Radiologic-Pathologic Correlation of Primary and Secondary Cardiomyopathies: MR Imaging and Histopathologic Findings in Hearts from Autopsy and Transplantation

Cellular and molecular mechanisms driving cardiac tissue fibrosis: On the precipice of personalized and precision medicine

Cardiac fibrosis is a significant contributor to heart failure, a condition that continues to affect a growing number of patients worldwide. Various cardiovascular comorbidities can exacerbate cardiac fibrosis. While fibroblasts are believed to be the primary cell type underlying fibrosis, recent and emerging data suggest that other cell types can also potentiate or expedite fibrotic processes. Over the past few decades, clinicians have developed therapeutics that can blunt the development and progression of cardiac fibrosis. While these strategies have yielded positive results, overall clinical outcomes for patients suffering from heart failure continue to be dire. Herein, we overview the molecular and cellular mechanisms underlying cardiac tissue fibrosis. To do so, we establish the known mechanisms that drive fibrosis in the heart, outline the diagnostic tools available, and summarize the treatment options used in contemporary clinical practice. Finally, we underscore the critical role the immune microenvironment plays in the pathogenesis of cardiac fibrosis.

Can right ventricular endomyocardial biopsy predict left ventricular fibrosis beforehand in dilated cardiomyopathy?

AIMS

Myocardial fibrosis of the left ventricle (LV) is a prognostic factor in dilated cardiomyopathy (DCM). This study aims to evaluate whether fibrosis of right ventricular (RV) endomyocardial biopsy (EMB) can predict the degree of LV fibrosis beforehand in DCM.

METHODS AND RESULTS

Fibrosis extent in 70 RV-EMB specimens of DCM diagnosis was compared with that in the whole cross-sectional LV of excised hearts in the same patients (52 explanted hearts for transplant and 18 autopsied hearts). The median interval between biopsy and excision was 4.1 (0.13-19.3) years. The fibrosis area ratio of the EMBs and excised hearts were evaluated via image analysis. The distribution of cardiovascular magnetic resonance-late gadolinium enhancement (LGE) in the intraventricular septum was classified into four quartile categories. The fibrosis area ratio in RV-EMB correlated significantly with that in the short-axis cut of the LV of excised hearts (r = 0.82, P < 0.0001) and with a diffuse pattern of LGE (r = 0.71, P = 0.003). In a multivariate model, after adjusting for the interval between biopsy performance and heart excision, the fibrosis area ratio in RV-EMB was associated with that in LV-excised heart (regression coefficient, 0.82; 95% confidence interval, 0.68-0.95; P < 0.0001).

CONCLUSIONS

The fibrosis observed in RV-EMB positively correlated with the extent of fibrosis in the LV of excised hearts in patients with DCM. The study findings may help predict LV fibrosis, considered a prognostic factor of DCM through relatively accessible biopsy techniques.

Arrhythmogenic Right Ventricular Cardiomyopathy Post-Mortem Assessment: A Systematic Review

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetic disorder characterized by the progressive fibro-fatty replacement of the right ventricular myocardium, leading to myocardial atrophy. Although the structural changes usually affect the right ventricle, the pathology may also manifest with either isolated left ventricular myocardium or biventricular involvement. As ARVC shows an autosomal dominant pattern of inheritance with variable penetrance, the clinical presentation of the disease is highly heterogeneous, with different degrees of severity and patterns of myocardial involvement even in patients of the same familiar group with the same gene mutation: the pathology spectrum ranges from the absence of symptoms to sudden cardiac death (SCD) sustained by ventricular arrhythmias, which may, in some cases, be the first manifestation of an otherwise silent pathology. An evidence-based systematic review of the literature was conducted to evaluate the state of the art of the diagnostic techniques for the correct post-mortem identification of ARVC. The research was performed using the electronic databases PubMed and Scopus. A methodological approach to reach a correct post-mortem diagnosis of ARVC was described, analyzing the main post-mortem peculiar macroscopic, microscopic and radiological alterations. In addition, the importance of performing post-mortem genetic tests has been underlined, which may lead to the correct identification and characterization of the disease, especially in those ARVC forms where anatomopathological investigation does not show evident morphostructural damage. Furthermore, the usefulness of genetic testing is not exclusively limited to the correct diagnosis of the pathology, but is essential for promoting targeted screening programs to the deceased's family members. Nowadays, the post-mortem diagnosis of ARVC performed by forensic pathologist remains very challenging: therefore, the identification of a clear methodological approach may lead to both a reduction in under-diagnoses and to the improvement of knowledge on the disease.

Eosinophilic myocarditis: Case report and brief review of the literature

Eosinophilic myocarditis (EM) is a cardiac manifestation of hypereosinophilic syndrome with a high mortality rate. EM shares imaging features similar to other restrictive cardiopathies, and include patchy intramural late gadolinium enhancement on cardiac magnetic resonance with or without presence of biventricular thrombus. Diagnosis is confirmed on histopathology, and is the current gold standard. Here we report clinical presentation and imaging findings of EM in a 70-year-old woman who presented with fever and chills.

