Usefulness of India ink artifact in steady-state free precession pulse sequences for detection and quantification of intramyocardial fat

Role of Cine-Magnetic Resonance Imaging in the Assessment of Mediastinal Masses with Uncertain/Equivocal Findings from Pre-Operative Computed Tomography Scanning

BACKGROUND

Malignant neoplasms originating from or involving the mediastinum represent a diagnostic and therapeutic challenge when they are in contact with nearby cardiovascular structures. We aimed to test the diagnostic accuracy of cine-magnetic resonance imaging (cine-MRI) in detecting the infiltration of cardiovascular structures in cases with uncertain or equivocal findings from contrast-enhanced Computed Tomography (CT) scanning.

METHODS

Fifty patients affected by tumors with a suspected invasion of mediastinal cardiovascular structures at the pre-operative chest CT scan stage underwent cine-MRI before surgery at our Institution. Intraoperative findings and the histological post-surgical report were used as a reference standard to define infiltration. Inter- and intra-observer agreement for CT scans and cine-MRI were also computed over a homogenous sample of 14 patients.

RESULTS

Cine-MRI had a higher negative predictive value (93% vs. 54%, p < 0.001) than CT scans, higher sensitivity (91% vs. 16%, p < 0.001), as well as greater accuracy (66% vs. 50%, p < 0.001) in detecting cardiovascular invasion. Cine-MRI also showed better inter- and intra-observer agreement for infiltration detection.

CONCLUSIONS

Cine-MRI outperforms conventional contrast-enhanced chest CT scans in the preoperative assessment of cardiovascular infiltration by mediastinal or pulmonary tumors, making it a useful imaging modality in the preoperative staging and evaluation of patients with equivocal findings at the chest CT scan stage.

Noninvasive Assessment of Lipomatous Metaplasia as a Substrate for Ventricular Tachycardia in Chronic Infarct

Myocardial lipomatous metaplasia (LM) has been increasingly reported in patients with prior myocardial infarction. Cardiac magnetic resonance and cardiac contrast-enhanced computed tomography have been used to noninvasively detect and quantify myocardial LM in postinfarct patients, and may provide useful information for understanding cardiac mechanics, arrhythmia susceptibility, and prognosis. This review aims to summarize the advantages and disadvantages, clinical applications, and imaging features of different cardiac magnetic resonance sequences and cardiac contrast-enhanced computed tomography for LM detection and quantification. We also briefly summarize LM prevalence in different cohorts of postinfarct patients and review the clinical utility of cardiac imaging in exploring myocardial LM as an arrhythmogenic substrate in patients with prior myocardial infarction.

Cardiac Masses Discovered by Echocardiogram; What to Do Next?

Cardiac tumors are rare conditions, typically diagnosed on autopsy, but with the advancement of imaging techniques they are now encountered more frequently in clinical practice. Echocardiography is often the initial method of investigation for cardiac masses and provides a quick and valuable springboard for their characterization. While some cardiac masses can be readily identified by echocardiography alone, several require incorporation of multiple data points to reach diagnostic certainty. Herein, we will provide an overview of the main clinical, diagnostic, and therapeutic characteristics of cardiac masses within the framework of their location.

Assessment of myocardial lipomatous metaplasia using an optimized out-of-phase cine steady-state free-precession sequence: Validation and clinical implementation

