Guide to use of ferumoxytol for hepatic vascular assessment as part of dual contrast MRI.

Magnetic resonance imaging (MRI) assessment of hepatic vasculature can be challenging in the setting of liver disease and liver lesions. The widely used hepatobiliary contrast agent gadoxetate is an extracellular contrast agent that provides excellent soft tissue characterization but has limitations as a vascular contrast agent. Ferumoxytol is an iron oxide nanoparticle with superparamagnetic properties that can be used as blood pool contrast agent to provide dedicated vascular assessment. We provide a detailed protocol for evaluation of pediatric liver vasculature using ferumoxytol, after imaging of the parenchyma with gadoxetate. We provide multiple examples and discuss practical considerations when incorporating ferumoxytol into practice.

Highly accelerated compressed sensing 4D flow MRI in congenital and acquired heart disease: comparison of aorta and main pulmonary artery flow parameters with conventional 4D flow MRI in children and young adults.

BACKGROUND: Four-dimensional flow (4D flow) MRI has become a clinically utilized cardiovascular flow assessment tool. However, scans can be lengthy and may require anesthesia in younger children. Adding compressed sensing can decrease scan time, but its impact on hemodynamic data accuracy needs additional assessment. OBJECTIVE: To compare 4D flow hemodynamics acquired with and without compressed sensing. MATERIALS AND METHODS: Twenty-seven patients (median age: 13 [IQR: 9.5] years) underwent conventional and compressed sensing cardiovascular 4D flow following informed consent. Conventional 4D flow was performed using parallel imaging and an acceleration factor of 2. Compressed sensing 4D flow was performed with an acceleration factor of 7.7. Regions of interest were placed to compare flow parameters in the ascending aorta and main pulmonary artery. Paired Student's t-tests, Wilcoxon signed-rank tests, Bland-Altman plots, and intraclass correlation coefficients were conducted. A P-value of < 0.05 was considered statistically significant. RESULTS: Mean scan acquisition time was reduced by 59% using compressed sensing (3.4 vs. 8.2 min, P < 0.001). Flow quantification was similar for compressed sensing and conventional 4D flow for the ascending aorta net flow: 47 vs. 49 ml/beat (P = 0.28); forward flow: 49 vs. 50 ml/beat (P = 0.07), and main pulmonary artery net flow: 49 vs. 51 ml/beat (P = 0.18); forward flow: 50 vs. 55 ml/beat (P = 0.07). Peak systolic velocity was significantly underestimated by compressed sensing 4D flow in the ascending aorta: 114 vs. 128 cm/s (P < 0.001) and main pulmonary artery: 106 vs. 112 cm/s (P = 0.02). CONCLUSION: For both the aorta and main pulmonary artery, compressed sensing 4D flow provided equivalent net and forward flow values compared to conventional 4D flow but underestimated peak systolic velocity. By reducing scan time, compressed sensing 4D flow may decrease the need for anesthesia and increase scanner output without significantly compromising data integrity.

MR angiography and 2-D phase-contrast imaging for evaluation of meso-rex bypass function.

BACKGROUND: The meso-Rex bypass restores blood flow to the liver in patients with extrahepatic portal vein thrombosis. Stenosis occurs in some cases, causing the reappearance of portal hypertension. Complications such as thrombocytopenia present on a spectrum and there are currently no guidelines regarding a threshold for endovascular intervention. While Doppler ultrasound (US) is common for routine evaluation, magnetic resonance (MR) angiography with two-dimensional phase-contrast MRI (2-D PC-MRI) may improve the assessment of meso-Rex bypass function. OBJECTIVES: To determine the feasibility and utility of MR angiography with 2-D PC-MRI in evaluating children with meso-Rex bypass and to correlate meso-Rex bypass blood flow to markers of portal hypertension. MATERIALS AND METHODS: MR angiography and 2-D PC-MRI in meso-Rex bypass patients were retrospectively analyzed. Minimum bypass diameter was measured on MR angiography and used to calculate cross-sectional area. Meso-Rex bypass blood flow was measured using 2-D PC-MRI and divided by ascending aortic flow to quantify bypass flow relative to systemic circulation. Platelet and white blood cell counts were recorded. Correlation was performed between minimum bypass area, blood flow and clinical data. RESULTS: Twenty-five children (median age: 9.5 years) with meso-Rex bypass underwent MR angiography and 2-D PC-MRI. The majority of patients were referred to imaging given clinical concern for complications. Eighteen of the 25 patients demonstrated >50% narrowing of the bypass cross-sectional area. The mean platelet count in 19 patients was 127 K/µL. There was a significant correlation between minimum cross-sectional bypass area and bypass flow (rho=0.469, P=0.018) and between bypass flow and platelet counts (r=0.525, P=0.021). CONCLUSION: Two-dimensional PC-MRI can quantify meso-Rex bypass blood flow relative to total systemic flow. In a cohort of 25 children, bypass flow correlated to minimum bypass area and platelet count. Two-dimensional PC-MRI may be valuable alongside MR angiography to assess bypass integrity.