Detection of myocardial fibrosis: Where we stand

Myocardial fibrosis, resulting from the disturbance of extracellular matrix homeostasis in response to different insults, is a common and important pathological remodeling process that is associated with adverse clinical outcomes, including arrhythmia, heart failure, or even sudden cardiac death. Over the past decades, multiple non-invasive detection methods have been developed. Laboratory biomarkers can aid in both detection and risk stratification by reflecting cellular and even molecular changes in fibrotic processes, yet more evidence that validates their detection accuracy is still warranted. Different non-invasive imaging techniques have been demonstrated to not only detect myocardial fibrosis but also provide information on prognosis and management. Cardiovascular magnetic resonance (CMR) is considered as the gold standard imaging technique to non-invasively identify and quantify myocardial fibrosis with its natural ability for tissue characterization. This review summarizes the current understanding of the non-invasive detection methods of myocardial fibrosis, with the focus on different techniques and clinical applications of CMR.

State of the Art on the Role of Postmortem Computed Tomography Angiography and Magnetic Resonance Imaging in the Diagnosis of Cardiac Causes of Death: A Narrative Review

The need of a minimally invasive approach, especially in cases of cultural or religious oppositions to the internal examination of the body, has led over the years to the introduction of postmortem CT (PMCT) methodologies within forensic investigations for the comprehension of the cause of death in selected cases (e.g., traumatic deaths, acute hemorrhages, etc.), as well as for personal identification. The impossibility to yield clear information concerning the coronary arteries due to the lack of an active circulation to adequately distribute contrast agents has been subsequently overcome by the introduction of coronary-targeted PMCT Angiography (PMCTA), which has revealed useful in the detection of stenoses related to calcifications and/or atherosclerotic plaques, as well as in the suspicion of thrombosis. In parallel, due to the best ability to study the soft tissues, cardiac postmortem MR (PMMR) methodologies have been further implemented, which proved suitable for the detection and aging of infarcted areas, and for cardiomyopathies. Hence, the purpose of the present work to shed light on the state of the art concerning the value of both coronary-targeted PMCTA and PMMR in the diagnosis of coronary artery disease and/or myocardial infarction as causes of death, further evaluating their suitability as alternatives or complementary approaches to standard autopsy and histologic investigations.

Efficacy of myocardial washout of 99mTc-MIBI/Tetrofosmin for the evaluation of inflammation in patients with cardiac sarcoidosis: comparison with 18F-fluorodeoxyglucose positron emission tomography findings

OBJECTIVE

Both myocardial perfusion scintigraphy and ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG PET) are useful for the diagnosis of cardiac sarcoidosis (CS). However, the association between the washout of ^99mTc-labeled tracer and FDG PET has not been established. This study aimed to evaluate the association between the washout of ^99mTc-labeled tracer and FDG PET findings in patients with CS.

METHODS

We retrospectively analyzed 64 patients (65.0 ± 11.2 years, 53% male) with suspected CS who underwent myocardial single-photon emission computed tomography (SPECT) with ^99mTc-labeled tracer and FDG PET. The SPECT images were acquired at 15 min (early images) and 3 h (delayed images) after injection and scored visually using a 17-segment model with a 5-point scoring system. The washout score was defined as the difference between the early and delayed total defect scores. FDG positivity was considered as focal or focal on diffuse patterns on visual assessment, and FDG uptake was quantified by measuring the standardized uptake value (SUV) of each of the 17 segments.

RESULTS

The washout score was significantly higher for the CS group than for the non-CS group (3.0 [-1.0-5.0] vs. 0.0 [-0.5-1.0], p = 0.010). Receiver operating characteristic analysis showed that a washout score of ≥ 2 had the best accuracy for detecting CS (88% sensitivity and 56% specificity) and FDG positivity (71% sensitivity and 89% specificity). In the segment-based analysis of 833 segments from 49 patients, excluding 15 patients with diffuse FDG uptake, the median SUVs for FDG uptake for the washout scores of ≤ 0, 1, and 2 were 2.3 (1.8-3.6), 4.2 (2.9-7.8), and 8.3 (6.5-9.4), respectively (p < 0.001).

CONCLUSIONS

The washout of ^99mTc-labeled tracer can be a useful marker for the evaluation of FDG PET findings in patients with CS.

Association of myocardial fibrosis detected by late gadolinium-enhanced MRI with clinical outcomes in patients with diabetes: a systematic review and meta-analysis

OBJECTIVE

This meta-analysis assessed the associations of myocardial fibrosis detected by late gadolinium-enhanced (LGE)-MRI with the risk of major adverse cardiac and cerebrovascular events (MACCEs) and major adverse cardiac events (MACEs) in patients with diabetes.

DESIGN

Systematic review and meta-analysis reported in accordance with the guidelines of the Meta-analysis of Observational Studies in Epidemiology statement.

DATA SOURCES

We searched the Medline, Embase and Cochrane by Ovid databases for studies published up to 27 August 2021.

ELIGIBILITY CRITERIA

Prospective or respective cohort studies were included if they reported the HR and 95% CIs for MACCEs/MACEs in patients with either type 1 or 2 diabetes and LGE-MRI-detected myocardial fibrosis compared with patients without LGE-MRI-detected myocardial fibrosis and if the articles were published in the English language.

DATA EXTRACTION AND SYNTHESIS

Two review authors independently extracted data and assessed the quality of the included studies. Pooled HRs and 95% CIs were analysed using a random effects model. Heterogeneity was assessed using forest plots and I² statistics.

