MR imaging of coarctation of the aorta and its postoperative complications in adults: assessment with spin-echo and cine-MR imaging

Evaluating the severity of aortic coarctation in infants using anatomic features measured on CTA

OBJECTIVES

A machine learning model was developed to evaluate the severity of aortic coarctation (CoA) in infants based on anatomical features measured on CTA.

METHODS

In total, 239 infant patients undergoing both thorax CTA and echocardiography were retrospectively reviewed. The patients were assigned to either mild or severe CoA group based on their pressure gradient on echocardiography. They were further divided into patent ductus arteriosus (PDA) and non-PDA groups. The anatomical features were measured on double-oblique multiplanar reconstructed CTA images. Then, the optimal features were identified by using the Boruta algorithm. Subsequently, the coarctation severity was classified using linear discriminant analysis (LDA). We further investigated the relationship between the anatomical features and re-coarctation using Cox regression.

RESULTS

Four anatomical features showed significant differences between the mild and severe CoA groups, including the smallest aortic cross-sectional area indexed to body surface area (p < 0.001), the narrowest aortic diameter (CoA diameter) indexed to height (p < 0.001), the diameter of the descending aorta at the diaphragmatic level (p < 0.001) and weight (p = 0.005). With these features, accuracy of 88.6% and 90.2%, sensitivity of 65.0% and 72.1%, and specificity of 92.9% and 100% were obtained for classifying the CoA severity in the non-PDA and PDA groups, respectively. Moreover, CoA diameter indexed to weight was associated with the risk of re-coarctation.

CONCLUSIONS

CoA severity can be evaluated by using LDA with anatomical features. When quantifying the severity of CoA and risk of re-coarctation, both anatomical alternations at the CoA site and the growth of the patients need to be considered.

KEY POINTS

• CTA is routinely ordered for infants with coarctation of the aorta; however, whether anatomical variations observed with CTA could be used to assess the severity of CoA remains unknown. • Using the diameter and area of the coarctation site adjusted to body growth as features, the LDA model achieved an accuracy of 88.6% and 90.2% in differentiating between the mild and severe CoA patients in the non-PDA group and PDA group, respectively. • The narrowest aortic diameter (CoA diameter) indexed to weight has a hazard ratio of 10.29 for re-coarctation.

Cardiovascular magnetic resonance: Diagnostic utility and specific considerations in the pediatric population

Cardiovascular magnetic resonance is a non-invasive imaging modality which is emerging as important tool for the investigation and management of pediatric cardiovascular disease. In this review we describe the key technical and practical differences between scanning children and adults, and highlight some important considerations that must be taken into account for this patient population. Using case examples commonly seen in clinical practice, we discuss the important clinical applications of cardiovascular magnetic resonance, and briefly highlight key future developments in this field.

Indications for cardiovascular magnetic resonance in children with congenital and acquired heart disease: an expert consensus paper of the Imaging Working Group of the AEPC and the Cardiovascular Magnetic Resonance Section of the EACVI

This article provides expert opinion on the use of cardiovascular magnetic resonance (CMR) in young patients with congenital heart disease (CHD) and in specific clinical situations. As peculiar challenges apply to imaging children, paediatric aspects are repeatedly discussed. The first section of the paper addresses settings and techniques, including the basic sequences used in paediatric CMR, safety, and sedation. In the second section, the indication, application, and clinical relevance of CMR in the most frequent CHD are discussed in detail. In the current era of multimodality imaging, the strengths of CMR are compared with other imaging modalities. At the end of each chapter, a brief summary with expert consensus key points is provided. The recommendations provided are strongly clinically oriented. The paper addresses not only imagers performing CMR, but also clinical cardiologists who want to know which information can be obtained by CMR and how to integrate it in clinical decision-making.

Indications for cardiovascular magnetic resonance in children with congenital and acquired heart disease: an expert consensus paper of the Imaging Working Group of the AEPC and the Cardiovascular Magnetic Resonance Section of the EACVI

This article provides expert opinion on the use of cardiovascular magnetic resonance (CMR) in young patients with congenital heart disease (CHD) and in specific clinical situations. As peculiar challenges apply to imaging children, paediatric aspects are repeatedly discussed. The first section of the paper addresses settings and techniques, including the basic sequences used in paediatric CMR, safety, and sedation. In the second section, the indication, application, and clinical relevance of CMR in the most frequent CHD are discussed in detail. In the current era of multimodality imaging, the strengths of CMR are compared with other imaging modalities. At the end of each chapter, a brief summary with expert consensus key points is provided. The recommendations provided are strongly clinically oriented. The paper addresses not only imagers performing CMR, but also clinical cardiologists who want to know which information can be obtained by CMR and how to integrate it in clinical decision-making.

