The use of CMR in cardiomyopathy has exploded in the last 5 years and many CMR centres now find cardiomyopathy patients form the largest proportion of the workload. The synergy of CMR with cardiovascular genetics has become clear, as has the need for CMR physicians to work closely with electrophysiology colleagues in assessing arrhythmic[41
] and sudden death risks. Rare forms of cardiomyopathy,[42
] which may be unclassified,[43
] are being studied and common themes of myocardial fibrosis development, pattern of deposition, and association with outcomes are being established.
Circumferential myocardial strain in cardiomyopathy with and without left bundle branch block
Cardiac resynchronization therapy (CRT) has been shown to improve clinical outcomes in patients with heart-failure. However, 30-40% of patients who receive CRT therapy do not show significant clinical improvement. There is much interest in refining our recognition of the latter group. In this study, Han et al sought to examine circumferential patterns in patients with LBBB and systolic dysfunction by applying tagged CMR[47
]. Septal dyskinesis was as expected a frequent abnormality. Three main patterns of abnormality were seen. Some patients with LBBB had severe mechanical dyssynchrony manifested as a specific contractile pattern with initial presystolic septal contraction during isovolumic contraction period followed by dyskinesis (positive εcc) of the interventricular septum during the entire systole. This pattern was present in the anteroseptum (Type Ia) in 30% of patients, and in the entire septum in 50% of patients (Type Ib). The remaining 20% of LBBB patients had a normal contractile pattern, similar to non-LBBB cardiomyopathy patients and healthy controls, although the magnitude of contraction was significantly reduced in both groups of cardiomyopathy patients compared to healthy controls. The recognition of the presence of different mechanical contraction patterns within the same conduction abnormality may be important for the selection of patients for CRT.
How do hypertrophic cardiomyopathy mutations affect myocardial function in carriers with normal wall thickness? Assessment with cardiovascular magnetic resonance
HCM is typically due to a sarcomeric gene mutation with an autosomal dominant pattern of inheritance. As such, early recognition of functional changes to either recognise gene carriers or as a putative target for therapy would be advantageous. In this study, Germans et al used CMR to assess global LA and LV volumes and regional intramural myocardial function in carriers with normal wall thickness[48
]. The asymmetry in wall thickness between the septum and lateral wall, which is characteristic for HCM, was already present in some carriers with normal wall thickness. Typical focal LGE was present in 2 carriers. Also, LA volumes were larger in carriers. In addition, HCM mutation carriership was identified as an independent determinant of reduced circumferential strain and strain rate, which was predominantly present in the basal lateral segments. Segmental peak systolic circumferential strain (SCS) and peak diastolic circumferential strain rate (DCSR) had a high accuracy to identify carriers, but did not completely exclude HCM mutation carriership.
Left ventricular T2 distribution in Duchenne Muscular Dystrophy
Duchenne Muscular Dystrophy (DMD) is associated with a skeletal and cardiac myopathy, the latter of which is coming under increasing scrutiny, in humans and animals,[49
] as a cause of death. A better understanding of the pathobiology and early changes will provide a potential opportunity to improve management. Significant research has been done to establish a role of T2 relaxation to detect myocardial edema,[50
] and in this study, of 26 Patients with DMD, Wansapura et al used the Full Width of Half Maximum (FWHM) of T2 distribution in the LV to quantify the myocardial structural heterogeneity in DMD patients[52
]. In DMD subject groups, FWHM of the T2 histogram rose progressively with age and decreasing EF. Further, FWHM was significantly higher in those with reduced circumferential strain. The myocardial structural abnormality suggested by the observed trend is likely due to concomitant presence of interstitial fibrosis and so in the early stage is not detected by the late enhancement technique. This study supports the view that the regional dysfunction depicted by reduced circumferential strain is associated with the ultrastructural myocardial cell abnormality present in DMD patients.
Quantitative analysis of late gadolinium enhancement in hypertrophic cardiomyopathy
The presence and amount of fibrosis in HCM appears to portend an adverse prognosis. An important practical challenge however has been defining and quantifying the presence of myocardial fibrosis by the late enhancement technique. Several methods based on a standard deviation or a full-width half maximum method have been proposed. Whilst these are highly reproducible in an infarct setting, in HCM where the fibrosis is more patchy and often diffuse, there is often the challenge of distinguishing true fibrosis from noise. In this study, Donato Aquaro and colleagues describe the merits of a cut-off derived from a Rayleigh curve as being potentially more accurate than using a fixed cut-off using a standard deviation algorithm[53
]. Further work is required to compare this to other algorithms based on a full-width half maximum method.
Right ventricular volumes and function in thalassemia major patients in the absence of myocardial iron overload
Beta-thalassemia major (TM) is a severe hereditary anemia requiring lifelong transfusions. There is a consequent iron overload, predominantly affecting the heart, liver and endocrine organs. Iron overload cardiomyopathy remains a major cause of death and therefore early detection of iron-induced cardiac toxicity is important, following by iron chelation treatment tailored to the heart[54
]. In addition to measurement of myocardial T2*, ventricular function can be impaired. Much of the current work has focused on the LV, however it is well established that RV dysfunction heart-failure carries an adverse prognosis. In this study, Carpenter and colleagues extended work evaluating the LV, to define a reference range for RV volumes, ejection fraction (EF) in thalassemia major patients (TM) without myocardial iron overload[55
]. This will be important in assessing the impact of myocardial iron overload in this cohort of patients and in assessing response to treatment.
