The main causes of acute heart failure include coronary heart disease, valvular disease, hypertension, and cardiomyopathies, such as toxic cardiomyopathy or hypothyroidism-related cardiomyopathy, as well as idiopathic cardiomyopathy. Myocarditis and arrhythmia-related causes can also lead to heart failure, but there are often triggers present clinically. Common triggers include poor treatment compliance, arrhythmias, anemia, infections, myocardial ischemia, excessive fluid intake, poor dietary control, and increased cardiac output, such as during strenuous activity and pregnancy, which can lead to increased cardiac output and cause heart failure. Conditions such as excessive fluid volume, hypertension, hyperthyroidism, and pulmonary embolism can also trigger heart failure.