The diagnosis of hypertrophic cardiomyopathy by cardiovascular magnetic resonance

Magnetic resonance imaging for hypertrophic cardiomyopathy update

OBJECTIVES

Hypertrophic cardiomyopathy (HCM) is a genetic disease of the myocardium. Although many patients remain asymptomatic, sudden cardiac death could be the first manifestation of HCM. Magnetic resonance imaging (MRI) plays an important role in the diagnosis and management of this disease.

METHODS

The epidemiology, pathophysiology, and diagnosis of HCM will be briefly reviewed. This is followed by a discussion on the role of cardiac MRI, recommended protocol, typical imaging findings of HCM, and advanced MRI techniques.

CONCLUSIONS

Although MRI is not intended to be a first-line tool for the assessment of HCM, MRI does provide valuable information to aid the management of patients either at risk of or diagnosed with HCM.

Advances of cardiovascular MRI in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease characterized by abnormal myocardial hypertrophy, which can lead to a wide clinical spectrum, including sudden cardiac death and heart failure. Cardiac MRI has a significant role in establishing the diagnosis of HCM. In the three principal management issues related to HCM; testing of family members of affected individuals; assessing the risk of sudden cardiac death from lethal ventricular arrhythmias; and selection of appropriate treatments for left ventricular outflow obstruction, cardiac MRI has established or emerging roles.

Review of Journal of Cardiovascular Magnetic Resonance 2012

There were 90 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2012, which is an 8% increase in the number of articles since 2011. The quality of the submissions continues to increase. The editors are delighted to report that the 2011 JCMR Impact Factor (which is published in June 2012) has risen to 4.44, up from 3.72 for 2010 (as published in June 2011), a 20% increase. The 2011 impact factor means that the JCMR papers that were published in 2009 and 2010 were cited on average 4.44 times in 2011. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is approximately 25%, and has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication.

Highlights of the 16th annual scientific sessions of the Society for Cardiovascular Magnetic Resonance

The 16th Annual Scientific Sessions of the Society for Cardiovascular Magnetic Resonance (SCMR) took place in San Francisco, USA at the end of January 2013. With a faculty of experts from across the world, this congress provided a wealth of insight into cutting-edge research and technological development. This review article intends to provide a highlight of what represented the most significant advances in the field of cardiovascular magnetic resonance (CMR) during this year's meeting.

Severe Midventricular Hypertrophic Obstructive Cardiomyopathy and Apical Aneurysm

A 40-year-old man was found to have hypertrophic cardiomyopathy (HCM) with severe mid ventricular obstruction. The obstruction produced two distinct left ventricular chambers with an estimated 60 mmHg continuous wave (CW) Doppler intraventricular gradient. Pulsed wave (PW) Doppler showed high velocity systodiastolic flow from apex to base and flow from base to apex confined mostly to the second half of diastole. Cardiac magnetic resonance (CMR) showed midventricular obstruction, due to septal, parietal, and to an hypertrophic, double posteromedial papillary muscle; an apical aneurysm was detected. Aneurysm is underdiagnosed by echocardiography in HCM and an accurate anatomic definition is needed if surgery is planned; thus, a CMR should always be obtained in these patients.

Myocardial fibrosis detected by cardiac CT predicts ventricular fibrillation/ventricular tachycardia events in patients with hypertrophic cardiomyopathy

BACKGROUND

Myocardial fibrosis (MF) occurs in up to 80% of subjects with asymptomatic or mildly symptomatic hypertrophic cardiomyopathy (HCM) and can constitute an arrhythmogenic substrate for re-entrant, life-threatening ventricular arrhythmias in predisposed persons.

OBJECTIVE

The aim was to investigate whether MF detected by delayed enhancement cardiac CT is predictive of ventricular tachycardia (VT) and fibrillation (VF) that require appropriate therapy by an implantable cardioverter defibrillator (ICD) in patients with HCM.