Safety of Blood Pool Contrast Agent Administration in Children and Young Adults.

OBJECTIVE: The objective of our study was to determine the adverse reaction rate associated with the administration of blood pool contrast material in children and young adults. MATERIALS AND METHODS: A review of the MRI and pharmacy databases identified all patients who received gadofosveset trisodium from October 1, 2011, to June 30, 2014. Patients were classified as having been anesthetized or not anesthetized for the MRI examinations. A review of the electronic medical records identified adverse reactions recorded within 24 hours of contrast administration. The adverse reactions were graded as mild, moderate, or severe. Risk ratios were calculated between the adverse reaction rate experienced by anesthetized patients and that experience by nonanesthetized patients. RESULTS: During the study period, 626 patients (mean age, 11.7 years) received 711 doses of gadofosveset trisodium; 137 adverse reactions were recorded, which yields a 19.3% (137/711) adverse reaction rate. There were 115 adverse reactions experienced by 367 anesthetized patients (31.3%): 93.0% (107/115) were mild and 7.0% (8/115) were moderate. The remaining 22 adverse reactions were experienced by 344 (6.4%) nonanesthetized patients, and 90.9% (20/22) were mild. Three nonanesthetized patients had allergiclike reactions; of these allergiclike reactions, one was mild and two were severe for a severe allergiclike reaction rate of 0.28% (2/711). Severe allergiclike reactions were treated without any adverse outcomes. Anesthetized patients were 5.7 times more likely to experience an adverse event than nonanesthetized patients; most reactions in anesthetized patients were seen after the administration of anesthesia alone. CONCLUSION: Most reactions after gadofosveset trisodium administration in children and young adults are mild; however, severe allergiclike reactions occur, so policies must be in place to treat patients with adverse reactions when using this contrast agent. These data may be useful to centers considering administering gadofosveset trisodium to pediatric patients.

Reoperation after vascular ring repair.

The majority of patients having surgical intervention for a vascular ring have resolution of their symptoms. However, 5% to 10% of these patients develop recurrent symptoms related either to airway or esophageal compression and may require reoperation. In our series of 300 patients with vascular rings, we performed a reoperation on 26 patients, not all of whom were originally operated on at our institution. The four primary indications for reoperation were Kommerell diverticulum (n = 18), circumflex aorta (n = 2), residual scarring (n = 2), and tracheobronchomalacia requiring aortopexy (n = 4). All patients undergoing reoperation have had preoperative evaluation with bronchoscopy and computed tomographic scanning (CT) with 3-dimensional reconstruction. Patients with dysphagia have had a barium esophagram and esophagoscopy. Patients with a Kommerell diverticulum have undergone resection of the diverticulum and transfer of the left subclavian artery to the left carotid artery. The aortic uncrossing procedure has been used in patients with a circumflex aorta. Aortopexy has been used to treat anterior compression of the trachea by the aorta. Results of these reinterventions have been successful in nearly all cases. Lessons learned from these reoperations can be applied to prevent the need for reoperation by properly selecting the correct initial operation. A dedicated team caring for these children consisting of medical imaging, otolaryngology, cardiovascular-thoracic surgery, and critical care is imperative.

Analysis of an automated background correction method for cardiovascular MR phase contrast imaging in children and young adults.

