Imaging of postoperative tetralogy of Fallot repair

Advanced Imaging Technologies for Assessing Tetralogy of Fallot: Insights Into Flow Dynamics

Tetralogy of Fallot is the most common cyanotic congenital heart defect requiring surgical repair. Although surgical interventions have significantly reduced mortality, postrepair complications, such as pulmonary valve regurgitation and stenosis, may lead to adverse outcomes, including right ventricular dysfunction and increased risks of morbidity and mortality. This review explores the potential of advanced imaging technologies, including 4-dimensional-flow magnetic resonance imaging and high-frame-rate echocardiography, in providing valuable insights into blood flow dynamics and energy parameters. Quantitative measures, such as energy loss and vorticity, along with qualitative flow analysis, can provide additional insights into adverse haemodynamics at a potentially earlier and more reversible stage. Furthermore, personalized patient-specific information from these imaging modalities aids in guiding treatment decisions and monitoring postoperative interventions effectively. By characterizing flow patterns, these advanced imaging techniques hold great promise in improving the assessment and management of tetralogy of Fallot, providing tailored insights. However, further research and longitudinal studies are required to fully establish their clinical utility and potential impact on patient care.

CMR parameters and CMR-FT in repaired tetralogy of Fallot

Background

Repaired tetralogy of Fallot patients develops postoperative complications that are in need for follow-up and re-intervention in some circumstances. CMR myocardial feature tracking is a novel method that allows quantification of bi-atrial and bi-ventricular mechanics of deformation. So our aim is to assess the added value of cardiac magnetic resonance imaging and its advanced feature tracking analysis in evaluation of repaired tetralogy of Fallot patients.

Results

CMR was done with feature tracking post-processing analysis for 56 patients with repaired tetralogy of Fallot and 56 healthy volunteers. The commonest postoperative complications in patients with repaired tetralogy of Fallot are in the following order: pulmonary regurgitation with subsequent right ventricular dilatation and tricuspid regurgitation followed by pulmonary stenosis, right ventricular dysfunction, right ventricular outflow tract dilatation, left ventricular dysfunction, aortic and mitral regurgitation and residual ventricular septal defect. All right ventricular volumes were found to be significantly increased compared to those of the healthy volunteers (p value < 0.001) also left ventricular end-diastolic and end-systolic volumes indexed were found to be increased in those patients compared to healthy volunteers (p value < 0.001). Right and left ventricular function were significantly lower in those patients compared to controls. Bi-ventricular CMR-FT indices and right atrial global longitudinal strain were found to be significantly lower in patients with repaired tetralogy of Fallot compared to controls. Right atrium global longitudinal strain was found to be significantly correlated with right ventricular global longitudinal strain and did not correlate with right ventricular ejection fraction and end-diastolic volume indexed; p value < 0.001, 0.109 and 0.565, respectively. Right ventricular global circumferential strain was found to be significantly increased in patients with right ventricular outflow tract obstruction compared to those without obstruction (− 16.26 ± 4.27% vs. − 12.2 ± 3.78%, respectively). Pulmonary regurgitant volume indexed was found to be significantly related to right ventricle longitudinal strain (p value 0.027).

Conclusion

Biventricular volumetric measures are increased in patients with repaired tetralogy of Fallot compared to controls; however, feature tracking parameters for both ventricles and right atrium are lower in those patients compared to controls.

Four-dimensional flow cardiovascular magnetic resonance in tetralogy of Fallot: a systematic review

BACKGROUND

Patients with repaired Tetralogy of Fallot (rTOF) often develop cardiovascular dysfunction and require regular imaging to evaluate deterioration and time interventions such as pulmonary valve replacement. Four-dimensional flow cardiovascular magnetic resonance (4D flow CMR) enables detailed assessment of flow characteristics in all chambers and great vessels. We performed a systematic review of intra-cardiac 4D flow applications in rTOF patients, to examine clinical utility and highlight optimal methods for evaluating rTOF patients.