Myocardial lipomatous metaplasia, which can serve as substrate for ventricular arrhythmias, is usually composed of regions in which there is an admixture of fat and nonfat tissue. Although dedicated sequences for the detection of fat are available, it would be time-consuming and burdensome to routinely use these techniques to image the entire heart of all patients as part of a typical cardiac MRI exam. Conventional steady-state free-precession (SSFP) cine imaging is insensitive to detecting myocardial regions with partial fatty infiltration. We developed an optimization process for SSFP imaging to set fat signal consistently "out-of-phase" with water throughout the heart, so that intramyocardial regions with partial volume fat would be detected as paradoxically dark regions. The optimized SSFP sequence was evaluated using a fat phantom, through simulations, and in 50 consecutive patients undergoing clinical cardiac MRI. Findings were validated using standard Dixon gradient-recalled-echo (GRE) imaging as the reference. Phantom studies of test tubes with diverse fat concentrations demonstrated good agreement between measured signal intensity and simulated values calculated using Bloch equations. In patients, a line of signal cancellation at the interface between myocardium and epicardial fat was noted in all cases, confirming that SSFP images were consistently out-of-phase throughout the entire heart. Intramyocardial dark regions identified on out-of-phase SSFP images were entirely dark throughout in 33 patients (66%) and displayed an India-ink pattern in 17 (34%). In all cases, dark intramyocardial regions were also seen in the same locations on out-of-phase GRE and were absent on in-phase GRE, confirming that these regions represent areas with partial fat. In conclusion, if appropriately optimized, SSFP cine imaging allows for consistent detection of myocardial fatty metaplasia in patients undergoing routine clinical cardiac MRI without the need for additional image acquisitions using dedicated fat-specific sequences.

Prognostic Cardiac Magnetic Resonance Markers of Left Ventricular Involvement in Arrhythmogenic Cardiomyopathy for Predicting Heart Failure Outcomes

Background

Left ventricular (LV) involvement is frequently observed in arrhythmogenic cardiomyopathy (ACM). We investigated the association of LV myocardial assessment using cardiac magnetic resonance (CMR) with clinical outcomes including heart failure (HF)‐related events in ACM.

Methods and Results

We retrospectively analyzed 60 patients with ACM between 2005 and 2020 according to the 2010 Task Force Criteria and assessed HF‐related events (HF hospitalization, heart transplantation, and cardiac death) and ventricular tachycardia events. We analyzed CMR findings including late gadolinium enhancement (LGE) in all subjects and obtained mapping values (native T1, extracellular volume, and T2) on 30 (50%) patients out of them. Among the study population (mean age 49 years, 77% male), 41 (68%) patients had LV LGE. During a median follow‐up of 34 months, there were 13 (22%) HF‐related events, and 20 (30%) ventricular tachycardia events. Kaplan‐Meier survival analysis revealed that HF‐related events occurred only in patients with LV LGE (+) (versus LV LGE (‐), log‐rank P=0.006), and the events were not significantly different regarding right ventricular LGE (log‐rank P>0.999). When categorized by median value for each mapping parameter, HF‐related events occurred more in patients with higher native T1 (versus lower native T1, log‐rank P=0.002), and higher T2 (versus lower T2, log‐rank P=0.002), higher extracellular volume (versus lower extracellular volume, log‐rank P=0.002). However, regarding ventricular tachycardia events, there were no significant differences according to these CMR markers.

Conclusions

LV myocardial assessment using CMR with LGE imaging and native T1, T2, and extracellular volume markers were significantly associated with HF‐related event risk in patients with ACM.

Lipomatous hypertrophy of the interatrial septum: A case report and insights from the literature

Lipomatous hypertrophy of the interatrial septum (LHIS) is a histologically benign cardiac lesion that is defined by excessive fat accumulation in the area of the interatrial septum (IAS) that does not include the fossa ovalis. Another unusual illness is lipomatosis, which is defined as a broad overgrowth of mature adipose tissue that involves a large portion of an extremity or trunk. We describe a rare case with significant LHIS accompanied by subcutaneous lipomatosis. Echocardiography revealed a mass in the right atrium in this patient. Magnetic resonance imaging revealed that this mass was composed of the adipose tissue and was an extension of a huge thickened IAS. Furthermore, this significant hypertrophy of the IAS was in direct continuation with the excessive mediastinal and epicardial fat.