BACKGROUND: Phase contrast magnetic resonance imaging (MRI) is a powerful tool for evaluating vessel blood flow. Inherent errors in acquisition, such as phase offset, eddy currents and gradient field effects, can cause significant inaccuracies in flow parameters. These errors can be rectified with the use of background correction software. OBJECTIVE: To evaluate the performance of an automated phase contrast MRI background phase correction method in children and young adults undergoing cardiac MR imaging. MATERIALS AND METHODS: We conducted a retrospective review of patients undergoing routine clinical cardiac MRI including phase contrast MRI for flow quantification in the aorta (Ao) and main pulmonary artery (MPA). When phase contrast MRI of the right and left pulmonary arteries was also performed, these data were included. We excluded patients with known shunts and metallic implants causing visible MRI artifact and those with more than mild to moderate aortic or pulmonary stenosis. Phase contrast MRI of the Ao, mid MPA, proximal right pulmonary artery (RPA) and left pulmonary artery (LPA) using 2-D gradient echo Fast Low Angle SHot (FLASH) imaging was acquired during normal respiration with retrospective cardiac gating. Standard phase image reconstruction and the automatic spatially dependent background-phase-corrected reconstruction were performed on each phase contrast MRI dataset. Non-background-corrected and background-phase-corrected net flow, forward flow, regurgitant volume, regurgitant fraction, and vessel cardiac output were recorded for each vessel. We compared standard non-background-corrected and background-phase-corrected mean flow values for the Ao and MPA. The ratio of pulmonary to systemic blood flow (Qp:Qs) was calculated for the standard non-background and background-phase-corrected data and these values were compared to each other and for proximity to 1. In a subset of patients who also underwent phase contrast MRI of the MPA, RPA, and LPA a comparison was made between standard non-background-corrected and background-phase-corrected mean combined flow in the branch pulmonary arteries and MPA flow. All comparisons were performed using the Wilcoxon sign rank test (α = 0.05). RESULTS: Eighty-five children and young adults (mean age 14 years; range 10 days to 32 years) met the criteria for inclusion. Background-phase-corrected mean flow values for the Ao and MPA were significantly lower than those for non-background-corrected standard Ao (P = 0.0004) and MPA flow values (P < 0.0001), respectively. However, no significant difference was seen between the standard non-background (P = 0.295) or background-phase-corrected (P = 0.0653) mean Ao and MPA flow values. Neither the mean standard non-background-corrected (P = 0.408) nor the background-phase-corrected (P = 0.0684) Qp:Qs was significantly different from 1. However in the 27 patients with standard non-background-corrected data, the difference between the Ao and MPA flow values was greater than 10%. There were 19 patients with background-phase-corrected data in which the difference between the Ao and MPA flow values was greater than 10%. In the subset of 43 patients who underwent MPA and branch pulmonary artery phase contrast MRI, the sum of the standard non-background-corrected mean RPA and LPA flow values was significantly different from the standard non-background-corrected mean MPA flow (P = 0.0337). The sum of the background-phase-corrected mean RPA and LPA flow values was not significantly different from the background-phase-corrected mean MPA flow value (P = 0.1328), suggesting improvement in pulmonary artery flow calculations using background-phase-correction. CONCLUSION: Our data suggest that background phase correction of phase contrast MRI data does not significantly change Qp:Qs quantification, and there are residual errors in expected Qp:Qs quantification despite background phase correction. However the use of background phase correction does improve quantification of MPA flow relative to combined RPA and LPA flow. Further work is needed to validate these findings in other patient populations, using other MRI units, and across vendors.

Comparison of quiescent inflow single-shot and native space for nonenhanced peripheral MR angiography.