METHODS

A comprehensive literature search was undertaken in March 2020 on Google Scholar and Scopus. A modified version of the Critical Appraisal Skills Programme (CASP) tool was used to assess and score the applicability of each study. Important clinical outcomes were assessed including similarities and differences.

RESULTS

Of the 635 articles identified, 26 studies met eligibility for systematic review. None of these were below 59% applicability on the modified CASP score. Studies could be broadly classified into four groups: (i) pilot studies, (ii) development of new acquisition methods, (iii) validation and (vi) identification of novel flow features. Quantitative comparison with other modalities included 2D phase contrast CMR (13 studies) and echocardiography (4 studies). The 4D flow study applications included stroke volume (18/26;69%), regurgitant fraction (16/26;62%), relative branch pulmonary artery flow(4/26;15%), systolic peak velocity (9/26;35%), systemic/pulmonary total flow ratio (6/26;23%), end diastolic and end systolic volume (5/26;19%), kinetic energy (5/26;19%) and vorticity (2/26;8%).

CONCLUSIONS

4D flow CMR shows potential in rTOF assessment, particularly in retrospective valve tracking for flow evaluation, velocity profiling, intra-cardiac kinetic energy quantification, and vortex visualization. Protocols should be targeted to pathology. Prospective, randomized, multi-centered studies are required to validate these new characteristics and establish their clinical use.

Can T1 mapping be an alternative of post-contrast magnetic resonance sequences in patients with surgically corrected tetralogy of Fallot?

Objective:

The objective of this study is to investigate the ability of native T1 mapping in the determination of myocardial fibrosis in patients with surgically corrected tetralogy of Fallot (TOF).

Methods:

We included 35 patients with surgically corrected TOF who underwent cardiac magnetic resonance imaging in this study. Additionally, we added pre- and post-contrast T1 mapping sequences at the right ventricular outflow tract (RVOT) and short-axis planes to the routine protocol. We visually evaluated the pre-contrast native T1 mapping images to determine the presence of areas with higher T1 times that indicate focal fibrosis. We compared the findings with the findings of post-contrast images.

Results:

In 22 of the 35 cases, RVOT enhancement was observed in the delayed enhancement images; however, none of these cases could be distinguished on the native T1 maps. When compared to post-contrast imaging, 28 of the 30 contrast enhancements at right ventricle insertion points and 14 of the 17 contrast enhancements at the remaining left ventricle walls were visually observed on the color-coded native T1 maps. The sensitivity, specificity, positive and negative predictive values of native T1 mapping for the detection of focal fibrosis at the right ventricle insertion points were found to be 93.3%, 100%, 100%, and 71.4%, respectively, whereas these values were found to be 82.4%, 100%, 100%, and 85.8% in the detection of fibrosis in the remaining left ventricle walls.

Conclusion:

Native T1 mapping is valuable in the detection of focal fibrosis at the right ventricle insertion points and the remaining left ventricle walls; however, it was not possible to visually detect RVOT fibrosis by native T1 mapping. Hence, T1 mapping may not replace the contrast-enhanced imaging in patients with surgically corrected TOF. (Anatol J Cardiol 2020; 24: 377-81)

CT and MRI for Repaired Complex Adult Congenital Heart Diseases

An increasing number of adult congenital heart disease (ACHD) patients continue to require life-long diagnostic imaging surveillance using cardiac CT and MRI. These patients typically exhibit a large spectrum of unique anatomical and functional changes resulting from either single- or multi-stage palliation and surgical correction. Radiologists involved in the diagnostic task of monitoring treatment effects and detecting potential complications should be familiar with common cardiac CT and MRI findings observed in patients with repaired complex ACHD. This review article highlights the contemporary role of CT and MRI in three commonly encountered repaired ACHD: repaired tetralogy of Fallot, transposition of the great arteries after arterial switch operation, and functional single ventricle after Fontan operation.

