D-transposition of the great arteries: the current era of the arterial switch operation

Children and Adolescents Show Altered Visual Working Memory Related Brain Activity More Than One Decade After Arterial Switch Operation for D-Transposition of the Great Arteries

This pilot study investigated neural correlates of visual working memory using functional magnetic resonance imaging (fMRI) in seven patients more than one decade after neonatal arterial switch operation for surgical correction of d-transposition of the great arteries (d-TGA, aged 10-18 years, 1 female). Compared with age and sex matched healthy controls patients showed similar visual working memory performance and a smaller increase in brain activity in the posterior parietal cortex with higher visual working memory load. These findings suggest that patients exhibit altered neural activity within a network that is known to support visuospatial memory and cognition.

Modulating microRNAs in cardiac surgery patients: Novel therapeutic opportunities?

This review focuses on microRNAs (miRs) in cardiac surgery, where they are emerging as potential targets for therapeutic intervention as well as novel clinical biomarkers. Identification of the up/down-regulation of specific miRs in defined groups of cardiac surgery patients can lead to the development of novel strategies for targeted treatment in order to maximise therapeutic results and minimise acute, delayed or chronic complications. MiRs could also be involved in determining the outcome independently of complications, for example in relation to myocardial perfusion and fibrosis. Because of their relevance in disease, their known sequence and pharmacological properties, miRs are attractive candidates for therapeutic manipulation. Pharmacological inhibition of individual miRs can be achieved by modified antisense oligonucleotides, referred to as antimiRs, while miR replacement can be achieved by miR mimics to increase the level of a specific miR. MiR mimics can restore the function of a lost or down-regulated miR, while antimiRs can inhibit the levels of disease-driving or aberrantly expressed miRs, thus de-repressing the expression of mRNAs targeted by the miR. The main delivery methods for miR therapeutics involve lipid-based vehicles, viral systems, cationic polymers, and intravenous or local injection of an antagomiR. Local delivery is particularly desirable for miR therapeutics and options include the development of devices specific for local delivery, light-induced antimiR, and vesicle-encapsulated miRs serving as therapeutic delivery agents able to improve intracellular uptake. Here, we discuss the potential therapeutic use of miRNAs in the context of cardiac surgery.

Mechanism responsible for D-transposition of the great arteries: Is this part of the spectrum of right isomerism?

D-transposition of the great arteries (TGA) is one of the most common conotruncal heart defects at birth and is characterized by a discordant ventriculoarterial connection with a concordant atrioventricular connection. The morphological etiology of TGA is an inverted or arrested rotation of the heart outflow tract (OFT, conotruncus), by which the aorta is transposed in the right ventral direction to the pulmonary trunk. The rotational defect of the OFT is thought to be attributed to hypoplasia of the subpulmonic conus, which originates from the left anterior heart field (AHF) residing in the mesodermal core of the first and second pharyngeal arches. AHF, especially on the left, at the early looped heart stage (corresponding to Carnegie stage 10-11 in the human embryo) is one of the regions responsible for the impediment that causes TGA morphology. In human or experimentally produced right isomerism, malposition of the great arteries including D-TGA is frequently associated. Mutations in genes involving left-right (L-R) asymmetry, such as NODAL, ACTRIIB and downstream target FOXH1, have been found in patients with right isomerism as well as in isolated TGA. The downstream pathways of Nodal-Foxh1 play a critical role not only in L-R determination in the lateral plate mesoderm but also in myocardial specification and differentiation in the AHF, suggesting that TGA is a phenotype in heterotaxia as well as the primary developmental defect of the AHF.

Cardiovascular Magnetic Resonance Findings Late After the Arterial Switch Operation

Background—

Despite its robust diagnostic capabilities in adolescents and adult patients after the arterial switch operation, little information is available on the cardiovascular magnetic resonance findings in this population.

