Discussion
congenital heart disease, paralysis
GENETIC SYNDROMES
In the long-term follow-up of the Single Ventricle Reconstruction Trial [Earlier data from the SVR Trial suggested that RV function as measured by echocardiography was impaired prior to Fontan surgery in patients who were palliated with a RVPAS versus those who received a mBTTS [While 75% of the patients in this study were able to undergo CMR and nearly all of those had interpretable RV function data, 25% of the patients were unable to undergo CMR. The two most common reasons were MRI-unsafe implanted devices and need for sedation or anesthesia. Over time, the number of patients excluded from CMR studies for both of these reasons can be decreased with advances in device technology, CMR technique and the MRI environment.Implanted devices are relative contraindications to CMR due to safety concerns and imaging artifacts. The presence of a cardiac implantable electronic device (CIED) was previously considered an absolute contraindication to MRI, but that has changed more recently. A growing body of literature in adults has demonstrated safety in scanning patients with non-MRI compatible devices [A recent single center review documented 20% anesthesia use in patients undergoing CMR exam for any reason at age 10 years [CMR in younger children without anesthesia may require free breathing techniques, as many children are unable to comply with breath holding through the entire scan. Furthermore, children undergoing CMR under general anesthesia often require similar free breathing techniques to minimize the use of paralysis and ventilator pauses during an exam. While CMR more frequently required a breath hold for adequate imaging in the past, there are free breathing techniques in standard clinical use including multiple signal averaging and accelerated acquisition using parallel imaging, as well as emerging techniques such as real time CMR [Study quality was adequate for measuring RVEF as the primary outcome using a free breathing CMR exam technique. Common artifacts experienced during the study included metallic susceptibility artifact, motion artifact, artifact from the MR environment (radiofrequency artifact) and phase contrast velocity encoding that was too low for the velocity of blood flow (aliasing). Older stainless steel coils and other implanted devices cause large susceptibility or “blooming” artifacts that obliterate much of the chest anatomy and were the most common reason for the inability to measure ejection fraction [Our study is limited by potential selection bias in our long-term follow up of this specific cohort. Patients who were eligible but not enrolled may have been sicker, had developmental delays, genetic syndromes or had known implantable devices that resulted in the patients and families declining participation. There is also a survival bias in our follow up cohort, and it is possible that the patients who were transplanted or died could have had more difficult, lengthy, or poor-quality studies. This research protocol was designed for efficient CMR exams and not for evaluating accuracy or reproducibility of the volumetric analysis; however, it is important to note the protocol follows current guidelines for CMR use in children and adults with congenital heart disease 