Advanced imaging and intervention in congenital heart disease

Abstract

The increased survival of CHD patients means this patient group will continue to grow, and physicians will be confronted with novel long-term complications. Innovation in the field of diagnostics and interventions for CHD is therefore crucial. In this thesis, we investigate the role of 4D flow CMR and several different percutaneous treatment strategies for CHD.

There are several reasons why 4D flow CMR is ideally suited for haemodynamic evaluation in CHD patients. First, it is a non-invasive modality and does not require the administration of iodinated contrast. This means the burden for the patient is low, which is important when there is a need for lifelong follow-up. Second, the ability of retrospective valve-tracking eliminates through-plane motion of the valve, making 4D flow CMR superior to 2D PC CMR in evaluating valvular flow, as we report in chapter 7. Regurgitation fraction and peak gradient (calculated from peak velocity) are important indicators in evaluating the need for valve replacement. It is therefore crucial to have serial measurements that are as precise as possible. Third, the ability to analyse a complete volume and retrospectively identify an area of interest compared to analysing single pre-defined planes is a great advantage and leads to a more accurate analysis of the blood flow, as we see in chapter 8. Finally, the fact that 4D flow CMR acquires a complete volume instead of a single plane, means that it can provide a wide range of advanced flow parameters, such as wall shear stress, energy loss and vorticity. As is the case with all novel imaging parameters, the clinical significance of these parameters needs to be investigated.

In the last decades, the scope of percutaneous interventions for CHD has widened to include valve replacement, stent placement for relief of arterial stenosis, closure of collateral vessels and closure of septal defects. In the future, we expect the scope to widen even further to the development of novel stents and devices. Evidence for the safety and efficacy of most percutaneous interventions for CHD is limited, even for procedures that are widely accepted and often performed.The reasons for this lack of evidence are clear: CHD is a relatively small group within the population of cardiovascular disease and it is a heterogenous population. However, this does not mean the need for evidence-based medicine is somehow less in this patient group, or that novel treatment strategies do not require thorough evaluation. Obviously, retrospective single-centre studies (as presented in this thesis) will not solve this issue. They can, however, be a first step towards a multicentre or national collaboration to investigate treatment strategies. In the future, more prospective, protocolized multicentre research is warranted for treatment of CHD and academic medical centres should initiate this research and collaborate to ultimately provide optimal care for the growing group of CHD patients.