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      Diffuse myocardial fibrosis in hypertrophic cardiomyopathy can be identified by cardiovascular magnetic resonance, and is associated with left ventricular diastolic dysfunction

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          Abstract

          Background

          The presence of myocardial fibrosis is associated with worse clinical outcomes in hypertrophic cardiomyopathy (HCM). Cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE) sequences can detect regional, but not diffuse myocardial fibrosis. Post-contrast T 1 mapping is an emerging CMR technique that may enable the non-invasive evaluation of diffuse myocardial fibrosis in HCM. The purpose of this study was to non-invasively detect and quantify diffuse myocardial fibrosis in HCM with CMR and examine its relationship to diastolic performance.

          Methods

          We performed CMR on 76 patients - 51 with asymmetric septal hypertrophy due to HCM and 25 healthy controls. Left ventricular (LV) morphology, function and distribution of regional myocardial fibrosis were evaluated with cine imaging and LGE. A CMR T 1 mapping sequence determined the post-contrast myocardial T 1 time as an index of diffuse myocardial fibrosis. Diastolic function was assessed by transthoracic echocardiography.

          Results

          Regional myocardial fibrosis was observed in 84% of the HCM group. Post-contrast myocardial T 1 time was significantly shorter in patients with HCM compared to controls, consistent with diffuse myocardial fibrosis (498 ± 80 ms vs. 561 ± 47 ms, p < 0.001). In HCM patients, post-contrast myocardial T 1 time correlated with mean E/e’ (r = −0.48, p < 0.001).

          Conclusions

          Patients with HCM have shorter post-contrast myocardial T 1 times, consistent with diffuse myocardial fibrosis, which correlate with estimated LV filling pressure, suggesting a mechanistic link between diffuse myocardial fibrosis and abnormal diastolic function in HCM.

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          Most cited references22

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          Hypertrophic cardiomyopathy: a systematic review.

          Throughout the past 40 years, a vast and sometimes contradictory literature has accumulated regarding hypertrophic cardiomyopathy (HCM), a genetic cardiac disease caused by a variety of mutations in genes encoding sarcomeric proteins and characterized by a broad and expanding clinical spectrum. To clarify and summarize the relevant clinical issues and to profile rapidly evolving concepts regarding HCM. Systematic analysis of the relevant HCM literature, accessed through MEDLINE (1966-2000), bibliographies, and interactions with investigators. Diverse information was assimilated into a rigorous and objective contemporary description of HCM, affording greatest weight to prospective, controlled, and evidence-based studies. Hypertrophic cardiomyopathy is a relatively common genetic cardiac disease (1:500 in the general population) that is heterogeneous with respect to disease-causing mutations, presentation, prognosis, and treatment strategies. Visibility attached to HCM relates largely to its recognition as the most common cause of sudden death in the young (including competitive athletes). Clinical diagnosis is by 2-dimensional echocardiographic identification of otherwise unexplained left ventricular wall thickening in the presence of a nondilated cavity. Overall, HCM confers an annual mortality rate of about 1% and in most patients is compatible with little or no disability and normal life expectancy. Subsets with higher mortality or morbidity are linked to the complications of sudden death, progressive heart failure, and atrial fibrillation with embolic stroke. Treatment strategies depend on appropriate patient selection, including drug treatment for exertional dyspnea (beta-blockers, verapamil, disopyramide) and the septal myotomy-myectomy operation, which is the standard of care for severe refractory symptoms associated with marked outflow obstruction; alcohol septal ablation and pacing are alternatives to surgery for selected patients. High-risk patients may be treated effectively for sudden death prevention with the implantable cardioverter-defibrillator. Substantial understanding has evolved regarding the epidemiology and clinical course of HCM, as well as novel treatment strategies that may alter its natural history. An appreciation that HCM, although an important cause of death and disability at all ages, does not invariably convey ominous prognosis and is compatible with normal longevity should dictate a large measure of reassurance for many patients.
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            Evaluation of diffuse myocardial fibrosis in heart failure with cardiac magnetic resonance contrast-enhanced T1 mapping.

            The purpose of this study was to investigate a noninvasive method for quantifying diffuse myocardial fibrosis with cardiac magnetic resonance imaging (CMRI). Diffuse myocardial fibrosis is a fundamental process in pathologic remodeling in cardiomyopathy and is postulated to cause increased cardiac stiffness and poor clinical outcomes. Although regional fibrosis is easily imaged with cardiac magnetic resonance, there is currently no noninvasive method for quantifying diffuse myocardial fibrosis. We performed CMRI on 45 subjects (25 patients with heart failure, 20 control patients), on a clinical 1.5-T CMRI scanner. A prototype T(1) mapping sequence was used to calculate the post-contrast myocardial T(1) time as an index of diffuse fibrosis; regional fibrosis was identified by delayed contrast enhancement. Regional and global systolic function was assessed by cine CMRI in standard short- and long-axis planes, with echocardiography used to evaluate diastology. An additional 9 subjects underwent CMRI and endomyocardial biopsy for histologic correlation. Post-contrast myocardial T(1) times correlated histologically with fibrosis (R = -0.7, p = 0.03) and were shorter in heart failure subjects than controls (383 +/- 17 ms vs. 564 +/- 23 ms, p < 0.0001). The T(1) time of heart failure myocardium was shorter than that in controls even when excluding areas of regional fibrosis (429 +/- 22 ms vs. 564 +/- 23 ms, p < 0.0001). The post-contrast myocardial T(1) time shortened as diastolic function worsened (562 +/- 24 ms in normal diastolic function vs. 423 +/- 33 ms in impaired diastolic function vs. 368 +/- 20 ms in restrictive function, p < 0.001). Contrast-enhanced CMRI T(1) mapping identifies changes in myocardial T(1) times in heart failure, which appear to reflect diffuse fibrosis.
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              The genetic basis for cardiomyopathy: from mutation identification to mechanistic paradigms.

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                Author and article information

                Journal
                J Cardiovasc Magn Reson
                J Cardiovasc Magn Reson
                Journal of Cardiovascular Magnetic Resonance
                BioMed Central
                1097-6647
                1532-429X
                2012
                29 October 2012
                : 14
                : 1
                : 76
                Affiliations
                [1 ]Heart Centre, Alfred Hospital, Melbourne, Australia
                [2 ]Baker IDI Heart and Diabetes Research Institute, Melbourne, Australia
                Article
                1532-429X-14-76
                10.1186/1532-429X-14-76
                3502601
                23107451
                9b7e77b6-edba-4440-a7c7-2b23e5ecce28
                Copyright ©2012 Ellims et al.; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 11 July 2012
                : 17 October 2012
                Categories
                Research

                Cardiovascular Medicine
                hypertrophic cardiomyopathy,myocardial fibrosis,magnetic resonance imaging,t1 mapping

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