Arrhythmogenic right ventricular dysplasia: MR features

Cardiac Magnetic Resonance Imaging Macroscopic Fibro-Fatty Infiltration of the Myocardium in Pediatric Patients with Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia

Background: Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is an inherited, progressive form of cardiomyopathy, which is characterized by fibrofatty replacement of the myocardium. While the gold standard for diagnosis remains pathologic evaluation of biopsy, advances in noninvasive imaging, including cardiac magnetic resonance imaging (CMRI), have led to improved clinical diagnosis.Case report: We report three additional cases of pediatric patients that have pathologically confirmed ARVC/D with CMRI images, demonstrating extensive macroscopic fatty infiltration of the right and left ventricular myocardium. The identification using CMRI allowed timely transplantation and patient survival.Conclusion: Our study is designed to highlight how fibrofatty changes are minimal using CMRI in the pediatric population and how this can be a valuable tool to provide an additional method of diagnosis.

Noninvasive Multimodality Imaging in ARVD/C

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is a familial cardiomyopathy resulting in progressive right ventricular (RV) dysfunction and malignant ventricular arrhythmias. Although ARVD/C is generally considered an inherited cardiomyopathy, the arrhythmogenic nature of the disease is striking. Affected individuals typically present in the second to fourth decade of life with arrhythmias originating from the right ventricle. Over the past decade, pathogenic ARVD/C-causing mutations have been identified in 5 genes encoding the cardiac desmosome. Disruption of the desmosomal connection system between cardiomyocytes may be represented structurally by ventricular enlargement, global or regional contraction abnormalities, RV aneurysms, or fibrofatty replacement. These abnormalities are typically observed in predilection areas, including the subtricuspid region, basal RV free wall, and left ventricular posterolateral wall. As such, structural and functional abnormalities on cardiac imaging constitute an important diagnostic criterion for the disease. This paper discusses the current status and role of echocardiography, cardiac magnetic resonance imaging, and computed tomography for suspected ARVD/C.

Imaging of the right heart--CT and CMR

Right ventricular (RV) structure and function is of substantial importance in a broad variety of clinical conditions. Cardiac magnetic resonance (CMR) and computed tomography (CT) each provide three-dimensional RV imaging, high-resolution evaluation of RV structure/anatomy, and accurate functional assessment without geometric assumptions. This is of particular significance for the RV, where complex geometry compromises reliance on indices derived from two-dimensional (2D) imaging planes. CMR flow-based imaging can be applied to right-sided heart valves, enabling evaluation of hemodynamic and valvular dysfunction that may contribute to or result from RV dysfunction. Tissue characterization imaging by both CMR and CT provides valuable complementary assessment of the RV. Changes in myocardial tissue composition provide a mechanistic substrate for RV dysfunction and cardiac arrhythmias. This review provides an overview of RV imaging by both CMR and CT, with focus on assessment of RV structure/function, flow, and tissue characterization. Emerging evidence and established guidelines are discussed in the context of imaging contributions to diagnosis, prognostic risk stratification and disease management of clinical conditions that impact the right ventricle.

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D)

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a progressive genetic cardiomyopathy characterized by progressive fatty and fibrous replacement of ventricular myocardium. The clinical presentation is marked by ventricular arrhythmias, some fatal. The disease has evolved from a primary electrical/electrophysiological disorder (in the 1980s-1990s) to a diagnostic imaging conundrum (in the 2000s) to the current day understanding of a genetic cardiomyopathy caused by defects in cell-cell adhesion proteins or intracellular signaling components. The pathogenesis, clinical presentation, and the genetics of the disease are discussed in this review.

Imaging spectrum of sudden athlete cardiac death

Sudden athlete death (SAD) is a widely publicized and increasingly reported phenomenon. For many, the athlete population epitomize human physical endeavour and achievement and their unexpected death comes with a significant emotional impact on the public. Sudden deaths within this group are often without prior warning. Preceding symptoms of exertional syncope and chest pain do, however, occur and warrant investigation. Similarly, a positive family history of sudden death in a young person or a known family history of a condition associated with SAD necessitates further tests. Screening programmes aimed at detecting those at risk individuals also exist with the aim of reducing fatalities. In this paper we review the topic of SAD and discuss the epidemiology, aetiology, and clinical presentations. We then proceed to discuss each underlying cause, in turn discussing the pathophysiology of each condition. This is followed by a discussion of useful imaging methods with an emphasis on cardiac magnetic resonance and cardiac computed tomography and how these address the various issues raised by the pathophysiology of each entity. We conclude by proposing imaging algorithms for the investigation of patients considered at risk for these conditions and discuss the various issues raised in screening.

Prevalence of fat deposition within the right ventricular myocardium in asymptomatic young patients without ventricular arrhythmias

PURPOSE

Variable amounts of intramyocardial fat can be found within the right ventricular muscle fibers. We aimed to determine the prevalence of intramyocardial fat deposition within the right ventricle (RV) in asymptomatic patients aged 40 years and younger who underwent imaging of the heart for coronary artery disease screening.

MATERIALS AND METHODS

Retrospective review of 540 consecutive patients aged 40 years or younger referred for coronary calcium scoring.

RESULTS

The images were reviewed by 2 dedicated cardiac radiologists, and the following specific observations were made: presence or absence of macroscopic fat in the RV by location, RV size as normal or enlarged, and presence of additional foci of fat deposition in the visualized thorax. The clinical data were reviewed from the patients' medical record, and the following information was recorded: age, sex, body mass index, and the presence of cardiac risk factors. The electrocardiographic examinations were reviewed as well. The study cohort included 398 males (73%) and 142 females (27%), with a mean age of 36.2+/-4.3 years and a range of 12 to 40 years. Sixty-two patients (11.5%) had macroscopic fatty deposition of the RV myocardium.

CONCLUSIONS

Fatty replacement of the free wall of the RV is common, occurring in up to 11% of asymptomatic patients younger than 40 years of age undergoing cardiac screening examinations. No statistically significant association with cardiac risk factors or body mass index was found.

Cardiac MRI evaluation of nonischemic cardiomyopathies

The purpose of this manuscript is to review the major MRI findings in patients with nonischemic cardiomyopathies. Cardiac MRI has become an integral part in the diagnosis and management of patients with nonischemic cardiomyopathies. Findings on cardiac MRI studies can help distinguish between different types of cardiomyopathies and can provide valuable diagnostic and prognostic information.

