CHAPTER 62: ARRHYTHMOGENIC CARDIOMYOPATHY

INTRODUCTION AND DEFINITION

Arrhythmogenic cardiomyopathy is a rare primary myocardial disease that is clinically characterized by life-threatening ventricular arrhythmias secondary to fibrofatty replacement of ventricular myocytes.^1,2,3

In the first systematic description of 24 adult cases in 1982, Marcus et al⁴ outlined the profile of right ventricular (RV) dysplasia as a pathologic condition primarily affecting the right ventricle and characterized by partial or total absence of RV musculature due to substitution by fatty and fibrous tissue. The authors distinguished conditions in which the RV myocardium was almost completely absent from those in which the fatty and fibrous tissue was limited to portions of the right ventricle. The former showed cardiomegaly and clinically manifested with congestive heart failure. The latter showed mild RV remodeling and minimally impaired cardiac dysfunction. When ventricular tachycardia was the principal manifestation, the condition was termed arrhythmogenic RV dysplasia (ARVD).⁴ The authors additionally described 34 adult cases and provided the clinical profile of the disease:

• Clinical presentation is characterized by ventricular tachycardia, supraventricular arrhythmias, right heart failure, or asymptomatic cardiomegaly.

• Electrocardiogram (ECG) shows T wave inversion in the right precordial leads.

• Increased RV diastolic dimensions.

• Onset is in young adult age.

• Prevalence is higher in males than in females.

In 1988, Thiene et al⁵ described the morphologic features of RV cardiomyopathy in 12 young people who died suddenly. Findings included:

• Normal or moderately increased heart weights

• Lipomatous transformation (6 of 12 patients) or a fibrolipomatous (6 of 12 patients) transformation of the RV free wall

• Substantially spared left ventricle

• Occasional myocardial degeneration and necrosis, with or without inflammatory infiltrates

In 1994, an International Task Force grouped criteria for the clinical diagnosis of arrhythmogenic RV cardiomyopathy/dysplasia (ARVC/D).⁶ These criteria were aimed at facilitating recognition and interpretation of the clinical and pathologic features of ARVC/D and were grouped according to:

• Structural and histologic features

• ECG and arrhythmic features

• Familial features

These features were incorporated into criteria that were subdivided into major and minor categories according to the specificity of their association with ARVC/D. These criteria revealed high specificity, but low sensitivity, for early and familial disease.⁶

In 2010, task force criteria were modified to improve the diagnosis and management of ARVC/D. The modified criteria incorporated new knowledge on the genetic basis of the disease, improving diagnostic sensitivity and maintaining diagnostic specificity (Table 62–1). The structural, histologic, ECG, arrhythmic, and genetic features were structured in major and minor criteria. The task force document formally introduced the biventricular variant and the left dominant variant.⁷ These latter criteria support the broader new term of arrhythmogenic cardiomyopathy (ACM). Therefore, the disease is currently called ACM, ARVC/D, ARVC, or ARVD. In this chapter, the disease is named according to the task force criteria—ACM.