Use of non-invasive phase contrast magnetic resonance imaging for estimation of atrial septal defect size and morphology: a comparison with transesophageal echo

Missed Connections: Identification of Atrial Septal Defect by MRI

In this case report, we describe a 55-year-old female patient with worsening exertional dyspnea who is referred to the cardiology department, due to the appearance of worsening pulmonary vascular disease on computed tomography (CT) of the chest. Previous transthoracic echocardiograms (TTE) identified right ventricle enlargement, but no other structural abnormalities. She completed cardiac magnetic resonance (CMR) imaging, which identified a large secundum atrial septal defect (ASD). She subsequently underwent surgical planning and correction of the lesion with improvement of her symptoms. This case and a growing body of literature support the use of CMR as an alternative imaging modality for the diagnosis of congenital heart disease (CHD).

Phase contrast cardiac magnetic resonance imaging versus transoesophageal echocardiography for the evaluation of feasibility for transcatheter closure of atrial septal defects

Background

This prospective study was aimed at comparing phase contrast cardiac magnetic resonance imaging (PC-CMR) with 2D transoesophageal echocardiography (TEE) for determining potential candidature for transcatheter closure in ostium secundum ASD (OS-ASD) patients. We included consecutive adult patients with OS-ASD for the evaluation of feasibility for transcatheter closure using 2D-TEE and PC-CMR over a period of 2 years. Patients who fulfilled the conventional criteria for transcatheter closure, i.e. maximum ASD diameter ≤ 34 mm, adequate rims (≥ 5 mm, except for anterosuperior rim), and normal pulmonary venous drainage on both imaging modalities, were taken for device closure. In patients where there was discrepancy in the measurements of ASD diameter or rim size, making them eligible for device closure on one imaging modality and ineligible on the other hand, provisional device closure was attempted. All patients who underwent transcatheter closure were followed up to 6 months to rule out any complications.

Results

A total of 58 patients (mean age 35.93 ± 10.59 years) were enrolled in the study. Overall, there was significant positive correlation between 2D-TEE and CMR measurements of maximal ASD diameter and rim size (p < 0.001). However, TEE significantly underestimated maximal ASD diameter and posteroinferior rim size in comparison with CMR (p = 0.013 and p = 0.023, respectively). 46 (79.3%) patients were suitable for transcatheter closure on CMR, while 44 (75.9%) were eligible on TEE. Transcatheter closure was attempted in 48 patients based on imaging findings and was successful in 46 (95.8%) patients. Device closure was unsuccessful in 2 patients with defect size < 34 mm on TEE but > 34 mm on CMR. Among 7 patients with deficient posteroinferior rim on TEE, 5 had sufficient rim on CMR and underwent successful transcatheter closure. CMR detected anomalous pulmonary venous drainage in one patient which was missed on TEE, hence excluding the patient from transcatheter closure. Mean device size was 28.3 ± 7.4 mm and correlated more strongly with the defect dimensions on PC-CMR (r = 0.85, p < 0.001) compared to TEE (r = 0.71, p = 0.02).

Conclusions

PC-CMR may to be superior to 2D-TEE for the preprocedural planning and feasibility assessment for transcatheter closure in adult patients with ostium secundum ASD.

Cardiovascular MRI Compared to Echocardiography to Identify Cardioaortic Sources of Ischemic Stroke: A Systematic Review and Meta-Analysis

Background: To compare the diagnostic yield of echocardiography and cardiovascular MRI (CMR) to detect structural sources of embolism, in patients with ischemic stroke with a secondary analysis of non-stroke populations.

Methods and Results: We searched MEDLINE/Embase (from 01.01.2000 to 24.04.2021) for studies including CMR to assess prespecified sources of embolism. Comparison included transthoracic and/or transesophageal echocardiography. Two authors independently screened studies, extracted data and assessed bias using the QUADAS-2 tool. Estimates of diagnostic yield were reported and pooled. Twenty-seven studies with 2,525 patients were included in a study-level analysis. Most studies had moderate to high risk of bias. Persistent foramen ovale, complex aortic plaques, left ventricular and left atrial thrombus were the most common pathologies. There was no difference in the yield of left ventricular thrombus detection between both modalities for stroke populations (4 studies), but an increased yield of CMR in non-stroke populations (28.1 vs. 16.0%, P < 0.001, 10 studies). The diagnostic yield in stroke patients for detection of persistent foramen ovale was lower in CMR compared to transoesophageal echocardiography (29.3 vs. 53.7%, P < 0.001, 5 studies). For both echocardiography and CMR the clinical impact of the management consequences derived from many of the diagnostic findings remained undetermined in the identified studies.