Phase-contrast MRI and applications in congenital heart disease

A review of phase-contrast magnetic resonance imaging techniques, with specific application to congenital heart disease, is presented. Theory, pitfalls, advantages, and specific examples of multiple, well-described congenital heart disease presentations are discussed.

Aortic aneurysms: delayed complications of coarctation of the aorta repair using Dacron patch aortoplasty

Coarctation of the aorta is a diaphragmlike ridge narrowing the lumen of the proximal descending aorta. Although surgical repair has proven to be a successful treatment of coarctation of the aorta, immediate and delayed postoperative complications are not rare. Of particular interest is the occurrence of aneurysms after Dacron patch aortoplasty--often decades after surgery. Delayed complication rates of up to 50% have been reported. We describe the clinical-radiologic presentations of 3 late complications of Dacron patch angioplasty: aortobronchopleural fistula, leaking pseudoaneurysm, and giant descending aortic aneurysm--all successfully treated with bypass grafts. Because of the high incidence of delayed complications, lifelong surveillance is necessary. The chest x-ray may be the first clue to a delayed complication. Knowledge of radiologic findings is helpful in the detection of complications-before they become symptomatic. Transesophageal echocardiography, computed tomography angiography, or magnetic resonance imaging with multiplanar reconstruction is diagnostic.

[Magnetic resonance imaging in long-term assessment after surgery for aortic coarctation]

OBJECTIVES

Spin echo or gradient echo magnetic resonance imaging provides enough information to plan patient management and can be completed with the use of three-dimensional magnetic resonance angiography to evaluate the need for reintervention, assess follow-up, or discharge the patient.

PATIENTS AND METHODS

From 1990-2003, we evaluated 101 patients after initial corrective surgery for aortic coarctation at the age of 3.1 +/- 3 years, with subsequent postoperative assessment at 1 year and again 12.4 +/- 4.2 years later. No mortality was registered during the follow-up. Corrective surgery was performed in 32 patients (31.6 %) before the first month of life. All the patients were evaluated with spin-echo and echo gradient and 34 were evaluated with magnetic resonance angiography. The patients were classified into two groups: group A consisted of 68 patients (11 < 1 month old) with no complications. End-to-end anastomosis was performed in 55, the Alvarez technique in five, the Waldhausen technique in six, and conduit in two. Group B consisted of 33 patients complicated with early aortic recoarctation (21 corrected before the age of 1 month). End-to-end anastomosis was performed in 29, the Alvarez technique in two, and grafting in two. During the follow-up, 43 reinterventions were performed. Isthmus diameter/descending aorta diameter at the diaphragmatic level and repaired site diameter/descending aorta diameter at the diaphragmatic level were measured.

RESULTS

Group A: the isthmus diameter/descending aorta diameter at the diaphragmatic level index was 0.92 +/- 0.08 and the repaired site diameter/ descending aorta diameter at diaphragmatic level index was 0.90 +/- 0.05. Twenty-three patients were assessed by means of three-dimensional magnetic resonance angiography, which revealed two late stenosis (one in a 10-year-old patient with an end-to-end anastomosis performed previously, and another in an 18-year-old patient with a proximal and distal obstructed conduit). Group B: the isthmus diameter/descending aorta diameter index was 0.84 +/- 0.1 and the repaired site diameter/ descending aorta diameter index was 0.82 +/- 0.11. Eleven patients were assessed by means of three-dimensional magnetic resonance angiography, which revealed five stenosis indexes (0.53-0.73) surgically corrected before the age of 2 months, four with an initial technique based on end-to-end anastomosis and one with a graft.

CONCLUSIONS

Our results support the influence of young age, the use of end-to-end anastomosis and grafts in recoarctation and their late influence on recurrent recoarctation. The patients in group A were discharged in childhood or adulthood after periodic follow-up every 5 years with magnetic resonance angiography for 18 years with results within the normal range, while patients in group B required longer follow-up.

Intercostal artery aneurysms complicating thoracic aortic coarctation: Diagnosis with magnetic resonance angiography

The case report of a 46-year-old woman diagnosed with complete aortic coarctation and multiple intercostal artery aneurysms using 'ultrafast time-resolved' multiphase contrast-enhanced magnetic resonance angiography and conventional single-phase, high-resolution breath-hold contrast-enhanced magnetic resonance angiogram techniques is presented. A review of intercoastal artery aneurysms occurring in conjunction with aortic coarctation and the various contrast-enhanced magnetic resonance angiography techniques currently available is provided.