RESULTS

Eight studies with 1121 patients with type 1 or type 2 diabetes were included in this meta-analysis, and the follow-up ranged from 17 to 70 months. The presence of myocardial fibrosis detected by LGE-MRI was associated with an increased risk for MACCEs (HR: 2.58; 95% CI 1.42 to 4.71; p=0.002) and MACEs (HR: 5.28; 95% CI 3.20 to 8.70; p<0.001) in patients with diabetes. Subgroup analysis revealed that ischaemic fibrosis detected by LGE was associated with MACCEs (HR 3.80, 95% CI 2.38 to 6.07; p<0.001) in patients with diabetes.

CONCLUSIONS

This study demonstrated that ischaemic myocardial fibrosis detected by LGE-MRI was associated with an increased risk of MACCEs/MACEs in patients with diabetes and may be an imaging biomarker for risk stratification. Whether LGE-MRI provides incremental prognostic information with respect to MACCEs/MACEs over risk stratification by conventional cardiovascular risk factors requires further study.

Prognostic value of right ventricular native T1 mapping in pulmonary arterial hypertension

BACKGROUND

Right ventricular function is an important prognostic marker for pulmonary arterial hypertension. Native T1 mapping using cardiovascular magnetic resonance imaging can characterize the myocardium, but accumulating evidence indicates that T1 values of the septum or ventricular insertion points do not have predictive potential in pulmonary arterial hypertension. We aimed to elucidate whether native T1 values of the right ventricular free wall (RVT1) can predict poor outcomes in patients with pulmonary arterial hypertension.

METHODS

This retrospective study included 30 patients with pulmonary arterial hypertension (median age, 45 years; mean pulmonary artery pressure, 41±13 mmHg) and 16 healthy controls (median age, 43 years) who underwent native T1 mapping. RVT1 was obtained from the inferior right ventricular free wall during end systole.

RESULTS

Patients with pulmonary arterial hypertension had significantly higher native RVT1 than did controls (1384±74 vs. 1217±57 ms, p<0.001). Compared with T1 values of the septum or ventricular insertion points, RVT1 correlated better with the effective right ventricular elastance index (R = -0.53, p = 0.003), ventricular-arterial uncoupling (R = 0.46, p = 0.013), and serum brain natriuretic peptide levels (R = 0.65, p<0.001). Moreover, the baseline RVT1 was an accurate predictor of the reduced right ventricular ejection fraction at the 12-month follow-up (delta -3%). RVT1 was independently associated with composite events of death or hospitalization from any cause (hazard ratio = 1.02, p = 0.002).

CONCLUSIONS

RVT1 was predictive of right ventricular performance and outcomes in patients with pulmonary arterial hypertension. Thus, native T1 mapping in the right ventricular free wall may be an effective prognostic method for pulmonary arterial hypertension.

Imaging techniques for the assessment of adverse cardiac remodeling in metabolic syndrome

Metabolic syndrome (MetS) includes different metabolic conditions (i.e. abdominal obesity, impaired glucose tolerance, hypertriglyceridemia, decreased HDL cholesterol, and/or hypertension) that concour in the development of cardiovascular disease and diabetes. MetS individuals often show adverse cardiac remodeling and myocardial dysfunction even in the absence of overt coronary artery disease or valvular affliction. Diastolic impairment and hypertrophy are hallmarks of MetS-related cardiac remodeling and represent the leading cause of heart failure with preserved ejection fraction (HFpEF). Altered cardiomyocyte function, increased neurohormonal tone, interstitial fibrosis, coronary microvascular dysfunction, and a myriad of metabolic abnormalities have all been implicated in the development and progression of adverse cardiac remodeling related to MetS. However, despite the enormous amount of literature produced on this argument, HF remains a leading cause of morbidity and mortality in such population. The early detection of initial adverse cardiac remodeling would enable the optimal implementation of effective therapies aiming at preventing the progression of the disease to the symptomatic phase. Beyond conventional imaging techniques, such as echocardiography, cardiac tomography, and magnetic resonance, novel post-processing tools and techniques provide information on the biological processes that underlie metabolic heart disease. In this review, we summarize the pathophysiology of MetS-related cardiac remodeling and illustrate the relevance of state-of-the-art multimodality cardiac imaging to identify and quantify the degree of myocardial involvement, prognosticate long-term clinical outcome, and potentially guide therapeutic strategies.

Automatic machine learning based on native T1 mapping can identify myocardial fibrosis in patients with hypertrophic cardiomyopathy

OBJECTIVES

To investigate the feasibility of automatic machine learning (autoML) based on native T1 mapping to predict late gadolinium enhancement (LGE) status in hypertrophic cardiomyopathy (HCM).

METHODS

Ninety-one HCM patients and 44 healthy controls who underwent cardiovascular MRI were enrolled. The native T1 maps of HCM patients were classified as LGE ( +) or LGE (-) based on location-matched LGE images. An autoML pipeline was implemented using the tree-based pipeline optimization tool (TPOT) for 3 binary classifications: LGE ( +) and LGE (-), LGE (-) and control, and HCM and control. TPOT modeling was repeated 10 times to obtain the optimal model for each classification. The diagnostic performance of the best models by slice and by case was evaluated using sensitivity, specificity, accuracy, and microaveraged area under the curve (AUC).

