the great arteries’ (TGA) constitute about 5% of all patients born with a congenital heart defect. They have an anatomic right ventricle (RV) that has to support the high-pressure systemic circulation instead of the low-pressure pulmonary circulation. There are two types of TGA patients with a systemic RV (sRV) in a biventricular physiology: patients with complete TGA after atrial switch procedure (TGA-Mustard/Senning) and patients with congenitally corrected TGA (ccTGA). Besides important pathophysiological differences between TGA-Mustard/Senning and ccTGA patients, the presence of associated lesions and other factors may lead to a variation in time of onset of clinical symptoms and adverse events. These adverse events include sRV dysfunction and heart failure, conduction problems, supraventricular and ventricular arrhythmias, sudden death, and systemic atrioventricular valve (SAVV, morphological tricuspid valve) regurgitation.

In this thesis we tried to better phenotype patients with a sRV by evaluating (1) the correlation of resting measure of sRV function with exercise capacity for both patient groups; (2) differences in myocardial deformation, myocardial extracellular volume and response to an exercise testing; (3) advanced analysis of pulmonary venous atrial (PVA) function; (4) SAVV morphology and dynamics; (5) the association between the appearance of fragmented QRS complexes -a presumed surrogate for fibrosis- and hard clinical endpoints related to the performance of the sRV in TGA-Mustard/Senning patients; and (6) the proposed protective effect of geometry alterations in the sRV of ccTGA patients by pulmonary outflow tract obstruction.

We found that (1) there is norelation between standard parameters of systolic sRV function at rest and exercise performance; (2) caution should be exercised when evaluating pooled analyses of sRV patients given the differences in myocardial contraction pattern, septal interstitial expansion and the exercise response of TGA-Mustard/Senning versus ccTGA patients. Exercise impairment in TGA-Mustard/Senning patients seems not related to myocardial contractility but to a lower heart rate response.; (3) deformation imaging of the PVA is feasible and preliminary results seem promising indicating to worse PVA function in TGA-Mustard/Senning patients; (4) a 3D dynamical analysis of the SAVV is feasible; (5) appearance of fQRS complexes is associated with adverse outcome in TGA-Mustard/Senning patients making it a promising tool to implement in daily practice; and (6) pulmonary outflow tract obstruction is associated with an improved event-free survival and a slower deterioration of SAVV function in adults with ccTGA, questioning the validity and merits of physiologic repair in the situation of a balanced VSD/subPS.