Conclusions: Echocardiography and CMR seem to have similar diagnostic yield for most cardioaortic sources of embolism except persistent foramen ovale and left ventricular thrombus. Randomized controlled diagnostic trials are necessary to understand the impact on the management and potential clinical benefits of the assessment of structural cardioaortic stroke sources.

Registration: PROSPERO: CRD42020158787.

Real-time volumetric relative dosimetry for magnetic resonance-image-guided radiation therapy (MR-IGRT)

The integration of magnetic resonance imaging (MRI) with linear accelerators (linac) has enabled the use of 3D MR-visible gel dosimeters for real-time verification of volumetric dose distributions. Several iron-based radiochromic 3D gels were created in-house then imaged and irradiated in a pre-clinical 1.5 T-7 MV MR-Linac. MR images were acquired using a range of balanced-fast field echo (b-FFE) sequences during irradiation to assess the contrast and dose response in irradiated regions and to minimize the presence of MR artifacts. Out of four radiochromic 3D gel formulations, the FOX 3D gel was found to provide superior MR contrast in the irradiated regions. The FOX gels responded linearly with respect to real-time dose and the signal remained stable post-irradiation for at least 20 min. The response of the FOX gel also was found to be unaffected by the radiofrequency and gradient fields created by the b-FFE sequence during irradiation. A reusable version of the FOX gel was used for b-FFE sequence optimization to reduce artifacts by increasing the number of averages at the expense of temporal resolution. Regardless of the real-time MR sequence used, the FOX 3D gels responded linearly to dose with minimal magnetic field effects due to the strong 1.5 T field or gradient fields present during imaging. These gels can easily be made in-house using non-reusable and reusable formulations depending on the needs of the clinic, and the results of this study encourage further applications of 3D gels for MR-IGRT applications.

Relationship between electrocardiographic signs and shunt volume in atrial septal defect

BACKGROUND

The aim of this study was to determine whether electrocardiographic signs correlate with hemodynamics and the magnitude of the intracardiac shunt in children with ostium secundum atrial septal defects (ASD).

METHODS

A total of 100 ASD patients (median age, 6 years 4 months; 54 girls) underwent cardiac catheterization between August 1980 and April 2010. We retrospectively investigated the relationship between electrocardiographic signs and the pulmonary/systemic blood flow ratio (Qp/Qs) in these patients. We also compared 63 postoperative electrocardiograms with those recorded before surgery.

RESULTS

The mean Qp/Qs ratio of the 100 patients was 2.46 ± 0.81 (range, 1.1-5.0). The Qp/Qs ratio in patients with and without right bundle branch block (RBBB) was 2.57 ± 0.82 (n = 73) and 2.15 ± 0.72 (n = 27), respectively (P = 0.016). The Qp/Qs ratio in patients with and without isolated negative T-wave was 2.85 ± 0.87 (n = 38) and 2.22 ± 0.68 (n = 62), respectively (P = 0.0003). None of the patients with low Qp/Qs ratio (Qp/Qs ratio ≤ 1.5) had both RBBB and isolated negative T-wave. The prevalence of these two signs decreased from 73.0% (n = 46) and 36.5% (n = 23) to 15.9% (n = 10) and 15.9% (n = 10) after surgical repair, respectively.

CONCLUSIONS

RBBB and isolated negative T-wave in the precordial leads are well correlated with high Qp/Qs ratio in ASD patients.

Atrial shunts: presentation, investigation, and management, including recent advances in magnetic resonance imaging

Atrial shunts are a common finding in both paediatric and adult populations. Recent developments in advanced imaging have widened the options for diagnosis and evaluation of such shunts. This paper reviews the various types of interatrial communications, discusses the features of clinical presentation in adults and children, and provides an overview of the clinical assessment including physical examination, electrocardiography, echocardiography, cardiac catheterisation, computed tomography, and magnetic resonance imaging. Focus will be placed on recent developments in magnetic resonance imaging that may improve the non-invasive evaluation of atrial shunts.

[Clinical indications for the use of cardiac MRI. By the SIRM Study Group on Cardiac Imaging]

Cardiac magnetic resonance (CMR) is considered an useful method in the evaluation of many cardiac disorders. Based on our experience and available literature, we wrote a document as a guiding tool in the clinical use of CMR. Synthetically we describe different cardiac disorders and express for each one a classification, I to IV, depending on the significance of diagnostic information expected.

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.