RESULTS

Ten prediction models were generated by TPOT for each of the 3 binary classifications. The diagnostic accuracy obtained with the best pipeline in detecting LGE status in the testing cohort of HCM patients was 0.80 by slice and 0.79 by case. In addition, the TPOT model also showed discriminability between LGE (-) patients and control (accuracy: 0.77 by slice; 0.78 by case) and for all HCM patients and controls (accuracy: 0.88 for both).

CONCLUSIONS

Native T1 map analysis based on autoML correlates with LGE ( +) or (-) status. The TPOT machine learning algorithm could be a promising method for predicting myocardial fibrosis, as reflected by the presence of LGE in HCM patients without the need for late contrast-enhanced MRI sequences.

KEY POINTS

• The tree-based pipeline optimization tool (TPOT) is a machine learning algorithm that could help predict late gadolinium enhancement (LGE) status in patients with hypertrophic cardiomyopathy. • The TPOT could serve as an adjuvant method to detect LGE by using information from native T1 maps, thus avoiding the need for contrast agent. • The TPOT also detects native T1 map alterations in LGE-negative patients with hypertrophic cardiomyopathy.

Toward Replacing Late Gadolinium Enhancement With Artificial Intelligence Virtual Native Enhancement for Gadolinium-Free Cardiovascular Magnetic Resonance Tissue Characterization in Hypertrophic Cardiomyopathy

BACKGROUND

Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) imaging is the gold standard for noninvasive myocardial tissue characterization but requires intravenous contrast agent administration. It is highly desired to develop a contrast agent-free technology to replace LGE for faster and cheaper CMR scans.

METHODS

A CMR virtual native enhancement (VNE) imaging technology was developed using artificial intelligence. The deep learning model for generating VNE uses multiple streams of convolutional neural networks to exploit and enhance the existing signals in native T1 maps (pixel-wise maps of tissue T1 relaxation times) and cine imaging of cardiac structure and function, presenting them as LGE-equivalent images. The VNE generator was trained using generative adversarial networks. This technology was first developed on CMR datasets from the multicenter Hypertrophic Cardiomyopathy Registry, using hypertrophic cardiomyopathy as an exemplar. The datasets were randomized into 2 independent groups for deep learning training and testing. The test data of VNE and LGE were scored and contoured by experienced human operators to assess image quality, visuospatial agreement, and myocardial lesion burden quantification. Image quality was compared using a nonparametric Wilcoxon test. Intra- and interobserver agreement was analyzed using intraclass correlation coefficients (ICC). Lesion quantification by VNE and LGE were compared using linear regression and ICC.

RESULTS

A total of 1348 hypertrophic cardiomyopathy patients provided 4093 triplets of matched T1 maps, cines, and LGE datasets. After randomization and data quality control, 2695 datasets were used for VNE method development and 345 were used for independent testing. VNE had significantly better image quality than LGE, as assessed by 4 operators (n=345 datasets; P<0.001 [Wilcoxon test]). VNE revealed lesions characteristic of hypertrophic cardiomyopathy in high visuospatial agreement with LGE. In 121 patients (n=326 datasets), VNE correlated with LGE in detecting and quantifying both hyperintensity myocardial lesions (r=0.77-0.79; ICC=0.77-0.87; P<0.001) and intermediate-intensity lesions (r=0.70-0.76; ICC=0.82-0.85; P<0.001). The native CMR images (cine plus T1 map) required for VNE can be acquired within 15 minutes and producing a VNE image takes less than 1 second.

CONCLUSIONS

VNE is a new CMR technology that resembles conventional LGE but without the need for contrast administration. VNE achieved high agreement with LGE in the distribution and quantification of lesions, with significantly better image quality.

Global longitudinal strain evaluated by speckle-tracking echocardiography as a surrogate marker for predicting replacement fibrosis detected by magnetic resonance-late gadolinium enhancement in patients with nonischemic cardiomyopathy

PURPOSE

This study aimed to investigate whether left ventricular (LV) global longitudinal strain (GLS) evaluated by speckle-tracking echocardiography (STE) can be used as a surrogate marker for the detection of replacement fibrosis by late gadolinium enhancement (LGE) on cardiovascular magnetic resonance (CMR) in patients with nonischemic cardiomyopathy (NICM).

METHODS

This study analyzed 41 NICM patients who successfully underwent both STE and CMR, and were divided into those with (Group A, n = 18) and those without CMR-LGE (Group B, n = 23). Echocardiographic indexes, including GLS, were compared between the two groups.

RESULTS

No significant differences were observed in LV end-diastolic and end-systolic volume indexes, LV ejection fraction, mitral E/A, deceleration time, E/e', left atrial volume index, and the systolic trans-tricuspid pressure gradient between Groups A and B. STE-GLS was significantly worse in Group A than in Group B (-7.6% ± 3.0% vs -9.9% ± 3.2%, P = .01). Receiver operating characteristic curve analysis showed that STE-GLS of -7.9% was the best cut-off value for detection of CMR-LGE (sensitivity, 78%; specificity, 74%; and area under the curve, 0.74).