Oxidized LDL-dependent pathway as new pathogenic trigger in arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is hallmarked by ventricular fibro-adipogenic alterations, contributing to cardiac dysfunctions and arrhythmias. Although genetically determined (e.g., PKP2 mutations), ACM phenotypes are highly variable. More data on phenotype modulators, clinical prognosticators, and etiological therapies are awaited. We hypothesized that oxidized low-density lipoprotein (oxLDL)-dependent activation of PPARγ, a recognized effector of ACM adipogenesis, contributes to disease pathogenesis. ACM patients showing high plasma concentration of oxLDL display severe clinical phenotypes in terms of fat infiltration, ventricular dysfunction, and major arrhythmic event risk. In ACM patient-derived cardiac cells, we demonstrated that oxLDLs are major cofactors of adipogenesis. Mechanistically, the increased lipid accumulation is mediated by oxLDL cell internalization through CD36, ultimately resulting in PPARγ upregulation. By boosting oxLDL in a Pkp2 heterozygous knock-out mice through high-fat diet feeding, we confirmed in vivo the oxidized lipid dependency of cardiac adipogenesis and right ventricle systolic impairment, which are counteracted by atorvastatin treatment. The modulatory role of oxidized lipids on ACM adipogenesis, demonstrated at cellular, mouse, and patient levels, represents a novel risk stratification tool and a target for ACM pharmacological strategies.

Oxidative stress and inflammation: determinants of anthracycline cardiotoxicity and possible therapeutic targets

Chemotherapy with anthracycline-based regimens remains a cornerstone of treatment of many solid and blood tumors but is associated with a significant risk of cardiotoxicity, which can manifest as asymptomatic left ventricular dysfunction or overt heart failure. These effects are typically dose-dependent and cumulative and may require appropriate screening strategies and cardioprotective therapies in order to minimize changes to anticancer regimens or even their discontinuation. Our current understanding of cardiac damage by anthracyclines includes a central role of oxidative stress and inflammation. The identification of these processes through circulating biomarkers or imaging techniques might then be helpful for early diagnosis and risk stratification. Furthermore, therapeutic strategies relieving oxidative stress and inflammation hold promise to prevent heart failure development or at least to mitigate cardiac damage, although further evidence is needed on their efficacy, either alone or as part of combination therapies with neurohormonal antagonists, which are the current adopted standard.

Left ventricular fibro-fatty replacement in arrhythmogenic right ventricular dysplasia/cardiomyopathy: prevalence, patterns, and association with arrhythmias

BACKGROUND

Left ventricular (LV) fibrofatty infiltration in arrhythmogenic right ventricular (RV) dysplasia/cardiomyopathy (ARVD/C) has been reported, however, detailed cardiovascular magnetic resonance (CMR) characteristics and association with outcomes are uncertain. We aim to describe LV findings on CMR in ARVD/C patients and their relationship with arrhythmic outcomes.

METHODS

CMR of 73 subjects with ARVD/C according to the 2010 Task Force Criteria (TFC) were analyzed for LV involvement, defined as ≥ 1 of the following features: LV wall motion abnormality, LV late gadolinium enhancement (LGE), LV fat infiltration, or LV ejection fraction (LVEF) < 50%. Ventricular volumes and function, regional wall motion abnormalities, and the presence of ventricular fat or fibrosis were recorded. Findings on CMR were correlated with arrhythmic outcomes.

RESULTS

Of the 73 subjects, 50.7% had CMR evidence for LV involvement. Proband status and advanced RV dysfunction were independently associated with LV abnormalities. The most common pattern of LV involvement was focal fatty infiltration in the sub-epicardium of the apicolateral LV with a "bite-like" pattern. LGE in the LV was found in the same distribution and most often had a linear appearance. LV involvement was more common with non-PKP2 genetic mutation variants, regardless of proband status. Only RV structural disease on CMR (HR 3.47, 95% CI 1.13-10.70) and prior arrhythmia (HR 2.85, 95% CI 1.33-6.10) were independently associated with arrhythmic events.

CONCLUSION

Among patients with 2010 TFC for ARVD/C, CMR evidence for LV abnormalities are seen in half of patients and typically manifest as fibrofatty infiltration in the subepicardium of the apicolateral wall and are not associated with arrhythmic outcomes.

The Role of Cardiovascular Magnetic Resonance in ARVC

PURPOSE OF REVIEW

Aim of the paper was to address all strengths and weakness of cardiac magnetic resonance (CMR) in arrhythmogenic cardiomyopathy, trying to highlight areas where further research and investigations should be carried out to fill current gaps in scientific knowledge.

