Tetralogy of Fallot: Preoperative assessment with MR and CT imaging

Contemporary multimodality non-invasive cardiac imaging protocols for tetralogy of Fallot

Tetralogy of Fallot is the most prevalent cyanotic congenital heart disease, requiring lifelong multimodality non-invasive cardiac imaging, such as echocardiography, cardiothoracic computed tomography, and cardiac magnetic resonance imaging. As imaging techniques continuously evolve and are gradually integrated into clinical practice, there is a critical need to update multimodality imaging protocols. Over the last two decades, cardiothoracic computed tomography imaging techniques have advanced remarkably, significantly enhancing its role in evaluating patients with tetralogy of Fallot. In this review, we describe contemporary multimodality non-invasive cardiac imaging protocols for tetralogy of Fallot, emphasizing the expanding role of cardiothoracic computed tomography. Additionally, we present standardized reporting forms designed to facilitate the clinical adoption of these protocols.

The Nakata index and McGoon ratio: correlation with the severity of pulmonary regurgitation after the repair of paediatric tetralogy of Fallot

BACKGROUND

Pulmonary regurgitation is the most common complication after the complete repair of tetralogy of Fallot, and severe pulmonary regurgitation after surgery requires pulmonary valve replacement. In this retrospective observational, cross-sectional study, we included a total of 56 children aged 6 years or younger who underwent complete repair of TOF at Shahid Rajaei Cardiovascular Medical and Research Center in Tehran, Iran. Preoperative dual-source computed tomography was used to measure the McGoon ratio and Nakata index. The patients were divided into two groups based on the severity of postoperative pulmonary regurgitation, as estimated by trans-thoracic echocardiography: the severe pulmonary regurgitation group and the non-severe pulmonary regurgitation group. The McGoon ratio and Nakata index were then compared between the two groups.

RESULTS

When comparing the two groups, we found that the corrected right pulmonary artery diameter, main pulmonary artery diameter, and McGoon ratio in the non-severe pulmonary regurgitation group were higher than in the severe pulmonary regurgitation group. However, none of these differences were statistically significant. Additionally, other variables, including the corrected left pulmonary artery diameter and Nakata index, showed higher measurements in children with severe pulmonary regurgitation, but again, the differences were not statistically significant.

CONCLUSIONS

This study indicates that pulmonary arteries diameter, Nakata index, and McGoon ratio were not significantly correlated with the severity of pulmonary regurgitation after the complete repair of tetralogy of Fallot.

Computed tomography in tetralogy of Fallot: pre- and postoperative imaging evaluation

Tetralogy of Fallot (TOF) is the most common cause of cyanotic congenital heart disease (CHD) and the most frequent complex CHD encountered in adulthood. Although children with TOF share four characteristic features (subaortic ventricular septal defect, overriding aorta, right ventricular hypertrophy, pulmonary stenosis), the clinical spectrum and course are in fact greatly heterogeneous. Echocardiography remains the mainstay for diagnosis, presurgical planning and postoperative follow-up. However, with continued technological advances, CT now plays an increasing role in TOF evaluation and management, helping to minimize routine invasive catheter angiography. Preoperatively, CT is uniquely suited to assess associated pulmonary arterial, aortic and coronary anomalies as well as extra-cardiovascular structures and is particularly helpful for delineating complex anatomy in the TOF subtypes of absent pulmonary valve and pulmonary atresia with major aortopulmonary collaterals. Postoperatively, CT is useful for identifying surgical complications and for long-term monitoring including volumetry quantification, especially in children for whom MRI is contraindicated or limited by implanted devices such as pacemakers and stents. In this article, we review key clinical features and considerations in the pre- and postoperative TOF patient and the burgeoning role of CT for facilitating accurate diagnosis and personalized intervention.