PURPOSE: To evaluate two nonenhanced MRA methods: quiescent-interval single-shot (QISS) and Native SPACE (NATIVE = Non-contrast Angiography of the Arteries and Veins; SPACE = Sampling Perfection with Application Optimized Contrast by using different flip angle Evolution), using contrast-enhanced MR angiography (CEMRA) as a reference standard. MATERIALS AND METHODS: Twenty patients (14 male; mean, 69.3 years old) referred for lower extremity MRA were recruited in a HIPAA-compliant prospective study. QISS and Native SPACE of the lower extremities were performed at 1.5 Tesla with a hybrid dual-injection contrast-enhanced MRA as reference. Image quality and stenosis severity were assessed in segments by two blinded radiologists. Methods were compared with logistic regression for correlated data for diagnostic accuracy. RESULTS: Of 496 arterial segments, 24 were considered nondiagnostic on the Native SPACE images. There were no QISS or CEMRA imaging segments considered to be nondiagnostic. Image quality was significantly higher for QISS than for Native SPACE. QISS stenosis sensitivity (84.9%) was not significantly different from Native SPACE (87.3%). QISS had better specificity (95.6%) than Native SPACE (87.0%), P = 0.0041. In comparison with QISS, Native SPACE proved less robust for imaging of the abdominal and pelvic segments. CONCLUSION: Native SPACE and QISS were sensitive for hemodynamically significant stenosis in this pilot study. QISS NEMRA demonstrated superior specificity and image quality, and was more robust in the abdominal and pelvic regions.

Evolution and Current Results of a Unified Strategy for Sinus Venosus Surgery.

BACKGROUND: Given recent reports of percutaneous closure of sinus venosus atrial septal defects, we reviewed our experience with surgical repair. Owing to the high incidence of arrhythmias with the two-patch technique, since 2001 we have used either one-patch repairs or the Warden procedure. METHODS: A retrospective review was performed of pediatric patients undergoing sinus venosus atrial septal defect repair at our institution from January 1, 1990, to July 1, 2018. Standard demographic data such as echocardiographic and cross-sectional imaging along with operative details and clinical echocardiographic outcomes were collected. RESULTS: The cohort included 144 patients with a median age of 4.3 years (interquartile range, 8.5). Inferior SVASD was present in 24 patients (17%). A single autologous untreated pericardial patch was used for 114 patients (79%), a two-patch technique for 20 patients (14%, last performed in 2000), and a Warden procedure in 10 patients (7%). Median length of stay was 4 days (interquartile range, 2). On echocardiogram follow-up, no patient had pulmonary vein stenosis. One patient who had the Warden procedure required a balloon dilation of the superior caval vein 2 years postoperatively and a stent 3 years later. Two-patch patients were substantially less likely to be in normal sinus rhythm (41%) on postoperative electrocardiograms compared with the other two techniques (81% one-patch and 89% Warden, P = .02). CONCLUSIONS: The great majority of patients with sinus venosus atrial septal defects can be successfully repaired with a single patch of autologous pericardium. We transitioned to using either a single pericardial patch or the Warden procedure, resulting in a higher frequency of normal sinus rhythm on postoperative electrocardiograms.

Descending Aortic Translocation and Right Pulmonary Artery Reimplantation for Midline Descending Aorta and Crossed Pulmonary Arteries in an Infant.

Left mainstem bronchial compression by a midline descending thoracic aorta is a rare anatomic variant. Translocation of the descending thoracic aorta to the ascending aorta has recently been described to treat this condition. We performed an aortic translocation and right pulmonary artery reimplantation in a 4-month-old infant with severe pulmonary hypertension secondary to right pulmonary artery stenosis and left bronchial compression by a midline descending thoracic aorta. The procedure was successful in ameliorating the patient's left mainstem bronchial compression and pulmonary hypertension. Descending aortic translocation should be considered when the left bronchus is compressed causing respiratory symptoms.

Double Aortic Arch With Kommerell Diverticulum.

BACKGROUND: Vascular rings with a Kommerell diverticulum (KD) most commonly occur in patients with a right aortic arch. We report on a less commonly seen subset of vascular ring patients-those with a double aortic arch and a KD. METHODS: Between 2002 and 2017, 66 patients underwent an operation for a double aortic arch. Ten of those patients also had excision of a KD. We performed a retrospective medical record review of these patients to characterize their demographics and outcomes. RESULTS: All 10 patients (7 male, 3 female) had a double aortic arch that was right dominant and also had a KD. The patients were a mean age of 4.9 ± 4.3 years (range, 6 months to 29 years), and median age was 4 years. All patients had preoperative computed tomographic angiography or magnetic resonance imaging and mean compression of the distal trachea of 63% ± 12% (range, 40% to 80%). The distal left arch was atretic in all patients. All patients underwent division of their left aortic arch, division of the ligamentum, and resection of the KD. The left subclavian artery was transferred to the left carotid artery in 2 patients. The mean size of the diverticulum was 9 × 10 mm. There were no major postoperative complications or readmissions. The postoperative length of stay was 3.1 ± 0.8 days. Five of the patients reported no related persisting symptoms. The remaining 5 patients reported substantial symptomatic relief with only minor respiratory symptoms. CONCLUSIONS: Vascular ring patients with a double aortic arch can also have a KD. In addition to dividing the smaller aortic arch and the ligamentum, we recommend excision of the KD.

