Characterization of Cardiac Tumors in Children by Cardiovascular Magnetic Resonance Imaging: A Multicenter Experience

OBJECTIVES: Individual centers have relatively little experience with diagnostic imaging of cardiac tumors in children, because of their low prevalence. The accuracy of cardiac MRI diagnosis on the basis of a pre-defined set of criteria has not been tested.The aim of this study was to report the results of an international multicenter experience of cardiac magnetic resonance imaging (MRI) evaluation of cardiac tumors in children, each with histology correlation or a diagnosis of tuberous sclerosis, and to determine which characteristics are predictive of tumor type.

METHODS: An international group of pediatric cardiac imaging centers was solicited for case contribution. Inclusion criteria comprised: 1) age at diagnosis 18 years; 2) cardiac MRI evaluation of cardiac tumor; and 3) histologic diagnosis or diagnosis of tuberous sclerosis. Data from the cardiac MRI images were analyzed for mass characteristics. On the basis of pre-defined cardiac MRI criteria derived from published data, 3 blinded investigators determined tumor type, and their consensus diagnoses were compared with histologic diagnoses.

RESULTS: Cases (n = 78) submitted from 15 centers in 4 countries had the following diagnoses: fibroma (n = 30), rhabdomyoma (n = 14), malignant tumor (n = 12), hemangioma (n = 9), thrombus (n = 4), myxoma (n = 3), teratoma (n = 2), and paraganglioma, pericardial cyst, Purkinje cell tumor, and papillary fibroelastoma (n = 1, each). Reviewers who were blinded to the histologic diagnoses correctly diagnosed 97% of the cases but included a differential diagnosis in 42%. Better image quality grade and more complete examination were associated with higher diagnostic accuracy.

CONCLUSIONS: Cardiac MRI can predict the likely tumor type in the majority of children with a cardiac mass. A comprehensive imaging protocol is essential for accurate diagnosis. However, histologic diagnosis remains the gold standard, and in some cases malignancy cannot be definitively excluded on the basis of cardiac MRI images alone.

PMID:

Management of Acute Aortic Syndromes

Acute aortic syndrome (AAS) is a modern term to describe interrelated emergency aortic conditions with similar clinical characteristics and challenges. These conditions include aortic dissection, intramural haematoma (IMH), and penetrating atherosclerotic ulcer (PAU and aortic rupture); trauma to the aorta with intimal laceration may also be considered. The common denominator of AAS is disruption of the media layer of the aorta with bleeding within IMH, along the aortic media resulting in separation of the layers of the aorta (dissection), or transmurally through the wall in the case of ruptured PAU or trauma.

Population-based studies suggest that the incidence of acute dissection ranges from 2 to 3.5 cases per 100 000 person-years; hypertension and a variety of genetic disorders with altered connective tissues are the most prevalent risk conditions. Patients with AAS often present in a similar fashion, regardless of the underlying condition of dissection, IMH, PAU, or contained aortic rupture.

Pain is the most commonly presenting symptom of acute aortic dissection and should prompt immediate attention including diagnostic imaging modalities (such as multislice computed tomography, transoesophageal ultrasound, or magnetic resonance imaging).

Prognosis is clearly related to undelayed diagnosis and appropriate surgical repair in the case of proximal involvement of the aorta; affection of distal segments of the aorta may call for individualized therapeutic approaches favouring endovascular in the presence of malperfusion or imminent rupture, or medical management.

PMID: 21810861

Myocardial Tagging by Cardiovascular Magnetic Resonance: Evolution of Techniques–Pulse Sequences, Analysis Algorithms, and Applications