Early detection of cardiac involvement in Miyoshi myopathy: 2D strain echocardiography and late gadolinium enhancement cardiovascular magnetic resonance
The first question raised by this title must be -'so what is Miyoshi myopathy'? Miyoshi Myopathy (MM) is a distinct form of muscular dystrophy caused by mutations within the dysferlin (DYSF) gene resulting in severe to complete deficiency of dysferlin expression. Clinically, these dysferlinopathies start in young adulthood with progressive muscle weakness and atrophy that advances to severe disability in older adulthood. While the profound effect of dysferlin deficiency in skeletal muscle has been the subject of much investigation, the effect of dysferlin deficiency in cardiac muscle have not been studied yet. In this study, Choi et al, demonstrated a reduction in longitudinal strain and the presence of replacement fibrosis in a subset of affected patients[56
]. This was detected prior to the development of cardiovascular symptoms or a reduction in overall LVEF. The ramifications are two-fold. Firstly in this uncommon myopathy demonstrating an opportunity for early detection. Secondly and more broadly, it extends the 'portfolio' of cardiomyopathies where CMR in conjunction with echo provides unique insights based on tissue characterization.
Troponin release following endurance exercise: is inflammation the cause? A cardiovascular magnetic resonance study
It is generally acknowledged that exercise is a good thing. Yet debate persists about the true health benefits of ultra-endurance forms exercise - particularly marathon running where a troponin rise is seen - often to the same levels as an acute myocardial infarction. In this study, O'Hanlon and colleagues examined if there were detectable tissue changes on CMR in a cohort of volunteers scanned following a marathon[57
]. A baseline control scan pre-exercise was performed in all participants. Exercise induced cardiac biomarker release was not associated with any functional changes by CMR or any detectable myocardial inflammation or fibrosis. This study contributes to understanding the link, aetiology and significance of the troponin rise post-exercise.
Epicardial adipose tissue in patients with heart failure
The role of epicardial adipose tissue (EAT) and its contribution to the development of cardiac pathology is quite ambiguous. There is growing evidence of a close functional and anatomical relationship between the adipose tissue and muscular components of the heart. Its close proximity to the myocardium suggests that EAT is a metabolically active organ and a source of several bioactive molecules may influence cardiac morphology and function. In this study, Doesch et al demonstrate that in patients with CHF and severely reduced impaired LV-EF (LV-EF < 35%), EAT is significantly reduced compared to healthy controls[58
]. The reduction of EAT is irrespective of the underlying aetiology of the cardiomyopathy. Like in healthy controls an increase in left ventricular mass also leads to an augmentation of the EAT mass in patients with CHF, however, contrary to previous studies, the EAT mass/LV-EDM ratio is significantly lower compared to healthy controls. Abnormalities and/or anatomic alterations due to disturbed cardiac function and geometry seem to play a key role and are a possible explanation for these findings.
Myocardial late gadolinium enhancement cardiovascular magnetic resonance in patients with cirrhosis
End stage liver disease (ELD) is associated with major alterations in the regulation of the cardiovascular system. Portal hypertension and/or hormonal changes in ELD induce a hyperdynamic circulatory state characterized by arterial hypotension and tachycardia and are often accompanied by ascites and electrolyte disturbances. Recent data also emphasizes the impact of liver function on renal (hepatorenal syndrome) and pulmonary (hepatopulmonary and portopulmonary syndrome) circulation. Whilst there is much focus on the causes and treatment of renal and pulmonary manifestations, relatively little is understood about the myocardial changes as a result of ELD. In this study, Lossnitzer et al show that myocardial alterations have a high prevalence among ELD patients[59
]. This is often in a pattern seen in myocarditis. Commonly identified features were a hyperdynamic LV function and a patchy pattern of replacement fibrosis. This work is useful in furthering our understanding of the effects of severe liver disease and may have potential value in guiding selection of Patients for liver transplantation - the latter needs larger prospective trials.
Accuracy of cardiovascular magnetic resonance in myocarditis: comparison of MR and histological findings in an animal model
In the evaluation of myocarditis, CMR has now frequently replaced the more traditional method of endomyocardial biopsies (EMB) to confirm the diagnosis. As well as being invasive and with a tangible risk of severe morbidity or mortality, EMB has frequently suffered from sampling bias resulting in a low sensitivity. In an animal model, the extent of LGE correlated to the histological severity of myocarditis and to serum-levels of troponin T on day 21[60
]. Areas of LGE had nearly identical topographic distribution as compared to histologically proven areas of inflammation and provided a good marker of cardiomyocyte necrosis. This is supportive data for the clinical use of CMR either as an alternative to EMB, or where it is important to know the pathogen, to guide the site of EMB.
Myocardial fibrosis in desmin-related hypertrophic cardiomyopathy
Desmin is the main intermediate filament protein expressed in skeletal, cardiac, and smooth muscle. It interacts with other proteins to form a continuous cytoskeletal network that maintains a spatial relationship between the contractile apparatus and other structural elements of the cell, thus providing maintenance of cellular integrity, force transmission, and mechano-chemical signalling. Primary desminopathies are caused by mutations in the desmin gene. This disease is characterized by an intracellular accumulation of insoluble protein aggregates eventually leading to cell death and replacement fibrosis. In this case report, fibrosis was detected by LGE in the absence of global or focal systolic wall motion abnormalities[61
]. LGE may have value therefore in the diagnosis and early evaluation of affected individuals.