Acute heart failure refers to the acute onset of heart failure or an exacerbated clinical syndrome, which can present as either newly developed acute or acute decompensation of chronic heart failure. Clinically, it is commonly divided into two main categories. One category is acute left heart failure, often caused by acute decompensation of chronic heart failure, or by acute coronary syndrome, hypertensive emergencies, acute cardiac valvular dysfunction, severe myocarditis, serious arrhythmias, and peripartum cardiomyopathy. The other category is acute right heart failure, which can be caused by right ventricular infarction, acute large pulmonary embolism, and right-sided valvular heart disease.