Cardiovascular magnetic resonance (CMR) tagging has been established as an essential technique for measuring regional myocardial function. It allows quantification of local intramyocardial motion measures, e.g. strain and strain rate. The invention of CMR tagging came in the late eighties, where the technique allowed for the first time for visualizing transmural myocardial movement without having to implant physical markers. This new idea opened the door for a series of developments and improvements that continue up to the current day. Different tagging techniques are currently available that are more extensive, improved, and sophisticated than they were twenty three years ago. Each of these techniques has different versions for improved resolution, signal-to-noise ratio (SNR), scan time, anatomical coverage, three-dimensional capability, and image quality. The tagging techniques covered in this article can be broadly divided into two main categories: 1) Basic techniques, which include magnetization saturation, spatial modulation of magnetization (SPAMM), delay alternating with nutations for tailored excitation (DANTE), and complementary SPAMM (CSPAMM); and 2) Advanced techniques, which include harmonic phase (HARP), displacement encoding with stimulated echoes (DENSE), and strain encoding (SENC). Although most of these techniques were developed by separate research groups and evolved from different backgrounds, they are in fact closely related to each other, and can be interpreted from more than one perspective. Some of these techniques even followed parallel paths of developments, as illustrated in the article. As each technique has its own advantages, some efforts have been made to combine different techniques for improved image quality or composite information acquisition. In this review, different developments in pulse sequences and related image processing techniques are described along with the necessities that led to their invention, which makes this article straightforward to read and the covered techniques easy to follow. Most major studies that applied CMR tagging for studying myocardial mechanics are also summarized. Finally, the current article includes a plethora of ideas and techniques with over 300 references that motivate the reader to think about the future of CMR tagging.

PMID: 21798021

Aortic Expansion Rate in Patients With Dilated Post-Stenotic Ascending Aorta Submitted Only To Aortic Valve Replacement Long-Term Follow-Up

OBJECTIVES: The appropriate treatment of post-stenotic ascending aorta dilation has been poorly investigated. This study was conceived to describe the evolution of aortic dimensions in patients with moderate post-stenotic ascending aorta dilation (50 to 59 mm) submitted to aortic valve replacement (AVR) alone.

METHODS: Ninety-three patients affected by severe isolated calcific aortic valve stenosis in the tricuspid aortic valve accompanied by moderate dilation of the ascending aorta (50 to 59 mm) were submitted to AVR only. All patients were followed for a mean of 14.7 ± 4.8 years by means of periodic clinical evaluations and echocardiography and tomography scans of the thorax.

RESULTS: Operative mortality was 1.0% (1 patient). During the follow-up, 16 patients died and 2 had to be reoperated for valve dysfunction. No patients experienced acute aortic events (rupture, dissection, pseudoaneurysm), and no patient had to be reoperated on the aorta. There was not a substantial increase in aortic dimensions: mean aortic diameter was 57 ± 11 mm at the end of the follow-up versus 56 ± 02 mm pre-operatively (p = NS). The mean ascending aorta expansion rate was 0.3 ± 0.2 mm/year.

CONCLUSION: In the absence of connective tissue disorders, AVR alone is sufficient to prevent further aortic expansion in patients with moderate post-stenotic dilation of the ascending aorta. Aortic replacement can probably be reserved for patients with a long life expectancy.

PMID: 21798419

Clinical Characteristics and Cardiovascular Magnetic Resonance Findings in Stress (Takotsubo) Cardiomyopathy

OBJECTIVES: Stress cardiomyopathy (SC) is a transient form of acute heart failure triggered by stressful events and associated with a distinctive left ventricular (LV) contraction pattern. Various aspects of its clinical profile have been described in small single-center populations, but larger, multicenter data sets have been lacking so far. Furthermore, it remains difficult to quickly establish diagnosis on admission. The objective was to comprehensively define the clinical spectrum and evolution of SC in a large population, including tissue characterization data from cardiovascular magnetic resonance (CMR) imaging; and to establish a set of CMR criteria suitable for diagnostic decision making in patients acutely presenting with suspected SC.

METHODS: Prospective study conducted at 7 tertiary care centers in Europe and North America between January 2005 and October 2010 among 256 patients with SC assessed at the time of presentation as well as 1 to 6 months after the acute event. The main outcome measure was complete recovery of LV dysfunction.

