Acute heart failure: epidemiology, classification, and pathophysiology

Abstract

Acute heart failure (AHF) is defined as the rapid development or change of symptoms and signs of heart failure that requires urgent medical attention and usually hospitalization. it represents the first reason for hospital admission in individuals aged 65 or more and accounts for nearly 70% of the total healthcare expenditure for heart failure. It is generally characterized by adverse prognosis, with an in-hospital mortality rate of 4-7%, a 2 to 3-month post-discharge mortality of 7-11% and a 2 to 3-month readmission rate of 25-30%. The majority of patients have a previous history of heart failure and present with symptoms and/or signs of congestion and normal or increased blood pressure, while about half of them have preserved left ventricular ejection fraction. A high prevalence of cardiovascular or non-cardiovascular comorbidities is further observed, including coronary artery disease, arterial hypertension, atrial fibrillation, diabetes mellitus, renal dysfunction, chronic lung disease, anemia and iron deficiency. Different classification criteria have been proposed for AHF, reflecting the clinical heterogeneity of the syndrome. Classifications according to the past history of heart failure (acutely decompensated chronic or de novo), the systolic blood pressure upon presentation (hypertensive, normotensive or hypotensive) and the presence or absence of congestion and peripheral hypoperfusion are among the most widely used. The pathophysiology of AHF involves several mechanisms, including volume overload, pressure overload, myocardial loss and restrictive filling, while several cardiovascular and non-cardiovascular precipitating factors lead to AHF. Regardless of the underlying mechanism, peripheral and/or pulmonary congestion is present in the vast majority of AHF, resulting from fluid retention and/or fluid redistribution, while a marked reduction in cardiac output with peripheral hypoperfusion occurs in a minority of cases. Myocardial injury and renal dysfunction are important factor involved in the precipitation and progression of the syndrome.