Acute AR is less common than chronic AR but carries a more ominous prognosis. Common causes of acute AR include trauma, bacterial endocarditis,
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and aortic dissection. The pathophysiology of acute AR centers around the fact that it causes an acute increase in the volume coming into the left ventricle. Because the left ventricle has not had time to undergo the process of eccentric hypertrophy, as it does in chronic AR, it is unprepared to accommodate this sudden increase in volume. As shown in the middle loop in Figure 2, this sudden increase in the LVEDP causes a rightward shift in the pressure-volume loop.13 A sympathetic response is activated ─ tachycardia and increased contractile state are the chief compensatory mechanisms for maintaining adequate cardiac output. Unless the AR is managed appropriately, these compensatory mechanisms rapidly fail, necessitating emergency cardiac surgery