The Current and Emerging Role of Cardiovascular Magnetic Resonance Imaging in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy with substantial heterogeneity in phenotypic expression and clinical course. Traditionally, two-dimensional echocardiography has been the easiest and most reliable technique for establishing a diagnosis of HCM. However, cardiovascular magnetic resonance (CMR) has emerged as a novel, three-dimensional tomographic imaging technique, which provides high spatial and temporal resolution images of the heart in any plane and without ionizing radiation. As a result, CMR is particularly well suited to provide detailed characterization of the HCM phenotype, including precise assessment of the location and distribution of left ventricular (LV) wall thickening. In this regard, CMR can identify hypertrophy (particularly in the anterolateral free wall and apex), not well appreciated (or underestimated) by two-dimensional echocardiography, with important implications for diagnosis. CMR can also provide detailed characterization of other myocardial structures such as the papillary muscles, which may impact on preoperative management strategies for patients who are candidates for surgical myectomy. Furthermore, CMR enables an accurate assessment of total LV mass, a robust marker of the overall extent of hypertrophy, which may have implications for risk stratification. In addition, a subgroup of HCM patients have normal LV mass (with focal hypertrophy), suggesting that a limited extent of hypertrophy is consistent with a diagnosis of HCM. Finally, following the intravenous administration of gadolinium, first-pass perfusion sequences can identify myocardial perfusion abnormalities, while late gadolinium enhancement (LGE) sequences can characterize areas of myocardial fibrosis/scarring. LGE is associated with systolic dysfunction and likelihood for ventricular tachyarrhythmias on ambulatory Holter monitoring in patients with HCM. However, the precise clinical implications of myocardial perfusion abnormalities and LGE in HCM are still uncertain; this information may have important implications with regard to identifying HCM patients at risk of sudden death and adverse LV remodeling associated with systolic dysfunction. Therefore, at present, CMR provides important information impacting on diagnosis and clinical management strategies in patients with HCM and will likely have an expanding role in the evaluation of patients with this complex disease.     

The histologic basis of late gadolinium enhancement cardiovascular magnetic resonance in hypertrophic cardiomyopathy

OBJECTIVES: We sought to identify the histologic basis of myocardial late gadolinium enhancement cardiovascular magnetic resonance (CMR) in hypertrophic cardiomyopathy (HCM). BACKGROUND: The histologic basis of late gadolinium CMR in patients with HCM is unknown. METHODS: A 28-year-old male patient with HCM and heart failure underwent late gadolinium enhancement CMR and, 49 days later, heart transplantation. The explanted heart was examined histologically for the extent of collagen and disarray, and the results were compared with a previous in vivo CMR scan. RESULTS: Overall, 19% of the myocardium was collagen, but the amount per segment varied widely (SD +/- 19, range 0% to 71%). Both disarray and collagen were more likely to be found in the mesocardium than in the endo- or epicardium. There was a significant relationship between the extent of late gadolinium enhancement and collagen (r = 0.7, p < 0.0001) but not myocardial disarray (p = 0.58). Segments containing >15% collagen were more likely to have late gadolinium enhancement. Regional wall motion was inversely related to the extent of myocardial collagen and late gadolinium enhancement but not disarray (p = 0.0003, 0.04, and NS, respectively). CONCLUSIONS: In this patient with HCM and heart failure, regions of myocardial late gadolinium enhancement by CMR represented regions of increased myocardial collagen but not disarray.     

Toward clinical risk assessment in hypertrophic cardiomyopathy with gadolinium cardiovascular magnetic resonance

OBJECTIVES: We sought to assess whether hyperenhancement by gadolinium cardiovascular magnetic resonance (CMR) occurs in hypertrophic cardiomyopathy (HCM) and correlates with the risk of heart failure and sudden death. BACKGROUND: The myocardial interstitium is abnormal in HCM at post-mortem. Focally increased interstitial myocardial space appears as hyperenhancement with gadolinium CMR. METHODS: In a blinded, prospective study, HCM patients were selected for the presence (n = 23) or absence (n = 30) of an increased clinical risk of sudden death and/or progressive adverse left ventricular (LV) remodeling. Gadolinium-enhanced CMR was performed. RESULTS: Myocardial hyperenhancement was found in 42 patients (79%), affecting 10.9% (range 0% to 48%) of the LV mass. There was a greater extent of hyperenhancement in patients with progressive disease (28.5% vs. 8.7%, p < 0.001) and in patients with two or more risk factors for sudden death (15.7% vs. 8.6%, p = 0.02). Improved discrimination was seen in patients >40 years old (29.6% vs. 6.7%, p < 0.001) for progressive disease and for patients <40 years old for risk factors for sudden death (15.7% vs. 2.1%, p = 0.002). Patients with diffuse rather than confluent enhancement had two or more risk factors for sudden death (87% vs. 33%, p = 0.01). CONCLUSIONS: Gadolinium CMR reveals myocardial hyperenhancement in HCM. The extent of hyperenhancement is associated with progressive ventricular dilation and markers of sudden death.     

