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Aortic Regurgitation: Pathophysiology
Aortic regurgitation (AR) results from reflux of blood from the aorta into the left ventricle during diastole, caused by aortic valve or aortic root disease. The pathophysiology of AR depends whether the AR is acute or chronic. Acute AR is a medical emergency characterized by abrupt left ventricular (LV) volume overload, leading to rapid increase in left ventricular end-diastolic pressures (LVEDPs). Conversely, chronic AR is a slowly progressing condition in which adaptive changes occur in the LV to accommodate for the increase in preload and afterload. LV filling pressures can remain normal for a long period. As chronic AR progresses, wall stress increases because LV dilatation and hypertrophy cannot compensate for the volume overload. Myocardial fibrosis develops, LV filling pressures increase, and symptoms of heart failure and coronary hypoperfusion may appear. Timely repair of AR, usually by surgical or percutaneous aortic valve replacement (AVR) and sometimes by surgical repair, may lead to improvement in LV size and function.
Aortic Regurgitation Pathophysiology
AR results from incomplete coaptation or closure of the aortic valve cusps during diastole, leading to reflux of blood from the aorta into the left ventricle. AR results from various causes involving the aortic valve cusps or aortic root. AR can also result from a paravalvular leak originating around the circumference of a prosthetic valve or from structural deterioration of a bioprosthetic valve. The pathophysiology, hemodynamics, and clinical presentation of AR depend on its severity and differ whether AR develops abruptly (acute AR) or progresses over time (chronic AR). Table 87.1 lists the main differences between these two distinct scenarios.
TABLE 87.1
Major Differences Between Acute and Compensated Chronic Severe Aortic Regurgitation (AR)
| Acute AR | Chronic AR | |
|---|---|---|
| Clinical presentation | Pulmonary edema, refractory heart failure | Often asymptomatic |
| Left ventricular size | Normal to slightly enlarged | Markedly enlarged |
| Left ventricular end-diastolic pressure | Markedly elevated | Normal to slightly elevated |
| Systolic aortic pressure | Normal or slightly decreased | Elevated |
| Diastolic aortic pressure | Normal or slightly decreased | Decreased |
| Pulse pressure | Normal or slightly increased | Increased |
| Cardiac output | Decreased | Normal |
| Heart rate | Elevated | Normal or slightly elevated |
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