Society for Cardiovascular Magnetic Resonance 2020 Case of the Week series

The Society for Cardiovascular Magnetic Resonance (SCMR) is an international society focused on the research, education, and clinical application of cardiovascular magnetic resonance (CMR). Case of the week is a case series hosted on the SCMR website (https://www.scmr.org) that demonstrates the utility and importance of CMR in the clinical diagnosis and management of cardiovascular disease. Each case consists of the clinical presentation and a discussion of the condition and the role of CMR in diagnosis and guiding clinical management. The cases are all instructive and helpful in the approach to patient management. We present a digital archive of the 2020 Case of the Week series of 11 cases as a means of further enhancing the education of those interested in CMR and as a means of more readily identifying these cases using a PubMed or similar search engine. Supplementary Information The online version contains supplementary material available at 10.1186/s12968-021-00799-0.

previously unnoticed atrial level shunt. She was referred for surgical closure of a presumed secundum atrial septal defect (ASD). However, on review of imaging prior to surgery, an enlarged coronary sinus was noted.
A pre-operative TTE confirmed the atrial shunt and dilated coronary sinus with mild dilation of the RA, RV, and pulmonary arteries (Additional file 1: Case 1 Movie 1). Additionally, the small perimembranous VSD was closed by tricuspid valve tissue. No left superior vena cava (SVC) was seen. The pulmonary venous return could not be confirmed by TTE.

CMR findings
Based on the concern for a dilated coronary sinus and inadequate confirmation of normal pulmonary venous return, a CMR was performed on a 1.5 T system (Aera, Siemens Healthineers, Erlangen, Germany). Cine imaging was technically suboptimal due to respiratory and metallic artifacts, but suggested a communication from the left atrium (LA) into the proximal coronary sinus with left to right shunt into the RA, consistent with a large unroofed coronary sinus (Additional files 2, 3: Case 1 Movies 2, 3). Both the RA and RV were qualitatively enlarged. A short axis stack was not performed as the study was done to delineate the atrial shunt and venous anatomy the day prior to surgery. On an axial cine stack, the indexed RV end-diastolic volume (RVEDVI) was 160 ml/m 2 (z-score + 5.2) which is severely enlarged. 4D flow imaging following contrast administration using Siemens WIP 785A clearly demonstrated the shunt pathway from the LA into the coronary sinus and the RA (Additional files 4, 5: Case 1 Movies 4, 5; Fig. 1: Case 1 Figure 1). There was normal pulmonary venous drainage and no left SVC. The pulmonary to systemic flow ratio was calculated to be greater than 2:1 by both 2D phase contrast and 4D flow.

Conclusion
TTE demonstrated evidence of a left to right shunt and a dilated coronary sinus. The differential diagnosis included a coronary sinus ASD, persistence of a left SVC to the coronary sinus, and anomalous pulmonary veins to the coronary sinus. CMR cine stacks demonstrated no left SVC, normal pulmonary venous drainage, and a likely unroofed coronary sinus, suggesting the diagnosis of a coronary sinus ASD. The 4D flow imaging clearly visualized the atrial shunt and normal pulmonary venous return. The CMR findings allowed for appropriate surgical planning and counseling. The intraoperative transesophageal echocardiogram (TEE) confirmed the intracardiac anatomy (Additional file 6: Case 1 Movie 6). The surgeon noted that the coronary sinus was almost completely unroofed and repaired the defect with a pericardial patch over the mouth of the coronary sinus. The post-operative TEE demonstrated no residual shunt and normal systolic function (Additional file 7: Case 1 Movie 7). The patient recovered quickly and was discharged home on post-operative day 2.

Perspective
ASDs are relatively common, with a reported prevalence of 1 to 2 per 1000 live births, accounting for 10 to 15% of congenital heart disease (CHD) [2]. However, coronary sinus type ASDs are much less frequent. From an anatomical standpoint, coronary sinus type ASDs are a misnomer; while their physiology is consistent with an ASD, there is no true deficiency of the atrial septum. Instead, there is a defect in the common wall between the coronary sinus and the LA which can vary from a few millimeters to complete absence of the wall of the coronary sinus. The usual method of repair is to place an autologous pericardial patch over the mouth of the coronary sinus. This results in a trivial right-to-left shunt due to coronary venous return entering the LA [3]. In cases of a coronary sinus ASD, it is common to have an associated left SVC entering the coronary sinus [4]. If the ostium of the coronary sinus is then closed, there would be a more significant right to left shunt leading to cyanosis and an alternative surgical approach is needed.
Diagnosis of coronary sinus type ASDs is challenging and often missed by TTE [5]. Additionally, a complete evaluation of systemic and venous anatomy is necessary for appropriate surgical planning and can be difficult to prove by TTE [6]. TEE can show excellent visualization of the atrial septum, though extracardiac anatomy can be difficult to see and it is a moderately invasive test. CMR can demonstrate rare intracardiac defects such as coronary sinus ASDs and quantify the hemodynamic effect of the shunt. To our knowledge, this is the first reported case of a coronary sinus ASD visualized and quantified with 4D flow CMR. 4D flow was able to clearly visualize the location of the shunt in the wall of the coronary sinus and demonstrate normal systemic and pulmonary venous drainage. 4D flow CMR has the potential to significantly increase diagnostic utility of detecting atrial shunts.

