The pressure-loaded right ventricle

Abstract

Heart failure due to primary failure of the right ventricle is a common cause of morbidity and mortality in patients with pulmonary hypertension and congenital heart disease. Imaging techniques to monitor function of the right ventricle and its valves are crucial for follow up. The goals of this thesis were: 1) to validate new imaging techniques in patients with pressure loaded right ventricles and 2) use these imaging techniques to compare RV remodeling and function between patients with pulmonary hypertension (with high morbidity and mortality) and patients with pulmonary stenosis or a systemic right ventricle (with lower morbidity and mortality). In the first part of the thesis we investigate a new technique to estimate right ventricular function and show that this new technique is reliable and reproducible. Compared to the traditional measurement method - values are much closer to the normal range. We further hypothesize it also gives a more accurate estimate of right ventricular ejection fraction – as it excludes trabeculae from the blood volume. We also validate 4D-flow MRI as a technique to estimate tricuspid valve flow and regurgitation – which is notoriously unreliable using 2D flow MRI. 4D-flow MRI shows reproducible results for tricuspid valve flow and regurgitation, even in this complex group of patients. The second part of this thesis compares patients with pulmonary hypertension to those with a systemic right ventricle or pulmonary stenosis – in both adults and children. Our main conclusions are that: patients with pulmonary stenosis have non-dilated ventricles with preserved function compared to right ventricular dilation and decrease of ejection fraction in both systemic right ventricles and pulmonary hypertension. It seems valvular stenosis triggers different remodeling than a high (for right ventricle) vascular resistance. Furthermore, overall function is much poorer in pulmonary hypertension compared to systemic right ventricles, this was mediated by decreased longitudinal and transverse function, as well as prolonged right ventricular free wall shortening – causing post-systolic shortening (=lost energy) and dyssynchrony between the right ventricular free wall and interventricular septum. Although, we are unable to elucidate the exact cause of this disparity in right ventricular function – these findings are consistent in children and adults. We believe that prolonged RV wall contraction in pulmonary hypertensive patients is an important mediator of both RV dysfunction and decreased left ventricular filling in this population. The prognostic value of this marker and development over time, in both pulmonary hypertension and congenital heart disease, need to be further investigated in follow-up studies.