RESULTS: Eighty-one percent of patients (n = 207) were postmenopausal women, 8% (n = 20) were younger women (aged ≤50 years), and 11% (n = 29) were men. A stressful trigger could be identified in 182 patients (71%). Cardiovascular magnetic resonance imaging data (available for 239 patients [93%]) revealed 4 distinct patterns of regional ventricular ballooning: apical (n = 197 [82%]), biventricular (n = 81 [34%]), midventricular (n = 40 [17%]), and basal (n = 2 [1%]). Left ventricular ejection fraction was reduced (48% [SD, 11%]; 95% confidence interval [CI], 47%-50%) in all patients. Stress cardiomyopathy was accurately identified by CMR using specific criteria: a typical pattern of LV dysfunction, myocardial edema, absence of significant necrosis/fibrosis, and markers for myocardial inflammation. Follow-up CMR imaging showed complete normalization of LV ejection fraction (66% [SD, 7%]; 95% CI, 64%-68%) and inflammatory markers in the absence of significant fibrosis in all patients.

CONCLUSIONS: The clinical profile of SC is considerably broader than reported previously. Cardiovascular magnetic resonance imaging at the time of initial clinical presentation may provide relevant functional and tissue information that might aid in the establishment of the diagnosis of SC.

PMID: 21771988

Low-Gradient Aortic Valve Stenosis – Myocardial Fibrosis and its Influence on Function and Outcome

OBJECTIVES: This prospective cohort study in patients with aortic stenosis (AS) aimed to identify surrogates of myocardial fibrosis that are easy to derive in clinical practice, allow the differentiation of low-gradient severe AS from moderate AS, and have an impact on clinical outcome. In patients with symptomatic aortic AS, a characteristic subgroup (i.e., up to one-third) exhibits severe AS with a concomitant low mean valve gradient either with preserved or reduced ejection fraction (EF). It is hypothesized that these patients tend to have an advanced stage of myocardial fibrosis and poor clinical outcome.

METHODS: Eighty-six patients with moderate or severe AS were examined by echocardiography including conventional aortic valve assessment, mitral ring displacement, and strain-rate imaging. Replacement fibrosis was quantified by late-enhancement magnetic resonance imaging. Biopsy samples were taken from patients with severe AS (n = 69) at aortic valve replacement. All patients were followed for 9 months.

RESULTS: Patients were divided into 4 groups according to aortic valve area (<1.0 cm(2)), mean valve gradient ≥40 mm Hg, and EF (<50%): group 1, moderate AS (n = 17); group 2, severe AS/high gradient (n = 49); group 3, severe AS/low gradient/preserved EF (n = 11); and group 4, severe AS/low gradient/decreased EF (n = 9). At baseline, a significant decrease in mitral ring displacement and systolic strain rate was detected in patients with low-gradient AS. In low-gradient groups, a higher degree of interstitial fibrosis in biopsy samples and more late-enhancement magnetic resonance imaging segments were observed. A close inverse correlation was found between interstitial fibrosis and mitral ring displacement (r = -0.79, p < 0.0001). Clinical outcome was best for patients in group 1, whereas mortality risk increased substantially in groups 2 through 4.

CONCLUSIONS: In severe AS, a low gradient is associated with a higher degree of fibrosis, decreased longitudinal function, and poorer clinical outcome despite preserved EF. Mitral ring displacement differentiates between moderate AS and low-gradient/severe AS with preserved EF.

PMID: 21757118

Relationship Between Location and Size of Myocardial Infarction and their Reciprocal Influences on Post-Infarction Left Ventricular Remodelling

OBJECTIVES: To assess the intricate relationship between myocardial infarction (MI) location and size and their reciprocal influences on post-infarction left ventricular (LV) remodelling.

METHODS: A cohort of 260 reperfused ST-segment elevation MI patients was prospectively studied with cardiovascular magnetic resonance at 1 week (baseline) and 4 months (follow-up). Area at risk (AAR) and MI size were quantified by T2-weighted and late-gadolinium enhancement imaging, respectively. Adverse LV remodelling was defined as an increase in LV end-systolic volume ≥15% at follow-up.

RESULTS: One hundred and twenty-seven (49%) patients had anterior MI and 133 (51%) patients had non-anterior MI. Although the degree of myocardial salvage was similar between groups (P = 0.74), anterior MI patients had larger AAR and MI size than non-anterior MI patients yielding worse regional and global LV function at baseline and follow-up. At univariable analysis, anterior MI was associated with increased risk of adverse LV remodelling (P = 0.017) and lower LV ejection fraction (EF) at follow-up (P = 0.001), but not when accounted for baseline MI size. Accordingly, at multivariable analysis, baseline MI size but not its location was an independent predictor of adverse LV remodelling (odds ratio = 1.061, P < 0.001) and EF at follow-up (β-coefficient = −0.255, P < 0.001).