Ferumoxytol-Enhanced Cardiac Magnetic Resonance Angiography and 4D Flow: Safety and Utility in Pediatric and Adult Congenital Heart Disease

Cardiac magnetic resonance imaging and angiography have a crucial role in the diagnostic evaluation and follow up of pediatric and adult patients with congenital heart disease. Although much of the information required of advanced imaging studies can be provided by standard gadolinium-enhanced magnetic resonance imaging, the limitations of precise bolus timing, long scan duration, complex imaging protocols, and the need to image small structures limit more widespread use of this modality. Recent experience with off-label diagnostic use of ferumoxytol has helped to mitigate some of these barriers. Approved by the U.S. FDA for intravenous treatment of anemia, ferumoxytol is an ultrasmall superparamagnetic iron oxide nanoparticle that has a long blood pool residence time and high relaxivity. Once metabolized by macrophages, the iron core is incorporated into the reticuloendothelial system. In this work, we aim to summarize the evolution of ferumoxytol-enhanced cardiovascular magnetic resonance imaging and angiography and highlight its many applications for congenital heart disease.

Detection of Coronary Artery and Aortic Arch Anomalies in Patients with Tetralogy of Fallot Using CT Angiography

Background: Tetralogy of Fallot (TOF) is the most common form of cyanotic congenital heart disease (CHD). Furthermore, the prevalence of anomalous origin of a coronary artery is higher in patients with TOF than in the general population (6% vs. ≤1%). Preoperative assessment of cardiovascular anatomy using computed tomography (CT) angiography enables the adaptation of the surgical approach to avoid potentially overlooked anomalies. Our purpose was to determine the prevalence of coronary artery and aortic arch anomalies in a cohort of TOF patients. Methods: In this retrospective analysis, data were collected from CT reports (2015–2021) of 105 TOF patients. All images were acquired using a 64-slice multi-detector CT (MDCT) scanner. Results: The median age of the patients was 38.7 months, with a male-to-female ratio of 1.39. The overall prevalence of coronary artery anomalies (CAAs) was 7.61% (8 of 105 cases). The anomalous origin and course of coronary arteries across the right ventricular outflow tract (RVOT; prepulmonic course) were defined in 5.71% of cases (six patients). In four of these, the left anterior descending artery (LAD) originated from the right coronary artery (RCA), while in two cases, the RCA arose from the LAD. In the remaining two patients, the coronary arteries followed an interarterial course. The most frequent anomalous aortic arch pattern in the overall TOF population was the right aortic arch (RAA) with mirror image branching, seen in 20% of patients (21 cases). The most frequent anomaly of the supra-aortic trunks was bovine configuration, found in 17.14% (18 cases). Conclusions: The prevalence of CAAs and aortic arch anomalies detected by CT angiography was in line with the data reported in anatomical specimens. Therefore, this technique represents a powerful tool for the evaluation of congenital cardiovascular anomalies.

The Case of a 44-Year-Old Survivor of Unrepaired Tetralogy of Fallot, Right Aortic Arch and Abdominal Aortopulmonary Collateral Vessels

The most common congenital cyanotic heart disease is described in the literature as the Tetralogy of Fallot. This abnormality is characterized by the presence of ventricular septal defect (VSD), obstruction of the right ventricular (RV) outflow tract, right ventricular hypertrophy, and overriding aorta. In patients with pulmonary atresia with ventricular septal defect (PA/VSD), major aortopulmonary collateral arteries (MAPCA) are common; however, although some of them do not have PA/VSD, they do have other particular anatomical variants. The case we are presenting in this article is a rare mild symptomatic adult noncorrected TOF, with preserved RV function, right aortic arch, and MAPCAs (“classic” thoracic MAPCAs but also abdominal MAPCAs). The anatomy of a complex congenital defect is well illustrated by cardiac magnetic resonance (CMR) and computer tomography angiography (CTA), and these imaging techniques are mostly used to understand the relative clinical “silence” TOF. Imaging scans thus play a key role in the evaluation of these patients, being very important to know the indications and limitations of each method, but also to learn to combine them with each other depending on the clinical picture of the patient’s presentation. Additionally, the close collaboration between clinicians and imagers is essential for a correct, complete and detailed preoperative evaluation, being subsequently essential for cardiovascular surgeons, the whole team thus deciding the best therapeutic management.

A geometrical pitfall of Area-Length method; -Is left ventricle volume evaluation of repaired Tetralogy of Fallot by angiocardiography accurate?