Methods and Results—

The cardiovascular magnetic resonance findings of 220 consecutive patients evaluated in our center were retrospectively reviewed (median age at cardiovascular magnetic resonance, 15.4 years; 66.8% male sex). Compared with published normal values, left and right ventricular end-diastolic volume z scores were mildly enlarged (0.48±1.76 and 0.33±1.5; P =0.0003 and 0.0038, respectively), with 26% of patients having left ventricular dilatation and 20% having right ventricular dilatation. Left ventricular dysfunction was present in 21.5% of patients (mild in most), and only 5.1% of patients had mild right ventricular dysfunction. Myocardial scar was found in 1.8% of patients. Dilatation of the neoaortic root was common (76%), and root z score increased at an average rate of 0.03 points per year. By multivariable analysis, neoaortic root dilatation was associated with worse neoaortic valve regurgitation (OR, 5.29; P =0.0016). The diameters of the thoracic aorta distal to the root were near-normal in most patients, whereas the neomain pulmonary artery was typically oval shaped with decreased anteroposterior and normal lateral diameters.

Conclusions—

Although the majority of arterial switch operation patients have normal ventricular size and function and myocardial scar is rare, an important minority exhibits ventricular enlargement or dysfunction. Neoaortic root dilatation, which is present in most patients and progresses over time, is strongly associated with significant neoaortic valve regurgitation. The findings of this study provide reference values against which arterial switch operation patients can be compared with their peers.

Transposition of the Great Arteries and Common Variants

OBJECTIVES

The objectives of this review are to discuss the physiology, perioperative management, surgical correction, and outcomes of infants with transposition of the great arteries and common variants undergoing the arterial switch operation.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSION

The widespread adoption of the arterial switch operation for transposition of great arteries has been one of the more gratifying advances in pediatric cardiovascular care, and represents the simultaneous improvements in diagnostics, surgical and bypass techniques, anesthesia in the neonate, improvements in intensive care technology, nursing strategies, and system-wide care delivery. Many of the strategies adopted for the neonate with transposition of the great arteries have been translated to neonatal care for other congenital heart lesions. Continued work is necessary to investigate the effects of perioperative care on long-term neurodevelopmental outcomes, as well as collaboration between centers to spread "best practices" for outcome, cost, and morbidity reduction.

Long-term outcomes of the arterial switch operation for transposition of the great arteries and ventricular septal defect and/or aortic arch obstruction

OBJECTIVES

Long-term outcomes after the arterial switch operation (ASO) for complex transposition of the great arteries (TGA) should be clarified.

METHODS

A retrospective study was conducted in patients operated on between 1982 and 1998. Overall 220 postoperative survivors, 79.1% with a ventricular septal defect, 13.2% with multiple ventricular septal defects, and 29.1% with aortic arch obstruction, were followed for 17 years (0-28 years).

RESULTS

The conditional survival rate was 96.7% [95% confidence interval (CI): 94.4-99.1] at 25 years. Late sudden death occurred in 2 asymptomatic patients. The cumulative incidence rate of death or reinterventions was 3.8% (95% CI: 2.9-4.8) at 25 years, with age at ASO <10 days and aortic regurgitation at discharge identified as independent risk factors. The cumulative incidence rate of neoaortic regurgitation was 41.6% (95% CI: 20.5-62.8) at 25 years with an aorto-pulmonary diameter mismatch at the time of the ASO, age at ASO <10 days and aortic regurgitation at discharge identified as independent risk factors. At the last follow-up, 53 patients (24.1%) had neoaortic root dilatation with an aortic sinus z-score ≥3 and 6 of them had a Bentall operation at a median delay of 14.1 years since the ASO. The only independent factors for neoaortic root dilatation were male sex and an aorto-pulmonary diameter mismatch at the time of the ASO.

CONCLUSIONS

Despite a continual rate of reinterventions, long-term survival and cardiovascular outcome are excellent after ASO for complex TGA. Dilatation of the neoaortic root and neoaortic regurgitation may be observed with time and 2 late sudden deaths occurred, justifying a close follow-up in all patients.