Clinical history
A 28 year old asymptomatic male with a history of Klippel-Feil syndrome was referred for a TTE because of his history of a genetic condition. The echocardiogram revealed a dilated RA and RV and possible left-to-right atrial level shunt.
The patient was diagnosed with Klippel-Feil syndrome at 16 years of age when he was found to have multiple vertebral anomalies (fusion of C2-3, C7-T1, T2-3) as part of an evaluation for scoliosis. He subsequently had an abdominal ultrasound which revealed an absent left kidney.
There was an incidental finding of an aortic arch abnormality. The aortic arch was right sided and took a retroesophageal course to descend on the left side of the thorax. The first head and neck vessel was the left common carotid artery followed, in order, by the right common carotid, right subclavian, and left subclavian (Additional files 11, 12 and 13: Case 2 Movies 4-6, Figs. 2, 3 and 4: Case 2 Figures 1-3).

Conclusion
This aortic arch anatomy is consistent with a diagnosis of a right sided aortic arch with a left descending aorta and a left arterial ductus arteriosus, also known as a right aortic arch with a retroesophageal segment or circumflex retroesophageal right aortic arch [7]. There is also a secundum ASD. The patient is being evaluated for percutaneous closure of the ASD. Division of the vascular ring is not being considered because of the patient's asymptomatic status.

Perspective
Klippel-Feil syndrome is a musculoskeletal condition defined by the fusion of at least 2 vertebrae in the neck [8]. The syndrome is associated with a short neck, low hairline, and restricted mobility of the upper spine [8]. It can also be associated with CHD, most commonly septal defects, as in this patient [9]. Arch anomalies such as coarctation of the aorta and a right-sided aortic arch have been previously described [9,10]. Rare reports of abnormalities of the head and neck arteries have also been described [11,12].
This case is consistent with a right-sided aortic arch as the transverse arch crosses over the right bronchus. A right sided aortic arch with a left descending aorta is a rare aortic arch abnormality occurring in < 10% of right sided aortic arches [13]. This diagnosis is associated with other CHD in 50% of patients [13]. With this arch anatomy, the aortic arch crosses the midline at the level of the T4-5 vertebrae [7]. The first branch can be the innominate artery or the left common carotid artery with an aberrant left subclavian artery, as in this case [7]. From an embryonic standpoint, the anatomy reported here is caused by dissolution of the embryonic fourth aortic arch causing the left seventh intersegmental artery to originate from the proximal descending aorta via the left dorsal aorta [14]. Persistence of the left sixth aortic arch results in a left sided ductus arteriosus [14]. This anatomy is consistent with a vascular ring. This differential diagnosis includes a double aortic arch with an atretic left arch [7]. These two diagnosis cannot be differentiated without surgical visualization; however, this case was unlikely a double aortic arch because of the absence of a remnant of the left atretic arch from the descending aorta. CMR was critical for the diagnosis of the aortic arch abnormality in this patient.

Clinical history
A 24 year old male with a history of neonatal pulmonic stenosis (PS) requiring emergent valvotomy shortly after delivery presented for evaluation of palpitations and presyncope. A 12-lead electrocardiogram (ECG) revealed sinus rhythm, RA abnormality, and diffuse nonspecific ST changes ( TTE revealed preserved left ventricular (LV) systolic function despite abnormal septal motion, mild RV dilation, mild RV systolic dysfunction (Additional files 14, 15: Case 3 Movies 1, 2), and pulmonic regurgitation (PR) without suggestion of residual PS (peak velocity 0.6 m/s; Additional file 16: Case 3 Movie 3). PR was difficult to quantify, and diastolic septal flattening suggested RV volume overload.

CMR findings
CMR was requested to comprehensively assess RV size/ function, quantify PR, and investigate the etiology of VT. CMR revealed normal LV size (LV end-diastolic volume index 63 ml/m 2 ), mild LV systolic dysfunction (LV ejection fraction (LVEF) 50%), basal septal thinning and

Scar imaging
Standard "bright blood" segmented inversion recovery images were not diagnostic, but "dark blood" phase sensitive inversion recovery (PSIR) images, Flow-independent dark-blood delayed enhancement (FIDDLE), clearly showed dense RA and RV endocardial late gadolinium enhancement (LGE) (Fig. 7: Case 3 Figure 3). FIDDLE was first described by Kim and colleagues for use in detection of myocardial infarction (MI) [15]. The technique relies on selection of an inversion time (TI) with tissue magnetization more than blood, which permits simultaneous myocardial hyper-enhancement and bloodpool suppression. As seen in Fig. 7: Case 3 Figure 3, FIDDLE accentuates the contrast between enhancing myocardium and the dark blood pool, and may increase the sensitivity for detection of LGE of thin-walled structures, such as the atria, RV, and papillary apparatus.
A secondary prevention implantable cardioverter defibrillator (ICD) was planned. ICD lead deployment was complicated by unusual difficulty imbedding the fixation coil into the RV endocardium and abnormally high pacing thresholds. In conjunction with the CMR findings, a diagnosis of RV endocardial fibroelastosis (EFE) secondary to critical, congenital PS was made.

