By the end of this chapter the student will be able to:
Identify the type of cardiomyopathy based on clinical features.
Describe the mechanism, natural history, and prognosis of a particular cardiomyopathy.
Understand the role of different modalities in diagnosis.
Determine the best treatment modality for a specific cardiomyopathy.
Apply the above knowledge in a clinical setting.
Cardiomyopathies refer to a group of diseases of the heart muscle. Cardiomyopathies are divided into 3 major types: (1) hypertrophic cardiomyopathy, (2) restrictive cardiomyopathy, and (3) dilated cardiomyopathy. While dilated cardiomyopathy is the most common type, and the ultimate outcome of all cardiomyopathies, it is nevertheless important to recognize all 3 types as they differ in presentation, diagnosis, and management. This chapter discusses each type of these cardiomyopathies in terms of clinical symptoms, natural history, clinical signs, diagnoses, and treatment, including pharmacological, surgical, and device management.
Hypertrophic cardiomyopathy (HCM) is an autosomal dominant disease affecting 1 in 500 of the general population in the United States as seen in the Coronary Artery Risk Development in Young Adults (CARDIA) study. Hypertrophic cardiomyopathy is defined as hypertrophy of the left ventricle that develops in the absence of hypertension, aortic valve disease, systemic infiltrative, or storage diseases (Fig. 14.1). Microscopically, hypertrophic cardiomyopathy is characterized by a misalignment and disarray of the enlarged myofibrils and myocytes (Fig. 14.2). The disease is caused by a mutation in 1 of 13 or more sarcomeric genes. The presentation can vary from sudden cardiac death (SCD), ventricular arrhythmias, or insidiously with symptoms of heart failure, although the majority are asymptomatic. Myosin heavy chain 7 (MYH7) mutations are the most common occurrence, manifesting in more than 30% of patients with HCM, followed by myosin-binding protein C (MYBPC3C) and cardiac troponin T (TNNT2), each of which occurs in more than 20% of cases. There are 10 major gene mutations, which are listed in Table 14.1.
Table 14.1Major gene mutations in hypertrophic cardiomyopathy ||Download (.pdf) Table 14.1 Major gene mutations in hypertrophic cardiomyopathy
|Sarcomere genes with mutations in order of frequency of occurrence |
|MYH7 (β-myosin heavy chain) |
|MYBPC3 (myosin-binding protein C) |
|TNNT2 (cardiac troponin T) |
|TNNI3 (cardiac troponin I) |
|TTN (titin) |
|TPM1 (α-tropomyosin) |
|TNNC1 (cardiac troponin C) |
|ACTC (α-actin) |
|MYL2 (myosin regulatory light chain) |
|MYL3 (myosin essential light chain) |
Gross specimen of a heart with hypertrophic cardiomyopathy. (Reproduced, with permission, from Kasper DL, Fauci AS, Hauser SL, Longo DL, Jameson JL, Loscalzo J, eds. Harrison’s Principles of Internal Medicine. 19th ed. New York, NY: McGraw-Hill; 2015. Image courtesy of Robert Padera, MD, PhD, Department of Pathology, Brigham and Women’s Hospital, Boston.)
Microscopic image of hypertrophic cardiomyopathy. ...