Chronological changes in stenosis of translocated coronary arteries on angiography after the arterial switch operation in children with transposition of the great arteries: comparison of myocardial scintigraphy and angiographic findings

BACKGROUND

The peri-operative mortality of the arterial switch operation in neonates with transposition of the great arteries is considerably low; however, long-term outcomes of translocated coronary arteries still remain one of the most crucial issues. Methods and results A total of 110 neonates with transposition of the great arteries after arterial switch operation were evaluated; three (2.7%) late deaths occurred. The remaining 107 patients except for one underwent follow-up angiography. Angiography showed coronary artery stenosis in nine (8.4%), with right coronary artery lesions in two and left main trunk lesions in seven. In two patients, right coronary artery stenosis regressed during follow-up. In left main trunk lesions, the severity of stenosis improved in four, did not change in one, and progressed to total occlusion in two patients. In children with coronary artery stenosis, myocardial scintigraphy showed perfusion defects in five out of six (83%) with left main trunk with ⩾75% stenosis and in four out of four with left main trunk stenosis ⩾90%. In contrast, patients whose coronary artery stenosis disappeared during follow-up had no perfusion defects on scintigraphy.

CONCLUSIONS

Regression of ostial stenosis of the transplanted coronary artery on angiogram was observed. The stenosis regressed over time in six patients; two coronary arteries with 99% stenosis and delayed angiographic enhancement of the distal coronary artery resulted in total occlusion within 1 year after the arterial switch operation. Combination of angiography and myocardial scintigraphy could be useful to differentiate deceptive stenosis from progressive stenosis.

Echocardiographic and Surgical Correlation of Coronary Artery Patterns in Transposition of the Great Arteries

OBJECTIVE

Determine the accuracy of echocardiography to diagnose coronary anatomy in transposition of the great arteries and to evaluate the effect of accuracy on surgical outcomes and changes in accuracy over time.

DESIGN

Retrospective chart review of neonates admitted February 1999 to March 2013 with transposition. Coronary pattern from the preoperative echocardiogram and operative reports were collected and compared with determine diagnostic accuracy. Coronary patterns were further confirmed by intraoperative images taken during surgery.

SETTING

Tertiary care children's hospital.

PATIENTS

Neonates with transposition of the great arteries and planned arterial switch operation with an echo and operative report or image describing the coronaries.

INTERVENTIONS

Not applicable.

OUTCOME MEASURES

Accuracy of echocardiography to diagnose coronary anatomy in transposition, and to identify factors related to correct diagnosis.

RESULTS

One hundred forty-two patients met inclusion criteria with 122 correctly diagnosed, 16 incorrect, and 4 inconclusive. Accuracy was 86%, with 95% accuracy in patients with typical coronary patterns, 85% with the most common variant (left coronary from the leftward sinus and right and circumflex from the rightward sinus), and 61% with less common patterns. Typical and common variants were more likely to be correct than atypical patterns (P < .001). Cases with ventricular septal defect were more likely to have correctly diagnosed coronaries than with an intact ventricular septum (94% vs. 79%, P = .01). There was no change in accuracy over time (P > .05). There was no difference in duration of cardiopulmonary bypass, cross-clamp times, length of stay, or postoperative stay between the correct and incorrectly diagnosed groups (P > .05).

CONCLUSIONS

In our center, accuracy of echocardiographic imaging of the coronary arteries in transposition was 86% without improvement over time, and perioperative outcomes were not affected by diagnostic accuracy. Further invasive imaging may not be necessary to determine the coronary pattern in this lesion.

Complete transposition of the great arteries with double outlet right ventricle in a dog

A 2-year old intact male Collie dog presented to the cardiology service at Oregon State University for evaluation of cyanosis and suspected congenital cardiac disease. Echocardiography revealed a constellation of cardiac abnormalities including a single large vessel exiting the right ventricle with a diminutive left ventricular outflow tract, a ventricular septal defect, and marked concentric right ventricular hypertrophy with moderate right atrial dilation. Cardiac-gated computed tomography confirmed the previous anomalies in addition to supporting a diagnosis of complete transposition of the great arteries, double outlet right ventricle, and pulmonic hypoplasia with a single coronary ostium. Prominent bronchoesophageal collateral vessels were concurrently identified. Clinically, the dog was stable despite mild cyanosis that worsened with exercise; no intervention was elected at the time. This case report describes a rare combination of congenital cardiac defects and the usefulness of cardiac-gated cross-sectional imaging in the anatomic diagnosis.