RECENT FINDINGS

Arrhythmogenic cardiomyopathy represents a multifaceted clinical entity associated with arrhythmias and sudden death. Even though different diagnostic tools are available for appropriate identification and risk stratification, over the last few years cardiac magnetic resonance (CMR) has surfaced as an unmatched non-invasive imaging tool. CMR is mandatory in the evaluation of arrhythmogenic cardiomyopathy. It is the only imaging technique providing the identification of myocardial fibrosis, particularly for left ventricular myocardium, as recent evidences demonstrated that left ventricular involvement in arrhythmogenic cardiomyopathy is associated with greater risk of sudden death than lone right ventricular involvement.

Prognostic Role of Left Ventricular Intramyocardial Fatty Metaplasia in Patients With Previous Myocarditis (MYOFAT Study)

Left ventricular intramyocardial fat (LV-IMF) is often found in patients with previous irreversible myocardial damage and may be detected by cardiac magnetic resonance (CMR). No data are currently available about the prevalence of LV-IMF in patients with previous myocarditis. Our aim was to assess the prevalence of LV-IMF in patients with previous myocarditis by repeating after >3 years a follow-up CMR examination and to evaluate its clinical and prognostic role. Patients with clinical suspected myocarditis who underwent CMR within the first week from the onset of their symptoms and underwent repeated CMR were enrolled. LV-IMF was detected as areas of left ventricular intramyocardial "India ink" black boundary with or without a hyperintense core. Overall, in 235 patients with a definitive diagnosis of acute myocarditis, CMR was repeated after a median of 4 (3 to 6) years from symptom onset. LV-IMF positive patients (n = 35, 15%) presented greater ventricular volumes and more frequently a mid-wall late gadolinium enhancement than those without LV-IMF (both p < 0.05). Patients presenting major cardiac events (sudden cardiac deaths, resuscitated cardiac arrest, and appropriate implantable cardioverter-defibrillator-firing) at follow-up had a greater prevalence of LV-IMF than those without (55% vs 11%, p < 0.001). Patients with LV-IMF had a higher incidence myocarditis relapse (27% vs 9%, p = 0.003) and a greater risk of major cardiac events (p < 0.0001) than those without. At logistic regression analysis, LV-IMF was an independent predictor of major cardiac events. In conclusion, LV-IMF is not an uncommon finding in patients with previous myocarditis and is associated with worse ventricular remodeling and prognosis.

The Role of MRI in Prognostic Stratification of Cardiomyopathies

PURPOSE OF THE REVIEW

The aim of this review was to discuss the role of cardiac magnetic resonance (CMR) for the prognostic stratification of cardiomyopathies, highlighting strengths and limitations.

RECENT FINDINGS

CMR is considered as a diagnostic pillar in the management of non-ischemic cardiomyopathies. Over the last years, attention has shifted from CMR's diagnostic capability towards prognostication in the various settings of cardiomyopathies. CMR is considered the gold standard imaging technique for the evaluation of ventricular volumes and systolic function as well as providing non-invasive virtual-histology by means of specific myocardial tissue characterization pulse sequences. CMR is an additive tool to risk stratifying patients and to identify those that require strict monitoring and more aggressive treatment.

Diagnostic and prognostic role of cardiac magnetic resonance in acute myocarditis

Acute myocarditis (AM) is commonly found in everyday clinical practice. Differential diagnosis between various causes of myocardial damage with non-obstructive coronary arteries can be cumbersome for clinician. Moreover, AM may be provoked by a number of different causes and clinical presentation can be heterogeneous with potential overlap going from asymptomatic or subclinical to severe heart failure, arrhythmias, and death. Cardiac magnetic resonance (CMR) over the last decades has proven to be the diagnostic technique of choice since it allows identifying AM with excellent diagnostic accuracy. Latest technological advancement with parametric imaging such as T1 and T2 mapping further increases sensitivity and provides additional help towards a correct diagnosis. CMR however is no longer to be considered as a mere diagnostic tool but also as a powerful source of prognostic information. Scientific evidence has corroborated CMR's role beyond diagnosis demonstrating how late gadolinium enhancement (LGE) presence is a powerful predictor of cardiac events and how the presence of septal LGE is to be considered of worst prognosis regardless of LGE extension even in patients with preserved global systolic function. CMR should be routinely performed in all patients with AM suspicion since its diagnostic and prognostic role is of paramount important and could modify therapeutic strategy and subsequent clinical decisions.