Biplane Area-Length (AL) method by left ventriculography (LVG) has been widely adopted as a standard method to estimate left ventricular volume. However, we have experienced difficulties in adopting the value by AL method for the children with Tetralogy of Fallot (TOF) due to the discrepancy among volumetric modalities. This study validated some limitations of AL method, considering the basic principles of its formulation. A single center retrospective cohort study was conducted for 1 year. The confirmed 22 cases with repaired TOF at our hospital were enrolled. The clinical characteristics, some cardiac MRI analyses, and all the cardiac catheterization studies were collected. Angiographic data were compared with historic cohorts of Kawasaki disease without any coronary artery lesions by using AL method. Cardiac MRI analyses of ten TOF patients were additionally available. LVG studies showed that the length of the long axis on anteroposterior view (AP) was not equal to that on lateral view (LT) due to anatomically apical elevation in TOF, followed by a significant difference found in the sagittal lengths of the LV long axis between AP and LT (P = 0.003). Because the difference critically affected the formula depending on biplane AL method, the calculated LVEDV of TOF group appeared overestimated, compared with the control group (TOF vs control group: 119.5% ± 6.3% vs 96.4 ± 3.5% of Normal, P = 0.006). Available cardiac MRI analyses of some patients in TOF group revealed 55% increase of LVEDV by AL method (angiocardiography 116 ± 7.0 vs CMR 75 ± 3.7 ml/m², P = 0.0025). A pitfall exists when applying biplane AL method to measure LV volume especially for TOF patients, because the long axis on AP view is not always identical to that on LT view.

Three steps approach for preoperative evaluation of tetralogy of Fallot patients: role of 128 MDCT

Background

Tetralogy of Fallot is the most common congenital cyanotic heart disease. Advances in surgical repair recently facilitate survival of the affected patients into adulthood with good quality of life. Despite imaging plays crucial role in diagnosis of TOF patients, no single diagnostic modality suffices for complete evaluation of TOF. Thus, different diagnostic tools should be used alone or in combination according to patient’s clinical question. This study aims to find out the agreement between the echocardiography and MDCT in evaluation of TOF patients prior to surgical repair.

Results

Three-step approach used in scanning TOF patients. Firstly, classic TOF findings, MDCT was comparable to echocardiography in overriding aorta (k = 0.6), VSD (k = 0.8), RVH (k = 0.4), and sub valvular pulmonary stenosis (k = 0.6). Echocardiography is superior to MDCT in evaluation of valvular stenosis (k = 0.4). MDCT was superior to echocardiography in supravalvular pulmonary stenosis. Secondary, surgical relevant findings, McGoon ratio calculated in 94.2%, small and major APCs in 45.5% and 28.5% respectively, PDA in 35% and anomalous coronary artery in 5.1%. Thirdly, other TOF-associated anomalies, common: ASD (34.3%) and RAA (28.3%), and persistent LSVC (10.3%). Uncommon: situs ambiguous (2.5 %), PAPVR (1.2%), and IVC anomalies (3.8%). MDCT was superior to echocardiography in surgical relevant findings and other TOF-associated anomalies.

Conclusion

MDCT is a crucial imaging tool for extra cardiac evaluation of TOF patients prior to surgical repair.

Pediatric Cardiothoracic CT Guideline Provided by the Asian Society of Cardiovascular Imaging Congenital Heart Disease Study Group: Part 2. Contemporary Clinical Applications

The use of pediatric cardiothoracic CT for congenital heart disease (CHD) was traditionally limited to the morphologic evaluation of the extracardiac thoracic vessels, lungs, and airways. Currently, the applications of CT have increased, owing to technological advancements in hardware and software as well as several dose-reduction measures. In the previously published part 1 of the guideline by the Asian Society of Cardiovascular Imaging Congenital Heart Disease Study Group, we reviewed the prerequisite technical knowledge for clinical applications in a user-friendly and vendor-specific manner. Herein, we present the second part of our guideline on contemporary clinical applications of pediatric cardiothoracic CT for CHD based on the consensus of experts from the Asian Society of Cardiovascular Imaging CHD Study Group. This guideline describes up-to-date clinical applications effectively in a systematic fashion.