Pulmonary Artery Aneurysm Compressing the Tracheobronchial Tree Following an Arterial Switch Operation

A neonate developed severe dyspnea following an arterial switch operation due to compression of the trachea and left main bronchus by a dilated pulmonary artery. This was relieved by a second procedure in which the dilated pulmonary artery was excised and reconstructed with bovine pericardium.

Outcomes of Patients After Arterial Switch Operation: 18 Years of Experience in a Single Medium-Volume Center

The objective of this paper was to describe the outcomes in patients submitted to arterial switch operation and to analyze the predictors of in-hospital mortality and further need of re-operation at a single-center institution. Between September 1995 and January 2014, 128 consecutive arterial switch operations were performed. Surgical mortality during this period was analyzed retrospectively, and a follow-up analysis of the survivors was conducted. Surgical era, cardiopulmonary bypass time (p = 0.001), and diagnosis category (p = 0.025) influenced in-hospital mortality. The estimated overall survival for the 91 hospital survivors was 96.8, 96.4, and 96.2 % at 5, 10, and 15 years, respectively. The median follow-up time was 67 months (range 0.71-222 months). Three patients (5 %) presented severe aortic regurgitation. Right ventricle outflow tract systolic gradient by echocardiography was above 60 mmHg in 2 %. Late re-interventions occurred in 12 (13 %) patients with mean time of 64 ± 34 months after the initial procedure. Actuarial freedom from re-interventions at 5, 10, and 15 years was 96.4, 69.7, and 61.9 %, respectively. Arterial switch operation remains the procedure of choice in patients with transposition of great arteries. It can be performed even in middle-volume institutions, leading to the same middle- and long-term outcomes of high-volume institutions. Early high mortality rate may occur due not only to learning curve, but also to cardiopulmonary bypass time and ventricular septal defect closure.

Genome-wide rare copy number variations contribute to genetic risk for transposition of the great arteries

BACKGROUND

Transposition of the great arteries (TGA) is an uncommon but severe congenital heart malformation of unknown etiology. Rare copy number variations (CNVs) have been implicated in other, more common conotruncal heart defects like tetralogy of Fallot (TOF), but there are as yet no CNV studies dedicated to TGA.

METHODS

Using high-resolution genome-wide microarrays and rigorous methods, we investigated CNVs in a group of prospectively recruited adults with TGA (n=101) from a single center. We compared rare CNV burden to well-matched cohorts of controls and TOF cases, adjudicating rarity using 10,113 independent population-based controls and excluding all subjects with 22q11.2 deletions. We identified candidate genes for TGA based on rare CNVs that overlapped the same gene in unrelated individuals, and pre-existing evidence suggesting a role in cardiac development.

RESULTS

The TGA group was significantly enriched for large rare CNVs (2.3-fold increase, p=0.04) relative to controls, to a degree comparable with the TOF group. Extra-cardiac features were not reliable predictors of rare CNV burden. Smaller rare CNVs helped to narrow critical regions for conotruncal defects at chromosomes 10q26 and 13q13. Established and novel candidate susceptibility genes identified included ACKR3, IFT57, ITGB8, KL, NF1, NKX1-2, RERE, SLC8A1, SOX18, and ULK1.

CONCLUSIONS

These data demonstrate a genome-wide role for rare CNVs in genetic risk for TGA. The findings provide further support for a genetically-related spectrum of congenital heart disease that includes TGA and TOF.

Persistent Pulmonary Hypertension of the Newborn with D-transposition of the Great Arteries: Management and Prognosis

OBJECTIVE

There is a paucity of data on clinical correlates and outcomes of pulmonary hypertension (PH) in patients with D-transposition of the great arteries (D-TGA) in the era of inhaled nitric oxide (iNO) and extracorporeal membrane oxygenation (ECMO). Our objective was to compare clinical characteristics and outcomes of infants with D-TGA with and without PH, defined as hypoxemia that required iNO and/or ECMO.

