Cardiac MR examinations performed from December 2015 to October 2017 in patients with congenital heart disease post-surgical repair referred for a clinically necessary standard of care cardiac MR examination from the cardiothoracic surgery and cardiology departments at our institute were collected for analysis. This study was approved by the ethics committee and the institutional review board at our institution.
Magnetic resonance imager
Both adults and children with congenital heart disease were scanned on a Philips Gyroscan Intera (1.5 T) whole-body MRI scanner housed in our radiology department.
All patients were examined in supine position, head first. The patients were offered headphones to reduce the repetitive gradient noise and at the same time allow the patient to hear the breath hold instructions. ECG leads and PEAR (phase encoding artifact reduction) sensors were applied. A small surface coil (C1 coil, Philips) was utilized for infants and toddlers, while the phased array body coil (Synergy, Philips) was utilized for older children and adults.
Infants and small children up to the age of 4 years were sedated by oral chloral hydrate (75 mg/kg body weight), while older children and adults underwent the examination without sedation.
The imaging protocol varied according to the age of the patient, relevant anatomy, and the expected post-operative complications. Sequences routinely performed included the following:
Black-blood spin echo (BBSE)
BBSE was used to delineate both cardiac and extracardiac anatomy due to its high tissue-to-blood characteristics. An additional advantage of BBSE was its low sensitivity to metallic susceptibility artifacts allowing better assessment of cardiac anatomy in the presence of intracardiac or intra-vascular metallic devices.
Bright-blood gradient echo cine imaging
This was obtained by utilizing balanced steady state free precession (B-SSFP). In this sequence, the blood appears white. This cine technique was used in the evaluation of the ventricular volumes, masses, and ejection fraction as well as permitting the identification of valvular regurgitation, stenosis, or turbulent flows across septal defects.
Phase-encoded flow imaging
This technique was used for quantification of flow volumes, regurgitation fraction, peak flow velocities and shunt volumes via measuring the ratio between pulmonary flow volume (Qp) and aortic flow volume (Qs), thus allowing the delineation of the severity of stenotic or regurgitant valves, peripheral pulmonary branch stenosis, and shunt fraction.
The imaging planes that were used in this study were the three standard orthogonal axes of the thorax: transverse, coronal, and sagittal images (black blood); short and long axis images of the heart (SSFP cine); and phase encoding flow quantification across the aortic and pulmonary valves.
In cases where late gadolinium enhancing (LGE) images were required, gadolinium chelate contrast material (0.1–0.2 mmol) gadopentetate dimeglumine was intravenously administered followed by a cardiac-gated segmented inversion recovery-prepared (200–300 ms) fast gradient-echo sequence 10–15 min later.
Cardiac MRI examinations were performed under the supervision of an expert radiologist (6 years experience) for exam acquisition, interpretation, and post-processing; then, the images were reviewed by 2 readers (6 and 10 years experience in cardiac MRI) for the following: complications such as pulmonary patch aneurysmal dilatation and pulmonary regurgitation fraction (RF). Grading of regurgitation was classified as mild if less than 20%, moderate if 20 to 40%, and severe if more than 40%, pulmonary artery branch stenosis, tricuspid valve regurgitation, and right ventricular ejection fraction (RVEF); classified as > 70% “hyperdynamic”, 55–70% “normal”, 45–54% “low-normal/borderline low” 40–45% “ mildly reduced”, 30–44% “moderately reduced”, < 30% “severely reduced”, where RV failure is considered if RVEF is < 40%, right ventricular end diastolic volume (RVEDV) index; classified as 100–110 “borderline”, 110–130 “mild”, 130–170 “moderate”, > 170 “severe”.
Additionally, valvular morphology and anatomical details such as situs, AV concordance, VA concordance, great vessel relationship, septation defects, size, and pericardial effusion were evaluated. Extracardiac findings including those affecting the aorta, pulmonary arteries, pulmonary venous drainage, systemic venous drainage, coronary arteries, lungs, and pleura, as well as upper abdominal abnormalities, were also noted and described when present.
IBM SPSS statistics [V.21.0, IBM Corp., USA, 2012] were used for data analysis.