Brom Aortoplasty for Supravalvular Aortic Stenosis.

BACKGROUND: Controversy remains regarding the optimal surgical approach for children with supravalvular aortic stenosis (SVAS). METHODS: Since 1997 we have used Brom three-patch aortoplasty for patients with SVAS. We prefer computed tomography (CT) imaging for preoperative evaluation rather than cardiac catheterization as it avoids the well-known morbidity of general anesthesia. The purpose of this study was to present our intermediate-term results of this strategy. RESULTS: Twenty consecutive patients with SVAS were treated with Brom aortoplasty. Mean age was 3.7 ± 5.9 years (median, 1.5 years). Twelve patients had Williams syndrome. Ten patients had preoperative advanced medical imaging (seven CT, three magnetic resonance imaging) and did not have cardiac catheterization. Mean times for cardiopulmonary bypass and cross-clamp were 172 ± 29 minutes and 110 ± 21 minutes, respectively. Ten patients had simultaneous pulmonary artery stenosis patching. Median length of stay was seven days. There was no operative or late mortality. Mean follow-up was 6 ± 5 years. There were no reoperations on the aortic root. Fifteen patients had mild or less aortic insufficiency (AI) and two had moderate AI. One patient who had infant balloon dilation of the aortic valve and postoperative subacute bacterial endocarditis had moderate-to-severe AI and aortic stenosis (AS). One patient had moderate residual SVAS; all others had no AS. No patients had late coronary insufficiency. CONCLUSION: Brom aortoplasty promotes restoration of normal aortic root geometry and relief of coronary ostial stenosis, which is important in preventing myocardial ischemia. Computed tomography imaging is our preferred diagnostic modality. Intermediate-term outcomes are excellent with no recurrent SVAS, coronary events, or reoperations on the aortic valve.

Discontinuous Pulmonary Artery.

We describe the diagnosis and surgical repair of a five-month-old infant with a congenital discontinuous right pulmonary artery. Initial echocardiogram failed to show the right pulmonary artery and revealed systemic left pulmonary artery pressure based on the tricuspid regurgitation jet. Computed tomographic angiography confirmed the diagnosis of discontinuous right pulmonary artery. The right pulmonary artery appeared essentially normal in size, and there were no significant aortopulmonary collateral arteries. Using cardiopulmonary bypass and aortic transection, we created an anastomosis between the right and the main pulmonary arteries augmented anteriorly by a pericardial patch. Postoperative lung perfusion scan demonstrated balanced pulmonary blood flow to the lungs. Pulmonary hypertension resolved over three weeks in the postoperative period, an expected outcome in this age-group.

Anomalous Aortic Origin of a Coronary Artery: Symptoms Do Not Correlate With Intramural Length or Ostial Diameter.

BACKGROUND: Anomalous aortic origin of a coronary artery (AAOCA) is a known cause of sudden death. Our hypothesis was that longer intramural length and smaller ostial diameter correlate with preoperative symptoms. If true, this would assist in the decision for surgical indications. We also assessed the accuracy of preoperative imaging to predict intramural length. METHODS: Retrospective analysis of patients who underwent AAOCA unroofing from 2006 to 2014. Patients had preoperative computed tomography angiography (CTA) or magnetic resonance imaging (MRI). Intramural length was measured. Intramural lengths and ostial diameters were also measured intraoperatively (operating room [OR]). Symptoms were noted. Intramural lengths and ostial diameters were compared between patients with and without preoperative symptoms. The accuracy of intramural length measured by CTA/MRI versus the length measured in the OR was assessed using a Bland-Altman analysis. RESULTS: Sixty-six patients underwent surgical repair of AAOCA. Fifty-two (79%) patients were symptomatic and 14 (21%) were asymptomatic. Mean age was 12.4 ± 4.0 years. There was no mortality. There was strong agreement between intramural length measured by CTA/MRI and measured in the OR. There was no significant difference in AAOCA intramural length in the symptomatic (8.6 ± 3.5 mm) and asymptomatic (8.9 ± 2.8 mm, P = .77) patients, which were measured both by CTA/MRI and intraoperatively (symptomatic 7.3 ± 2.5 mm, asymptomatic 6.9 ± 2.8 mm; P = .62). There was also no significant difference in AAOCA ostial diameters between groups (symptomatic = 1.9 ± 0.5 mm, asymptomatic = 1.6 ± 0.5 mm; P = .09). CONCLUSION: Preoperative CTA/MRI was very accurate in predicting the length of surgical unroofing. There was no demonstrable correlation between preoperative symptoms and intramural AAOCA length or AAOCA ostial diameter.