METHODS

We undertook a single-center retrospective chart review involving infants with gestational age ≥32 weeks with D-TGA who, underwent arterial switch operation over a 12-year period. Demographic and clinical data, details of the repair and postoperative complications were abstracted.

RESULTS

Our cohort (n = 93), 61 (66%) of whom were males, had a mean (SD) gestational age and birth weight of 38.7 (1.8) weeks and 3.2 (0.6) kg, respectively. PH requiring iNO and/or ECMO was noted in 20 (21.5%) infants. Infants with PH had significantly lower birth weight [2.8 (0.56) vs. 3.33 (0.61)] and gestational age [37.7 (2.1) vs. 38.9 (1.7)] than those without PH. Rates of postoperative complications (duration of pressors, sedative medicaiton and duration of hospital stay, and mechanical ventilation were higher in the group with PH. Of the five (5.4%) infants who died, four received iNO and ECMO. Death or postoperative complications tended to be associated with lower gestational age [OR 0.689; 95% CI: 0.469-1.012, P = 0.058] but not with D-TGA category or bypass duration.

CONCLUSIONS

Despite aggressive treatment with iNO and ECMO, the coexistence of PH in this population is associated with higher rates of mortality and postoperative complications. Our results also suggest that an early term birth may be associated with PH in infants with D-TGA.

Coronary artery problems late after arterial switch operation for transposition of the great arteries

BACKGROUND

The incidence of late coronary artery abnormalities after arterial switch operation (ASO) for d-loop transposition of the great arteries may be underestimated.

METHODS AND RESULTS

We retrospectively reviewed coronary artery morphology in 40 of 97 patients who survived the first year after ASO. Seven asymptomatic patients developed significant late coronary artery abnormalities. One patient died suddenly at home with severe left coronary artery (LCA) ostial stenosis at age 3.8 years. The second patient collapsed during exercise at age 9.6 years due to ventricular fibrillation and severe LCA ostial stenosis despite prior negative exercise stress test (EST) and myocardial perfusion imaging (MPI). The third patient was found to have moderate ostial stenosis of the LCA with negative EST and MPI. The fourth patient with exercise-induced ST-T depression and myocardial perfusion defect was shown to have complete LCA occlusion with collateral vessel formation. Three other patients had complete proximal obliteration of either of the coronary arteries with collateral supply. An additional 4 asymptomatic patients had trivial-mild narrowing of the LCA on routine selective coronary angiogram.

CONCLUSIONS

Incidence of late coronary stenosis or occlusion was not infrequent after ASO (11.3%) and presented usually without preceding symptoms and often after negative non-invasive screening. We advocate routine coronary imaging in all patients after ASO before they participate in competitive sports.

Main pulmonary artery area limits exercise capacity in patients long-term after arterial switch operation

OBJECTIVES

Despite excellent survival in patients after the arterial switch operation, reintervention is frequently required and exercise capacity is decreased in a substantial number of patients. This study relates right-sided imaging features in patients long-term after the arterial switch operation to exercise capacity and ventilatory efficiency to investigate which lesions are functionally important.

METHODS

Patients operated in the UMC Utrecht, the Netherlands (1976-2001) and healthy controls underwent cardiac magnetic resonance imaging and cardiopulmonary exercise testing within 1 week. We measured main, left, and right pulmonary artery cross-sectional areas, pulmonary blood flow distribution, peak oxygen uptake, and minute ventilation relative to carbon dioxide elimination.