CONCLUSIONS

STE-GLS may be a potential surrogate marker for the detection of CMR-LGE-derived replacement fibrosis in patients with NICM.

Multimodality Imaging Assessment of Myocardial Fibrosis

Myocardial fibrosis, seen in ischemic and nonischemic cardiomyopathies, is associated with adverse cardiac outcomes. Noninvasive imaging plays a key role in early identification and quantification of myocardial fibrosis with the use of an expanding array of techniques including cardiac magnetic resonance, computed tomography, and nuclear imaging. This review discusses currently available noninvasive imaging techniques, provides insights into their strengths and limitations, and examines novel developments that will affect the future of noninvasive imaging of myocardial fibrosis.

Highly sensitive T1-T2dual-mode MRI probe based on ultra-small gadolinium oxide-decorated iron oxide nanocrystals

Single-mode magnetic resonance imaging (MRI) contrast agents (CAs) in clinical settings are easily disturbed by calcification, bleeding, and adipose signals, which result in inaccurate diagnoses. In this study, we developed a highly efficient T₁-T₂dual-mode MRI CA using an ultra-small gadolinium oxide-decorated magnetic iron oxide nanocrystal (GMIO). The gadolinium element could effectively alter the magnetic properties of the GMIO from soft-ferromagnetism to superparamagnetism. In addition, when the Gd/Fe ratio was 15 % (designated as GMIO-2), the GMIO-2 possessed the best superparamagnetism and highest magnetism. Subsequently, T₁and T₂values of GMIO-2 were measured through a series of turbo spin-echo images and then multi-spin echo (MSE) sequence, respectively. Based on this, T₁and T₂relaxivities of GMIO-2 were calculated and were the highest (r₁: 1.306 m M^-1s^-1and r₂: 234.5 m M^-1s^-1) when compared to other groups. The cytotoxicity of GMIO-2 was negligible under a wide range of dosages, thus exhibiting excellent cell biocompatibility. Moreover, GMIO-2 could quickly diffuse into cells, leading to its effective accumulation. The systemic delivery of GMIO-2 resulted in an excellent T₁-T₂dual-mode MRI contrast effect in kidneys, which is expected to improve the diagnosis of kidney lesions. Therefore, this work provides a promising candidate for the development of a T₁-T₂dual-mode MRI CA.

Scar identification, quantification, and characterization in complex atrial tachycardia: a path to targeted ablation?

Successful catheter ablation of scar-related atrial tachycardia depends on correct identification of the critical isthmus. Often, this is a represented by a small bundle of viable conducting tissue within a low-voltage area. It's identification depends on the magnitude of the signal/noise ratio. Ultra-high density mapping, multipolar catheters with small (eventually unidirectional) and closely-spaced electrodes improves low-voltage electrogram detection. Background noise limitation is also of major importance for improving the signal/noise ratio. Electrophysiological properties of the critical isthmus and the characteristics of the local bipolar electrograms have been recently demonstrated as hallmarks of successful ablation sites in the setting of scar-related atrial tachycardia.

Late gadolinium enhancement is a risk factor for major adverse cardiac events in unrecognised myocardial infarction without apparent symptoms: a meta-analysis

AIM

To assess the prognostic role of unrecognised myocardial infarction (UMI) detected at late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMRII).

MATERIALS AND METHODS

Electronic databases including PubMed, EMBASE, Medline, and Cochrane were searched systematically for studies exploring the predictive value of UMI detected by LGE-CMRI for major adverse cardiac events (MACEs) and all-cause mortality in patients without apparent symptoms. Pooled hazard ratios (HRs) along with their 95% confidence intervals (CIs) were obtained from a random-effects model. Subgroup analyses were performed according to the different participants and outcomes.

RESULTS

Eight studies (2,009 participants) were identified comprising 442 patients with UMI detected at LGE-CMRI and 1,567 without UMI. The presence of UMI on LGE was associated with a significantly increased risk for MACEs (HRs: 3.44, 95% CI: 2.06 to 5.75; p<0.001) and all-cause mortality (HRs: 2.43, 95% CI: 1.00 to 5.87; p=0.05). In the subgroup analysis, the presence of UMI on LGE remained significantly associated with the risk of MACEs in patients with suspected coronary artery disease (HRs: 3.82, 95% CI: 2.49 to 5.85; p<0.01) and diabetes mellitus (HRs: 4.97, 95% CI: 3.02 to 8.18; p<0.01).

CONCLUSION

The presence of UMI detected by LGE-CMRI is associated with an increased risk of MACEs and all-cause mortality in patients without symptoms. LGE-CMRI could provide important prognostic information and guide risk stratification in patients with UMI.

Global longitudinal diastolic strain rate as a novel marker for predicting adverse outcomes in hypertrophic cardiomyopathy by cardiac magnetic resonance tissue tracking

AIM

To examine the prognostic value of global peak diastolic strain rate (PDSR) derived from cardiac magnetic resonance (CMR) tissue tracking (CMR-TT) in predicting adverse outcomes in hypertrophic cardiomyopathy (HCM) patients.

MATERIALS AND METHODS

A total of 98 patients diagnosed with HCM (44 patients had left ventricle [LV] outflow tract obstruction [LVOTO] and 54 patients did not) were enrolled and followed for the specified endpoint. LV global myocardial mechanics was assessed in all participants using CMR-TT at study entry.