Velocity-encoded magnetic resonance image assessment of regional aortic flow in coarctation patients

BACKGROUND

During primary coarctation repair, collateral blood vessels contribute significantly to distal perfusion. We sought to determine if velocity-encoded cine magnetic resonance imaging (VENC-MRI) could provide insight into anatomy and hemodynamics of collateral flow in patients with unrepaired coarctation.

METHODS

Sixteen patients (median age, 6.2 years; range, 1 to 18) with discrete coarctation (65% severe, 29% mild-moderate) and 10 controls (median age, 12.0 years; range, 9 to 15) without left-sided heart lesions were referred for cardiac MRI. Flow volumes were calculated from VENC-MRI images at the coarctation (proximal), diaphragm (distal), and midway between the two points (midpoint). A means model, repeated-measure analysis, was performed for volumes.

RESULTS

In coarctation patients, flow volumes increased by 59% (p = 0.0002) from coarctation to diaphragm, primarily between the proximal and midpoint sites (by 77%, p < 0.0001). In controls, flow volumes decreased by 11% along the entire aortic study length. Coarctation volumes were lower than controls by 54% (p = 0.0003) at the proximal site but showed no statistical difference at the midpoint or diaphragm.

CONCLUSIONS

Coarctation flow volumes maximally increase in the upper thoracic aorta, but approach normal flow volumes in the lower thoracic region. Arteries arising from mid and lower thoracic level, such as those supplying the anterior spinal cord, may have nearly normal flow if collaterals are present. Velocity-encoded MRI can evaluate flow in patients who have poor collateral circulation to improve surgical planning and decrease neurologic complications of coarctation repair.

Magnetic resonance imaging-guided balloon angioplasty of coarctation of the aorta: a pilot study

BACKGROUND

MRI guidance of percutaneous transluminal balloon angioplasty (PTA) of aortic coarctation (CoA) would be desirable for continuous visualization of anatomy and to eliminate x-ray exposure. The aim of this study was (1) to determine the suitability of MRI-controlled PTA using the iron oxide-based contrast medium Resovist (ferucarbotran) for catheter visualization and (2) to subsequently apply this technique in a pilot study with patients with CoA.

METHODS AND RESULTS

The MRI contrast-to-noise ratio and artifact behavior of Resovist-treated balloon catheters was optimized in in vitro and animal experiments (pigs). In 5 patients, anatomy of the CoA was evaluated before and after intervention with high-resolution respiratory-navigated 3D MRI and multiphase cine MRI. Position monitoring of Resovist-treated catheters was realized with interactive real-time MRI. Aortic pressures were continuously recorded. Conventional catheterization was performed before and after MRI to confirm interventional success. During MRI, catheters filled with 25 micromol of iron particles per milliliter of Resovist produced good signal contrast between catheters and their background anatomy but no image distortion due to susceptibility artifacts. All MRI procedures were performed successfully in the patient study. There was excellent agreement between the diameters of CoA and pressure gradients as measured during MRI and conventional catheterization. In 4 patients, PTA resulted in substantial widening of the CoA and a decrease in pressure gradients. In 1 patient, PTA was ineffective.

CONCLUSIONS

The MRI method described represents a potential alternative to conventional x-ray fluoroscopy for catheter-based treatment of patients with CoA.

Magnetic resonance imaging predictors of coarctation severity

BACKGROUND

MRI is increasingly used for anatomic assessment of aortic coarctation (CoA), but its ability to predict the transcatheter pressure gradient, considered the reference standard for hemodynamic severity, has not been studied in detail. This study evaluated the ability of MRI to distinguish between mild versus moderate and severe CoA as determined by cardiac catheterization.

METHODS AND RESULTS

The clinical, MRI, and catheterization data of 31 subjects referred for assessment of native or recurrent CoA were reviewed retrospectively. Patients were divided into 2 groups on the basis of peak coarctation gradient by catheterization: <20 mm Hg (n=12) and > or =20 mm Hg (n=19). Patients with cardiac index <2.2 L x min(-1) x m(-2) by catheterization were excluded. By logistic regression analysis, the following variables simultaneously predicted coarctation gradient > or =20 mm Hg: (1) smallest aortic cross-sectional area (adjusted for body surface area) measured by planimetry from gadolinium-enhanced 3D magnetic resonance angiography (OR 1.71 for 10 mm2/m2 decrease, P=0.005) and (2) heart rate-corrected mean flow deceleration in the descending aorta measured by phase-velocity cine MRI (OR 1.68 for 100 mL/s(1.5) increase, P=0.018). For the combination of these variables, a predicted probability >0.38 had 95% sensitivity, 82% specificity, 90% positive and negative predictive values, and an area under the receiver-operator characteristics curve of 0.938. In a subsequent validation study, the prediction model correctly classified 9 of 10 patients, with no false-negatives.