The Hypertrophic Cardiomyopathy Phenotype Viewed Through the Prism of Multimodality Imaging: Clinical and Etiologic Implications

Noninvasive contemporary imaging with echocardiography and cardiovascular magnetic resonance (CMR) provide comprehensive characterization of the hypertrophic cardiomyopathy (HCM) heart including precise definition of left ventricle (LV) wall thickness and reliable identification of morphologic abnormalities of the mitral valve, LV chamber, and myocardial tissue characterization with late gadolinium enhancement (LGE) (fibrosis). Imaging also contributes to identification of patients at risk for sudden death including novel high-risk features such as LV apical aneurysm and extensive LGE. Exercise (stress) echocardiography should be considered to demonstrate physiologic provocation of LV outflow gradients and to distinguish from patients with nonobstructive HCM. Multimodality imaging identifies patients who are optimal candidates for invasive septal reduction therapy and directs preoperative planning for extended myectomy and to optimize alcohol septal ablation. Contemporary imaging interwoven with current management strategies have resulted in a low HCM-related mortality rate.     

Correlation between late gadolinium enhancement and diastolic function in hypertrophic cardiomyopathy assessed by magnetic resonance imaging.

BACKGROUND: Diastolic dysfunction is common in patients with overt hypertrophic cardiomyopathy (HCM). Steady-state cine magnetic resonance imaging (MRI) enables measurement of the diastolic function of the left ventricle (LV), and late gadolinium enhanced MRI can delineate the presence and extent of fibrosis in HCM. The purpose of this study was to determine the relationship between the extent of myocardial fibrosis demonstrated by late gadolinium-enhanced MRI and diastolic dysfunction. METHODS AND RESULTS: Seventeen patients (13 men, mean age 57.7+/-9.8 years) with HCM were studied. The severity index of late gadolinium enhancement was determined by scoring the extent of enhanced tissue in 30 myocardial segments. The peak filling rate (PFR), LV ejection fraction and LV mass were determined by cine MRI. Contrast-enhanced MRI demonstrated late gadolinium enhancement in 97 of 510 segments (19%) and 13 of the 17 patients (77%). The severity index of late gadolinium enhancement demonstrated a significant negative correlation with PFR (r= -0.86, p<0.01) and with the LV ejection fraction (r= -0.59, p<0.05). No significant correlation was observed between the severity index of late gadolinium enhancement and LV mass (r=0.23, p=0.30). CONCLUSION: The extent of myocardial fibrosis revealed by late gadolinium-enhanced MRI has a strong relationship to diastolic dysfunction in patients with HCM.     

正电子发射断层成像术在肥厚型心肌病中的应用:发现微血管功能异常所致的心肌低灌注

Hypertrophic cardiomyopathy (HCM) is characterized by extreme clinical heterogeneity, ranging from sudden cardiac death to long-term disease progression and heart failure-related complications. Myocardial ischemia, occurring at the microvascular level, is a major determinant of clinical expression and outcome. Accordingly, the severity of this microvascular dysfunction has been shown to represent an early and powerful predictor of unfavorable outcome in HCM. The assessment of microvascular function in vivo is technically challenging, although critical to a truly comprehensive evaluation and risk stratification of HCM patients. Available technologies include positron emission tomography and cardiac magnetic resonance (CMR). Studies of regional myocardial blood flow using positron emission tomography have demonstrated that the vasodilator response to dipyridamole is impaired in most HCM patients, not only in the hypertrophied ventricular septum but also in the less hypertrophied or non-thickened left ventricular free wall. CMR also allows measurement of myocardial flow, although the technique is currently time-consuming and largely limited to research situations. CMR provides further insight into the effects of ischemia in HCM patients, by visualizing the distribution and extent of fibrosis at the intramyocardial level. Late gadolinium enhancement ( LGE) is a potential predictor of risk in HCM patients, and is believed to largely reflect replacement fibrosis resulting from recurrent microvascular ischemia. LCE is associated with increased prevalence of ventricular arrhythmias, and associated with microvascular dysfunction. The present review is to provide a concise overview for the available evidence of microvascular ischemia and its consequences in HCM.     

The role of cardiovascular magnetic resonance imaging in the diagnosis and prognosis of patients with heart failure