RESULTS

Compared with the non-obstructive subgroup, the obstructive subgroup demonstrated deteriorated magnitude of LV global radial, circumferential, and longitudinal PDSR (all p<0.05). After a mean follow-up period of 4.5 years, 24 patients reached an endpoint before the end of the study. Furthermore, when using the specified cut-off value (0.33 1/s) of longitudinal PDSR, the Kaplan-Meier curve demonstrated that patients with lower longitudinal PDSR had a significantly lower freedom from major adverse cardiovascular events (MACE) compared with their counterparts in the non-obstructive, obstructive, and overall cohorts (all log-rank p<0.05). Multivariable analysis showed that longitudinal PDSR remained the strongest predictor of outcome after adjusting for baseline and CMR variables (hazard ratio, 2.65; 95% confidence interval, 2.21-11.44; p<0.05).

CONCLUSION

CMR-TT-derived longitudinal PDSR is probably considered a novel and easy-to-perform marker for predicting adverse outcomes in HCM patients, which is beneficial to risk stratification. Further confirmatory studies are needed.

Prognostic Value of Myocardial Extracellular Volume Fraction and T2-mapping in Heart Transplant Patients

OBJECTIVES

The purpose of this study was to examine prognostic value of T1- and T2-mapping techniques in heart transplant patients.

BACKGROUND

Myocardial characterization using T2 mapping (evaluation of edema/inflammation) and pre- and post-gadolinium contrast T1 mapping (calculation of extracellular volume fraction [ECV] for assessment of interstitial expansion/fibrosis) are emerging modalities that have been investigated in various cardiomyopathies.

METHODS

A total of 99 heart transplant patients underwent the magnetic resonance imaging (MRI) scans including T1- (n = 90) and T2-mapping (n = 79) techniques. Relevant clinical characteristics, MRI parameters including late gadolinium enhancement (LGE), and invasive hemodynamics were collected. Median clinical follow-up duration after the baseline scan was 2.4 to 3.5 years. Clinical outcomes include cardiac events (cardiac death, myocardial infarction, coronary revascularization, and heart failure hospitalization), noncardiac death and noncardiac hospitalization.

RESULTS

Overall, the global native T1, postcontrast T1, ECV, and T2 were 1,030 ± 56 ms, 458 ± 84 ms, 27 ± 4% and 50 ± 4 ms, respectively. Top-tercile-range ECV (ECV >29%) independently predicted adverse clinical outcomes compared with bottom-tercile-range ECV (ECV <25%) (hazard ratio [HR]: 2.87; 95% confidence interval [CI]: 1.07 to 7.68; p = 0.04) in a multivariable model with left ventricular end-systolic volume and LGE. Higher T2 (T2 ≥50.2 ms) independently predicted adverse clinical outcomes (HR: 3.01; 95% CI: 1.39 to 6.54; p = 0.005) after adjustment for left ventricular ejection fraction, left ventricular end-systolic volume, and LGE. Additionally, higher T2 (T2 ≥50.2 ms) also independently predicted cardiac events (HR: 4.92; CI: 1.60 to 15.14; p = 0.005) in a multivariable model with left ventricular ejection fraction.

CONCLUSIONS

MRI-derived myocardial ECV and T2 mapping in heart transplant patients were independently associated with cardiac and noncardiac outcomes. Our findings highlight the need for larger prospective studies.

Metabolic and Molecular Imaging of the Diabetic Cardiomyopathy

The term diabetic cardiomyopathy is defined as the presence of abnormalities in myocardial structure and function that occur in the absence of, or in addition to, well-established cardiovascular risk factors. A key contributor to this abnormal structural-functional relation is the complex interplay of myocardial metabolic remodeling, defined as the loss the flexibility in myocardial substrate metabolism and its downstream detrimental effects, such as mitochondrial dysfunction, inflammation, and fibrosis. In parallel with the growth in understanding of these biological underpinnings has been developmental advances in imaging tools such as positron emission tomography and magnetic resonance imaging and spectroscopy that permit the detection and in many cases quantification, of the processes that typifies the myocardial metabolic remodeling in diabetic cardiomyopathy. The imaging readouts can be obtained in both preclinical models of diabetes mellitus and patients with diabetes mellitus facilitating the bi-directional movement of information between bench and bedside. Moreover, imaging biomarkers provided by these tools are now being used to enhance discovery and development of therapies designed to reduce the myocardial effects of diabetes mellitus through metabolic modulation. In this review, the use of these imaging tools in the patient with diabetes mellitus from a mechanistic, therapeutic effect, and clinical management perspective will be discussed.

Quantification of late gadolinium enhancement cardiovascular MRI in patients with coronary artery chronic total occlusion

AIM

To determine the most accurate and reproducible semi-automated greyscale thresholding technique for quantifying late gadolinium enhancement (LGE) in cardiovascular magnetic resonance imaging (CMRI), by using positron-emission tomography (PET) as the reference standard in patients with coronary artery chronic total occlusion (CTO).