Cardiovascular immune-related adverse events: Evaluation, diagnosis and management

Cardiotoxicities are associated with immune checkpoint inhibitor (ICI) therapy. Recent case series and retrospective studies have shown that cardiac immune‐related adverse events (irAEs) are rare but potentially fatal complications of immunotherapy, with various underlying risk factors such as combinations of different ICIs. High mortality rates and overreactive inflammation have been observed with ICI‐associated cardiotoxicities, highlighting the necessity of baseline and serial evaluations and the identification and management of cardiac irAEs as early as possible. The clinical presentations of irAEs range from asymptomatic cardiac biomarker elevation, myocarditis and pericardial diseases to heart failure and mild to fatal arrhythmia. Troponin measurement and electrocardiogram are sensitive initial tests, whereas cardiac magnetic resonance imaging and endomyocardial biopsy are both gold standard components of the diagnostic criteria. Close monitoring and timely consultation with a cardiologist are important for the diagnosis of ICI‐related cardiotoxicities, with decisions of stopping or rechallenging ICIs and strategies to manage heart injuries. Treatment principles are made according to risk stratifications. The first‐line medication is glucocorticoids of various doses, and the second‐line immunosuppression includes intravenous immunoglobin, antithymocyte globulin and other immunosuppressants, which are recommended in life‐threatening cases or in cases of resistance/no response to steroids.

Postmortem cardiac magnetic resonance in sudden cardiac death

Postmortem imaging is increasingly used in forensic practice as good complementary tool to conventional autopsy investigations. Over the last decade, postmortem cardiac magnetic resonance (PMCMR) imaging was introduced in forensic investigations of natural deaths related to cardiovascular diseases, which represent the most common causes of death in developed countries. Postmortem CMR application has yielded interesting results in ischemic myocardium injury investigations and in visualizing other pathological findings in the heart. This review presents the actual state of postmortem imaging for cardiovascular pathologies in cases of sudden cardiac death (SCD), taking into consideration both the advantages and limitations of PMCMR application.

Prognostic Role of Cardiac Magnetic Resonance in Arrhythmogenic Right Ventricular Cardiomyopathy

We sought to evaluate the prognostic role of cardiac magnetic resonance (CMR) in patients with definite, borderline and possible diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC) as defined by the International Task Force (TF) in 2010. CMR was performed in 175 patients: 52 with definite, 50 with borderline and 73 possible ARVC. Abnormal-CMR was defined as the presence of ≥1 CMR abnormalities (including abnormalities of right ventricular and left ventricular wall motion, fat infiltration, late gadolinium enhancement, dilation and dysfunction of either ventricles). During the follow-up time 35 patients had hard cardiac events (sudden cardiac death, appropriate implantable cardioverter defibrillator shock and resuscitated cardiac arrest), and 34 of them occurred in patients with abnormal-CMR (negative predictive value = 96.9%). At the multivariate Cox-regression analysis LV involvement at CMR (fat infiltration and/or late gadolinium enhancement), and episode of nonsustained ventricular tachycardia (NSVT) were independent predictors of cardiac events in both the whole population (LV involvement: HR 3.69, 95% CI 1.57-8.65, p = 0.0002; NSVT: HR 5.8, 95% CI 2.82-11.9, p < 0.0001), and in the group of patients with definite ARVC (LV involvement: HR 3.03, 95% CI 1.15 to 8.02, p = 0.02; NSVT: HR 12.1, 95% CI 4.02-36.5, p < 0.0001). In conclusion, CMR evidence of LV involvement is a strong independent predictor of cardiac events in patients with definite, borderline or possible ARVC diagnosis. Abnormal CMR has very high negative predictive value for hard cardiac events.