Perspective
EFE may be either primary (idiopathic), or secondary to myocardial stress (most commonly aortic stenosis (AS) or inflammatory triggers [16]. In this patient, we suspect that EFE developed in utero secondary to critical PS and elevated RV systolic pressures. TTE is not reliable to detect EFE. Two small series of seven children have shown that CMR could detect EFE by LGE imaging [16,17]. This case highlights the improved diagnostic utility of dark blood scar imaging for endocardial LGE   Figure 3. CMR scar imaging. Comparison of standard "bright blood" segmented inversion recovery images (A) with "dark blood" technique (FIDDLE, B). RA and RV endocardial late gadolinium enhancement (LGE) is readily apparent on dark blood imaging assessment as compared to standard bright blood scar imaging [15,18].
CMR may be a critical modality in the assessment of VT, especially when associated with RV dilation and/or systolic dysfunction [19,20]. The differential diagnosis of VT in the presence of RV systolic dysfunction is broad and includes arrhythmogenic right ventricular cardiomyopathy (ARVC), sarcoidosis, MI, myocarditis, volume loading (congenital shunting, valvular regurgitation), and pressure-loading (PS, pulmonary artery hypertension) [21].
In this case, the CMR findings of dense endocardial RA and RV LGE suggested endocardial fibroelastosis, and this diagnosis was further supported by the abnormal findings during ICD implantation. CMR phase contrast velocity encoded flow imaging is superior to echocardiography in the quantification of PR, especially in patients with CHD [20]. In this particular patient, CMR revealed that abnormal septal motion was likely primarily due to basal septal thinning and fibrosis, rather than volume overload from severe PR. This case highlights the utility of dark blood LGE imaging and flow mapping in the assessment of RV size/function, morphology, and valvular insufficiency in an adult patient with repaired CHD and VT.

Sources of funding
Research reported in this publication was supported by the National Heart, Lung, and Blood Institute of the National Institutes of Health under Award Number T32HL007411. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Clinical history
A 20 year old man with past medical history of spontaneous left pneumothorax presented with atypical chest pain, palpitations and lightheadedness. His TTE showed normal LVEF, with prominent RV trabeculations with mildly reduced RV function, and RV dilation (Additional file 20: Case 4 Movie 1). Subsequent bubble study done with agitated saline injection in the left antebrachial vein resulted in early opacification of a dilated coronary sinus before the RA, which was suggestive of persistent left SVC. When agitated saline was injected into the right antebrachial vein, the RA opacified before the coronary sinus confirming a normal right SVC. The RV findings raised a concern for ARVC or RV non-compaction. CMR was ordered to further evaluate the RV.

CMR findings
A CMR and 3-dimensional time-resolved magnetic resonance angiography (MRA) showed normal LV wall thickness with mild cavity dilation and normal systolic function (LV end diastolic volume index 123.5 ml/m 2 , LVEF 61%) RV cavity size at upper limits of normal with normal systolic function (RVEDVI 103 ml/m 2 , RVEF 51%). No RV regional wall motion abnormalities or dyskinesis were present. T1, T2 weighted images pre and post contrast revealed no fatty infiltration or fibrosis of RV. Hence, CMR did not meet the criteria for ARVC or RV non-compaction. Instead, CMR and 3D MRA identified two venous anomalies: A persistent left SVC draining into the RA via the coronary sinus and the azygos continuation of the inferior vena cava (IVC) with an absent hepatic segment of IVC. (Additional files 21, 22 and 23: Case 4 Movies 2-4). Also seen is the hemiazygos vein draining into the persistent LSVC.

Conclusion
In view of the patient's young age and abnormal RV findings on TTE, ARVC was considered as a possible etiology of his clinical presentation. As a gold standard for RV assessment, the CMR and MRA study clarified that the patient had a normal RV size, normal RV function and tissue characteristics and also revealed two major anomalous venous connections. This case highlights the versatility of CMR and MRA in the evaluation patients with suspected RV or CHD.

Perspective
Azygos continuation of the IVC with absence of the hepatic segment of IVC is a rare finding with a prevalence of 0.6% among patients with CHD [22]. It has been shown to be sometimes associated with other congenital anomalies like heterotaxy syndromes, cor biloculare, persistent LSVC, anomalous pulmonary venous return, double outlet RV, large ASD, and pulmonary atresia [22]. The embryonic event is theorized to be failure of the union of the right subcardinal and hepatic anastomosis, with resulting atrophy of the right subcardinal vein [22].
The renal portion of the IVC receives blood from both kidneys and passes posterior to the diaphragmatic crura to enter the thorax as the azygos vein. The azygos vein joins the SVC at the normal location in the right paratracheal space through a dilated azygos arch [23]. Since the advent of multimodality imaging this entity is now being increasingly recognized in otherwise asymptomatic patients [24]. It is important to recognize the enlarged azygos vein at the confluence with the SVC and in the retrocrural space to avoid misdiagnosis as a right-sided paratracheal mass or retrocrural adenopathy [25]. Preoperative knowledge of the anatomy may be important in planning cardiopulmonary bypass and to avoid difficulties in cardiac catheterization.

Clinical history
A 57 year old female with a past medical history of eosinophilic granulomatosis with polyangiitis (EGPA), Loeffler's endocarditis (LE), asthma, hypertension, and syncope with an implantable loop recorder presented for a follow up CMR to assess for disease progression and response to therapy. She has had known EGPA since 2007 and has had multiple prior CMR studies, which have been significant for biventricular subendocardial enhancement on LGE imaging with overlying thrombus. The patient has been chronically anticoagulated with warfarin and on chronic oral prednisone therapy since her initial diagnosis. Due to progression of myocardial eosinophilic infiltration noted on CMR in 2018, she was started on mepolizumab (Nucala) 300 mg every 4 weeks.
Upon presentation for the current study, her ECG demonstrated normal sinus rhythm and a right bundle branch block. No recent laboratory testing was available as the patient follows with hematology at a separate institution.