MATERIALS AND METHODS

LGE in CMRI, single-photon-emission computed tomography (SPECT), and PET were performed within 1 week in each of 63 patients with known CTO. The presence and quantity of LGE were determined with greyscale thresholds of 2, 4, 5, 6, and 8 standard deviations (SDs) above the mean signal intensity for normal remote myocardium and full width at half maximum (FWHM). The infarcted myocardium was delineated by PET.

RESULTS

Sixty-three patients and 1,008 segments were analysed. Based on patient analysis, with PET as the reference standard, the 5 SD method yielded the strongest correlation (r=0.85, p<0.0001) compared with the 2 SDs (r=0.42), 4 SDs (r=0.73), 6 SDs (r=0.81), 8 SDs (r=0.71), and FWHM (r=0.69; p<0.001 for all comparisons). The 5 SDs threshold quantification showed high interobserver and intra-observer agreement (intraclass correlation coefficient [ICC]=0.90, p<0.0001; ICC=0.93, p<0.0001, respectively).

CONCLUSIONS

Semi-automated LGE CMRI greyscale thresholding with 5 SDs above the mean signal intensity for normal remote myocardium yields the strongest correlation to the extent of LGE identified using PET and is highly reproducible in patients with CTO.

Review: Contrast-enhanced magnetic resonance in the diagnosis and management of cardiac sarcoidosis

Sarcoidosis is a relatively rare inflammatory condition which potentially carries high morbidity and substantial mortality. Due to the fact that it does not subject patients to ionizing radiation, has high temporal, spatial and contrast resolutions, cardiovascular magnetic resonance imaging (CMR) has become an important diagnostic and prognostic modality in the evaluation for cardiac involvement in this condition. This review provides relevant clinical and pathophysiological background on cardiac sarcoidosis, whilst detailing the role of CMR imaging in the diagnosis, and management of this condition.

Assessment of Left Ventricular Myocardial Diseases with Cardiac Computed Tomography

Rapid advances in cardiac computed tomography (CT) have enabled the characterization of left ventricular (LV) myocardial diseases based on LV anatomical morphology, function, density, and enhancement pattern. Global LV function and regional wall motion can be evaluated using multi-phasic cine CT images. CT myocardial perfusion imaging facilitates the identification of hemodynamically significant coronary artery disease. CT delayed-enhancement imaging is used to detect myocardial scar in myocardial infarction and to measure the extracellular volume fraction in non-ischemic cardiomyopathy. Multi-energy cardiac CT allows the mapping of iodine distribution in the myocardium. This review summarizes the current techniques of cardiac CT for LV myocardial assessment, highlights the key findings in various myocardial diseases, and presents future applications to complement echocardiography and cardiovascular magnetic resonance.

Cardiac Fibroblasts and Cardiac Fibrosis: Precise Role of Exosomes

Exosomes are a group of extracellular microvesicles that deliver biologically active RNAs, proteins, lipids and other signaling molecules to recipient cells. Classically, exosomes act as a vehicle by which cells or organs communicate with each other to maintain cellular/tissue homeostasis and to respond to pathological stress. Most multicellular systems, including the cardiovascular system, use exosomes for intercellular communication. In heart, endogenous exosomes from cardiac cells or stem cells aid in regulation of cell survival, cell proliferation and cell death; and thus tightly regulate cardiac biology and repair processes. Pathological stimulus in heart alters secretion and molecular composition of exosomes, thus influencing the above processes. The past decade has yielded increasing interest in the role of exosomes in the cardiovascular system and significant contribution of cardiac fibroblast (CF) and mediated cardiac fibrosis in heart failure, in this review we had overviewed the relevant literatures about fibroblast exosomes, its effect in the cardiovascular biology and its impact on cardiovascular disease (CVD). This review briefly describes the communication between fibroblasts and other cardiac cells via exosomes, the influence of such on myocardial fibrosis and remodeling, and the possibilities to use exosomes as biomarkers for acute and chronic heart diseases.

Multi-modality imaging in transthyretin amyloid cardiomyopathy

Transthyretin amyloid (TTR) cardiomyopathy is a disease of insidious onset, which is often accompanied by debilitating neurological and/or cardiac complications. The true prevalence is not fully known due to its elusive presentation, being often under-recognized and usually diagnosed only late in its natural history and in older patients. Because of this, effective treatment options are usually precluded by multiple comorbidities and frailty associated with such patients. Therefore, high clinical suspicion with earlier and better detection of this disease is needed. In this review, the novel applications of multimodality imaging in the diagnostic pathway of TTR cardiomyopathy are explored. These include the complimentary roles of transthoracic echocardiography, cardiac magnetic resonance, nuclear scintigraphy and positron emission tomography in quantifying cardiac dysfunction, diagnosis and risk stratification. Recent advances in novel therapeutic options for TTR have further enhanced the importance of a timely and accurate diagnosis of this disease.

Myocardial delayed enhancement on dual-energy computed tomography: The prevalence and related factors in patients with suspicion of coronary artery disease

BACKGROUND

We aimed to assess the prevalence of myocardial delayed enhancement (MDE) in patients with suspected obstructive coronary artery disease (CAD), and to investigate factors related to the presence or absence of MDE.

METHODS

We retrospectively evaluated 191 consecutive patients who underwent coronary computed tomography angiography (CCTA) with MDE imaging for clinical suspicion of CAD from December 2014 to December 2016. The presence of MDE on iodine-density images using dual-energy CT was assessed by two independent readers. Multivariable logistic regression analyses were used to determine factors associated with the presence of MDE.