Canadian Cardiovascular Society Consensus Conference guidelines on heart failure, update 2009: diagnosis and management of right-sided heart failure, myocarditis, device therapy and recent important clinical trials

The Canadian Cardiovascular Society published a comprehensive set of recommendations on the diagnosis and management of heart failure in January 2006. Based on feedback obtained through a national program of heart failure workshops and through active solicitation of stakeholders, several topics were identified because of their importance to the practicing clinician. Topics chosen for the present update include best practices for the diagnosis and management of right-sided heart failure, myocarditis and device therapy, and a review of recent important or landmark clinical trials. These recommendations were developed using the structured approach for the review and assessment of evidence adopted and previously described by the Society. The present update has been written from a clinical perspective to provide a user-friendly and practical approach. Specific clinical questions that are addressed include: What is right-sided heart failure and how should one approach the diagnostic work-up? What other clinical entities may masquerade as this nebulous condition and how can we tell them apart? When should we be concerned about the presence of myocarditis and how quickly should patients with this condition be referred to an experienced centre? Among the myriad of recently published landmark clinical trials, which ones will impact our standards of clinical care? The goals are to aid physicians and other health care providers to optimally treat heart failure patients, resulting in a measurable impact on patient health and clinical outcomes in Canada.

Role of cardiovascular magnetic resonance imaging in arrhythmogenic right ventricular dysplasia

Arrhythmogenic right ventricular dysplasia (ARVD) is a genetic cardiomyopathy characterized clinically by ventricular arrhythmias and progressive right ventricular (RV) dysfunction. The histopathologic hallmark is fibro-fatty replacement of RV myocardium. It is inherited in an autosomal pattern with variable penetrance. ARVD is unique in that it most commonly presents in young, otherwise healthy and highly athletic individuals. The cause of ARVD is not well-known but recent evidence suggests strongly that it is a disease of desmosomal dysfunction. The disease involvement is not limited only to the RV as left ventricle (LV) has also been reportedly affected. Diagnosis of ARVD is challenging and is currently based upon a multi-disciplinary work-up of the patient as defined by the Task Force. Currently, implanted cardioverter defibrillators (ICD) are routinely used to prevent sudden death in patients with ARVD. Cardiovascular MR is an important non-invasive diagnostic modality that allows both qualitative and quantitative evaluation of RV. This article reviews the genetics of ARVD, current status and role of CMR in the diagnosis of ARVD and LV involvement in ARVD.

Utility of myocardial fibrosis and fatty infiltration detected by cardiac magnetic resonance imaging in the diagnosis of arrhythmogenic right ventricular dysplasia--a single centre experience

INTRODUCTION

Cardiac magnetic resonance imaging (CMR) has evolved as a major diagnostic tool to evaluate arrhythmogenic right ventricular dysplasia (ARVD). However, there is a lack of consensus in the interpretation of findings such as fatty infiltration or myocardial fibrosis. We examined the diagnostic utility of these two features in the diagnosis of ARVD.

METHODS

We performed fast imaging employing steady-state acquisition cine imaging, T(1)-weighted black blood imaging with and without fat suppression and post-contrast delayed enhancement on a 1.5-T scanner to evaluate ventricular function and morphology, fatty infiltration and regional myocardial fibrosis in 52 subjects with suspected ARVD.

RESULTS

Eight subjects met the international diagnostic criteria for ARVD. Right ventricle (RV) delayed hyper-enhancement was found in 7 of 8 (88%) ARVD subjects compared to 6 of 44 (14%) subjects without ARVD (p<0.001). Fatty infiltration was only identified in 1 ARVD patient, and 1 non-ARVD patient. On multiple logistic regression analysis RV enhancement remained an independent predictor for the diagnosis of ARVD (p<0.05).

CONCLUSION

RV delayed enhancement is common in patients with ARVD, whereas detection of fatty infiltration of the right ventricle was rare in our patient population. The inclusion of RV fibrosis on CMR as a feature of ARVD may improve the diagnostic accuracy of this condition.

Role of magnetic resonance imaging in arrhythmogenic right ventricular dysplasia: insights from the North American arrhythmogenic right ventricular dysplasia (ARVD/C) study

BACKGROUND

Prior reports describing magnetic resonance (MR) imaging abnormalities in arrhythmogenic right ventricular dysplasia (ARVD/C) were limited by nonuniform inclusion criteria. The aim of our study was to define the prevalence, sensitivity, and specificity of quantitative MR imaging findings in the probands of multidisciplinary study of right ventricular dysplasia.

METHODS

Individuals with ventricular arrhythmias of left bundle-branch block morphology meeting the Task Force criteria for ARVD/C underwent MR imaging. The MR images were compared with 10 patients with idiopathic ventricular tachycardia (VT) and 25 controls. Of the 42 study probands, 40 met the Task Force criteria exclusive of MR imaging findings. All MR images were interpreted in a blinded fashion.

RESULTS

Right ventricle fat infiltration was reported in 24 (60%) probands and none of the patients with idiopathic VT or controls. Six patients (15%) had fat infiltration of the left ventricle. Right ventricle regional dysfunction was observed in 32 probands (80%) and none of the patients with idiopathic VT or controls. Qualitative RV function was abnormal in 26 probands (60%); however, quantitative RV ejection fraction was abnormal in 85% (24/28) of the probands. An RV ejection fraction <50% had a sensitivity of 73% and a specificity of 95% in diagnosis of ARVD/C.

CONCLUSIONS

Fat infiltration is seldom the only MR imaging abnormality and is less sensitive for ARVD/C diagnosis compared with RV regional dysfunction. Qualitative estimates of RV function may underestimate the prevalence of RV dysfunction in ARVD/C. Quantitative evaluation of RV by MR imaging may have a high sensitivity and specificity for ARVD/C diagnosis.