Vascular rings.

The term vascular ring refers to congenital vascular anomalies of the aortic arch system that compress the esophagus and trachea, causing symptoms related to those two structures. The most common vascular rings are double aortic arch and right aortic arch with left ligamentum. Pulmonary artery sling is rare and these patients need to be carefully evaluated for frequently associated tracheal stenosis. Another cause of tracheal compression occurring only in infants is the innominate artery compression syndrome. In the current era, the diagnosis of a vascular ring is best established by CT imaging that can accurately delineate the anatomy of the vascular ring and associated tracheal pathology. For patients with a right aortic arch there recently has been an increased recognition of a structure called a Kommerell diverticulum which may require resection and transfer of the left subclavian artery to the left carotid artery. A very rare vascular ring is the circumflex aorta that is now treated with the aortic uncrossing operation. Patients with vascular rings should all have an echocardiogram because of the incidence of associated congenital heart disease. We also recommend bronchoscopy to assess for additional tracheal pathology and provide an assessment of the degree of tracheomalacia and bronchomalacia. The outcomes of surgical intervention are excellent and most patients have complete resolution of symptoms over a period of time.

Right pulmonary artery to left atrial fistula in a neonate: case report and review of the literature.

A communication between the right pulmonary artery (RPA) and the left atrium is a rare congenital anomaly that presents with cyanosis and heart failure. We describe the surgical repair of an RPA to left atrial fistula using cardiopulmonary bypass in a neonate. Advanced imaging (computed tomography scan) guided the surgical approach. Although previous reports have associated a patent ductus arteriosus with high neonatal mortality, in our case, the ductus arteriosus was actually important for maintaining enough total pulmonary blood flow.

Intramural coronary length correlates with symptoms in patients with anomalous aortic origin of the coronary artery.

BACKGROUND: Anomalous aortic origin of a coronary artery (AAOCA) from the opposite sinus of Valsalva is a rare congenital anomaly with the potential for myocardial ischemia and sudden death. This review evaluated our series of AAOCA patients, who underwent coronary artery unroofing, to test our hypothesis that the intramural length of the anomalous coronary artery correlates with symptoms. METHODS: A retrospective analysis of symptoms, preoperative imaging (computed tomography and magnetic resonance imaging), intraoperative assessment, perioperative course, and follow-up were reviewed. RESULTS: From 2005 to 2010, 27 patients (70% male) underwent surgical AAOCA repair. Mean age was 14.3±12 (range, 6 to 52) years. In 25 patients with right AAOCA, 14 had chest pain and 4 had syncope. Both patients with left AAOCA had chest pain. AAOCA unroofing was done in 25 and side-to-side anastomosis in 2. The intramural coronary artery length measured intraoperatively correlated with preoperative symptoms (symptoms=10±3.58 mm, no symptoms=5.2±1.5 mm, p<.002), as did preoperative imaging measurements (symptoms=7.8±2.8 mm, no symptoms=5.3±0.8 mm, p<.001). Preoperative imaging strongly predicted the intraoperative measurement (r=0.81, p=0.00001). There were no deaths, significant morbidity, or recurrence of symptoms. CONCLUSIONS: Coronary unroofing for AAOCA is a safe method of enlarging the coronary orifice and eliminating the intramural course. Symptomatic patients had a longer intramural course than asymptomatic patients, as assessed by preoperative imaging and intraoperative measurements. These results may have important clinical implications in determining indications for operation.