Load dependence of the effective regurgitant orifice area in a sheep model of aortic regurgitation

Abstract

Treatment of patients with aortic regurgitation with vasodilators reduces regurgitant volume, ventricular dilation and left ventricular mass. Although these effects are presumably due to afterload reduction, it is also possible that the aortic regurgitant orifice area is not constant. To test the latter hypothesis, aortic regurgitation was created in 10 open chest sheep by partial resection of the noncoronary leaflet under direct visualization. Regurgitant flow was measured with an aortic supravalvular electromagnetic probe; aortic and left ventricular pressures were measured with catheter-tipped micromanometer pressure transducers. The effective regurgitant orifice area was calculated by a modification of the continuity equation in a manner similar to the Gorlin equation. The regurgitant orifice area was measured three times: after aortic regurgitation was created, after mean arterial pressure was increased by 15 to 25 mm Hg with intravenous dopamine and after mean arterial pressure was reduced by 15 to 25 mm Hg with intravenous sodium nitroprusside. Comparison of regurgitant volumes and areas obtained after creation of aortic regurgitation and at the conclusion of the experiment in the absence of dopamine or sodium nitroprusside demonstrated no significant change over time. Dopamine administration was associated with an 86 +/- 81% increase in regurgitant volume (p less than 0.01) and a 38 +/- 44% increase in regurgitant orifice area (p less than 0.01). Sodium nitroprusside administration resulted in a 51 +/- 14% decrease in regurgitant volume (p less than 0.001) and a 28 +/- 21% reduction in regurgitant orifice area (p = 0.007). In this model of acute aortic regurgitation, the effective regurgitant orifice area was altered by increasing or decreasing the aortic transvalvular pressure gradient.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative Echocardiographic Determinants of Clinical Outcome in Asymptomatic Patients With Aortic Regurgitation

“…Emerging clinical tools by quantitative echocardiography, measuring absolute AR-degree (RVol or ERO) and total LV consequences of AR (LV volumes) raised new hopes. These tools were developed in physiologic studies (18,24,28), codified by guidelines of the American Society of Echocardiography (10,15), and endorsed by major American and European cardiac societies, but their impact on clinical outcome was unknown. In view of insensitivity and prognostic inferiority of traditional tools (LV diameters) for detecting high-risk patients (6), the present data are essential in managing asymptomatic patients with AR and preserved EF, among which high-risk subsets can now be identified and aggressively managed.…”

Acute Valvular Regurgitation

“…Hemodynamic data have demonstrated the variability in effective regurgitant orifice area and regurgitant volume in acute regurgitation depending on afterload and loading conditions. 18,19 Thus, rarely will quantitative measures contribute significantly to management decisions in acute regurgitation. In addition to assessment of severity and ventricular function, transthoracic echocardiography should also demonstrate the mechanism of regurgitation, such as dissection or ruptured mitral chordae.…”

Effect of load alterations on the effective regurgitant orifice area in chronic aortic regurgitation

“…Thus the load dependence and dynamic nature of the ROA have been proposed as possible mechanisms to explain the benefit of vasodilator treatment in chronic aortic regurgitation. Reimold and colleagues demonstrated the load dependence of effective ROA in an animal model of acute aortic regurgitation, 9 and reported the same result in an in vitro model using calf heart and aorta. 10 However, there have been no reports of chronic animal models with ventricular and aortic remodelling.…”