Evolving role of multidetector computed tomography in evaluation of arrhythmogenic right ventricular dysplasia/cardiomyopathy

The purpose of this study was to report 1 center's experience with multidetector computed tomography (MDCT) in the evaluation of patients suspected to have arrhythmogenic right ventricular (RV) dysplasia/cardiomyopathy (ARVD/C). RV dilatation/dysfunction is 1 of the most important criteria for establishing the diagnosis of ARVD/C. Cardiac magnetic resonance imaging (MRI) is the most preferred imaging modality for the diagnosis of ARVD/C. However, many patients with suspected ARVD/C have implantable cardioverter-defibrillators, prohibiting the use of MRI. Thirty-one patients (19 men; mean age 41 +/- 12 years) referred for evaluation of known or suspected ARVD/C had a complete reevaluation including contrast-enhanced cardiac MDCT at the center. Two patients underwent both cardiac MRI and MDCT. Seventeen of 31 patients met Task Force criteria for ARVD/C and were confirmed to have ARVD/C. Multidetector computed tomographic images were analyzed for qualitative and quantitative characteristic findings of ARVD/C. Increased RV trabeculation (p <0.001), RV intramyocardial fat (p <0.001), and scalloping (p <0.001) were significantly associated with the final diagnosis of ARVD/C. RV volumes, RV inlet dimensions, and RV outflow tract surface area were increased in patients with ARVD/C compared with patients who did not meet the criteria. RV and left ventricular functional analysis was performed in 2 patients. In conclusion, cardiac MDCT has a strong potential to detect many qualitative and quantitative abnormalities of the right ventricle in patients with ARVD/C. Limitations include implantable cardioverter-defibrillators and motion artifacts, along with well-known radiation and contrast-induced reaction.

Thermal mapping of right ventricular outflow tract tachycardia

BACKGROUND

Acute and long-term success of catheter ablation of right ventricular outflow tract tachycardia (RVOT VT) may be limited by the inability to reproduce the arrhythmia at the time of activation (AM) and pace mapping (PM). We have observed early initiation of the clinical VT when subtherapeutic radiofrequency (RF) energy was applied to the target area (TA), defined as a 2-cm(2) area around a pace match. We describe a novel approach using thermal mapping (TM) to guide the ablation of RVOT VT.

METHODS

Thirteen patients (10 female, mean age 46.2 +/- 13.7 years) with symptomatic VT of left bundle branch block (LBBB) inferior axis morphology and no structural heart disease underwent standard electrophysiologic evaluation with PM (n = 13), AM (n = 13), and 3D noncontact mapping (n = 4). Thermal mapping was performed after standard techniques failed to induce stable sustained VT for mapping in all 13 patients: RF was applied for 5-10 seconds in the TA to achieve a tip temperature of 45-50 degrees C. At sites where morphologically consistent with the clinical VT was induced, RF was applied at target temperature between 50 and 60 degrees C for 30-60 seconds. TM was repeated before and after intravenous Isoproterenol infusion until no further VT could be induced by low temperature application.

RESULTS

Noninducibility was achieved in all 13 patients. During a mean follow-up of 29 months (9-69 months), all patients remain arrhythmia-free, off antiarrhythmic medications.

CONCLUSION

Thermal mapping is a safe and effective adjunctive technique for the mapping and ablation of RVOT VT when sustained tolerated clinical VT cannot be induced.

Magnetic Resonance Imaging of Arrhythmogenic Right Ventricular Dysplasia

OBJECTIVES

The purpose of this study was to determine interobserver agreement for interpretation of magnetic resonance imaging (MRI) examinations of arrhythmogenic right ventricular dysplasia (ARVD) and to determine sensitivity and specificity of fat detection versus functional parameters measured by MRI.

BACKGROUND

The interobserver variability of MRI and the relative importance of different MRI parameters (fat detection, regional and global right ventricular [RV] function) for ARVD diagnosis is unknown.

METHODS

Two experienced observers blinded to the clinical history independently analyzed MRI datasets obtained from 40 patients evaluated for ARVD. Twenty normal subjects underwent MRI and served as control subjects. The MRI scans were performed according to a standard protocol on a 1.5-T scanner. The observers reported on fat infiltration, global and regional RV function, myocardial thinning, and chamber dilatation qualitatively. The RV volumes were measured on the cine sequences.

RESULTS

Interobserver kappa scores for fat infiltration, global and regional RV function, wall thinning, and RV outflow dilatation were 0.74, 0.94, 0.89, 0.93, and 0.93, respectively. Correlation coefficients between observers for RV end-diastolic volume, end-systolic volume, and ejection fraction were 0.93, 0.94, and 0.95, respectively (p < 0.001). Fifteen patients were diagnosed with ARVD using Task Force criteria. Sensitivity of fat infiltration, RV enlargement, and regional RV dysfunction for diagnosing ARVD was 84%, 68%, and 78%, and specificity was 79%, 96%, and 94%, respectively.

CONCLUSIONS

Qualitative assessment of RV structure and function is highly reproducible for experienced observers. Among the qualitative parameters, fat infiltration is less reproducible and lacks specificity compared with RV kinetic abnormalities.

Cardiovascular magnetic resonance in arrhythmogenic right ventricular cardiomyopathy revisited: comparison with task force criteria and genotype

OBJECTIVES

We sought to assess the utility of cardiovascular magnetic resonance (CMR) in the evaluation of arrhythmogenic right ventricular cardiomyopathy (ARVC) in relation to diagnostic criteria and genotype.

BACKGROUND

Timely diagnosis of ARVC is difficult as clinical findings may be subtle and nonspecific in early disease. The role of CMR is controversial owing to the absence of a standardized protocol, insufficient experience with the modality, and inherent difficulties in imaging the right ventricle.

METHODS

Comprehensive CMR examination was performed in 232 patients undergoing evaluation for suspected ARVC. CMR outcomes were compared with: 1) prospective clinical diagnosis using Task Force guidelines, with and without the proposed modifications for familial ARVC; and 2) gene-carrier status in 35 individuals from genotyped families.

RESULTS

CMR studies were positive in all 64 patients who prospectively fulfilled Task Force criteria, resulting in 100% sensitivity. Specificity in relation to Task Force criteria was low (29%). Of the 119 apparent false positives detected by CMR, however, 63 fulfilled modified diagnostic criteria for familial ARVC and 7 were obligate gene carriers, suggesting that CMR frequently identifies individuals with early disease, in whom Task Force criteria are relatively insensitive. This was borne out by evaluation of genotyped individuals (26 gene-positive and 9 gene-negative), in whom CMR had a sensitivity of 96% and a specificity of 78%.

