Contrast enhancement of mitral regurgitation to estimate left ventricular systolic pressure

Abstract

Continuous wave Doppler measurement of prosthetic valve gradients correlate with gradients obtained by cardiac catheterization for most prostheses. 1 For mechanical valves and prostheses with smaller and multiple orifices, however, significant discrepancies between Doppler-derived and catheter gradients have been reported. 2, 3 Transvalvular gradients in excess of 50mm Hg exist in approximately 10% of patients with normally functioning aortic prostheses. 4 This apparent overestimation of the transvalvular gradient by continuous wave Doppler has been attributed to the effects of localized pressure gradients and pressure recovery. 3 Overestimation of gradients caused by pressure recovery may lead to the erroneous diagnosis of prosthetic valve dysfunction. To circumvent potential errors in measurement of prosthetic valve gradients, it may be possible to estimate transvalvular gradients with indirect measurements of left ventricular and aortic systolic pressures. The approach used to estimate the left ventricular systolic pressure (LVSP) is based on the common echocardiographic practice used to determine right ventricular systolic pressure from the jet of tricuspid regurgitation. 5 In this case peak velocity of the mitral regurgitant (MR) jet obtained by continuous wave Doppler is used as an index of the gradient between the left ventricle and the left atrium (APLv-LA). This gradient, when added to a presumed left atrial pressure (LAP), results in an estimation of the LVSP (LVSP = LAP + APLv_LA). Left atrial pressure is assumed at 15 mm Hg, an estimate that would be expected to result in only minimal error for most patients. The aortic systolic pressure (Ao P) is estimated from the blood pressure recorded noninvasively in the brachial artery. The estimated LVSP and Ao P are then used to calculate a pressure gradient between the left ventricle and aorta, thereby avoiding the inherent problems associated with Doppler gradients across prosthetic valves. This approach requires that the jet of MR be of sufficient strength to accurately measure velocity. It has been well established that low concentrations of transpulmonary contrast agents enhance both spectral and color Doppler signals in the left heart. 6 Simultaneous administration of intravenous sonicated albumin for potentiation of the mi-