Entropy of left ventricular late gadolinium enhancement and its prognostic value in hypertrophic cardiomyopathy a new CMR assessment method

A Practical Approach to Multimodality Imaging in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy remains underdiagnosed despite a growing number of effective treatment interventions that can improve care. Multimodality imaging has become integral to diagnosing and managing hypertrophic cardiomyopathy, providing a comprehensive assessment of the disease. In particular, it enhances the diagnostic accuracy and deepens the understanding of the mechanisms underlying patient symptoms, enabling targeted therapeutic approaches. Additionally, multimodality imaging allows for better risk stratification, assessment of therapy response, and guidance of interventions to deliver personalized medicine. The practical tools outlined in this review can help providers integrate multimodality imaging strategies to provide better care and improve the patient experience.

Exploring the Current Status of Risk Stratification in Hypertrophic Cardiomyopathy: From Risk Models to Promising Techniques

Improving clinical prediction of sudden cardiac death is a crucial step in the management of patients with hypertrophic cardiomyopathy. However, finding the optimal method for risk evaluation has been challenging, given the complexity and the wide variation in clinical phenotypes. This is particularly important, as these patients are often of younger age and defibrillator implantation is associated with a low but tangible long-term risk of adverse events. A number of risk factors, including degree of hypertrophy, presence of syncope and family history of sudden cardiac death, have typically been considered to indicate a higher risk. The European risk score for prediction of sudden cardiac death is widely used; however, it may not apply well in patients with specific forms of the condition, such as those with extreme hypertrophy. Increasing evidence suggests that the presence and extent of myocardial fibrosis assessed with cardiac magnetic resonance imaging should be considered in clinical decision-making. Some research suggests that integrating electrophysiological studies into traditional risk assessment models may further optimize risk prediction and significantly improve accuracy in detecting high risk patients. Novel cardiac imaging techniques, better understanding of the genetic substrate and artificial intelligence-based algorithms may prove promising for risk refinement. The present review article provides an updated and in-depth viewpoint.

The Role of Signalling Pathways in Myocardial Fibrosis in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most prevalent hereditary cardiovascular disorder, characterised by left ventricular hypertrophy and cardiac fibrosis. Cardiac fibroblasts, transformed into myofibroblasts, play a crucial role in the development of fibrosis. However, interactions between fibroblasts, cardiomyocytes, and immune cells are considered major mechanisms driving fibrosis progression. While the disease has a strong genetic background, its pathogenetic mechanisms remain complex and not fully understood. Several signalling pathways are implicated in fibrosis development. Among these, transforming growth factor-beta and angiotensin II are frequently studied in the context of cardiac fibrosis. In this review, we summarise the most current evidence on the involvement of signalling pathways in the pathogenesis of HCM. Additionally, we discuss the potential role of monitoring pro-fibrotic molecules in predicting clinical outcomes in patients with HCM.

Late gadolinium enhancement on cardiac MRI: A systematic review and meta-analysis of prognosis across cardiomyopathies

BACKGROUND

Late gadolinium enhancement (LGE) on cardiac MRI has been shown to predict adverse outcomes in a range of cardiac diseases. However, no study has systematically reviewed and analyzed the literature across all cardiac pathologies including rare diseases.

METHODS

PubMed, EMBASE and Web of Science were searched for studies evaluating the relationship between LGE burden and cardiovascular outcomes. Outcomes included all-cause mortality, MACE, sudden cardiac death, sustained VT or VF, appropriate ICD shock, heart transplant, and heart failure hospitalization. Only studies reporting hazards ratios with LGE as a continuous variable were included.

RESULTS

Of the initial 8928 studies, 95 studies (23,313 patients) were included across 19 clinical entities. The studies included ischemic cardiomyopathy (7182 patients, 33 studies), hypertrophic cardiomyopathy (5080 patients, 17 studies), non-ischemic cardiomyopathy not otherwise specified (2627 patients, 11 studies), and dilated cardiomyopathy (2345 patients, 14 studies). Among 42 studies that quantified LGE by percent myocardium, a 1 % increase in LGE burden was associated with life-threatening ventricular arrhythmias (LTVA) with a pooled hazard ratio of 1.04 (CI 1.02-1.05), and MACE with a pooled hazard ratio of 1.06 (CI 1.04-1.07). The risk of these events was similar across disease types, with minimal heterogeneity.