CONCLUSIONS

CMR is a valuable component of the diagnostic workup for ARVC when performed with a dedicated protocol by specialists with experience in analysis of volumes, right ventricular wall motion, and delayed-enhancement imaging.

Serial Reevaluation for ARVD/C Is Indicated in Patients Presenting with Left Bundle Branch Block Ventricular Tachycardia and Minor ECG Abnormalities

INTRODUCTION

Diagnosis of arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is based on a set of criteria proposed by the International Task Force (TF) for Cardiomyopathies in 1994. To fulfill these criteria, presence of both electrocardiographic and anatomical abnormalities must be assessed with ECG and imaging techniques, respectively. This may be difficult in patients with early/mild forms of the disease as detectable structural abnormalities may still be absent. We evaluated in which patients presenting with right ventricular tachycardia (VT) serial reevaluation for ARVD/C is indicated.

METHODS AND RESULTS

Sixty consecutive patients (41 men, mean age 40+/-15 years) were evaluated by the TF criteria for possible ARVD/C because of presentation with a left bundle branch block (LBBB) VT, representing 1 minor criterion. The presence on the ECG of a T-wave inversion beyond lead V2 (1 minor), right precordial QRS prolongation (1 major), or an epsilon wave (1 major) was assessed together with the visualization of severe regional/global right ventricle dysfunction (1 major) or mild segmental dilatation/regional hypokinesia (1 minor) by standard imaging techniques. Initially, 22 (37%) patients were diagnosed as having ARVD/C. After 47+/-39 (range 6-146) months, 23 initially TF-negative patients were reevaluated because of recurrent symptoms, with 12 (52%) additional patients now meeting the TF criteria. Eleven of these 12 (92%) patients presented initially with ECG abnormalities only, but developed structural abnormalities on imaging at follow-up.

CONCLUSION

ECG abnormalities may precede structural abnormalities warranting serial reevaluation for ARVD/C in initially TF-negative patients presenting with LBBB VT with only ECG abnormalities.

Usefulness of magnetic resonance imaging for the diagnosis of right ventricular dysplasia in children

Cardiac magnetic resonance (CMR) has been helpful in adults in the diagnosis of arrhythmogenic right ventricular dysplasia. Short of direct surgical observation or autopsy, no gold standard exists. CMR diagnostic criteria include right atrial and ventricular dilation, regional right ventricular (RV) wall motion abnormalities, outflow tract ectasia, and myocardial fatty infiltration. To determine whether adult diagnostic criteria are useful in children referred for CMR for this diagnosis, the images and records of 81 patients (aged 11.5 +/- 5.5 years) over an 8-year period were reviewed. Histories included ventricular tachycardia, palpitations, dilated right ventricle, syncope, near sudden death, or family history of RV dysplasia. Four families were studied with parents who had RV dysplasia diagnosed by surgery, explanted heart, or CMR. CMR imaging included T1-weighted imaging, cine, 1-dimensional RV myocardial tagging, and phase-encoded velocity mapping, and 2 patients underwent delayed-enhancement CMR. Only 1 of the 81 patients met 5 of the criteria. None of the others met >2 of the criteria, and only 2 patients met 1 or 2 criteria. For questionable regional wall motion abnormalities, RV myocardial tagging was helpful. In conclusion, CMR of patients with a history suspicious for the diagnosis of RV dysplasia is a low-yield test in children. This may be due to the evolving nature of the disease, which does not manifest itself from a morphologic or ventricular-function standpoint until later in development. Follow-up studies as patients age may be advantageous.

Right ventricle shape and contraction patterns and relation to magnetic resonance imaging findings

OBJECTIVE

To analyze and to describe the shape and contraction of the normal right ventricle (RV) as visualized by magnetic resonance imaging (MRI).

METHODS

Thirty normal volunteers were imaged using cine MRI in axial, short-axis, and long-axis planes. The shape and contraction of the RV were qualitatively evaluated. Quantitative evaluation of RV shape was performed by calculating the angle subtended between the planes of horizontal long-axis view (HLA) and axial view and the RV base-to-apex distance. Multiplanar reformation was used to visualize changes between corresponding views.

RESULTS

The spectrum of major RV shape (wedge, box, and round) was more variable on axial images (17%, 43%, and 23%, respectively) than on HLA images (63%, 20%, and 0%, respectively). Focal outpouching of the RV free wall was more frequent on the axial view than on the HLA view. The subtended plane angle and base-to-apex distance showed statistically significant dependence indicative of an artificially foreshortened RV in the axial view with a direct influence on RV variations.

CONCLUSIONS

With increasing subtended angles, variation of the normal RV appearance is substantially higher on axial views compared with HLA views.

The value of magnetic resonance imaging for the diagnosis of arrhythmogenic right ventricular cardiomyopathy

This study evaluated the diagnostic significance of a magnetic resonance imaging (MRI) based scoring model for identification of arrhythmogenic right ventricular cardiomyopathy (ARVC) in patients with MRI evidence of RV abnormalities. Fifty-three patients with RV myocardial abnormalities on MRI were divided into a group with ARVC 1 (n=17) and a group with other RV arrhythmias (n=37). Decision tree learning (DTL) and linear classification (based on a modified ARVC scoring model of major and minor criteria) were used to identify and assess MRI criterion information value, and to induce ARVC diagnostic rules. All major ARVC criteria were more frequent in the ARVC group. Among minor criteria regional RV hypokinesia, mild segmental RV dilatation, and prominent trabeculae were more frequent in the ARVC group while mild global RV dilatation was more frequent in the non-ARVC group. RV aneurysm achieved highest importance in ARVC diagnosis (predictive accuracy 76.8%). Better diagnostic accuracy (sensitivity 93.3%, specificity 89.5%) was achieved when the MRI score for the major and minor criteria reached threshold value of four: two major criteria, or one major and two minor, or four minor criteria. Combinations between major and minor criteria contributed to a statistically valid model for ARVC diagnosis.

Quantification of fatty tissue mass by magnetic resonance imaging in arrhythmogenic right ventricular dysplasia

INTRODUCTION

Arrhythmogenic right ventricular dysplasia (ARVD) is a heart muscle disorder in which the pathological substrate is a fatty or fibro-fatty replacement of the right ventricular (RV) myocardium.