CMR findings
CMR imaging was performed approximately one year prior in January 2019 on a 1.5 Tesla scanner (MAG-NETOM Avanto, Siemens Healthineers), showing subendocardial fibrosis within the LV and RV apices, extending to the mid-ventricular level. There was also enhancement of the basal anterolateral subendocardium ( Fig. 8: Case 5 Figure 1).
CMR was repeated in February 2020 on a 1.5 Tesla (MAGNETOM Sola; Siemens Healthineers) for reassessment. The LVEF was 50% and the RVEF was 52%. The burden of LGE extended to the mid-ventricular level, with also involvement of the basal anterolateral subendocardium ( Fig. 9: Case 5 Figure 2). LV thrombus LGE images acquired with GRE readout and PSIR reconstruction. Prior CMR from 2019 with subendocardial enhancement in the LV and RV apices, extending to the mid-ventricular level, and of the basal anterolateral subendocardium was not identified, and this was also not present on the prior exam. Using blood pool nulling, the areas of subendocardial enhancement were more clearly demonstrated due to the increased contrast to noise ratio between fibrotic regions and the LV cavity blood pool compared to the prior exam from 2019. The magnitude images from the current study demonstrate the use of blood pool nulling ( corresponding to extensive fibrosis within the LV and RV apices.

Conclusion
The presence of subendocardial fat, as seen in this case, has not been previously described in LE associated with EGPA. We postulate that this may represent an atypical feature of the disease or alternatively represent a finding unrelated to the disease process of LE. This finding is unlikely to represent artifact as the phenomena was demonstrated on images acquired with multiple sequence types. The case underscores the important role of CMR for tissue characterization in various disease processes. The use of multi-echo based fat-water separation techniques overcomes the limitations of spectral frequency based fat saturation. Additionally, using double/triple inversion spin echo, abnormalities at the myocardialblood pool interface may be obscured due to incompletely suppressed blood. The Dixon technique exploits LGE images acquired with gradient echo (GRE) readout and phase sensitive inversion recovery (PSIR) reconstruction. Follow up CMR from 2020 with subendocardial enhancement in the LV and RV apices. Note the improved contrast to noise between the fibrotic layer and the LV cavity blood pool when blood pool nulling is used phase cycling between fat and water which completes approximately every 4.4 ms at 1.5 T. At this field strength, the resonant frequencies of fat and water are separated by 220 Hz. Therefore, at an echo time of approximately 2.2 ms, fat and water are at opposite phase (separated by ½ cycle or 180°), but are in-phase relative to one another at 4.4 ms. Fat only and water only images can be reconstructed based on this principle [26]. Finally, the use of blood pool nulling can improve the conspicuity of fibrosis at the LV blood pool/subendocardial interface to markedly improve visualization of subendocardial enhancement.

Perspective
EGPA is a systemic small to medium vessel vasculitis, associated with asthma and peripheral eosinophilia [27]. Though primarily involving the upper respiratory tract,  multi-organ involvement is often described. Cardiac manifestations can be seen in up to 62% of patients and include myocarditis, heart failure, acute coronary syndrome (ACS), pericarditis, or pericardial effusion [28]. The three stages of myocardial involvement due to hypereosinophilia include an initial necrotic phase, followed by thrombus formation and ultimately endomyocardial fibrosis.
The finding of fat deposition seen on fat water separation imaging has not been described in the literature with LE, although it has been documented as a finding in other entities that involve fibrosis of the subendocardial and mid myocardial layers (such as post-MI scar and dilated cardiomyopathy) [29,30]. The mechanism of fatty infiltration post-MI may be due to ineffective fatty acid metabolism in injured myocytes leading to fat deposition or abnormal differentiation of cells into adipocytes in regions or fibrosis/scar [30,31]. The potential mechanism in this case is unknown.
Blood pool nulling compared to viable myocardium nulling has been shown to improve the detection of ischemic scar. Specifically, it improves visualization of subendocardial hyperenhancement due to improved contrast to noise between the scar and LV blood pool [18,32]. Based on this, acquisition of viable myocardium nulled images would have been reasonably expected to underestimate the subendocardial fibrosis burden, and therefore were not acquired. Patients with LE may have a dramatic response to treatment with imatinib, particularly early in the disease course [33]. Near complete reversal has been noted by CMR [34]. Contraction and/ or regression of the subendocardial fibrotic layer has been postulated as an explanation. Drug therapy with Imatinib may have anti-fibrotic mechanisms acting through inhibition of the platelet derived growth factor (PDGF) receptor [35]. Serial assessment of the subendocardium by CMR as response to therapy has not been explored. PSIR blood pool nulling would provide more accurate identification of subendocardial enhancement in this context. Our patient was being followed by CMR for response to the therapy, with several treatment decisions being linked to CMR findings (for instance, LV thrombus) in the past. Overall, we have highlighted the utility of blood pool nulling and its usefulness in visualization of subendomyocardial fibrosis in our patient with LE.

Clinical history
A 59-year-old man, admitted with a history of non-STelevation MI and treated with percutaneous coronary intervention (PCI), underwent TTE and found to have a mass attached to the septal leaflet of the tricuspid valve suggestive of a papillary fibroelastoma. CMR was requested to exclude other differential diagnosis such as thrombus and vegetation.   LGE imaging demonstrated contrast enhancement throughout the mass (Fig. 15: Case 6 Figure 3).

Conclusion
CMR findings of the tricuspid valve mass were suggestive of a tricuspid valve papillary fibroelastoma. The patient underwent elective surgical resection and the histopathological findings were consisting with the diagnosis of papillary fibroelastoma.