Towards accurate and precise T 1 and extracellular volume mapping in the myocardium: a guide to current pitfalls and their solutions

Mapping of the longitudinal relaxation time (T₁) and extracellular volume (ECV) offers a means of identifying pathological changes in myocardial tissue, including diffuse changes that may be invisible to existing T₁-weighted methods. This technique has recently shown strong clinical utility for pathologies such as Anderson-Fabry disease and amyloidosis and has generated clinical interest as a possible means of detecting small changes in diffuse fibrosis; however, scatter in T₁ and ECV estimates offers challenges for detecting these changes, and bias limits comparisons between sites and vendors. There are several technical and physiological pitfalls that influence the accuracy (bias) and precision (repeatability) of T₁ and ECV mapping methods. The goal of this review is to describe the most significant of these, and detail current solutions, in order to aid scientists and clinicians to maximise the utility of T₁ mapping in their clinical or research setting. A detailed summary of technical and physiological factors, issues relating to contrast agents, and specific disease-related issues is provided, along with some considerations on the future directions of the field.

Usefulness of Combined Functional Assessment by Cardiac Magnetic Resonance and Tissue Characterization Versus Task Force Criteria for Diagnosis of Arrhythmogenic Right Ventricular Cardiomyopathy

Current task force criteria (TFC) of cardiac magnetic resonance (CMR) for the diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC/D) were generated by comparing probands (mean age of 44 years) to healthy participants of the multi-ethnic study of atherosclerosis (mean age of 60 years). These age differences may be a selection bias because right ventricular end-diastolic volume index decreases 4.6% per decade. Moreover, fat infiltration and late gadolinium enhancement were not included. We evaluated the diagnostic accuracy of TFC using the same methodology used by the task force but comparing probands and age- and gender-matched healthy controls and considering also other morphofunctional and tissue abnormalities detected by CMR. Forty-seven probands with previous diagnosis of ARVC/D (excluding probands if CMR was used for diagnosis) were compared with 216 age- and gender-matched healthy controls. TFC had optimal specificity (100%) but poor sensitivity (20% for major and 13% for minor criteria). The presence of any pre- and post-contrast signal abnormalities had 100% specificity and 81% sensitivity. The best diagnostic accuracy (98%) was achieved by the combined evaluation of any right ventricular wall motion abnormality (excluding hypokinesia) with any signal abnormality (including left ventricular fat infiltration and late gadolinium enhancement) yielding a 100% specificity and 96% sensitivity. Left ventricular was involved in 45% of the probands. Current TFC for CMR presented optimal specificity but poor sensitivity to identify patient with ARVC/D. Signal and wall motion parameters of CMR should be considered together to achieve the best diagnostic accuracy for the diagnosis of ARVC/D.

Cardiac magnetic resonance 'virtual catheterization' for the quantification of valvular regurgitations and cardiac shunt

Cardiac magnetic resonance (CMR) is considered the gold-standard noninvasive technique for the quantification of ventricular volumes by cine-imaging and of vascular flows by velocity-encoded phase contrast (VENC). In routine CMR scans, it is common to found clinical conditions, as valve regurgitations and cardiac shunts, producing a volume overload and significant mismatch between the right and left ventricular stroke volumes (RSV and LSV). In the presence of a valve regurgitation, the volume overload involves the respective ventricular chamber, whereas in cardiac shunts, the location of the volume overload depends on the site of the anatomic defect. Moreover, when a cardiac shunt is present, pulmonary and systemic cardiac outputs are different (Qp/Qs < 1 or Qp/Qs > 1), whereas in the presence of valve regurgitation, Qp/Qs = 1. Therefore, by combining the cine-imaging with the VENC technique, it is possible to investigate the cardiac physiology underlying different pathological conditions producing volume overload, and to quantify this overload (the regurgitant volume and/or shunt volume). In this report, we discussed the technical, theoretical and methodological aspects of this sort of 'virtual catheterization' by CMR, providing a simple algorithm to make the correct diagnosis.