METHODS AND RESULTS

Magnetic resonance imaging (MRI) studies were performed in 10 patients with arrhythmogenic right ventricular dysplasia and in 24 matched controls in order to assess right ventricular epicardial/intramyocardial fatty tissue mass, RV myocardial mass, and RV functional parameters. Functional abnormalities were found in all ARVD cases. Patients with ARVD showed increased fatty tissue compared to controls (8.2 +/- 4 g vs. 2.0 +/- 1.0 g; P = 0.001), whereas no significant differences were found in RV myocardial mass (29.5 +/- 9.2 g vs. 23.2 +/- 6.7 g; P = NS). A correlation coefficient between 0.87 and 0.97 was found for repeated measurements.

CONCLUSION

Quantification of fatty tissue with MRI is feasible and constitutes an objective method for differentiating normal from pathological conditions. This approach may lead to a complete diagnostic assessment of ARVD with the potential application for monitoring the evolution of the disease.

Regional differences in systolic and diastolic function in arrhythmogenic right ventricular dysplasia/cardiomyopathy using magnetic resonance imaging

Global and regional biventricular functions were analyzed in 14 patients diagnosed with arrhythmogenic right ventricular dysplasia/cardiomyopathy using cine magnetic resonance imaging and compared with similar data from 18 age-matched controls. In this study, we report results of quantitative evaluation of biventricular global and regional function using peak ejection rate and peak filling rate as measures of systolic and diastolic function, respectively (volumetric method).

Misdiagnosis of arrhythmogenic right ventricular dysplasia/cardiomyopathy

INTRODUCTION

Diagnosis of arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) has major implications for the management of patients and their first-degree relatives. Diagnosis is based on a set of criteria proposed by the International Task Force for Cardiomyopathies. We report our experience in providing a re-evaluation for patients who previously have been diagnosed with ARVD/C.

METHODS AND RESULTS

We studied 89 patients who requested a re-evaluation for diagnosis of ARVD/C at our center. Each of these patients had been diagnosed with ARVD/C at their initial evaluation. Each patient was re-evaluated with clinical history, physical examination, and noninvasive testing at our center. Invasive testing, which included electrophysiologic testing, right ventricular angiography, and endomyocardial biopsy, was performed when clinically indicated. Sixty (92%) of the 65 patients who had undergone magnetic resonance imaging (MRI) at an outside institution were reported to have an abnormal MRI consistent with ARVD/C. Among these patients, the only abnormality identified was the qualitative finding of intramyocardial fat/wall thinning in 46 patients. On re-evaluation, these qualitative findings were not confirmed. None of these 46 patients ultimately were diagnosed with ARVD/C. Among the entire patient group, only 24 (27%) of the 89 patients met the Task Force criteria for ARVD/C.

CONCLUSION

This study demonstrates that the high frequency of "misdiagnosis" of ARVD/C is due to over-reliance on the presence of intramyocardial fat/wall thinning on MRI, incomplete diagnostic testing, and lack of awareness of the Task Force criteria. Diagnosis of ARVD/C cannot rely solely upon qualitative features on MRI.

Arrhythmogenic Right Ventricular Dysplasia: Ex Vivo and in Vivo Fat Detection with Black-Blood MR Imaging

PURPOSE

To assess electrocardiographically gated spin-echo (SE) and double inversion-recovery fast SE magnetic resonance (MR) imaging in the depiction of intramyocardial fat in cadaveric heart specimens and patients with arrhythmogenic right ventricular dysplasia (ARVD).

MATERIALS AND METHODS

A phantom was used to determine the effective in-plane spatial resolution of SE and fast SE MR imaging protocols. Two cadavers with proved ARVD were imaged with identical sequences with spectrally selected fat suppression. Contrast-to-noise ratios (CNRs) of intramyocardial fat in the right ventricle (RV) were compared by using analysis of variance and Student t test with Bonferroni correction. Eleven patients with ARVD and 10 control subjects underwent fast SE MR imaging. Two blinded readers semiquantitatively evaluated images for fat conspicuity and image quality.

RESULTS

Fast SE MR imaging achieved better spatial resolution but lower CNR than that of gated SE imaging. CNRs in cadaveric specimens were higher for double R-R than for single R-R fast SE sequences for all section thicknesses (P <.0001). Absolute CNR values were higher for fat-suppressed fast SE sequences than for those without fat suppression. Cadaveric specimens demonstrated fatty infiltration from epicardium toward endocardium of the RV free wall. Intramyocardial fat was detected in eight of 11 (73%) patients with ARVD and in no control subjects (P <.001).

CONCLUSION

Intramyocardial fat detection in ARVD was better with fast SE MR imaging alone and combined with fat suppression than was gated SE MR imaging. When fast SE imaging is applied in vivo, however, breath-holding constraints limit the spatial resolution for RV fat detection.

Relative utility of magnetic resonance imaging and right ventricular angiography to diagnose arrhythmogenic right ventricular cardiomyopathy

INTRODUCTION

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by fibrofatty replacement of the RV myocardium. Two imaging techniques used to assess patients suspected of having ARVC are magnetic resonance imaging (MRI) and right ventricular angiography (RVA). Traditionally, RVA has played a central role in the diagnosis of ARVC, but the non-invasive nature of MRI and its unique ability to detect fatty tissue infiltration has increased its popularity as a diagnostic tool. The objective of this study was to assess the relative diagnostic accuracy of MRI and RVA for ARVC.

METHODS AND RESULTS

Seventeen patients (9 men, 8 women; ages 42 +/- 17 [range 16-78] years) with documented ventricular arrhythmias were investigated for ARVC. A positive diagnosis of ARVC was based on criteria set forth by the ISFC Working Group on Cardiomyopathies and Dysplasia. ECG-gated spin-echo and gradient-echo MR images in multiple planes and RAO/LAO RV angiograms were compared for diagnostic concordance. Based on working group criteria, 7 patients were diagnosed with ARVC. In ten patients, MRI suggested ARVC. The remaining 7 patients had no MRI findings suggestive of the disease. Four patients with MRI findings of ARVC were incorrectly diagnosed based on Task Force criteria. Conversely, 1 patient with a normal MRI met Task Force criteria for the diagnosis of ARVC. Based on RV angiograms, 7 patients had findings suggestive of ARVC. The 10 patients without AVRD (based on RVA) also did not meet the necessary criteria for diagnosis of ARVC using Task Force standards. RVA was 100% specific and 100% sensitive compared to MRI that was only 86% sensitive and 60% specific. MRI proved to be most reliable when the images demonstrated gross, lipomatous infiltration, evidenced by a large area of hyperintensity. When the results of MRI and RVA were congruent, the diagnosis was always accurate.