RESULTS

A total of 71 patients (median age, 20 [12-35] years, 73% were male) and 21 healthy controls (median age, 26 [21-35] years, 48% were male) were included. Main, left, and right pulmonary artery areas were decreased compared with controls (190 vs 269 mm(2)/m(2), 59 vs 157 mm(2)/m(2), 98 vs 139 mm(2)/m(2), respectively, all P < .001); however, pulmonary blood flow distribution was comparable (P = .722). Peak oxygen uptake and minute ventilation relative to carbon dioxide elimination were 88% ± 20% and 23.7 ± 3.8, respectively, with 42% and 1% of patients demonstrating abnormal results (≤ 84% and ≥ 34, respectively). The main pulmonary artery area significantly correlated with peak oxygen uptake (r = 0.401, P = .001) and pulmonary blood flow distribution with minute ventilation relative to carbon dioxide elimination (r = -0.329, P = .008). Subanalysis (<18, 18-25, >25 years) showed that the main pulmonary artery area was smaller in older age groups. In multivariable analysis, the main pulmonary artery area was independently associated with peak oxygen uptake (P = .032).

CONCLUSIONS

In adult patients after the arterial switch operation, narrowing of the main pulmonary artery is a common finding and is the main determinant of limitation in functional capacity, rather than pulmonary branch stenosis.

Aortopulmonary Fistula after Multiple Pulmonary Artery Stenting and Dilatation for Postarterial Switch Supravalvular Stenosis

We present a case of iatrogenic aortopulmonary fistula following pulmonary artery (PA) stenting late after arterial switch operation (ASO) for D-transposition of the great arteries (D-TGA), an unusual complication that may be encountered more frequently in contemporary adult cardiology clinics. The diagnosis should be sought in the face of unexplained heart failure in patients who underwent ASO and subsequent PA angioplasty. Treatment should be instituted in a timely fashion, and options include surgical correction or implantation of a duct occluder or covered stent.

Prenatal diagnosis of transposition of the great arteries over a 20-year period: improved but imperfect

OBJECTIVE

To evaluate temporal trends in the prenatal diagnosis of transposition of the great arteries with intact ventricular septum (TGA/IVS) and its impact on neonatal morbidity and mortality.

METHODS

We included in this study cohort newborns with TGA/IVS who were referred for surgical management to our center over a 20-year period (1992-2011). The study period was divided into five 4-year periods and the primary outcome was rate of prenatal diagnosis. Secondary outcomes included neonatal preoperative status and perioperative survival.

RESULTS

Of the 340 patients with TGA/IVS, 81 (23.8%) had a prenatal diagnosis. The rate of prenatal diagnosis increased over the study period, from 6% in 1992-1995 to 41% in 2008-2011 (P < 0.001). Compared to patients with a postnatal diagnosis, balloon atrial septostomy (BAS) was performed earlier in patients with a prenatal diagnosis (0 days after delivery vs 1 day after delivery, respectively; P < 0.001) and fewer prenatally diagnosed neonates required mechanical ventilation (55.6% vs 68.0%; P = 0.03). Between patients with a prenatal or postnatal diagnosis of TGA/IVS, there were no statistically significant differences in the incidence of preoperative acidosis (16.0% vs 25.5%; P = 0.1), need for preoperative extracorporeal membrane oxygenation (2.5% vs 2.7%; P = 1.0) or mortality (one preoperative and no postoperative deaths among prenatally diagnosed patients compared with four preoperative and six postoperative deaths among postnatally diagnosed patients).

CONCLUSIONS

The prenatal detection rate of TGA/IVS has improved but still remains below 50%, suggesting the need for strategies to increase detection rates. The mortality rate was not statistically significantly different between prenatally and postnatally diagnosed patients, however, there were significant preoperative differences with regard to earlier BAS and fewer neonates that required mechanical ventilation. Ongoing work is required to ascertain whether prenatal diagnosis confers long-term benefits.

Anesthetic Considerations and Management of Transposition of the Great Arteries

Transposition of the great arteries was once an almost uniformly fatal disease in infancy. Six decades of advances in surgical techniques, intraoperative care, and perioperative management have led to at least 90% of patients reaching adulthood, most with a good quality of life. This review summarizes medical and surgical decision making during the neonatal perioperative period, with a special emphasis on factors pertinent to the anesthetic evaluation and care during primary surgical repair of transposition of the great arteries. A review is also provided of anesthetic considerations for noncardiac surgery later in childhood or adulthood, for those survivors of the arterial switch operation, Rastelli procedure, Nikaidoh procedure, and the réparation á l’étage ventriculaire procedure.