Fibrofatty Changes: Incidence at Cardiac MR Imaging in Patients with Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy

Purpose To determine the incidence of ventricular fatty replacement and late gadolinium enhancement (LGE) at cardiac magnetic resonance (MR) imaging in patients with arrhythmogenic right ventricular (RV) dysplasia/cardiomyopathy (ARVD/C) and the relationship of these findings to disease severity. Materials and Methods This was a retrospective institutional review board-approved HIPAA-compliant study. All subjects provided written informed consent. Seventy-six patients with ARVD/C were enrolled from 2002 to 2012. Quantitative and qualitative cardiac MR imaging analyses of the RV and the left ventricle (LV) were performed to determine cardiac MR imaging-specific Task Force Criteria (TFC) and non-TFC features (ARVD/C-type pattern of fatty infiltration and/or nonischemic pattern LGE). Patients were separated into four groups on the basis of cardiac MR imaging TFC: (a) patients with major cardiac MR imaging criteria, (b) patients with minor criteria, (c) patients with partial criteria, and (d) patients with no criterion. Continuous variables were compared by using the independent Student t test and analysis of variance. Categoric variables were compared by using the Fisher exact test. Results Of 76 patients (mean age, 34.2 years ± 14 [standard deviation]; 51.3% men), 42 met major cardiac MR imaging criteria, seven met minor criteria, seven met partial criteria, and 20 met no criterion. Most probands (36 [80.0%] of 45) met major or minor cardiac MR imaging criteria. Only 13 (41.9%) of 31 family members met any cardiac MR imaging criterion. The most common non-TFC MR imaging features were RV fatty infiltration (28.9%) and LV LGE (35.5%). Non-TFC cardiac MR imaging features were seen in 88.1% of subjects with major criteria, in 28.6% of those with minor criteria, in 71.4% of those with partial criteria, and in 10.0% of those with no criteria. Conclusion In this large cohort of patients with ARVD/C, non-TFC findings of ventricular fatty infiltration and LGE were frequent and were most often found in those who met major cardiac MR imaging criteria and in probands. (©) RSNA, 2016 Online supplemental material is available for this article.

Characterization of myocardial T1-mapping bias caused by intramyocardial fat in inversion recovery and saturation recovery techniques

BACKGROUND

Quantitative measurement of T1 in the myocardium may be used to detect both focal and diffuse disease processes such as interstitial fibrosis or edema. A partial volume problem exists when a voxel in the myocardium also contains fat. Partial volume with fat occurs at tissue boundaries or within the myocardium in the case of lipomatous metaplasia of replacement fibrosis, which is commonly seen in chronic myocardial infarction. The presence of fat leads to a bias in T1 measurement. The mechanism for this artifact for widely used T1 mapping protocols using balanced steady state free precession readout and the dependence on off-resonance frequency are described in this paper.

METHODS

Simulations were performed to illustrate the behavior of mono-exponential fitting to bi-exponential mixtures of myocardium and fat with varying fat fractions. Both inversion recovery and saturation recovery imaging protocols using balanced steady state free precession are considered. In-vivo imaging with T1-mapping, water/fat separated imaging, and late enhancement imaging was performed on subjects with chronic myocardial infarction.

RESULTS

In n = 17 subjects with chronic myocardial infarction, lipomatous metaplasia is evident in 8 patients (47%). Fat fractions as low as 5% caused approximately 6% T1 elevation for the out-of-phase condition, and approximately 5% reduction of T1 for the in-phase condition. T1 bias in excess of 1000 ms was observed in lipomatous metaplasia with fat fraction of 38% in close agreement with simulation of the specific imaging protocols.

CONCLUSIONS

Measurement of the myocardial T1 by widely used balanced steady state free precession mapping methods is subject to bias when there is a mixture of water and fat in the myocardium. Intramyocardial fat is frequently present in myocardial scar tissue due lipomatous metaplasia, a process affecting myocardial infarction and some non-ischemic cardiomyopathies. In cases of lipomatous metaplasia, the T1 biases will be additive or subtractive depending on whether the center frequency corresponds to the myocardium and fat being in-phase or out-of-phase, respectively. It is important to understand this mechanism, which may otherwise lead to erroneous interpretation.