RESULTS

MDE was detected in 58 (30%) patients. Male gender, hypertension, prior heart failure (HF) hospitalization, and CCTA-detected CAD were independent factors related to the presence of MDE. When CCTA-detected CAD was excluded to narrow down the analysis to factors obtainable before CCTA, interventricular septum thickness (IVST) ≥12 mm was added as another independent factor. The combination of the following four factors: female gender, no history of hypertension, no history of prior HF hospitalization, and IVST < 12 mm demonstrated high specificity (98.3%) and positive predictive value (96.2%) for predicting the absence of MDE.

CONCLUSIONS

Male gender, hypertension, prior HF hospitalization, and CAD were independently associated with the presence of MDE in patients with suspected CAD. The combination of female gender, no history of hypertension, no history of prior HF hospitalization, and IVST < 12 mm is likely to be a helpful predictor in discriminating patients without MDE before CCTA.

Role of Cardiac Computed Tomography in the Diagnosis of Left Ventricular Myocardial Diseases

Multimodality imaging is indicated for the evaluation of left ventricular (LV) myocardial diseases. Cardiac magnetic resonance (CMR) allows morphological and functional assessment of the LV along with soft tissue characterization. Technological advances in cardiac computed tomography (CT) have led to the development of techniques for diagnostic acquisition in LV myocardial disease. Cardiac CT facilitates the characterization of LV myocardial disease based on anatomy, function, and enhancement pattern. LV regional and global functional parameters are evaluated using multi-phasic cine CT images. CT myocardial perfusion facilitates the identification of hemodynamically significant coronary artery stenosis. Cardiac CT with delayed enhancement is used to detect myocardial scarring or fibrosis in myocardial infarction and non-ischemic cardiomyopathy, and for the measurement of extracellular volume fraction in non-ischemic cardiomyopathy. In this review, we review imaging techniques and key imaging features of cardiac CT used for the evaluation of myocardial diseases, along with CMR findings.

An Intervention Target for Myocardial Fibrosis: Autophagy

Myocardial fibrosis (MF) is the result of metabolic imbalance of collagen synthesis and metabolism, which is widespread in various cardiovascular diseases. Autophagy is a lysosomal degradation pathway which is highly conserved. In recent years, research on autophagy has been increasing and the researchers have also become cumulatively aware of the specified association between autophagy and MF. This review highlights the role of autophagy in MF and the potential effects through the administration of medicine.

Personalized medicine in inflammatory cardiomyopathy

Inflammatory cardiomyopathy is the result of persistent myocardial inflammation which can arise from both infectious or noninfectious causes. While most patients with acute myocarditis recover, up to 20% develop inflammatory cardiomyopathy with chronic heart failure. The interaction between host factors and factors of the agent that triggered myocardial inflammation must be considered to fully understand the individual mechanism of disease. Several inflammatory biomarkers, histology, immunohistochemistry, advanced imaging technologies as well as molecular high-throughput sequencing techniques help to identify disease pathways and to establish a comprehensive, individualized treatment approach, which can include anti-inflammatory medication, antiviral drugs and heart failure therapy. This might help to prevent transition from acute inflammation to persistent heart failure and to restore cardiac function.

Complement 5a Receptor deficiency does not influence adverse cardiac remodeling after pressure-overload in mice

Hypertension is one of the most common risk factors for the development heart failure in the general population. Inflammation plays a central role in this adverse remodeling and eventually to the development of heart failure. Circulating levels of Complement factor 5a (C5a) are increased in hypertensive patients and the C5a receptor is associated with the presence of cardiac fibrosis and inflammation in an experimental hypertension model. To test if C5aR is involved in adverse cardiac remodeling following pressure-overload, we induced transverse aortic constriction (TAC) in wildtype and C5a receptor deficient mice (C5aR^-/-). Six weeks after TAC, C5aR-/- animals showed a similar degree of cardiac hypertrophy and decrease in cardiac function as wild type mice (End Systolic Volume; 50.30±5.32 µl vs. 55.81±8.16 µl). In addition, other features of adverse cardiac remodeling like cardiomyocyte cell size (WGA staining), fibrosis (picrosirius red staining) or collagen degradation (matrix metalloproteinase activity assay) did not differ either. In conclusion, full body C5aR deficiency does not affect adverse cardiac remodeling after pressure-overload. However, our finding are in contrast with C5a inhibition studies. Our observations do present the role of C5a-C5aR in adverse cardiac remodeling and heart failure as controversial at the least.

Current Understanding of the Pathophysiology of Myocardial Fibrosis and Its Quantitative Assessment in Heart Failure

Myocardial fibrosis is an important part of cardiac remodeling that leads to heart failure and death. Myocardial fibrosis results from increased myofibroblast activity and excessive extracellular matrix deposition. Various cells and molecules are involved in this process, providing targets for potential drug therapies. Currently, the main detection methods of myocardial fibrosis rely on serum markers, cardiac magnetic resonance imaging, and endomyocardial biopsy. This review summarizes our current knowledge regarding the pathophysiology, quantitative assessment, and novel therapeutic strategies of myocardial fibrosis.