Cardiomyopathies are diseases of the heart muscle that hinder its ability to pump blood, with three main types: dilated, hypertrophic, and restrictive cardiomyopathy. Symptoms include tiredness, weakness, shortness of breath, and swelling in various parts of the body, while management includes medication, lifestyle changes, and potential surgical interventions. Nursing management focuses on assessing cardiac output, coping strategies, activity intolerance, and fluid volume management to optimize patient care.