Editor-in-Chief's Picks From 2014: Part One

As I spent countless hours pouring over hundreds of manuscripts to select those that rose to the top over the past year, I became incredibly excited about being part of a Journal that produces such wonderfully rich and diverse content each year. I have personally selected the papers (both original investigations and review articles) from 13 distinct specialties for your review. There are approximately 150 articles selected across this 2-part series, which represents less than 3% of the papers submitted to JACC in 2014. In order to present the full breadth of this important research in a consumable fashion, we will present these manuscripts over the course of 2 issues of JACC. Part One includes the sections: Congenital Heart Disease, Coronary Disease & Interventions, Genetics, Omics, & Tissue Regeneration, CV Prevention & Health Promotion, Cardiac Failure, and Cardiomyopathies (1-70). Part Two includes the sections: Hypertension, Imaging, Metabolic Disorders & Lipids, Neurovascular & Neurodegenerative Disorders, Rhythm Disorders, Valvular Heart Disease, and Vascular Medicine.

Managing Heart Failure in Transposition of the Great Arteries

BACKGROUND

Transposition of the great arteries (TGA) is a congenital heart defect that is associated with congestive heart failure, tricuspid regurgitation, and arrhythmias.

METHODS

This review identifies and critiques the existing methods of assessing and managing TGA with a focus on right ventricular function.

RESULTS

Echocardiography with novel strain methods and cardiac magnetic resonance imaging (MRI) are noninvasive imaging options, with cardiac MRI being the gold standard. Cardiopulmonary stress testing can be used to determine the severity of symptoms. For the medical management of right ventricular dysfunction in TGA, a closely monitored dosage of beta blockers and the concomitant use of diuretics for symptomatic relief have the strongest supporting data. Surgical options for patients with TGA include the insertion of a pacemaker to treat arrhythmias, which are more common in this population, or tricuspid valve replacement to alleviate systemic tricuspid regurgitation. If symptoms in a patient with TGA are not alleviated by these management techniques, more advanced options include the use of an Impella device (Abiomed), the insertion of ventricular assist devices, or orthotopic heart transplant.

CONCLUSION

Physicians managing patients with TGA should take a multidisciplinary specialist approach to decide which route to pursue (medical or surgical) and when more advanced treatment options are necessary.

Using 4D Cardiovascular Magnetic Resonance Imaging to Validate Computational Fluid Dynamics: A Case Study

Computational fluid dynamics (CFD) can have a complementary predictive role alongside the exquisite visualization capabilities of 4D cardiovascular magnetic resonance (CMR) imaging. In order to exploit these capabilities (e.g., for decision-making), it is necessary to validate computational models against real world data. In this study, we sought to acquire 4D CMR flow data in a controllable, experimental setup and use these data to validate a corresponding computational model. We applied this paradigm to a case of congenital heart disease, namely, transposition of the great arteries (TGA) repaired with arterial switch operation. For this purpose, a mock circulatory loop compatible with the CMR environment was constructed and two detailed aortic 3D models (i.e., one TGA case and one normal aortic anatomy) were tested under realistic hemodynamic conditions, acquiring 4D CMR flow. The same 3D domains were used for multi-scale CFD simulations, whereby the remainder of the mock circulatory system was appropriately summarized with a lumped parameter network. Boundary conditions of the simulations mirrored those measured in vitro. Results showed a very good quantitative agreement between experimental and computational models in terms of pressure (overall maximum % error = 4.4% aortic pressure in the control anatomy) and flow distribution data (overall maximum % error = 3.6% at the subclavian artery outlet of the TGA model). Very good qualitative agreement could also be appreciated in terms of streamlines, throughout the cardiac cycle. Additionally, velocity vectors in the ascending aorta revealed less symmetrical flow in the TGA model, which also exhibited higher wall shear stress in the anterior ascending aorta.