CONCLUSION

RVA is more sensitive and specific to diagnose ARVC diagnosis than MRI, at least until MRI protocols are better developed. MRI results are most robust when indicators of ARVC are grossly apparent. False-positive diagnosis by MRI was primarily related to perceived motion abnormalities that were not seen by RVA. One of its greatest potential assets (fat detection) did not enhance diagnostic specificity.

Arrhythmogenic right ventricular cardiomyopathy: diagnostic and prognostic value of the cardiac MRI in relation to arrhythmia-free survival

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a potentially fatal disease, which is often difficult to diagnose. As a non-invasive test cardiac magnetic resonance imaging (CMR) has become an important tool in establishing the diagnosis. The aim of this study was to evaluate the diagnostic and prognostic value of CMR in patients with suspected ARVC and to assess the long-term outcome of patients with CMR-diagnosed ARVC. Thirty-six patients with suspected ARVC (26 male, 10 female, median age 41 years) underwent non-invasive and invasive clinical tests as gold standard for ARVC diagnosis. ARVC was clinically diagnosed in 19 patients and excluded in 17 patients. Both groups underwent CMR, and diagnosis was confirmed by CMR in 16/18 patients with clinically diagnosed ARVC (sensitivity 89%), and correctly excluded in 14/17 of patients with clinically excluded ARVC (specificity 82%). This result indicates a positive predictive value of the CMR of 84%, and a negative predictive value of 88%, respectively (p < 0.0001). Using a scoring system, multiple CMR parameters were compared in the two groups in regard of the clinical diagnosis. By univariate analysis, right ventricular fatty tissue infiltration (p = 0.0003) was predictive for diagnosis. Compared by outcome, 37% of patients with clinically and by CMR-diagnosed ARVC had an arrhythmic event during a mean follow-up of 16 +/- 11 months. These data suggest that CMR is a highly sensitive and specific method to diagnose or exclude ARVC, and thus, has an important prognostic impact on predicting arrhythmia free survival.

Value of fat suppression in the MRI evaluation of suspected arrhythmogenic right ventricular dysplasia

OBJECTIVE

Arrhythmogenic right ventricular dysplasia (ARVD) is characterized by intramyocardial fibrofatty change. Fat suppression performed during conventional spin-echo imaging has been used to confirm fatty infiltration. The utility of fat suppression for enhancing the interpretation of studies of suspected ARVD has not previously been formally tested. We investigated the value of fat suppression for enhancing the interpretation of intramyocardial fatty infiltration.

MATERIALS AND METHODS

Twenty-six consecutive patients clinically referred for evaluation of possible ARVD underwent cardiac MRI. Two independent observers reviewed the images retrospectively. Intramyocardial areas (n = 101) that had increased signal intensity relative to normal surrounding myocardium on T1-weighted conventional spin-echo images ("index areas") were identified. The index areas were interpreted for presence of fatty infiltration using two sets of images: The first set was obtained without fat suppression, and the second set was obtained with fat suppression. Agreement between reviewers and confidence of interpretation were determined and compared.

RESULTS

Interobserver agreement was measured using a 5-point scale: 1, definitely not fat; 2, probably not fat; 3, equivocal; 4, probably fat; and 5, definitely fat. The resulting kappa values were 0.35 for non-fat-suppressed images and 0.55 for fat-suppressed images. Interobserver kappa increased from 0.67 without fat suppression to 0.90 with fat suppression using a 3-point scale: 1, not fat; 2, equivocal; and 3, fat. Confidence in the diagnosis increased from 7.2 without fat suppression to 8.8 with fat suppression (p < 0.0001) on a 10-point scale ranging from 1, not confident, to 10, very confident.

CONCLUSION

The use of fat-suppressed in addition to non-fat-suppressed conventional T1-weighted spin-echo imaging increased interobserver agreement and confidence in diagnosis and evaluation of intramyocardial fatty infiltration in patients who were suspected to have ARVD.

IRM et dysplasie arythmogène du ventricule droit (DAVD)

PURPOSE

To retrospectively evaluate the contribution of MRI to the diagnosis of arrhythmogenic right ventricular dysplasia (ARVD).

PATIENTS AND METHODS

Thirty two men and 18 women (mean age: 48.7 years) were imaged using gated spin echo scans and short axis cine MR. References were McKenna criteria (gold standard), and also what we called "strong presumption" which may correspond to early or localized patterns, but correspond to negative McKenna scores.

RESULTS

One patient was claustrophobic; another one was lost to follow-up. In reference to McKenna score, diagnosis of ARVD was established in 12 patients (2 of whom had familial dilated biventricular cardiomyopathy with rhythmic expression). Sensitivity, specificity, positive predictive value, negative predictive value and prevalence were respectively: 75%, 75%, 50%, 90% and 25%. Using "strong presumption" criteria, we observed 14 true positives (with sensitivity of 82%, specificity of 87%, PPV of 78%, NPV of 90% and prevalence of 35%).

CONCLUSION

In our group, MRI was always performed before angiography. In our series, right ventricular wall T1W hyperintensity was the most frequent finding.

Magnetic resonance and computed tomography imaging of arrhythmogenic right ventricular dysplasia

Arrhythmogenic right ventricular dysplasia (ARVD) is a familial cardiomyopathy that causes fibro-fatty replacement of the right ventricle (RV), leading to sudden death due to ventricular arrhythmias. The disease is an important cause of sudden death in individuals younger than 35 years of age. Structural and functional abnormalities of the RV constitute an important diagnostic criterion for the disease. Diagnosis of ARVD is often a challenge as conventional imaging modalities have significant limitations to visualize the RV. Recently, magnetic resonance imaging (MRI) and computed tomographic (CT) imaging have emerged as robust clinical tools for evaluation of myocardial pathology. In addition to providing morphologic and functional information, both imaging modalities have the ability to demonstrate intramyocardial fat, which is the pathological hallmark in ARVD. This article discusses the current status and role of MRI and CT imaging in the diagnosis of ARVD.