Missed Tetralogy of Fallot in an Elderly Woman With a Known Ventricular Septal Defect

Tetralogy of Fallot is a congenital heart disease comprised of a tetrad of ventricular septal defect, pulmonary stenosis, overriding aorta, and right ventricular hypertrophy. In developed countries, most cases are diagnosed in babies; mortality is high if not surgically corrected in a timely manner. We describe herein a woman who was diagnosed at age 73 years. Several factors accounted for her unusual longevity. We highlight the importance of multimodal imaging to look for other associated anomalies of tetralogy of Fallot in cases of apparent simple ventricular septal defect when the echocardiographic images are either suggestive or suboptimal.

Tetralogy of Fallot: cardiac imaging evaluation

Thanks to advances in pediatric cardiology, most infants with tetralogy of Fallot (TOF) now survive into adulthood. This relatively new population of adult patients may face long-term complications, including pulmonary regurgitation (PR), right ventricular (RV) tract obstruction, residual shunts, RV dysfunction, and arrythmias. They will often need to undergo pulmonary valve (PV) replacement and other invasive re-interventions. However, the optimal timing for these procedures is challenging, largely due to the complexity of evaluating RV volume and function. The options for the follow-up of these patients have rapidly evolved from an angiography-based approach to the surge of advanced imaging techniques, mainly echocardiography, cardiac magnetic resonance (CMR), and computer tomography (CT). In this review, we outline the indications, strengths and limitations of these modalities in the adult TOF population.

Image quality and radiation dose of different scanning protocols in DSCT cardiothoracic angiography for children with tetralogy of fallot

The aim of this study was to investigate the image quality and radiation dose of different scanning protocols in dual-source CT cardiothoracic angiography for children with tetralogy of Fallot (TOF). Seventy-five consecutive children with known or suspected TOF were enrolled to undergo prospective ECG-triggering sequential dual-source CT (DSCT) cardiothoracic angiography. According to the scanning protocols, these patients were randomly divided into 3 groups: fixed delay time (FDT, n = 25, group A), automatic bolus-tracking (ABT, n = 25, group B) and manual bolus-tracking (MBT, n = 25, group C). Subjective and objective image quality were evaluated. The radiation doses were recorded. The image quality scores of group C were significantly higher than those of group A and B. The absolute value of difference (D-value) on CT attenuation between left (CT_LV) and right ventricle (CT_RV) in group C was significantly lower than that in group A and B. The total effective dose of groups A, B and C were 0.39 ± 0.06 mSv, 0.40 ± 0.07 mSv and 0.40 ± 0.08 mSv, respectively. There was no significant difference among 3 groups (P = 0.722). Scanning protocol has significantly impacts on the image quality of cardiovascular structures for TOF patients. Compared with the conventional scanning protocols FDT and ABT, the MBT technique provides high image quality and achieves more homogenous attenuation among different patients with TOF.

Three-dimensional rotational angiography in congenital heart disease: Present status and evolving future

Three-dimensional rotational angiography (3D-RA) enables volumetric imaging through rotation of the C-arm of an angiographic system and real-time 3D reconstruction during cardiac catheterization procedures. In the field of congenital heart disease (CHD), 3D-RA has gained considerable traction, owing to its capability for enhanced visualization of spatial relationships in complex cardiac morphologies and real time image guidance in an intricate interventional environment. This review provides an overview of the current applications, strengths, and limitations of 3D-RA acquisition in the management of CHD and potential future directions. In addition, issues of dosimetry, radiation exposure, and optimization strategies will be reviewed. Further implementation of 3D-RA will be driven by patient benefits relative to existing 3D imaging capabilities and fusion techniques balanced against radiation exposure.

Clinical Study to Individual Treatment for Major Aortopulmonary Collaterals of Tetralogy of Fallot

Objectives

To build a guideline for the individual treatment of Tetralogy of Fallot (TOF) with major aortopulmonary collaterals (MAPCAs) and tentatively establish the occlusion index of MAPCAs.

