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M A G I N G V I G N E T T E

ypertrophic Cardiomyopathy: Identification oforphological Subtypes by Echocardiographynd Cardiac Magnetic Resonance Imaging

mran S. Syed, MD,* Steve R. Ommen, MD, FACC,* Jerome F. Breen, MD,†. Jamil Tajik, MD, FACC‡

Y P E R T R O P H I C C A R D I O M Y O P A T H Y ( H C M ) can be defined as myocardial hypertrophy

n the absence of a causative condition and is thought to emanate from genetic mutations that result

n alterations in the cardiac myofilament. Hypertrophic cardiomyopathy is characterized by marked

enotypic, phenotypic, and clinical heterogeneity. Ventricular septal hypertrophy is the most common

orm of hypertrophy with mid-ventricular and apical forms of hypertrophy being far less common. The

attern of ventricular septal hypertrophy is variable and can broadly be divided into the following

orphological subtypes: reverse curvature, sigmoid, and neutral.

dacaH

myosin.

ppropriate identification of these morphological

ubtypes may be helpful because they appear to be

losely related to the presence or absence of a

CM-related genetic abnormality. In a recent

tudy, the majority of patients (79%) with reverse

urvature septum HCM harbored an identifiable

CM-associated mutation, whereas only a small

roportion of patients (16%) without a reverse cur-

ature septum were genotype positive (1). Table 1

emonstrates the reported relative frequency of gene

bnormalities in different HCM septal morphologic

ubtypes (1). These data have significant implica-

ions with respect to genetic counseling and the

linical application of genetic testing. Specifically,

he possibility of echocardiography-guided genetic

esting in HCM is evident. Furthermore, other

iagnostic modalities such as cardiac magnetic res-

nance imaging are helpful in delineating different

henotypic expressions of HCM (2). When using

he delayed enhancement technique, magnetic reso-

ance imaging also allows for the detection of myocar-

rom the *Division of Cardiovascular Diseases and the †Department ohe ‡Division of Cardiovascular Diseases, Mayo Clinic, Scottsdale, Ar

ial fibrosis, which has been demonstrated to bessociated with other high risk markers for suddenardiac death in HCM patients (3). Echocardiographicnd magnetic resonance imaging examples of eachCM morphologic subtype are shown in Figure 1.

Table 1. Frequency of Genetic Mutations in HCM by Septal

Characteristics Reverse Sigmoid Neutral

Genotype positive (%) 79 8 41

Family history of HCM (%) 45 21 34

Family history of SCD (%) 19 10 16

Type of mutation

None (%) 21 92 59

MYBPC3 (%) 34 5 19

MYH7 (%) 29 2 13

MYL2 (%) 4 0 3

TNNT2 (%) 3 1 0

TNNI3 (%) 2 1 3

TPM1 (%) 2 0 0

ACTC (%) 1 0 0

Multiple mutations (%) 5 0 3

ACTC � actin; HCM � hypertrophic cardiomyopathy; MYBPC3 � myoprotein C; MYH7 � myosin heavy chain; MYL2 � myosin light chain; SCDcardiac death; TNNI3 � troponin I; TNNT2 � troponin T; TPM1 � �-tropo

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Figure 1. HCM Subtypes Imaged by Echocardiography

Upper images: Hypertrophic cardiomyopathy (HCM)morphologic subtypes are demonstrated by echo-cardiography. End-diastolic (left) and end-systolic (right)images of the heart are shown.

Lower images: The HCM subtypes are well demonstratedby magnetic resonance imaging in the same patients.Left and middle columns show steady-state freeprecession images of the heart in a 3-chamberorientation 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 predominantmid-septal convexity toward the left ventricular (LV) cav-ity with the cavity itself often having an overall crescentshape. Dynamic subaortic obstruction is present in thisexample with systolic anterior motion (SAM) of the mitralleaflets and turbulent flow in the outflow tract. Promi-nent foci of MDE that indicate myocardial fibrosis arepresent in the anteroseptum and inferoseptum.

(B) Sigmoid septum HCM shows a generally ovoid LVcavity with the septum being concave to the LV cavityand a prominent basal septal bulge. Subaortic obstruc-tion is present in this example with SAM of the mitralleaflets and a posteriorly directed jet of mitral regurgita-tion. A small amount of MDE is seen in the septum.

(C) Neutral septum HCM shows an overall straight sep-tum that is neither predominantly convex nor concavetoward the LV cavity. Subaortic obstruction is present inthis example. A small focus of MDE is seen in theseptum.

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Figure 1 Continued.

(D) Apical HCM shows a predominant apical distribution ofhypertrophy. Myocardial delayed enhancement is seen inthe LV apex at the site of maximal hypertrophy in thisexample.

(E) Mid-ventricular HCM shows predominant hypertrophyat the mid-ventricular level. In this example, a thinned anddyskinetic apical pouch is also present. Obstruction is atthe level of the papillary muscles, where turbulence wasidentified. No mitral SAM. Myocardial delayed en-hancement is seen in the dyskinetic apical pouch.

E F E R E N C E S

. Binder J, Ommen SR, Gersh BJ, et al. Echocardiography-guided genetic testing inhypertrophic cardiomyopathy: septal morphological features predict the presence ofmyofilament mutations. Mayo Clin Proc 2006;81:459–67.

. Rickers C, Wilke NM, Jerosch-Herold M, et al. Utility of cardiac magnetic resonanceimaging in the diagnosis of hypertrophic cardiomyopathy. Circulation 2005;112:855–61.

. Moon JC, McKenna WJ, McCrohon JA, Elliott PM, Smith GC, Pennell DJ. Towardclinical risk assessment in hypertrophic cardiomyopathy with gadolinium cardiovascularmagnetic resonance. J Am Coll Cardiol 2003;41:1561–7.

Correspondence to: Dr. Imran S. Syed, Division ofCardiovascular Diseases, Mayo Clinic, 200 FirstStreet SW, Rochester, Minnesota 55905. E-mail:syed.imran@mayo.edu.