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Figure 1. Definition and Classification of Cardiomyopathies.
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Akira Matsumori, MD, PhD, Kyoto University Graduate School of Medicine, discussed classification systems for cardiomyopathies and presented a proposed new system. The current classification systems (AHA, ESC) mix the etiologies and phenotypes of cardiomyopathies. Dr. Matsumori proposed that classification of cardiomyopathies should be based on etiology, anatomical structure, physiology (mechanical), and electrical types. For example, dilated cardiomyopathy (DCM) of viral origin would be classified etiologically as infectious (IB), anatomically as dilated left ventricle (LV) (IIAa), and physiologically as systolic failure (IIIA), resulting in a classification of IB, IIAa, IIIA (Figure 1).
In Japanese patients, asymmetrical apical hypertrophy (AAH) is characterized by deeply inverted T wave inversion more than 1.2 mV in the left precordial leads with LVH, normal intraventricular septum (IVS) and LV posterior wall (LVPW) thickness, and localized hypertrophy near the LV apex. Apical hypertrophy is characterized as having giant negative T waves, spade-like configuration, average apical thickness greater than hypertrophic obstructive cardiomyopathy (HOCM), and apical to mid-anterior free wall ratio greater than normal, HOCM, and hypertrophic non-obstructive cardiomyopathy (HNCM).
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Figure 2. Viral Infection of the Heart.
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Figure 3. Hypertrophic Obstructive Cardiomyopathy Associated with HCV Infection.
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Figure 4. Apical Hypertrophic Cardiomyopathy Associated with HCV Infection.
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Figure 5. Clinical Profiles of Patients with Hypertrophic Cardiomyopathy with Positive Anti-Hepatitis C Virus Antibody.
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In US patients, the features of apical HCM are different than in Japanese patients, with IVS hypertrophy confined to the apical half, relatively mild T wave inversion, and no spade-like LV. Doi et al reported considerable differences between Japanese and Western patients with HCM in prevalence, symptoms, family history, sex, presence of giant negative T waves, and extent of apical hypertrophy.
A nationwide survey of patients with cardiomyopathy in Japan estimated prevalence to be 14.0 for DCM (N= 17,700), 17.3 for HCM (N=21,900), and 0.2 for restrictive cardiomyopathy (RCM) (N=300). A study of Japanese patients with HCM showed that the 5-year survival rate was 86.4%.
Cardiomyopathy caused by cardiac viral infection is thought to be the result of viral injury to myocytes, which results in different disorders depending on the location of the injury (Figure 2). Hepatitis C virus (HCV) has been associated with HCM and other cardiomyopathies. Figure 3 shows features of HOCM associated with HCV infection and Figure 4 shows features of apical HCM associated with HCV infection. Figure 5 shows clinical profiles of patients with HCM with positive anti-HCV antibody.
Susceptibility gene mapping for HCV-associated DCM and HCM showed that susceptibility to HCV-DCM was mapped at the locus spanning from NFKBIL1 to BAT1 loci within the HLA class III subregion. HCV-HCM was associated with DPB1 alleles. According to Dr. Matsumori, these candidate genes may encode molecules involved in immunity and inflammation.
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