Regurgitant Fraction Measured by Using the Proximal Isovelocity Surface Area Method in Dogs with Chronic Myxomatous Mitral Valve Disease

Abstract

Previous studies have demonstrated that regurgitant fraction can be measured by using the proximal isovelocity surface area (PISA) method. For this study, we utilized this Doppler echocardiographic method to estimate the magnitude of mitral regurgitation in dogs with myxomatous mitral valve disease. Seventeen older, small dogs with chronic mitral regurgitation and no to mild myocardial failure were studied. A blinded observer judged the clinical severity of mitral regurgitation to be mild, moderate, or severe by using echocardiographic assessment of left heart size. The regurgitant fraction was calculated by using the PISA method and spectral Doppler echocardiography. The regurgitant fraction was compared to the clinical assessment of severity for each dog and to calculations of left atrial size. Five dogs had clinically mild mitral regurgitation. Four of these dogs had a regurgitant fraction between 22 and 41%, whereas 1 had a regurgitant fraction of 73%. The 3 dogs with clinical evidence of moderate mitral regurgitation had a regurgitant fraction of 46-65%. All 9 dogs with clinically severe mitral regurgitation had a regurgitant fraction greater than 75% (78-88%). The regurgitant fraction was statistically different between each group (P Ͻ .001). A good but curvilinear relationship was found between left atrial size and regurgitant fraction (r 2 ϭ 0.72). In this study, dogs with clinically severe mitral regurgitation consistently had hemodynamically severe regurgitation (regurgitant fraction Ͼ 75%), whereas dogs with clinically mild to moderate disease had lesser degrees of regurgitation. Good correlation was found between regurgitant fraction and left atrial size. We conclude that the major determinant of left atrial size and disease severity in dogs with mitrial regurgitation is the degree of mitral regurgitation.Key words: Congestive heart failure; Doppler echocardiography; Heart disease B ased on the measurement of the left ventricular endsystolic diameter, myocardial function seems to be normal or only mildly compromised in most small and medium-sized dogs with chronic mitral regurgitation secondary to myxomatous mitral valve disease, even when heart failure is present.1,2 Therefore, it is reasonable to surmise that the blood volume ejected into the left atrium in systole (ie, the amount of mitral regurgitation) is the major determinant of the degree of left heart volume overload in these dogs and is the primary variable that produces heart failure because it is the only other primary variable, other than myocardial function, that determines the degree of compensatory volume overload in this disease. Although regurgitant fraction has been measured previously in dogs with myxomatous mitral valve disease, the relationship between the severity of the mitral regurgitation and clinical status has not been clearly delineated. 3The present study was designed to prospectively measure the percentage of stroke volume ejected into the left atrium in systole (ie, the regurgitant fraction) in small to mediumsized dogs...

Assessment of Mitral Regurgitation Severity by Doppler Color Flow Mapping of the Vena Contracta in Dogs

“…The records were selected according to the following inclusion criteria: diagnosis of MVD; complete medical records referring to the first visit; thoracic radiography in presence of clinical signs2, 11; electrocardiographic examination2, 11; complete data for echocardiographic and Doppler examinations as recommended by the authors to achieve grading of MR severity (ARJ/LAA ratio), mitral inflow pattern analyzed by pulsed wave (PW), signal intensity (jet density) of the continuous wave (CW), and envelope of the MR jet assessment of MR severity achieved by quantitative PISA and semiquantitative methods 1, 8, 11, 21, 22, 24, 26. We first graded the disease by means of quantitative methods and semiquantitative methods (different from VCW) and then observed how VCW values were distributed among different grade of MR severity (average based on ≥ 3 measurements for each parameter) 1, 2, 3, 10, 11, 12, 13. Exclusion criteria included presence of congenital heart disease; presence of atrial fibrillation, any other arrhythmias, or both that severely altered the beat to beat time interval11; VCW, PISA, or both not clearly visualized11; presence on CFD imaging of more than 1 mitral regurgitant jet evidenced through accurate recording at the time of the examination 8…”

“…We first graded the disease by means of quantitative methods and semiquantitative methods (different from VCW) and then observed how VCW values were distributed among different grade of MR severity (average based on ≥ 3 measurements for each parameter) 1, 2, 3, 10, 11, 12, 13. Exclusion criteria included presence of congenital heart disease; presence of atrial fibrillation, any other arrhythmias, or both that severely altered the beat to beat time interval11; VCW, PISA, or both not clearly visualized11; presence on CFD imaging of more than 1 mitral regurgitant jet evidenced through accurate recording at the time of the examination 8…”

“…EROA and RV were calculated by using the PISA method (EROA (cm 2 ) = flow rate (mL/s)/V (cm/s); RV (mL) = EROA (cm 2 ) × VTI cm) 2, 11 (Fig 1). To take account of animal size, the parameters were indexed according to body surface area (BSA m 2  =  K m  × BW gr 0.67 /10 −4 ) to give EROA index (measured as cm 2 /m 2 ) and RV index (measured as mL/m 2 ) 3, 27, 28…”

“…Various semiquantitative methods by using color flow Doppler (CFD) mode (eg, area of regurgitant jet area signal to left atrium area ratio (ARJ/LAA), and quantitative methods (eg, proximal isovelocity surface area method (PISA), also called flow convergence) have been proposed for detecting MR severity in humans and dogs 1, 2, 3, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17. However, all these methods have some limitations, and none of them are simple enough to be universally recognized and safely applied without restrictions.…”

“…The VCW method is widely used in human medicine but is not applied in veterinary medicine, though to the best of our knowledge a range of measures of VCW is not available in large canine populations 2, 8, 10, 11, 22, 24, 25…”