Perspective
Cardiac tumors are rare with an estimated prevalence, according to autopsy reports, of 0.002-0.3% [36]. The majority of these tumors (75%) are benign and their clinical presentation is influenced by the size, location and embolism tendency [37]. papillary fibroelastomas are the second most common cardiac tumor and 70-80% of valvular tumors are papillary fibroelastomas [38]. Other valvular tumors include myxoma, nonbacterial thrombotic endocarditis, and infective vegetation [39].
The majority of papillary fibroelastomas are related to the aortic valve where they usually arise from the aortic side of the valve and can present with MI due to dynamic obstruction of the coronary ostia or transit ischemic attack and strokes due to thromboembolism. The mitral and tricuspid valves are the second most common sites of involvement and the tumor usually arises at the atrial side of the valves. Pulmonary valve papillary fibroelastomas are very rare with few cases reported in the literature [40].
Imaging plays an essential role in the diagnosis of cardiac papillary fibroelastomas. Most cardiac papillary fibroelastomas are detected by TTE, TEE is more sensitive compared to TTE [41]. Typically, cardiac papillary fibroelastoma appears on TTE as a rounded, oval or irregular shaped lesion with well-demarcated margin that attaches to a cardiac valve with a short mobile stalk [42]. CMR can accurately differentiate cardiac tumors from thrombus by utilizing the inversion recovery technique acquired with a prolonged inversion time (> 600 ms) after contrast administration. Tumors usually have intermediate signal intensity to the myocardium and the blood pool whereas thrombus and vegetations appear dark. On LGE sequence, thrombus and vegetations do not enhance as they are avascular structures. On the other hand, the majority of cardiac tumors are usually hyperintense owing to their vascularity [37]. Nevertheless, cardiac tumors such as lipoma, rhabdomyoma and lymphoma can show no contrast enhancement [43].
Surgical resection is usually appropriate for symptomatic patients who are candidates for surgery. However, older age, comorbid conditions and the uncertainty of the thromboembolic risk can influence the decision of surgery [41]. Long term anticoagulation is recommended for symptomatic patients who are not fit for surgery however, no data strongly validate the efficacy of this approach [41]. There are no clear guidelines for the management of papillary fibroelastomas detected incidentally. Nevertheless, many surgeons recommend surgical resection for all left-sided papillary fibroelastomas due to the potential risk of thromboembolism [44,45]. Although extremely rare, recurrence of cardiac fibroelastoma following surgical resection has been reported [41,46,47].

Case 7. New murmur in a patient with pectus deformity
Clinical history A 14-year-old male presented to a pediatric cardiologist following referral for a new murmur heard on sports physical examination and for cardiac evaluation of connective tissue disease due to concern for Marfanoid features. His cardiac history was unremarkable, and there was no family history of connective tissue disease or sudden unexplained death. His medical history was notable for 2 years of progressive pectus carinatum. He was followed by orthopedics and was recommended for treatment with a brace. Physical exam was notable for a harsh grade III/VI systolic murmur best heard at the mid-left sternal border. Physical exam findings were also notable for a superiorly positioned pectus excavatum and an inferiorly positioned asymmetric pectus carinatum. A positive wrist sign and pes planus were noted on exam. Notably absent were hindfoot deformity, thumb sign, and reduced elbow extension. A TTE was performed, which demonstrated dynamic compression of the RV outflow tract with flow acceleration starting in the sub-valvar region and extending throughout the pulmonary trunk by Doppler assessment. The maximum velocity through the RV outflow tract was 2.0-2.5 m/s. The mitral and aortic valves were normal.

CMR findings
A CMR scan was performed on a 3 T CMR system (Sola, Siemens Healthineers). The CMR scan revealed a prominent pectus carinatum with chest wall asymmetry (prominence of the right chest) resulting in extrinsic compression of the RV outflow tract and mild sub-pulmonary stenosis (Figs. 16, 17: Case 7 Figures 1, 2). The compression and narrowed infundibulum were demonstrated in multiple imaging planes (Additional files 31, 32: Case 7 Movies 1, 2). The peak velocity was 2.45 m/s. The anteroposterior (AP) diameter of the chest was noted to be significantly narrowed in the axial plane (Additional file 33: Case 7 Movie 3). The mitral valve and aortic valve were normal.

Conclusion
The progression of the patient's pectus carinatum and chest wall asymmetry during adolescence caused external compression of his RV outflow tract, creating a functionally hypoplastic infundibulum with mild sub-pulmonary stenosis. Based on his comprehensive cardiac evaluation, he did not meet clinical criteria for Marfan syndrome.

Perspective
Pectus excavatum and pectus carinatum are common anterior chest well deformities in children [48,49]. Pectus excavatum, the most common chest wall deformity, is defined as intrusion of the anterior chest wall into the thoracic cavity, which progresses as children age into adolescence [48,50]. These deformities can be seen in patients with connective tissue disorders, such as the Marfan Syndrome and Noonan Syndrome [49].
CMR is a newer imaging modality used to diagnose pectus deformities and evaluate the degree of deformity in pre-surgical planning [51]. Patients can be asymptomatic; however, in one large adult cohort, 80% of patients had cardiac compression documented with symptoms of chest pain, dyspnea, palpitations, or exercise limitations [52]. Syncope has also been reported with a patient with severe pectus excavatum with compression of the RV and LA in the AP plane by CMR [53].
CMR in recent years has provided dynamic assessment of cardiac structure and function during the respiratory cycle with exaggerated septal excursion and increased LV eccentricity seen during the inspiratory phase [48,54]. CMR also allows for a more comprehensive assessment of the effect of the pectus deformity on RV dimensions and systolic function, as ultrasound has been shown to be discrepant when evaluating ventricular function [48,55]. Our patient was found to have normal RV function by both modalities, despite a reduced effective RV outflow tract. CMR is a useful modality to evaluate the dynamic effects of pectus deformities on cardiac anatomy and function, and should be considered in a patient with a new murmur and pectus deformity.

