Influence of aortic pressure on effective regurgitant orifice area in aortic regurgitation

Background. The regurgitant volume in aortic regurgitation is determined by the diastolic filling period, the pressure gradient between the left ventricle and aorta, and the hemodynamic size of the regurgitant orifice area. Methods and Results. To test the hypothesis that the aortic regurgitant orifice area is related to aortic pressure and aortic root size, 16 fresh calf heart and aorta specimens were studied in vitro using a continuous-flow system over a range of aortic pressures. Regurgitant orifice areas were calculated as the ratio of flow divided by peak velocity through the valve measured by image-guided continuous-wave Doppler, and aortic root areas were measured by two-dimensional echocardiography. When the defect was created at the edge of the noncoronary leaflet (n=10), regurgitant orifice area gradually increased 51±33% when aortic pressure was increased from approximately 40 to 152 cm of water (29.6 to 112.5 mm Hg) (p<0.0001). Similarly, the aortic root size increased 82±29% when the defect was created at the leaflet edge (p<0.0001). In contrast, when defects were created at the center of the noncoronary leaflet (n=6), only a small increase in regurgitant orifice area (9±7%) was observed with increasing pressure (p=0.043). The aortic root area remained strongly pressure dependent in specimens with defects at leaflet centers (p<0.0001). Conclusions. The aortic regurgitant orifice area is dependent on both aortic pressure and the nature of the defect in the valve. Because not all regurgitant aortic valves are alike, further study of the nature of the regurgitant orifice area in humans may allow identification of patients who would benefit most from aggressive pharmacological therapy.