Ex vivo cardiovascular magnetic resonance diffusion weighted imaging in congenital heart disease, an insight into the microstructures of tetralogy of Fallot, biventricular and univentricular systemic right ventricle

PURPOSE

Common types of congenital heart disease exhibit a variety of structural and functional variations which may be accompanied by changes in the myocardial microstructure. We aimed to compare myocardial architecture from magnetic resonance diffusion tensor imaging (DTI) in preserved pathology specimens.

MATERIALS AND METHODS

Pathology specimens (n = 24) formalin-fixed for 40.8 ± 7.9 years comprised tetralogy of Fallot (TOF, n = 10), dextro-transposition of great arteries (D-TGA, n = 8) five with ventricular septal defect (VSD), systemic right ventricle (n = 4), situs inversus totalis (SIT, n = 1) and levo-TGA (L-TGA, n = 1). Specimens were imaged using a custom spin-echo sequence and segmented automatically according to tissue volume fraction. In each specimen T1, T2, fractional anisotropy, mean diffusivity, helix angle (HA) and sheet angle (E2A) were quantified. Pathologies were compared according to their HA gradient, HA asymmetry and E2A mean value in each myocardial segment (anterior, posterior, septal and lateral walls).

RESULTS

TOF and D-TGA with VSD had decreased helix angle gradient by - 0.34°/% and remained symmetric in the septum in comparison to D-TGA without VSD. Helix angle range was decreased by 45°. It was associated with a decreased HA gradient in the right ventricular (RV) wall, i.e. predominant circumferential myocytes. The sheet angle in the septum of TOF was opposing those of the left ventricular (LV) free wall. Univentricular systemic RV had the lowest HA gradient (- 0.43°/%) and the highest HA asymmetry (75%). HA in SIT was linear, asymmetric, and reversed with a sign change at about 70% of the depth at mid-ventricle. In L-TGA with VSD, HA was asymmetric (90%) and its gradients were decreased in the septum, anterior and lateral wall.

CONCLUSION

The organization of the myocytes as determined by DTI differs between TOF, D-TGA, L-TGA, systemic RV and SIT specimens. These differences in cardiac structure may further enlighten our understanding of cardiac function in these diverse congenital heart diseases.

Spectrum of changes on cardiac magnetic resonance in repaired tetralogy of Fallot: Imaging according to surgical considerations

Imaging of repaired tetralogy of Fallot (TOF) is one of the common indications for cardiac magnetic resonance (CMR) examinations. With advances in CMR imaging techniques like phase contrast imaging and functional imaging, it has superseded investigations like echocardiography for anatomical and functional assessment of the pathophysiological changes in repaired TOF. Common repair procedures for TOF include infundibulectomy, transannular patch repair and right ventricle to pulmonary artery (RV-PA) conduit. While each of these procedures cause dynamic changes in heart and pulmonary arteries resulting in some expected imaging findings, CMR also helps in diagnosing the complications associated with these repair procedures like pulmonary stenosis, right ventricular outflow tract aneurysm, pulmonary regurgitation, RV-PA conduit stenosis, tricuspid regurgitation, right ventricular failure, and residual ventricular septal defects. Hence, it is imperative for a radiologist to be familiar with the expected changes on CMR in repaired TOF along with some of the common complications that may be encountered on imaging in such patients.

Differences in right ventricular-pulmonary vascular coupling and clinical indices between repaired standard tetralogy of Fallot and repaired tetralogy of Fallot with pulmonary atresia

PURPOSE

The purpose of this study was to compare ventricular vascular coupling ratio (VVCR) between patients with repaired standard tetralogy of Fallot (TOF) and those with repaired TOF-pulmonary atresia (TOF-PA) using cardiovascular magnetic resonance (CMR).

MATERIALS AND METHODS

Patients with repaired TOF aged>6 years were prospectively enrolled for same day CMR, echocardiography, and exercise stress test following a standardized protocol. Sanz's method was used to calculate VVCR as right ventricle (RV) end-systolic volume/pulmonary artery stroke volume. Regression analysis was used to examine associations with exercise test parameters, New York Heart Association (NYHA) class, RV size and biventricular systolic function.