Clinical history
We report a case of suspected hypertrophic cardiomyopathy (HCM) with a rare diagnosis that was uncovered using CMR. A 75-year-old man presented with a family history positive for HCM. His TTE revealed asymmetrical myocardial thickening (Fig. 18: Case 8 Figure 1) without outflow obstruction or papillary muscles hypertrophy, mild to moderate mitral regurgitation, and normal sized RV and LV. CMR was requested for further assessment of HCM, hemodynamics and tissue characterization. Fig. 19: Case 8 Figure 2, Additional files 34, 35 and 36 Case 8 Movies 1-3) showed a normal LV cavity size with mild hypertrophy of the basal septum (12 mm). The remaining myocardial segments were of normal thickness (basal anterior and anterolateral walls: 7-8 mm). There was hyperdynamic systolic function with hyperdynamic contraction of the LV basal posterolateral wall below the posterior mitral annulus. Papillary muscles were also normal. There was no obstruction in the LV outflow tract. Additionally, there was bi-leaflet mitral valve prolapse (MVP) with thickened mitral leaflets, mitral annular disjunction (MAD) and mild to moderate mitral regurgitation. Importantly, LGE showed focal annular fibrosis in the posterior mitral annulus (Fig. 20: Case 8 Figure 3).

Conclusion
In conclusion, the pattern of ventricular hypertrophy was not typical for HCM. CMR diagnosis was MVP, MAD and focal annular myocardial fibrosis. ECG monitoring was recommended after CMR.

Perspective
The mitral annulus is a fibro-cartilagenous structure. MVP is bowing with a displacement of > 2 mm of mitral leaflets into the LA, beyond annular plane. The pathology of mitral degeneration includes chronic activation of the valvular interstitial cells as well as the degradation of the collagen and elastin of the mitral valve by proteolytic enzymes. Histopathological types of mitral degeneration include Barlow's disease; which is the classic type, and the fibroelastic type which leads to MAD. MAD is the separation of the atrio-mitral valve junction from the LV attachment allowing for increased mobility of the LGE in short axis base (A, B), three chamber (C), and corresponding short axis base (D). Fibrosis in the inferolateral wall basal segment confirmed by the reference image through the three chamber mitral valve apparatus [56]. MAD by itself is considered arrhythmogenic [57]. TTE can usually detect MVP and any associated mitral regurgitation. CMR clearly demonstrates the degree of MVP and MAD as well as the hyperdynamic basal lateral wall the basal segments' mild focal hypertrophy [58,59]. This asymmetric septal hypertrophy on TTE may simulate a pattern of HCM. Moreover, CMR is capable of depicting further important surrogates for instance fibrosis. The combination of MVP, MAD and focal fibrosis increases the risk of fatal heart rhythm in those patients.
The triad of MAD, MVP and focal fibrosis is arrhythmogenic, and could represent a fatal triad. It is therefore paramount to early recognize it especially in young patients using the different imaging modalities [60]. Further studies are recommended to determine whether monitoring younger patients using CMR would be essential.

Clinical history
A 68 year-old woman, a former smoker, presented to the emergency department after 24 h of malaise, sore throat and pleuritic chest pain. There was no other relevant past medical history. She was afebrile without other symptoms. Physical examination revealed audible crackles at bilateral lung bases with associated hypoxia. ECG (Fig. 21: Case 9 Figure 1) demonstrated widespread ST depression in the inferolateral leads as well as Q waves and ST elevation in I and aVL. Portable TTE showed a severely impaired LV function with global severe hypokinesia of mid segments, hypokinesia of apical segments and a hyperdynamic base. Both cardiac troponins and creatinine kinase were severely elevated (Troponin T 1020 [< 14 ng/l]; CKMB 14 µg/l [< 5 µg/l]).
The patient underwent an invasive angiography which did not show significant coronary artery disease (CAD). During angiography, she suffered sudden clinical deterioration with severe hypoxemia that improved after administration of high dose furosemide. A portable chest radiograph ( Fig. 22: Case 9 Figure 2) on ward admission showed features consistent with pulmonary edema. Because of the absence of significant coronary disease on angiography the working diagnosis of myocardial infarction with non-obstructive coronary arteries (MINOCA) was established. Urgent CMR was requested.

CMR findings
Myocarditis protocol was performed at 1.5 T (Aera, Siemens Healthineers). Cine images (  On T2 sequences, a mildly increased signal intensity was present predominantly in the mid anteroseptal and mid to apical anterior and lateral walls (  Figure 4) in a non-infarct pattern. These features were most consistent with active myocardial inflammation due to myocarditis although concomitant fibrosis cannot be excluded. The clinical presentation is less consistent with stress cardiomyopathy, but this entity may also produce abnormal T1 and T2 signal on CMR due to edema and inflammation.
As documented in patients with acute MI, the existence of short T1 times and a hypointense core within areas of edema or LGE are suggestive of microvascular obstruction (MVO) or myocardial hemorrhage [61].
Nonetheless, in our patient there were some inconsistencies. Often, the hypointense core is easily visible and, more importantly, T2 times should be clearly abnormal. In contrast, the features in the apex (hyperintensity on bSSFP, subtle hypointense core after fat saturation and contrast administration, low T1 but normal T2 times) fit with the presence of intramyocardial fat in the context of myocardial inflammation most likely due to acute myocarditis, although stress cardiomyopathy may be possible (mild diffuse myocardial edema, native T1 increase diffusely, and areas of delayed enhancement).

