Hypertrophic Cardiomyopathy: Identification of Morphological Subtypes by Echocardiography and Cardiac Magnetic Resonance Imaging
Imran S. Syed, MD*,*,
Steve R. Ommen, MD, FACC*,
Jerome F. Breen, MD ,
A. Jamil Tajik, MD, FACC
* Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota
Department of Radiology, Mayo Clinic, Rochester, Minnesota
Division of Cardiovascular Diseases, Mayo Clinic, Scottsdale, Arizona.
HYPERTROPHIC CARDIOMYOPATHY (HCM) can be defined as myocardial hypertrophy in the absence of a causative condition and is thought to emanate from genetic mutations that result in alterations in the cardiac myofilament. Hypertrophic cardiomyopathy is characterized by marked genotypic, phenotypic, and clinical heterogeneity. Ventricular septal hypertrophy is the most common form of hypertrophy with mid-ventricular and apical forms of hypertrophy being far less common. The pattern of ventricular septal hypertrophy is variable and can broadly be divided into the following morphological subtypes: reverse curvature, sigmoid, and neutral.
Appropriate identification of these morphological subtypes may be helpful because they appear to be closely related to the presence or absence of a HCM-related genetic abnormality. In a recent study, the majority of patients (79%) with reverse curvature septum HCM harbored an identifiable HCM-associated mutation, whereas only a small proportion of patients (16%) without a reverse curvature septum were genotype positive (1). Table 1
demonstrates the reported relative frequency of gene abnormalities in different HCM septal morphologic subtypes (1). These data have significant implications with respect to genetic counseling and the clinical application of genetic testing. Specifically, the possibility of echocardiography-guided genetic testing in HCM is evident. Furthermore, other diagnostic modalities such as cardiac magnetic resonance imaging are helpful in delineating different phenotypic expressions of HCM (2). When using the delayed enhancement technique, magnetic resonance imaging also allows for the detection of myocardial fibrosis, which has been demonstrated to be associated with other high risk markers for sudden cardiac death in HCM patients (3). Echocardiographic and magnetic resonance imaging examples of each HCM morphologic subtype are shown in Figure 1.
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Figure 1 HCM Subtypes Imaged by Echocardiography
Upper images: Hypertrophic cardiomyopathy (HCM) morphologic subtypes are demonstrated by echocardiography. End-diastolic (left) and end-systolic (right) images of the heart are shown.
Lower images: The HCM subtypes are well demonstrated by magnetic resonance imaging in the same patients. Left and middle columns show steady-state free precession images of the heart in a 3-chamber orientation in end-diastole and end-systole, respectively. Right column shows myocardial delayed enhancement (MDE) images using an inversion recovery gradient-recalled-echo technique.
(A) Reverse curvature septum HCM shows a predominant mid-septal convexity toward the left ventricular (LV) cavity with the cavity itself often having an overall crescent shape. Dynamic subaortic obstruction is present in this example with systolic anterior motion (SAM) of the mitral leaflets and turbulent flow in the outflow tract. Prominent foci of MDE that indicate myocardial fibrosis are present in the anteroseptum and inferoseptum.
(B) Sigmoid septum HCM shows a generally ovoid LV cavity with the septum being concave to the LV cavity and a prominent basal septal bulge. Subaortic obstruction is present in this example with SAM of the mitral leaflets and a posteriorly directed jet of mitral regurgitation. A small amount of MDE is seen in the septum.
(C) Neutral septum HCM shows an overall straight septum that is neither predominantly convex nor concave toward the LV cavity. Subaortic obstruction is present in this example. A small focus of MDE is seen in the septum.
(D) Apical HCM shows a predominant apical distribution of hypertrophy. Myocardial delayed enhancement is seen in the LV apex at the site of maximal hypertrophy in this example.
(E) Mid-ventricular HCM shows predominant hypertrophy at the mid-ventricular level. In this example, a thinned and dyskinetic apical pouch is also present. Obstruction is at the level of the papillary muscles, where turbulence was identified. No mitral SAM. Myocardial delayed enhancement is seen in the dyskinetic apical pouch.
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* Correspondence to: Dr. Imran S. Syed, Division of Cardiovascular Diseases, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905. (Email: syed.imran{at}mayo.edu).
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REFERENCES
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- Binder J, Ommen SR, Gersh BJ, et al. Echocardiography-guided genetic testing in hypertrophic cardiomyopathy: septal morphological features predict the presence of myofilament mutations Mayo Clin Proc 2006;81:459-467.[Abstract/Free Full Text]
- Rickers C, Wilke NM, Jerosch-Herold M, et al. Utility of cardiac magnetic resonance imaging in the diagnosis of hypertrophic cardiomyopathy Circulation 2005;112:855-861.[Abstract/Free Full Text]
- Moon JC, McKenna WJ, McCrohon JA, Elliott PM, Smith GC, Pennell DJ. Toward clinical risk assessment in hypertrophic cardiomyopathy with gadolinium cardiovascular magnetic resonance J Am Coll Cardiol 2003;41:1561-1567.[Abstract/Free Full Text]
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