*1.1. Dilated Cardiomyopathy: Prevalence, Causes, and Clinical Manifestations*

Cardiovascular diseases (CVD) contribute to approximately 30% of global morbidity and mortality, representing a major public health concern [1]. Among the several types of CVD, dilated cardiomyopathies (DCM) are an important cause of congestive heart failure and cardiac disease requiring heart transplantation [2]. DCM is a disease of the heart muscle characterized by increased ventricle chamber volume and impaired systolic function involving the left or both ventricles. DCM can develop at any age, is a common form of cardiomyopathy in the pediatric population, and can lead to sudden cardiac death in adolescents and young adults [2,3]. Although the etiology of DCM remains unknown in 66% of cases, myocarditis and neuromuscular diseases are the most commonly recognized causes of DCM. In 20–48% of cases, the disease is inherited and is referred to as familial dilated cardiomyopathy [2,3].

DCM is commonly underdiagnosed because most individuals are asymptomatic in the early stages of the disease. Typically, DCM is diagnosed during screening for cardiac dysfunction in individuals considered at risk, such as in family members of DCM patients. Early symptoms are nonspecific and include easy fatigability, decreased appetite, effort-induced shortness of breath, intermittent chest pain, fainting, syncope, and/or palpitations [3]. Undiagnosed, patients will later present with symptoms of end organ dysfunction due to systolic defects and peripheral hypoperfusion [3]. Physical examination can reveal sinusoidal tachycardia, gallop rhythm, a heart murmur, jugular-venous distention, pallor, cool hands and feet, and hepatomegaly at more advanced stages. Patients with severe DCM demonstrate symptoms and complications of congestive heart failure, such as dyspnea with exertion or at rest, chest pain, abdominal pain, and peripheral edema. Arrhythmias, thromboembolism, and sudden death are also common in DCM and may occur at any stage [3,4].