MR Imaging of arrhythmogenic right ventricular cardiomyopathy: morphologic findings and interobserver reliability

BACKGROUND

Magnetic resonance (MR) imaging is frequently used to diagnose arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D). However, the reliability of various MR imaging features for diagnosing ARVC/D is unknown. The purpose of this study was to determine which morphologic MR imaging features have the greatest interobserver reliability for diagnosing ARVC/D.

METHODS

Forty-five sets of films of cardiac MR images were sent to 8 radiologists and 5 cardiologists with experience in this field. There were 7 cases of definite ARVC/D as defined by the Task Force criteria. Six cases were controls. The remaining 32 cases had MR imaging because of clinical suspicion of ARVC/D. Readers evaluated the images for the presence of (a) right ventricle (RV) enlargement, (b) RV abnormal morphology, (c) left ventricle enlargement, (d) presence of high T(1) signal (fat) in the myocardium, and (e) location of high T(1) signal (fat) on a Likert scale with formatted responses.

RESULTS

Readers indicated that the Task Force ARVC/D cases had significantly more (chi(2) = 119.93, d.f. = 10, p < 0.0001) RV chamber size enlargement (58%) than either the suspected ARVC/D (12%) or no ARVC/D (14%) cases. When readers reported the RV chamber size as enlarged they were significantly more likely to report the case as ARVC/D present (chi(2)(= )33.98, d.f. = 1, p < 0.0001). When readers reported the morphology as abnormal they were more likely to diagnose the case as ARVC/D present (chi(2) = 78.4, d.f. = 1, p < 0.0001), and the Task Force ARVC/D (47%) cases received significantly more abnormal reports than either suspected ARVC/D (20%) or non-ARVC/D (15%) cases. There was no significant difference between patient groups in the reported presence of high signal intensity (fat) in the RV (chi(2) = 0.9, d.f. = 2, p > 0.05).

CONCLUSIONS

Reviewers found that the size and shape of abnormalities in the RV are key MR imaging discriminates of ARVD. Subsequent protocol development and multicenter trials need to address these parameters. Essential steps in improving accuracy and reducing variability include a standardized acquisition protocol and standardized analysis with dynamic cine review of regional RV function and quantification of RV and left ventricle volumes.

Magnetic resonance imaging of primary cardiomyopathies

Cardiomyopathies are diseases of the myocardium of unknown etiology associated with cardiac dysfunction. On the grounds of their morphology and pathophysiology, primary or idiopathic cardiomyopathies may be classified into a number of disorders; namely, hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy, and restrictive cardiomyopathy. The term "secondary cardiomyopathies" is reserved to specific heart muscle diseases clinically very similar to primary cardiomyopathies. Cardiac magnetic resonance imaging has long been used to study cardiac morphology and, more recently, to assess blood flow, perfusion, and contractile function. The emerging role of magnetic resonance imaging for the understanding and treatment of primary cardiomyopathies cannot be underestimated. From a clinical point of view, an examination based on a single, efficient, and noninvasive MR study focusing on the clinically relevant features of cardiomyopathies is an objective and reproducible means for diagnosing and monitoring hypertrophic, arrhythmogenic, dilated, and restrictive cardiomyopathies.

Prediction rule for diagnosis of arrhythmogenic right ventricular dysplasia based on wall thickness measured on MR imaging

MRI is seeing an increasing role in the evaluation of suspected arrhythmogenic right ventricular dysplasia (ARVD). Our aims were to establish wall thickness criteria for diagnosis of ARVD based on MR imaging measurements. A cross-sectional case-control retrospective study of 21 cardiac MR exams over a 3 year period identified five patients (two men, three women) of average age 43 years (range 36-48) who were diagnosed with ARVD and 16 patients (nine men, seven women) of average age 52 years (range 25-78) who were diagnosed with normal right ventricular wall motion. Patient demographic characteristics (age, sex) and right ventricular free wall thickness (RVFWT) were evaluated for predictive ability. Calculated RVFWT was (mean+/-SD, in mm); (4.4+/-1.4) for ARVD, and (7.8+/-2.9), controls with P<0.001. Logistic regression analysis indicated that sex and age were not significant independent predictors (P>0.05). RVFWT allowed for a prediction rule with Area under the receiver operator curve of 0.94 to be generated. In our study, measurement of the thickness of the right ventricular free wall using cardiac-gated MRI proved to be a statistically significant predictor of ARVD.

MRI assessment of right ventricular dysplasia

Right ventricular dysplasia is a new entity of unknown origin in the classification of cardiomyopathies. Also known as arrhythmogenic right ventricular cardiomyopathy (ARVC) or arrhythmogenic right ventricular dysplasia, it is a disease of the heart muscle characterised by fibroadipose atrophy mainly involving the right ventricle and responsible for severe ventricular arrhythmias and sudden death also in young people. Magnetic resonance imaging provides evidence of ventricular dilatation at the outflow tract, thinning and thickening of the wall, diastolic bulging areas (especially located at the level of the right ventricle outflow tract) and fatty substitution of the myocardium mainly at the level of the right ventricle. Many radiologists erroneously consider the previously described fatty substitution as the main sign of ARVC, even though an evaluation of fat substitution alone may be a source of error for two reasons: firstly, because isolated areas of fatty replacement are not synonymous with ARVC since small non-transmural focal fatty areas of fat are also present in the normal patients; and secondly, because the MRI detection of fat may be overestimated due to partial-volume artefacts with normal subepicardial fat. Cardiac MRI can also be employed for the diagnosis of idiopathic right ventricular outflow tract tachycardia. Considering the evolutive nature of the disease, the non-invasiveness of MRI allows the follow-up of these patients and may be considered an excellent screening modality for the diagnosis of ARVC in family members. Finally, MRI can be employed in electrophysiological studies to locate the arrhythmogenic focus and reduce sampling errors.

Magnetic resonance imaging findings in patients meeting task force criteria for arrhythmogenic right ventricular dysplasia

INTRODUCTION

Magnet resonance imaging (MRI) findings in patients meeting Task Force criteria for the diagnosis of arrhythmogenic right ventricular dysplasia (ARVD) have not been systematically described. We report qualitative and quantitative MRI findings in ARVD using state-of-the-art MRI.