The role of cardiovascular magnetic resonance in adults with congenital heart disease

The comprehensive coverage and versatility of cardiovascular magnetic resonance (CMR), providing functional as well as anatomical information, make it an important facility in a center specializing in the care of adults with congenital heart disease. Imaging specialists using CMR to investigate acquired heart disease should also be able to recognize and evaluate previously unsuspected congenital malformations. Conditions that may present or be picked up during imaging in adulthood include atrial septal defect, anomalously connected pulmonary veins, double-chambered right ventricle, congenitally corrected transposition of the great arteries, aortic coarctation, and patent arterial duct. To realize its full potential and to avoid pitfalls, CMR of adults with congenital heart disease requires specific training and experience. Appropriate pathophysiological understanding is needed to evaluate cardiovascular function after surgery for tetralogy of Fallot, after transposition of the great arteries, and after Fontan operations. For these and other more complex cases, CMR should ideally be undertaken by specialists committed to long-term collaboration with the clinicians and surgeons managing the patients in a tertiary referral center.

Imaging congenital heart disease in adults

Transthoracic echocardiography is the first-line modality for cardiovascular imaging in adults with congenital heart disease (ACHD). The windows of access that are possible with transthoracic echocardiography are, however, rarely adequate for all regions of interest. The choice of further imaging depends on the clinical questions that remain to be addressed. The strengths of MRI include comprehensive access and coverage, providing imaging of all parts of the right ventricle, the pulmonary arteries, pulmonary veins and aorta. Cine images and velocity maps are acquired in specifically aligned planes, with stacks of cines or dynamic contrast angiography providing more comprehensive coverage. Tissues can be characterised if necessary, and MRI provides relatively accurate measurements of biventricular function and volume flow. These parameters are important in the assessment and follow-up of adults after repairs for tetralogy of Fallot or transposition of the great arteries and after Fontan operations. The superior spatial resolution and rapid acquisition of CT are invaluable in selected situations, including the visualisation of anomalous coronary or aortopulmonary collateral arteries, the assessment of luminal patency after stenting and imaging in patients with pacemakers. Ionising radiation is, however, a concern in younger patients who may need repeated investigation. Adults with relatively complex conditions should ideally be imaged in a specialist ACHD centre, where dedicated echocardiographic and cardiovascular MRI services are a necessary facility. General radiologists should be aware of the nature and pathophysiology of congenital heart disease, and should be alert for previously undiagnosed cases presenting in adulthood, including cases of atrial septal defect, aortic coarctation, patent ductus arteriosus, double-chambered right ventricle and congenitally corrected transposition.

Pre-procedural planning for percutaneous atrial septal defect closure: transesophageal echocardiography compared with cardiac computed tomographic angiography

BACKGROUND

The safety and efficacy of percutaneous closure of atrial septal defects (ASDs) is determined by several variables, including defect size, presence of adequate rim tissue, relationship to other cardiac structures, and associated congenital anomalies.

OBJECTIVE

We sought to determine the accuracy of computed tomographic angiography (CTA) in predicting a defect's size compared with pre-procedural transesophageal echocardiography (TEE) and to the current "gold standard" balloon sizing by intracardiac echocardiography (ICE).

METHODS

Thirty-five consecutive patients referred for possible percutaneous closure of suspected secundum ASD were evaluated with gated multislice CTA after initial TEE screening. Axial and sagittal image planes of the ASD from the CTA multiplanar reformation (MPR) images were used to measure the defect size and surface area.

RESULTS

Of the 35 patients with secundum-type ASDs, 5 subjects had disqualifying anatomy by CTA and 2 had an unsuccessful closure, resulting in a procedural success rate of 93%. Measurement of defect area by gated MPR images provided the strongest correlate to ICE balloon size. In large ASDs, TEE was less well correlated to the maximum defect size and identification of the inferior/inferoposterior rims than CTA.

CONCLUSIONS

Cardiac CTA is an accurate and useful technique for pre-procedural assessment of ASDs and may be superior to conventional TEE in large defects that have deficient inferior rims.

Assessment of atrial septal defects in adults comparing cardiovascular magnetic resonance with transoesophageal echocardiography

BACKGROUND

Many adult patients with secundum-type atrial septal defects (ASDs) are able to have these defects fixed percutaneously. Traditionally, this has involved an assessment of ASD size, geometry and atrial septal margins by transoesophageal echocardiography (TOE) prior to percutaneous closure. This is a semi-invasive technique, and all of the information obtained could potentially be obtained by non-invasive cardiovascular magnetic resonance (CMR). We compared the assessment of ASDs in consecutive patients being considered for percutaneous ASD closure using CMR and TOE.

METHODS

Consecutive patients with ASDs diagnosed on transthoracic echocardiography (TTE) were invited to undergo both CMR and TOE. Assessment of atrial septal margins, maximal and minimal defect dimensions was performed with both techniques. Analyses between CMR and TOE were made using simple linear regression and Bland Altman Analyses.