CONCLUSIONS

The combination of anatomic and flow data obtained by MRI provides a sensitive and specific test for predicting catheterization gradient > or =20 mm Hg.

Mesure des diamètres aortiques dans le suivi IRM des coarctations

OBJECTIVE

During aortic coarctation follow-up, accurate diameter measurements using MRI are required. The purpose of this study was to compare the reproducibility of aortic measurements on axial and sagittal views using black blood (Fast-Spin-Echo) and three-dimensional Gadolinium-enhanced MR angiography.

SUBJECTS AND METHODS

We studied 34 patients who underwent evaluation after surgical treatment in the first year of life. The aortic measurements were made at six thoracic levels. We calculated the mean difference between the two sequences, and used Bland and Altman method and the comparison to zero.

RESULTS

With black blood, either on axial or sagittal views, aortic measurements were in agreement. Between two sequences, we considered as acceptable a mean difference of 0,5 mm with limits of agreement of +/- 3 mm. Difficulties were found for proximal ascending aorta measurements on all sequences. Using MR angiography, the highest agreement at the site of repair was on sagittal view, while the highest agreement at other sites was on axial views.

CONCLUSION

Black blood sequence provides a better reproducibility for aortic measurements than native slices of MR angiography.

Role of MRI in clinical cardiology

Rapid progress has been made in cardiac MRI (CMRI) over the past decade, which has firmly established it as a reliable and clinically important technique for assessment of cardiac structure, function, perfusion, and myocardial viability. Its versatility and accuracy is unmatched by any other individual imaging modality. CMRI is non-invasive and has high spatial resolution and avoids use of potentially nephrotoxic contrast agent or radiation. It has been extensively studied against other established non-invasive imaging modalities and has been shown to be superior in many scenarios, particularly with respect to assessment of cardiac and great vessel morphology and left ventricular function. Furthermore, its clinical use continues to expand with increasing experience and proliferation of CMRI centres. As worldwide prevalence of cardiovascular disease continues to rise, CMRI provides opportunity for improved and cost-effective non-invasive assessment. Continued progress in CMRI technology promises to further widen its clinical application in coronary imaging, myocardial perfusion, comprehensive assessment of valves, and plaque characterisation.

Long-term follow-up of 82 patients with chronic disease of the thoracic aorta using spin-echo and cine gradient magnetic resonance imaging

The objective of this study to examine the clinical impact of magnetic resonance imaging in long-term follow-up of patients (pts) with chronic disease of the thoracic aorta such as coarctation of the aorta, chronic aortic dissection and true aortic aneurysm. A total of 322 magnetic resonance examinations obtained in 82 pts with chronic disease of the thoracic aorta (31 pts with coarctation of the aorta (CoA), 29 pts with chronic aortic dissection and 22 pts with true aneurysm) over a period of 0.25 to 13.5 (mean +/- SD: 6.5 +/- 3.4) years were retrospectively reviewed. Diameters of the thoracic aorta were measured at predefined levels and morphological and functional parameters of special interest were analysed in each patient group. Pts were classified as having constant or progressive disease and clinical end-points were defined as (re-)operation or death. 43 pts (52%) (CoA 15 pts, chronic dissection 16 pts, true aneurysm 12 pts) had constant findings. None of them underwent (re-)operation and seven patients (16%) died, three of them from their aortic disease more than five years later after their last magnetic resonance examination, one from an arrhythmogenic event, and in the remaining 3 pts the cause of death could not be definitely established. 39 pts (48%) (CoA 16 pts, chronic dissection 13 pts, true aneurysm 10 pts) had progressive disease as demonstrated by repetitive magnetic resonance imaging. Of these 39 pts 24 pts underwent (re-)operation, in 15 pts operation was postponed. Four pts died from their aortic disease. Repetitive magnetic resonance imaging is a clinically feasible technique for long-term follow-up of pts with chronic disease of the thoracic aorta because it can detect progressive disease in a large subset of pts requiring elective surgery. The results of magnetic resonance imaging provided the rationale for either (re-)operation or conservative management, thus guiding patient management.

Coarctation of the aorta

Coarctation of the aorta may seem to be a relatively simple lesion, but controversy persists about the optimal management strategy for this condition. A plethora of options are available, and strong evidence to guide clinical decision making is lacking. The age of the patient at presentation and anatomic variations have a significant effect on the type of therapy chosen and the outcome of intervention, which can include death, recurrence of obstruction, and persistent or late hypertension. The current trend in practice is to favor surgical repair in neonates and infants and transcatheter balloon dilation in older children and adults.