METHODS AND RESULTS

MRI was performed on 12 patients with ARVD who were prospectively diagnosed using the Task Force criteria. The imaging protocol included breath-hold double inversion recovery spin-echo and gradient-echo images. Ventricular volumes and dimensions were compared to 10 age- and sex-matched normal volunteers. High intramyocardial T1 signal similar to fat signal was observed in 9 (75%) of the 12 patients and in none of the controls. Right ventricular (RV) hypertrophy was seen in 5 (42%) patients, trabecular disarray in 7 (59%), and wall thinning in 3 (25%). Both the RV end-diastolic diameter and the outflow tract area were significantly higher in ARVD patients compared to controls (51.2 vs 43.2 mm, P < 0.01; and 14.5 vs 9.3 cm2, P < 0.01, respectively). ARVD patients had a higher RV end-diastolic volume index and lower RV ejection fraction compared with controls (127.4 vs 87.5, P < 0.01; and 41.6% vs 57%, P < 0.01, respectively).

CONCLUSION

High intramyocardial T1 signal indicative of fat is seen in a high percentage (75%) of patients who meet the Task Force criteria for ARVD. Trabecular disarray is seen more frequently than wall thinning and aneurysms. RV dimensions and volumes differ significantly in ARVD compared to controls, indicating a role for quantitative evaluation in the diagnosis of ARVD.

MR evaluation of arrhythmogenic right ventricular cardiomyopathy in pediatric patients

OBJECTIVE

The aim of our study was to correlate the findings of three MR imaging sequences with the clinical findings of possible arrhythmogenic right ventricular cardiomyopathy in pediatric patients.

MATERIALS AND METHODS

Twenty-six consecutive pediatric patients underwent MR imaging with ECG-gated non-breath-hold spin-echo T1-weighted non-fat-suppressed and fat-suppressed sequences. The MR images were evaluated for thinning or fat signal in the right ventricular wall and for enlargement or increased trabeculation of the right ventricle or right ventricular outflow tract. Cine MR imaging was used to assess wall motion abnormalities. Cardiac biopsy was performed in 17 patients. Biopsy results and other clinical findings suggesting arrhythmogenic right ventricular cardiomyopathy were tabulated.

RESULTS

Two MR imaging studies were of poor quality as a result of arrhythmias, and one study was incomplete. In the 23 remaining patients, there were (mean +/- SD) 1.5 +/- 1.0 and 0.8 +/- 1.0 findings of possible arrhythmogenic right ventricular cardiomyopathy in the non-fat-suppressed and the fat-suppressed sequences, respectively. Fat-compatible signal in the myocardium was detected in 16 (70%) of 23 non-fat-suppressed studies and in five (22%) of 23 fat-suppressed studies (p = 0.003). The non-fat-suppressed sequence had a higher sensitivity (75% vs 43%) and a lower specificity (38% vs 75%) for fatty infiltration than did the fat-suppressed sequence when correlated with the biopsies. The linear correlation between all MR findings and all clinical diagnostic criteria, including biopsy, was better for the combination of cine and both T1 sequences (r = 0.58) than for the non-fat-suppressed (r = 0.53) or fat-suppressed (r = 0.46) T1 sequences alone.

CONCLUSION

MR imaging showed moderate correlation with the clinical criteria in the diagnosis of arrhythmogenic right ventricular cardiomyopathy.

MR imaging of arrhythmogenic right ventricular dysplasia

MR imaging is helpful in the management of patients in whom the diagnosis of ARVD or RVOTT is suspected. Careful attention to cardiac rate control will minimize or eliminate ventricular extrasystolic beats during examination, which will improve image quality and confidence in diagnosis. Use of thin-section cine gradient echo acquisition provides a means of identifying regional wall motion abnormalities, characteristic of the regional dysfunction in these diseases. Furthermore, application of spin echo or double inversion recovery imaging may provide visualization of abnormally thin or fat-infiltrated regions of right ventricular free wall myocardium, providing additional diagnostic criteria for the diagnosis of these diseases.

Diagnosis of arrhythmogenic right ventricular dysplasia: a review

Arrhythmogenic right ventricular dysplasia (ARVD) is a myocardial disorder of primarily the right ventricle, with unknown cause and prevalence and with a frequent familial occurrence. The typical clinical manifestation consists of ventricular arrhythmias with a left bundle branch block (LBBB) pattern that occur predominantly in young adults. ARVD may result in sudden death. Other manifestations are electrocardiographic repolarization and depolarization changes, structural abnormalities that range from subtle wall aneurysms within the so-called "triangle of dysplasia" to biventricular regional or global dysfunction, and localized or widespread fibrofatty infiltration of the right ventricular myocardium. The diagnosis of ARVD is based on the presence of major and minor criteria encompassing genetic, electrocardiographic, pathophysiologic, and histopathologic factors. The imaging modalities used to evaluate right ventricular abnormalities include conventional angiography, echocardiography, radionuclide angiography, ultrafast computed tomography, and magnetic resonance (MR) imaging. Among these techniques, MR imaging allows the clearest visualization of the heart. Because MR imaging depicts both functional and structural abnormalities, positive MR imaging findings should be used as important additional criteria in the clinical diagnosis of ARVD. MR imaging appears to be the optimal technique for detection and follow-up of clinically suspected ARVD.

MR imaging of arrhythmogenic right ventricular dysplasia

Arrhythmogenic right ventricular displasia (ARVD) is a heart disease characterized by a total or partial fat replacement of the myocardium. Echocardiography, which has been most commonly used for the diagnosis of ARVD, usually only demonstrates right ventricular enlargement with associated hypokinesia and with normal left ventricular chamber size. Angiocardiography is very effective in the evaluation of ARVD, especially, in the detection of wall motion abnormalities and bulgings. However, angiocardiography is invasive. Magnetic resonance imaging is a non-invasive, repeatable technique, which allows a more accurate evaluation of the right ventricular chamber and free wall. Therefore MRI is very effective in the differentiation of the high signal intensity of the fat from other medium intensity tissue, such as muscle, and in detection of fibro-fatty replacement of myocardium. It provides an accurate assessment of right-chamber enlargement, right ventricle outflow tract ectasia and wall motion abnormalities by cine-MR GE technique.