CONCLUSIONS: Anterior MI patients experience more pronounced post-infarction LV remodelling and dysfunction than non-anterior MI patients due to a greater magnitude of irreversible ischaemic LV damage without any independent contribution of MI location.

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Acute, Subacute, and Chronic Myocardial Infarction: Quantitative Comparison of 2D and 3D Late Gadolinium Enhancement MR Imaging

OBJECTIVES: To assess a late gadolinium enhancement (LGE) single-breath-hold three-dimensional (3D) inversion recovery magnetic resonance (MR) imaging sequence for the quantification of myocardial scar mass and transmurality in comparison with a clinically established two-dimensional (2D) sequence.

METHODS: All patients gave written informed consent to participate in this institutional review board-approved study. Ninety patients (84 men; mean age, 54.4 years ± 10.8 [standard deviation]) with acute (n = 30), subacute (n = 30), or chronic (n = 30) myocardial infarction were included. Imaging was performed by using a 1.5-T clinical MR imaging system. Spatial resolution was identical for 3D and 2D images (1.5 × 1.5 mm(2); section thickness, 8 mm; no section gap). Quantitative comparisons of myocardial mass (in grams), scar mass (in grams), and scar transmurality (on a five-point scale) were performed by using the Pearson correlation and Bland-Altman analysis (for myocardial and scar mass) or κ statistics (for transmurality).

RESULTS: There were no significant differences between 2D and 3D data sets in terms of mean myocardial mass (2D: 148.3 g ± 35.1; 3D: 148.1 g ± 34.6; P = .76) and scar tissue mass (2D: 31.8 g ± 14.6; 3D: 31.6 g ± 15.5; P = .39), with strong and significant correlation regarding both myocardial mass (r = 0.982; P < .001) and scar tissue mass (r = 0.980; P < .001). Bland-Altman analysis showed a mean difference of 0.21 g ± 6.64 (range, -19.64 to 18.44 g) for myocardial mass and a mean difference of 0.26 g ± 2.88 (range, -7.15 to 7.74 g) for scar mass between the 2D and 3D data sets. Agreement regarding scar transmurality was good (κ = 0.75). Acquisition time was significantly shorter for 3D data sets (26.7 seconds ± 4.4 vs 367.7 seconds ± 56.4; P < .001).

CONCLUSIONS: Three-dimensional LGE MR imaging enables quantitative evaluation of scar tissue mass and transmurality in patients with acute, subacute, or chronic myocardial infarction at significantly reduced acquisition times compared with 2D LGE MR imaging.

PMID: 21467254

Cardiovascular MRI for Assessment of Infectious and Inflammatory Conditions of the Heart

OBJECTIVES: This article reviews the role of cardiovascular MRI in the diagnosis and characterization of the spectrum of infectious and inflammatory disorders of the heart. An imaging protocol is described, and typical MRI findings are discussed and illustrated.

CONCLUSIONS: Radiologists should be aware of the spectrum of infectious and inflammatory conditions that can affect the heart and the role of MRI in conjunction with other imaging techniques in their assessment.

PMID: 21701017

Mitral Valve Abnormalities Identified by Cardiovascular Magnetic Resonance Represent a Primary Phenotypic Expression of Hypertrophic Cardiomyopathy

OBJECTIVES: Whether morphological abnormalities of the mitral valve represent part of the hypertrophic cardiomyopathy (HCM) disease process is unresolved. Therefore, we applied cardiovascular magnetic resonance to characterize mitral valve morphology in a large HCM cohort.

METHODS: Cine cardiac magnetic resonance images were obtained in 172 HCM patients (age, 42±18 years; 62% men) and 172 control subjects. In addition, 15 HCM gene-positive/phenotype-negative relatives were studied.

