Acute heart failure: epidemiology, classification, and pathophysiology

Abstract

Acute heart failure is defined as the rapid development or change of symptoms and signs of heart failure that requires urgent medical attention and usually hospitalization. Acute heart failure is the first reason for hospital admission in individuals aged 65 or more and accounts for nearly 70% of the total health care expenditure for heart failure. It is characterized by an adverse prognosis, with an in-hospital mortality rate of 4-7%, a 2-3-month post-discharge mortality of 7-11%, and a 2-3-month readmission rate of 25-30%. The majority of patients have a previous history of heart failure and present with normal or increased blood pressure, while about half of them have a preserved left ventricular ejection fraction. A high prevalence of cardiovascular or non-cardiovascular comordid conditions is further observed, including coronary artery disease, arterial hypertension, atrial fibrillation, diabetes mellitus, renal dysfunction, chronic lung disease, and anaemia. Different classification systems have been proposed for acute heart failure, reflecting the clinical heterogeneity of the syndrome; the categorization to acutely decompensated chronic heart failure vs de novo acute heart failure and to hypertensive, normotensive, and hypotensive acute heart failure are among the most widely used and clinically relevant classifications. The pathophysiology of acute heart failure involves several pathogenetic mechanisms, including volume overload, pressure overload, myocardial loss, and restrictive filling, while several cardiovascular and non-cardiovascular causes or precipitating factors lead to acute heart failure through a single of these mechanisms or a combination of them. Regardless of the underlying mechanism, peripheral and/or pulmonary congestion is the hallmark of acute heart failure, resulting from fluid retention and/or fluid redistribution. Myocardial injury and renal dysfunction are also involved in the precipitation and progression of the syndrome.