Conclusion
Given the clinical picture of atypical chest pain, LV dysfunction, ST segment changes on ECG, documented myocardial damage and consistent CMR findings (abnormal native T1, non-ischemic LGE and edema) the diagnosis of myocarditis was made. No specific etiology was identified. Stress cardiomyopathy is possible but less likely clinically. The abnormal appearances on bSSFP images and abnormal T1 times were deemed as incidental presence of myocardial fat. This was confirmed after comparing to the previous abdominal computed tomography (CT) studies where the heart had been partially covered; on these studies there were areas of focal low attenuation in the same apical segments described in the CMR study (Fig. 29: Case 9 Figure 9).

Perspective
The diagnostic workup of acute MI without obstructed coronary arteries is not always straightforward as it encompasses multiple etiologies from overlooked coronary artery disease to non-coronary acute myocardial damage (i.e. myocarditis) [62]. CMR is the mainstay in the diagnosis of suspected myocarditis. Tissue sampling using endomyocardial biopsy is not often performed due to the invasive nature of the procedure, so it is common practice to accept the diagnosis of myocarditis when the Lake Louise criteria (revised in 2018) are met [63,64]. These include: T1 criteria (non-ischemic pattern of LGE enhancement, prolonged T1 or increased extracellular volume) and T2 criteria (myocardial edema on STIR, lengthened T2 times). Importantly, both T1 and T2 criteria have to be present. These were identified in the case of our patient who presented with clinical, biochemical, ECG and CMR compatible findings.
However, the existence of intramyocardial fat played a confounding role initially raising the possibility of inflammation associated with severe damage. Lipomatous metaplasia of the myocardium following myocardial infarction, fibro-fatty replacement of the myocardium in ARVC, fat-containing intramyocardial lesions in tuberous sclerosis and intramyocardial lipomas are known It is also important to note that the presence of nonpathological ectopic myocardial fat is relatively common in healthy adults, and has no clinical implications [31]. Based on one cardiac CT study an incidence of up to 11% has been estimated [65]. The most usual location is the RV (free wall, RV outflow tract, moderator band or apex) however, it can also be found in the interventricular septum or LV apex. It is important to recognize this incidental fat as the features can sometimes be misleading (e.g. forming a small mass in the case of adipose degeneration of the moderator band or myocardial damage as in our case) and to correlate its presence to patient's presentation and clinical history.
On CMR, fat can sometimes have similarities with MVO or hemorrhage, as both fat and MVO or hemorrhage cause T1 time shortening. On T2 STIR, saturated fat can give the impression of a hypointense core. Nevertheless, this appearance will be subtle whereas when the microcirculation is disrupted or there are hemoglobin products the hypointense core will generally be prominent and surrounded by obviously abnormal myocardium. The confirmation can be obtained on T2 and T2* maps: the times will be normal in cases of intramyocardial fat but abnormally low in MVO or hemorrhage. Whenever possible, previous imaging such as body CT studies will help to confirm the presence of fat, as fat has a characteristically low attenuation of − 20 to − 130 Hounsfield Units on CT, similar to the epicardial or the subcutaneous adipose tissue.  column-B, E) and apical (right column-C, F) short axis views. Although relatively subtle, on STIR images there is myocardial hyperintensity (green asterisks) in the basal to apical anterior and lateral walls and mid anteroseptum, which is suggestive of myocardial edema. On LGE images there is subepicardial enhancement (arrows) in the basal to mid antero-and inferoseptum. The existence of epicardial fat (blue asterisks) might be confounded by subepicardial enhancement. Typically, epicardial fat appears hyperintense on the LGE sequence but is suppressed on STIR images  The CMR of Case 9 (Additional file CMR link, https:// www. cloud cmr. com/ 0757-1973-9978-0149/).

Clinical history
A 52-year old female without prior medical history was admitted with Influenza A myocarditis progressing to cardiogenic shock. She eventually required extracorporeal membrane oxygenation for biventricular failure on multiple inotropic medications. Nine days into admission, she received implantation of a HeartMate II LV assist device (LVAD) and was subsequently discharged. Over the next 6 months, myocardial function and clinical status improved. Her LVEF on TTE improved to 55-60%, with low LVAD speeds. Her LVAD was explanted.
One year later she experienced an isolated episode of transient double vision for a few minutes. A TTE did not reveal a thrombus but raised a suspicion of noncompaction and was felt to be of limited image quality. A CMR was performed to assess for non-compaction and thrombus formation.

CMR findings
Her CMR revealed normal RV and LV dyskinetic apical segments. The CMR also revealed a felt plug placed at the time of LVAD explantation. The felt plug was visualized as a mass at the LV apex measuring 5.2 cm in length, 1.6 cm in width on the localizer images. Two cm was contained within the LV cavity and 3.1 cm was present outside the LV cavity. The mass was isointense with the myocardium on bSSFP cine images (Additional files 37,  Table 1: Case 10. As part of the clinical evaluation, the CMR did not reveal any evidence of non-compaction or obvious thrombus.