RESULTS

A total of 248 subjects were included; of these 222 had repaired TOF (group I, 129 males; mean age, 15.9±4.7 [SD] years [range: 8-29 years]) and 26 had repaired TOF-PA (group II, 14 males; mean age, 17.0±6.3 [SD] years [range: 8-29 years]). Mean VVCR for all subjects was 1.54±0.64 [SD] (range: 0.43-3.80). Mean VVCR was significantly greater in the TOF-PA group (1.81±0.75 [SD]; range: 0.78-3.20) than in the standard TOF group (1.51±0.72 [SD]; range: 0.43-3.80) (P=0.03). VVCR was greater in the 68 NYHA class II subjects (1.79±0.66 [SD]; range: 0.75-3.26) compared to the 179 NYHA class I subjects (1.46±0.61 [SD]; range: 0.43-3.80) (P<0.001).

CONCLUSION

Non-invasive determination of VVCR using CMR is feasible in children and adolescents. VVCR showed association with NYHA class, and was worse in subjects with repaired TOF-PA compared to those with repaired standard TOF. VVCR shows promise as an indicator of pulmonary artery compliance and cardiovascular performance in this cohort.

Incidental detection of calcified left coronary artery pseudoaneurysm years after surgery for TOF

We present images from computed tomography angiography in a 40-year-old female with a calcified pseudo-aneurysm in her left coronary artery, who had previously undergone repair of tetralogy of Fallot.

Perioperative Echocardiography in the Adult With Congenital Heart Disease

Survival of patients with congenital heart disease has significantly improved over the last 2 decades, confronting interventionalists, surgeons, anesthesiologists, cardiologists, and intensivists with often unfamiliar complex pathophysiology in the perioperative setting. Aside from cardiac catheterization, echocardiography has become the main imaging modality in the hospitalized adult with congenital heart disease. The great variety of congenital lesions and their prior surgical management challenges practitioners to generate optimal imaging, reporting, and interpretation of these complex anatomic structures. Standardization of echocardiographic studies can not only provide significant benefits in the surveillance of these patients, but also facilitate understanding of pathophysiologic mechanism and assist clinical management in the perioperative setting. Knowledge in obtaining and interpreting uniform imaging protocols is essential for the perioperative clinician. In this publication, the authors review current international consensus recommendations on echocardiographic imaging of adults with congenital heart disease and describe the fundamental components by specific lesion. The authors will emphasize key aspects pertinent to the clinical management when imaging these patients in the perioperative setting. The goal of this review is to familiarize the perioperative physician on how to structure and standardize echocardiographic image acquisition of congenital heart disease anatomy for optimal clinical management.

A Review of Tetralogy of Fallot and Postoperative Management

This article discusses the anatomy and physiology of tetralogy of Fallot (TOF) and TOF variants. Indications for surgical repair, morbidity/mortalities, and surgical repair techniques are also reviewed. The article concludes with review of common postoperative complications and management strategies for arrhythmias, right ventricular dysfunction, low cardiac output, and residual defects.

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.

Post-operative imaging of pulmonary vessels

Complications following cardiothoracic surgery are responsible for prolonged hospital stay, increase cost in patient care and increased morbidity and mortality. Vascular complications in particular are significant contributors to poor patient outcome due to either hemorrhage or thrombosis and ischemia. Evaluation of vascular complications in the postoperative patient requires a rapid and reliable imaging approach. Vascular complications after cardiothoracic surgery include pulmonary artery thrombosis, pseudoaneurysm, pulmonary vein thrombosis, vascular fistulas, stenosis and infarction. Multidetector CT (MDCT), often the imaging modality of choice, offers a one-stop-shop capability to visualize the entire cardiothoracic vasculature, airways, lung parenchyma, mediastinum and chest wall with excellent temporal and spatial resolution.