CONCLUSIONS

Despite mechanistic differences in myocardial injury, LGE appears to have a fairly consistent, dose-dependent effect on risk of LTVA, MACE, and mortality. These data can be applied to derive a patient's absolute risk of LTVA, and therefore can be clinically useful in informing decisions on primary prevention ICD implantation irrespective of the disease etiology.

[Clincial Research Progress in Using Magnetic Resonance Imaging to Assess Myocardial Fibrosis in Hypertrophic Cardiomyopathy]

Hypertrophic cardiomyopathy (HCM) is the most common type of primary cardiomyopathy that causes sudden cardiac death in adolescents and athletes. With over 1 million HCM patients, China has the largest population of HCM patients in the world, and the total number of cases is increasing year on year. Myocardial fibrosis is the most important histopathological characterization in HCM and is regarded as the primary cause of malignant ventricular arrhythmia, cardiac remodeling, and heart failure. At present, cardiac magnetic resonance imaging (MRI) serves as the gold-standard imaging modality for noninvasive evaluation of myocardial fibrosis. Several techniques, such as late gadolinium enhancement and T1 mapping, are showing considerable promise for potential applications. These techniques have emerged as viable imaging approaches to the elucidation of HCM tissue characterization. They are also helpful in predicting the long-term prognosis of patients. Herein, we summarized recent advances in using cardiac MRI to assess myocardial fibrosis in HCM from four perspectives, including late gadolinium enhancement, T1 mapping, T1ρ mapping, and MRI-based radiomics and machine learning models.

The Prognostic Value of Left Ventricular Entropy From T1 Mapping in Patients With Hypertrophic Cardiomyopathy

Background

The prognostic value of left ventricular (LV) entropy in hypertrophic cardiomyopathy (HCM) is unclear.

Objectives

This study aimed to assess the prognostic value of LV entropy from T1 mapping in HCM.

Methods

A total of 748 participants with HCM, who underwent cardiovascular magnetic resonance (CMR), were consecutively enrolled. LV entropy was quantified by native T1 mapping. A competing risk analysis and a Cox proportional hazards regression analysis were performed to identify potential associations of LV entropy with sudden cardiac death (SCD) and cardiovascular death (CVD), respectively.

Results

A total of 40 patients with HCM experienced SCD, and 65 experienced CVD during a median follow-up of 43 months. Participants with increased LV entropy (≥4.06) were more likely to experience SCD and CVD (all P < 0.05) in the entire study cohort or the subgroup with low late gadolinium enhancement (LGE) extent (<15%). After adjustment for the European Society of Cardiology predictors and the presence of high LGE extent (≥15%), LV mean entropy was an independent predictor for SCD (HR: 1.03; all P < 0.05) by the multivariable competing risk analysis and CVD (HR: 1.06; 95% CI: 1.03-1.09; P < 0.001) by multivariable Cox regression analysis.

Conclusions

LV mean entropy derived from native T1 mapping, reflecting myocardial tissue heterogeneity, was an independent predictor of SCD and CVD in participants with HCM. (Cardiac Magnetic Resonance Imaging Clinical Application Registration Study; ChiCTR1900024094).

Scanning the Imaging Horizon for Hypertrophic Cardiomyopathy

In this article some of the recent advances in the use of noninvasive imaging applied to patients with hypertrophic cardiomyopathy (HCM) are discussed. Echocardiography and cardiac computed tomography are briefly discussed with respect to their power to detect apical aneurysmal disease. Echocardiographic phenotype-genotype correlations and the use of echocardiography to characterize myocardial work are reviewed. Positron emission tomography is reviewed in the context of ischemia imaging and also in the context of the use of a new tracer that might allow for recognition of early activation of the fibrosis pathway. Next, the technical capabilities of cardiovascular magnetic resonance to measure myocardial perfusion, oxygenation, and disarray are discussed as they apply to HCM. The application of radiomics to improve prediction of sudden cardiac death is touched upon. Finally, a deep learning approach to the recognition of HCM vs phenocopies is presented as a potential future diagnostic aid in the not-too-distant future.