RESULTS: Anterior mitral leaflet (AML) and posterior mitral leaflet lengths were greater in HCM patients than in control subjects (26±5 versus 19±5 mm, P2 SDs above controls). Leaflet length was increased compared with controls in virtually all HCM age groups, including young patients 15 to 20 years of age (AML, 26±5 versus 21±4 mm; P=0.0002) and those ≥60 years of age (AML, 26±4 versus 19±2 mm; P2.0 was associated with subaortic obstruction (P=0.001). In addition, AML length in 15 genotype-positive relatives without LV hypertrophy exceeded that of matched control subjects (21±3 versus 18±3 mm; P

CONCLUSIONS: In HCM, mitral valve leaflets are elongated independently of other disease variables, likely constituting a primary phenotypic expression of this heterogeneous disease, and are an important morphological abnormality responsible for LV outflow obstruction in combination with small outflow tract dimension. These findings suggest a novel role for cardiac magnetic resonance in the assessment of HCM.

PMID: 21670234

Environmental Impact of Cardiac Imaging Tests For the Diagnosis of Coronary Artery Disease

OBJECTIVES: The use of cardiovascular imaging is growing inexorably and concerns have been expressed about its cost and radiation safety.

METHODS: In this study, the relative environmental impact of MRI, single photon emission tomography and cardiac ultrasound (echo) for the diagnosis of coronary artery disease were examined.

RESULTS: The results emphasise that echo causes the least environmental impact at each stage of its life cycle. The effect of one echo on human health, ecosystem effects and resource use was of the order of 1-20% of those of the alternative methods.

CONCLUSIONS: Although there are circumstances in which one imaging modality is preferred on clinical grounds, when everything else is equal, these results support the selection of echocardiography as the preferred test on environmental grounds.

PMID: 21685481

Cardiac Resynchronisation Therapy Guided by Late Gadolinium-Enhancement Cardiovascular Magnetic Resonance

OBJECTIVES: Myocardial scarring at the LV pacing site leads to incomplete resynchronization and a suboptimal symptomatic response to CRT. We sought to determine whether the use of late gadolinium cardiovascular magnetic resonance (LGE-CMR) to guide left ventricular (LV) lead deployment influences the long-term outcome of cardiac resynchronization therapy (CRT).

METHODS: 559 patients with heart failure (age 70.4 +/- 10.7 yrs [mean +/- SD]) due to ischemic or non-ischemic cardiomyopathy underwent CRT. Implantations were either guided (+CMR) or not guided (-CMR) by LGE-CMR prior to implantation. Fluoroscopy and LGE-CMR were used to localize the LV lead tip and and myocardial scarring retrospectively. Clinical events were assessed in three groups: +CMR and pacing scar (+CMR+S); CMR and not pacing scar (+CMR-S), and; LV pacing not guided by CMR (-CMR).

RESULTS: Over a maximum follow-up of 9.1 yrs, +CMR+S had the highest risk of cardiovascular death (HR: 6.34), cardiovascular death or hospitalizations for heart failure (HR: 5.57) and death from any cause or hospitalizations for major adverse cardiovascular events (HR: 4.74) (all P < 0.0001), compared with +CMR-S. An intermediate risk of meeting these endpoints was observed for -CMR, with HRs of 1.51 (P = 0.0726), 1.61 (P = 0.0169) and 1.87 (p = 0.0005), respectively. The +CMR+S group had the highest risk of death from pump failure (HR: 5.40, p<0.0001) and sudden cardiac death (HR: 4.40, p = 0.0218).

CONCLUSIONS: Compared with a conventional implantation approach, the use of LGE-CMR to guide LV lead deployment away from scarred myocardium results in a better clinical outcome after CRT. Pacing scarred myocardium was associated with the worst outcome, in terms of both pump failure and sudden cardiac death.

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X-Ray Magnetic Resonance Fusion to Internal Markers and Utility in Congenital Heart Disease Catheterization

OBJECTIVES: X-ray magnetic resonance fusion (XMRF) allows for utilization of 3D data during cardiac catheterization. However, to date, technical requirements have limited the use of this modality in clinical practice. Here we report on a new internal marker XMRF method that we have developed and describe how we used XMRF during cardiac catheterization in congenital heart disease.

METHODS: XMRF was performed in a phantom and in 23 patients presenting for cardiac catheterization who also needed cardiac MRI for clinical reasons. The registration process was performed in less than 5 minutes per patient with minimal radiation (0.004 – 0.024 mSv) and without contrast. Registration error was calculated in a phantom and in 8 patients using the maximum distance between angiographic and 3D model boundaries.

