An episode of acute heart failure syndromes (AHFS) can be defined as a rapid or gradual onset of signs and symptoms of heart failure that result in hospital admission. Over 70% of AHFS events are the result of worsening chronic heart failure. Other causes of AHFS include new-onset heart failure due to an acute coronary event, such as a myocardial infarction (MI), and end-stage or refractory heart failure that is not responsive to therapy. It is a growing problem, and the prognosis for patients with AHFS remains poor. Current understanding of the pathophysiology of AHFS can aid in the identification of potential therapeutic targets.
The pathophysiology of AHFS is complex, and can arise from a variety of pathophysiological mechanisms. Approximately 60% of hospitalised patients have a history of coronary artery disease (CAD), 53% to 70% have hypertension, fewer than 30% have atrial fibrilation (AF) or a history of AF, and more than 40% have type 2 diabetes (see Table 1).
Potential pathophysiological targets for therapy include treating congestion, controlling blood pressure, preventing myocardial injury, improving renal function, and treating the associated conditions that contribute to the pathophysiology of AHFS.
Controlling Blood PressureÔÇöVascular and Cardiac Heart Failure
'VascularÔÇÖ failure accounts for up to half of all AHFS admissions, and is characterized by elevated systolic blood pressure. The elevated blood pressure usually develops rapidly and is possibly related to increased filling pressures and increased sympathetic tone, and results in redistribution of fluids (from systemic to pulmonary circulation) and further activation of neurohormones. These patients are often older and are more likely to be women with a relatively preserved ejection fraction. Symptoms in these patients usually develop abruptly and the patients have pulmonary rather than systemic congestion (e.g. peripheral edema).
'CardiacÔÇÖ failure is the other common type of acute heart failure and represents 40% to 50% of admissions for AHFS. It is characterized by a normal systolic blood pressure, usually with a history of progressive or chronic heart failure. These patients are often younger, with symptoms and signs developing gradually over days or weeks, and typically have significant systemic congestion and a reduced ejection fraction. They may also have minimal pulmonary congestion (clinical and/or radiographic) despite high ventricular filling pressures. This type of heart failure will be referred to as 'cardiacÔÇÖ failure. This classification of 'vascularÔÇÖ and 'cardiacÔÇÖ failure provides a conceptual framework that needs further validation.