Conclusion
To the best of our knowledge, this is the first report of CMR imaging of an LVAD felt plug. Although there wasn't any metal artifact on the CMR, to ensure patient safety for future scans, a CT scan of the chest was performed ( Fig. 33: Case 10 Figure 4). With the expanding indications and increasing safety of LVADs, the implantation rates have increased. A small percentage of patients improve their function, leading to removal of the LVAD. Multiple approaches have been described for explantation, including primary closure, patch closure, titanium plug insertion, felt plug insertion and dividing the driveline and leaving the entire pump in situ [66]. CMR studies in patients after LVAD explantation and primary closure reveal apical akinesis and tethering on cine imaging and apical scarring and transmural apical infarction on LGE [67]. This case highlights CMR findings and safety of felt plug imaging with CMR after LVAD explantation.

Perspective
Although the felt plug was not imaged by CMR in the past, it is CMR safe based on our study. Given the multiple approaches to explantation, it is important for CMR centers to review operative notes, X-rays, and any other imaging available in detail to assess for any metal remnants prior to scanning a patient after LVAD explantation. As there were concern of thrombogenicity of the plug remnants we discussed initiation of anticoagulation with surgeons and heart-failure specialists. Finally, it was decided to not initiate anticogulation. There were no immediate or delayed complications from the procedure. While LVAD presence is an absolute contraindication for CMR, these scans can be safely performed after explantation, even in the case of felt plug placement. The CMR of Case 10 (Additional file CMR link, https:// www. cloud cmr. com/ 1557-1973-7138-0192/).  Figure 3, Additional file 40: Case 11 Movie 1). It was located close to the SVC opening but did not appear to obstruct the tricuspid valve or systemic inflow. A tiny echogenicity was also observed in the LA (images not shown).

CMR findings
CMR and brain MRI were done to evaluate the intracardiac and intracranial lesions, respectively. CMR was mainly used to characterize the cardiac mass and exclude concomitant masses. It showed a solitary RA mass abutting the posterior RA wall and located close to the interatrial septum ( Fig. 37: Case 11 Figure 4). It appeared homogenously isointense to myocardium on both T1 weighted and T2 weighted sequences   Figure 5). The tricuspid valve was not involved and showed a normal opening. No extracardiac extension was seen. Previously sonographically suspected left atrial lesion was not identified on CMR. Brain MRI performed after CMR that showed multiple small subependymal hamartomata and a larger, avidly enhancing mass highly suspicious of subependymal giant cell astrocytoma ( Fig. 39: Case 11 Figure 6).

Conclusion
Genetic testing subsequently confirmed the diagnosis of tuberous sclerosis. Patient was started on Everolimus due to the presence of intracranial subependymal giant cell astrocytoma. Patient tolerated the medication with good drug compliance.

Perspective
Cardiac rhabdomyoma is the initial presenting feature of tuberous sclerosis in up to 59% of patients [68]. They are benign hamartomas of the myocardium, 33-50% of which regress within the first 2-4 years of life [69][70][71]. They are commonly intramyocardial or intracavitary, and located within the ventricles, making the RA location of our case rare [72,73]. Cardiac rhabdomyoma is usually asymptomatic but may present with outflow tract obstruction, arrhythmia, and heart failure. Multiple masses occur in up to 60% of cases, particularly if associated with tuberous sclerosis [74,75]. On TTE, rhabdomyoma generally appears as a hyperechoic solid mass. On CMR, they appear isointense to hyperintense on T1 weighted images and hyperintense on T2 weighted images. They are hypo-enhancing on contrast administration relative to the myocardium. TTE and CMR do not entail ionizing radiation, which is particularly important in children. They can be complementary to each other as small tumors (< 0.5 cm) or completely intramural lesions may not be detected by CMR, which is superior in detecting tumors within the cavities and for extracardiac extension assessment, particularly in preoperative cases. CMR can be highly accurate in predicting tumor type in children (Table 2: Case 11) presenting with cardiac mass [72]. In our case, CMR was useful to exclude multiple masses and to confirm and accurately characterize suspicious findings  Commonly associated with indwelling central venous catheters, congenital heart disease and Kawasaki's disease seen on echocardiogram. Additionally, brain MRI was necessary for assessing cerebral mass, which was possible to perform at the same time, allowing optimal pretreatment planning. CMR should not be routinely performed in all cases of cardiac rhabdomyoma in infants. TTE is often adequate for evaluation of cardiac rhabdomyoma. The consensus statement from the Tuberous Sclerosis Alliance recommends that CMR in infants should be limited by necessity, due to its need for general anesthesia or sedation [76]. The use of CMR should be considered on a case-bycase basis. In our case, the diagnosis of tuberous sclerosis was not yet established at the time of imaging and there was doubt on the TTE diagnosis due to its less common right atrial location and solitary nature. CMR was performed with patient under sedation and we managed to obtain good quality images within a relatively short scanning time (under 30 min).
Treatment is often not necessary as many masses gradually regress. However, surgery may be indicated in patients with severe inflow or outflow obstruction or arrhythmia [77]. Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, has been documented on various case studies to be effective and safe in treating patients with cardiac rhabdomyoma, particularly in tumors which are not resectable [77]. In our patient, the indication for use of Everolimus was primarily for early-onset intracranial subependymal giant cell astrocytoma instead. One would expect the cardiac rhabdomyoma to shrink in our patient as well, both due to its natural course of the disease and the use of Everolimus. TTE can be used for follow-up to document shrinkage or resolution.
CMR is a useful technique in the assessment and follow-up of pediatric cardiac masses. Even though most cardiac masses in tuberous sclerosis are presumed to be rhabdomyoma and spontaneous resolution is often expected, CMR may sometimes be a useful adjunct to TTE in selected cases and is useful in detecting multiple masses, inflow/outflow obstruction, and evaluation for an extracardiac extension.