METHODS

Twenty-six patients with HCM with previously (for at least 1 year) implanted ICD underwent MF evaluation by cardiac CT. MF was quantified by myocardial delayed enhanced cardiac CT. Data on ICD firing were recorded every 3 months after ICD implantation. Risk factors for sudden cardiac death in patients with HCM were evaluated in all patients.

RESULTS

MF was present in 25 of 26 patients (96%) with mean fibrosis mass of 20.5 ± 15.8 g. Patients with appropriate ICD shocks for VF/VT had significantly greater MF mass than patients without (29.10 ± 19.13 g vs 13.57 ± 8.31 g; P = .01). For a MF mass of at least 18 g, sensitivity and specificity for appropriate ICD firing were 73% (95% CI, 49%-88%) and 71% (95% CI, 56%-81%), respectively. Kaplan-Meier curves indicated a significantly greater VF/VT event rate in patients with MF mass ≥18 g than in patients with MF <18 g (P = .02). In the Cox regression analysis, the amount of MF was independently associated with VF/VT in ICD-stored electrograms.

CONCLUSION

The mass of MF detected by cardiac CT in patients with HCM at high risk of sudden death was associated with appropriate ICD firings.

Reproducibility of in-vivo diffusion tensor cardiovascular magnetic resonance in hypertrophic cardiomyopathy

BACKGROUND

Myocardial disarray is an important histological feature of hypertrophic cardiomyopathy (HCM) which has been studied post-mortem, but its in-vivo prevalence and extent is unknown. Cardiac Diffusion Tensor Imaging (cDTI) provides information on mean intravoxel myocyte orientation and potentially myocardial disarray. Recent technical advances have improved in-vivo cDTI, and the aim of this study was to assess the interstudy reproducibility of quantitative in-vivo cDTI in patients with HCM.

METHODS AND RESULTS

A stimulated-echo single-shot-EPI sequence with zonal excitation and parallel imaging was implemented. Ten patients with HCM were each scanned on 2 different days. For each scan 3 short axis mid-ventricular slices were acquired with cDTI at end systole. Fractional anisotropy (FA), mean diffusivity (MD), and helix angle (HA) maps were created using a cDTI post-processing platform developed in-house. The mean ± SD global FA was 0.613 ± 0.044, MD was 0.750 ± 0.154 × 10-3 mm2/s and HA was epicardium -34.3 ± 7.6°, mesocardium 3.5 ± 6.9° and endocardium 38.9 ± 8.1°. Comparison of initial and repeat studies showed global interstudy reproducibility for FA (SD = ± 0.045, Coefficient of Variation (CoV) = 7.2%), MD (SD = ± 0.135 × 10-3 mm2/s, CoV = 18.6%) and HA (epicardium SD = ± 4.8°; mesocardium SD = ± 3.4°; endocardium SD = ± 2.9°). Reproducibility of FA was superior to MD (p = 0.003). MD was significantly higher in the septum than the reference lateral wall (0.784 ±0.188 vs 0.714 ±0.155 ×10-3 mm2/s, p <0.001) [corrected]. Septal HA was significantly lower than the reference lateral wall in all 3 transmural layers (from -8.3° to -10.4°, all p < 0.001).

CONCLUSIONS

To the best of our knowledge, this is the first study to assess the interstudy reproducibility of DTI in the human HCM heart in-vivo and the largest cDTI study in HCM to date. Our results show good reproducibility of FA, MD and HA which indicates that current technology yields robust in-vivo measurements that have potential clinical value. The interpretation of regional differences in the septum requires further investigation.

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

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.

Heart failure in patients with normal coronary anatomy: diagnostic algorithm and disease pattern of various etiologies as defined by cardiac MRI

In a subgroup of patients with acute heart failure coronary artery disease can be excluded. To explain symptoms and optimize therapy cardiac magnetic resonance (CMR) imaging can contribute to elucidate the underlying pathology in non-ischemic heart disease. A diagnostic algorithm for the work-up of these patients using CMR is suggested. The review discusses various modules of a dedicated CMR protocol. It explains diagnostic markers and challenges of CMR imaging in non-ischemic heart disease. Based on these suggestions the literature in the field is reviewed.