Methods

According to the diameter of the aortopulmonary collaterals (R: mm) and the bodyweight of the children (weight: kg), K= ((∑R²)/Wt) was set as the occlusion index of TOF with MAPCAs. A retrospective study was initially performed in 171 patients who suffered from TOF with MAPCAs and underwent cardiac malformation repair to investigate the intervals of the K value: K≥2, 1<K<2, and K≤1. In order to examine the reliability of the intervals derived from the retrospective study, a prospective study was conducted in the following 209 cases. When K≥2, the collaterals occlusion was performed immediately behind surgical corrections. The postoperative condition changes in patients with 1<K<2 were observed first and managed by extending mechanical ventilation, while taking further treatments as their conditions worsen. As for patients with K≤1, no occlusion was performed. Finally, the circumstances of collaterals occlusion, postoperative ventilator assist time, and ICU resident time were collected and analyzed.

Result

The proportion of the patients treated with occlusion and the postoperative ICU resident time (p<0.05) in patients with 1<K<2 in the prospective study did dramatically decrease when compared with those of the retrospective studies.

Conclusion

Due to restrictions on medical conditions in China with a large population base, a standard individual treatment of TOF with MAPCAs should be established based on the Aortopulmonary Collaterals Occlusion Index K= ((∑R²)/Wt), which can effectively avoid unnecessary collateral occlusion, minimize trauma, and shorten the length of ICU and hospital stay. When K≥2, the collateral occlusion and surgical correction are recommended to be performed simultaneously. When 1<K<2, whether to occlude collaterals depends on the patients' postoperative conditions with extending ventilator time. When K≤1, do not deal with collaterals.

Exercise stress CMR reveals reduced aortic distensibility and impaired right-ventricular adaptation to exercise in patients with repaired tetralogy of Fallot

BACKGROUND

The aim of our study was to evaluate the feasibility of exercise cardiac magnetic resonance (CMR) in patients with repaired tetralogy of Fallot (RTOF) and to assess right and left ventricular adaptation and aortic wall response to exercise in comparison with volunteers.

METHODS

11 RTOF and 11 volunteers underwent prospective CMR at rest and during exercise. A supine bicycle ergometer was employed to reach twice the resting heart rate during continuous exercise, blood pressure and heart rate were recorded. Bi-ventricular parameters and aortic stiffness were assessed using accelerated cine sequences and flow-encoding CMR. A t-test was used to compare values between groups. A Mann Whitney test was used to compare values within groups.

RESULTS

In RTOF both ventricles showed an impaired contractile reserve (RVEF rest 36.2±8.3%, +1.3±3.9% increase after exercise; LVEF rest 53.8±6.1%, +5.7±6.4% increase after exercise) compared to volunteers (RVEF rest 50.5±5.0%, +10.4±7.1% increase after exercise, p = 0.039; LVEF rest 61.9±3.1%, +12.2±4.7% increase after exercise, p = 0.014). RTOF showed a reduced distensibility of the ascending aorta during exercise compared to volunteers (RTOF: 3.4±1.9 10-3.mmHg-1 vs volunteers: 5.1±1.4 10-3.mmHg-1; p = 0.027). Ascending aorta distensibility was correlated to cardiac work in the volunteers but not in RTOF.

CONCLUSION

RTOF showed an impaired contractile reserve for both ventricles. The exercise unmasked a reduced distensibility of the ascending aorta in RTOF, which may be an early sign of increased aortic rigidity.

Imaging in Congenital and Hereditary Abnormalities of the Interventricular Septum: Clinical Anatomy and Diagnostic Clues

Early identification of congenital heart diseases, specifically those affecting the structural integrity and function of the interventricular septum, in childhood is important toward decreasing the morbidity and mortality of those affected. We review the pertinent clinical and imaging manifestations for those with ventricular septal defects, ventricular septal aneurysms, tetralogy of Fallot, and hypertrophic (obstructive) cardiomyopathy, in addition to discussing first-line imaging studies, including echocardiography, and indications for advanced imaging.