RESULTS

Total CMR scan time was 20 minutes, and comparable to the TOE examination time. A total of 20 patients (M:F = 5:15, mean age 42.8 years +/- 15.7) were included in the analyses. There was an excellent agreement between CMR and TOE for estimation of maximum defect size (R = 0.87). The anterior inferior, anterior superior and posterior inferior margins could be assessed in all patients with CMR. The posterior superior margin could not be assessed in only one patient. Furthermore, in 1 patient in whom TOE was unable to be performed, CMR was used to successfully direct percutaneous ASD closure.

CONCLUSIONS

CMR agrees with TOE assessment of ASDs in the work-up for percutaneous closure. Potentially CMR could be used instead of TOE for this purpose.

Recommendations for cardiovascular magnetic resonance in adults with congenital heart disease from the respective working groups of the European Society of Cardiology

This paper aims to provide information and explanations regarding the clinically relevant options, strengths, and limitations of cardiovascular magnetic resonance (CMR) in relation to adults with congenital heart disease (CHD). Cardiovascular magnetic resonance can provide assessments of anatomical connections, biventricular function, myocardial viability, measurements of flow, angiography, and more, without ionizing radiation. It should be regarded as a necessary facility in a centre specializing in the care of adults with CHD. Also, those using CMR to investigate acquired heart disease should be able to recognize and evaluate previously unsuspected CHD such as septal defects, anomalously connected pulmonary veins, or double-chambered right ventricle. To realize its full potential and to avoid pitfalls, however, CMR of CHD requires training and experience. Appropriate pathophysiological understanding is needed to evaluate cardiovascular function after surgery for tetralogy of Fallot, transposition of the great arteries, and after Fontan operations. For these and other complex CHD, CMR should be undertaken by specialists committed to long-term collaboration with the clinicians and surgeons managing the patients. We provide a table of CMR acquisition protocols in relation to CHD categories as a guide towards appropriate use of this uniquely versatile imaging modality.

The utility of modified Butler-Leggett criteria for right ventricular hypertrophy in detection of clinically significant shunt ratio in ostium secundum-type atrial septal defect in adults

BACKGROUND

This study was performed to test the hypothesis that there exists a correlation between the Butler-Leggett (BL) criterion for right ventricular hypertrophy on the electrocardiogram and the Qp/Qs shunt ratio in adults with ostium secundum atrial septal defects (ASDs).

METHODS

Demographic, cardiac catheterization, ASD closure, and electrocardiographic data were acquired on 70 patients with secundum ASDs closed percutaneously. Simple linear regression and logistic regression models were created to test the hypothesis.

RESULTS

The mean Qp/Qs ratio and BL criterion value were 1.61 +/- 0.46 and 0.11 +/- 0.41, respectively. The BL criterion values correlated with shunt ratios (r(2) = 0.11 and P = .004). A BL criterion value greater than 0 mV predicted a significant shunt ratio (Qp/Qs > or = 1.5) (odds ratio, 4.8; 95% confidence interval, 1.3, 18.1; P = or <.0001) with a sensitivity of 0.68 and specificity of 0.65.

CONCLUSION

Our results indicate that there is limited utility of the BL criterion at detecting right ventricular volume overload, although a BL criterion value greater than 0 mV being used to identify patients with significant intracardiac shunts yielded a sensitivity of 0.68 and specificity of 0.65.

Blood Flow Imaging?A New Angle-Independent Ultrasound Modality for the Visualization of Flow in Atrial Septal Defects in Children

BACKGROUND

Color Doppler imaging (CDI) is the most applied method for evaluation of flow in atrial septal defects (ASD). A new real time ultrasound flow imaging modality called blood flow imaging (BFI) is able to visualize the blood flow in any direction of the image and is not limited by velocity aliasing. The method thereby overcomes the two limitations most often encountered in CDI. In this study we compared BFI with CDI for the visualization of interatrial blood flow in children.

METHODS

We studied ASD flow in 13 children using both CDI and BFI in the same examination. CDI and BFI cineloops were prepared off-line and both optimal and suboptimal (increased color artifacts) images were presented in random order to four observers. They were asked to range from 0-100 on a visual analogue scale how certain they were of interatrial blood flow. The CDI and BFI ratings were compared using the exact Wilcoxon signed rank test for paired samples.

RESULTS

All ASDs visualized with CDI were confirmed using BFI. Two of the observers ranked BFI as being significantly better than CDI when the images were optimized. When the images were suboptimal three of the observers rated BFI as being significantly better.

CONCLUSIONS

This pilot study indicates that BFI improves the visualization of interatrial blood flow in children. To include BFI in the ordinary echocardiography examination is easy and not time consuming. The method may prove to be a useful supplement to CDI in ASD imaging.