Cardiovascular magnetic resonance (CMR) imaging is a tomographic technique, which allows three-dimensional slice orientation without limitations from acoustic windows inherent to echocardiography. Further advantages of CMR are its high temporal and spatial resolution, its excellent soft tissue resolution and its high blood-to-tissue contrast. Cardiovascular magnetic resonance is currently the only imaging technique, which provides a comprehensive study of both structure and function of the heart as well as myocardial perfusion and viability. Moreover, post-processing of CMR images does not require any geometric assumptions as in echocardiography to determine ventricular dimensions. This is particularly important when evaluating ventricles of patients with chronic heart failure with severely altered morphology that may have regional variations in wall thickness and contractility at least in ischemic cardiomyopathy. The highly reproducible results of CMR imaging have turned this technique into a reference standard for the non-invasive assessment of ventricular dimensions, mass and function. In cases with indeterminate results of clinical, electrocardiographic and particularly echocardiographic findings CMR should be used early in the process of diagnosis of patients with heart failure. Not only can altered structure and degree of ventricular and valvular dysfunctions be accurately assessed but also regional perfusion deficits and/or myocardial scars are easily detected. For therapeutic and prognostic reasons a simple differentiation between ischemic and non-ischemic cardiomyopathy should be achieved as the first diagnostic step. In addition, the type and localization of the late gadolinium enhancement (LGE) phenomenon may aid in non-invasively differentiating the etiology of non-ischemic cardiomyopathy. CMR may also improve the assessment and extent of interventricular and intraventricular dyssynchrony in patients to be selected for cardiac resynchronization therapy (CRT). Lastly, the LGE phenomenon may provide independent prognostic information in patients with a CRT system implanted, as well as in patients with ischemic and non-ischemic cardiomyopathy. Thus, CMR imaging should be implemented early in the diagnostic process of patients with heart failure to significantly improve the speed and accuracy of diagnostic procedures, to control the effect of therapeutic measures, and to select patients with a limited prognosis by assessing the degree of ventricular dysfunction and the extent of myocardial scarring.     

Nonobstructive Hypertrophic Cardiomyopathy with Left Ventricular Aneurysm: The Role of Cardiac Magnetic Resonance

Hypertrophic cardiomyopathy with concomitant left ventricular aneurysm is rare and has important clinical implications, including an increased risk of sudden cardiac death. Most patients with this rare combination have obstructive hypertrophic cardiomyopathy, but we treated a 26-year-old woman who had nonobstructive hypertrophic cardiomyopathy and a family history of probable sudden cardiac death. In our patient, coronary angiograms showed distal occlusion of the left anterior descending coronary artery. Late gadolinium-enhanced cardiac magnetic resonance images showed scattered fibrosis within and beyond the left ventricular aneurysm. Precautionary therapy with an implantable cardioverter-defibrillator yielded an uneventful outcome. Cardiac magnetic resonance has emerged as a promising method for diagnosing these aneurysms and detecting associated myocardial fibrosis, thereby enabling patient risk stratification and the determination of appropriate therapeutic options. We discuss the role of cardiac magnetic resonance imaging in the management of this rare clinical entity.Key words: Cardiomyopathy, hypertrophic, familial/complications/pathology/therapy; coronary aneurysm/complications/diagnosis/therapy; death, sudden, cardiac/etiology; defibrillators, implantable; gadolinium/diagnostic use; image enhancement/instrumentation/methods; magnetic resonance imaging; risk assessmentNonobstructive hypertrophic cardiomyopathy (HCM) with left ventricular (LV) apical aneurysm is a rare clinical entity for which diagnostic, prophylactic, and therapeutic approaches are evolving. We describe the case of a patient who was diagnosed with this combination of conditions, and we discuss the role of cardiac magnetic resonance (CMR) in the therapeutic management of such patients.     

Distribution of late gadolinium enhancement in various types of cardiomyopathies:Significance in differential diagnosis,clinical features and prognosis

The recent development of cardiac magnetic resonance(CMR)techniques has allowed detailed analyses of cardiac function and tissue characterization with high spatial resolution.We review characteristic CMR features in ischemic and non-ischemic cardiomyopathies(ICM and NICM),especially in terms of the location and distribution of late gadolinium enhancement(LGE).CMR in ICM shows segmental wall motion abnormalities or wall thinning in a particular coronary arterial territory,and the subendocardial or transmural LGE.LGE in NICM generally does not correspond to any particular coronary artery distribution and is located mostly in the mid-wall to subepicardial layer.The analysis of LGE distribution is valuable to differentiate NICM with diffusely impaired systolic function,including dilated cardiomyopathy,end-stage hypertrophic cardiomyopathy(HCM),cardiac sarcoidosis,and myocarditis,and those with diffuse left ventricular(LV)hypertrophy including HCM,cardiac amyloidosis and Anderson-Fabry disease.A transient low signal intensity LGE in regions of severe LV dysfunction is a particular feature of stress cardiomyopathy.In arrhythmogenic right ventricular cardiomyopathy/dysplasia,an enhancement of right ventricular(RV)wall with functional and morphological changes of RV becomes apparent.Finally,the analyses of LGE distribution have potentials to predict cardiac outcomes and response to treatments.     

Evolving Anatomic, Functional, and Molecular Imaging in the Early Detection and Prognosis of Hypertrophic Cardiomyopathy

Evolving imaging modalities in hypertrophic cardiomyopathy (HCM), such as tissue Doppler, speckle tracking, measures of myocardial blood flow, and cardiac magnetic resonance with gadolinium enhancement, have advanced our understanding of the pathogenesis of myocardial dysfunction in hypertrophic cardiomyopathy. These modalities have the potential to differentiate HCM from other causes of left ventricular hypertrophy when there is uncertainty about the diagnosis and to identify affected individuals in the pre-clinical phase of the disease process. Furthermore, preliminary data suggests that functional imaging techniques may add incremental value to conventional risk stratification tools to identify individuals at high risk for sudden death or progression to congestive heart failure.