RESULTS: In the phantom the measured error in the AP projection had a mean of 1.15 mm (standard deviation 0.73). The measured error in patients had a median of 2.15 mm (IQR 1.65 – 2.56 mm). Internal markers included bones, airway, image artifact, calcifications, and the heart and vessel borders. The MRI data was used for road mapping in 17/23 (74%) cases and camera angle selection in 11/23 (48%) cases.

CONCLUSIONS: Internal markers based registration can be performed quickly, with minimal radiation, without the need for contrast, and with clinically acceptable accuracy using commercially available software. We have also demonstrated several potential uses for XMRF in routine clinical practice. This modality has the potential to reduce radiation exposure and improve catheterization outcomes.

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Prognostic Value and Determinants of a Hypointense Infarct Core in T2-Weighted Cardiac Magnetic Resonance in Acute Reperfused ST-Elevation Myocardial Infarction

OBJECTIVES: A hypointense core of infarcted myocardium in T2-weighted cardiovascular MR (CMR) has been used as a noninvasive marker for intramyocardial hemorrhage. However, the clinical significance of such findings not yet been established. Aim of this study was to evaluate determinants and prognostic impact of a hypointense infarct core in T2-weighted CMR images, studied in patients after acute, reperfused ST-elevation myocardial infarction (STEMI).

METHODS: We analyzed 346 STEMI patients undergoing primary angioplasty <12 hours after symptoms onset. T2-weighted and contrast-enhanced CMR was used for assessment of the area-at-risk, myocardial salvage, infarct size, hypointense core in T2-weighted images and late microvascular obstruction (MO). Patients were categorized into 2 groups defined by the presence or absence of a hypointense core. Primary endpoint of the study was occurrence of major adverse cardiovascular events (MACE) defined as death, reinfarction and congestive heart failure within 6 months after infarction.

RESULTS: A hypointense core was present in 122 (35%) patients and was associated with larger infarcts, greater amount of MO, less myocardial salvage and impaired left ventricular (LV) function (p<0.001, respectively). The presence of a hypointense core was a strong univariable predictor of MACE (hazard ratio: 2.59, confidence interval: 1.27-5.27) and was significantly associated with an increased MACE rate (16.4% versus 7.0%, p=0.006) six months after infarction.

CONCLUSIONS: A hypointense infarct core within the area at risk of reperfused infarcted myocardium in T2-weighted CMR is closely related to infarct size, MO and impaired LV function with subsequent adverse clinical outcome.

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Aortic Root Geometry in Aortic Stenosis Patients (A SEAS Substudy)

OBJECTIVES: To report aortic root geometry by echocardiography in a large population of healthy, asymptomatic aortic stenosis (AS) patients in relation to current vendor-specified requirements for transcatheter aortic valve implantation (TAVI).

METHODS: Baseline data in 1481 patients with asymptomatic AS (mean age 67 years, 39% women) in the Simvastatin Ezetimibe in AS study were used. The inner aortic diameter was measured at four levels: annulus, sinus of Valsalva, sinotubular junction and supracoronary, and sinus height as the annulo-junctional distance. Analyses were based on vendor-specified requirements for the aortic root geometry for current available prostheses, CoreValve and Edwards-Sapien.

RESULTS: The ratio of sinus of Valsalva height to sinus width was 1:2. In multivariate linear regression analysis, larger sinus of Valsalva height was associated with older age, larger sinus of Valsalva diameter, lower ejection fraction and smaller supracoronary diameter (multiple R(2) = 0.19, P< 0.01). The required annulus diameter for implantation of CoreValve was met in 61.9%, and for the Edwards-Sapien prosthesis in 66.9%. Overall, annular dimension feasible for TAVI using any available prosthesis was found in 78.2% of patients and in 77.7% of patients also the required minimum sinus of Valsalva height was found. Comparing the group of patients who met TAVI requirements to those who did not, the latter included more women and patients with lower body height and weight and significantly smaller aortic root diameters (all P < 0.05).

CONCLUSIONS: Among AS patients in the SEAS study, 27% of women and 19% of men did not have aortic root geometry fulfilling current requirements for TAVI.

PMID: 21508001