DK2985_C000 1..28 - AlSharqia Echo Club

118 Transesophageal EchocardiographyG. Regurgitant Volumes and FractionsAccording to the principle of conservation of mass(volume), the volumetric flow across all the cardiacvalves is equal as long as there is no regurgitation or intracardiacshunt. When valvular regurgitation occurs, aregurgitant volume is added to the forward SV presentthrough all the valves. Therefore, the SV measuredacross a regurgitant valve is higher compared with theother competent valves by a value equal to the regurgitantvolume. The regurgitant volume can be calculated by thefollowing equation:Regurgitant Volume ¼ SV regurgitant valveSV competent valve (5:49)The stroke volume across the aortic valve (SV ao )isgiven by the following equation:SV ao ¼ 0:785d 2 LVOT TVI LVOT (5:50)where d LVOT is the diameter (in cm) of the left ventricularoutflow tract measured at the base of the aortic cusps in theleft parasternal long-axis view from inner edge to inneredge and TVI LVOT is the time–velocity integral (in cm)measured by PWD with the sample volume in the centerof the LVOT, tracing the peak (outer edge of the) velocityDoppler signal envelope.The stroke volume across the mitral valve (SV MV )isgiven by the following equation:SV MV ¼ 0:785d 1 d 2 TVI MV (5:51)where d 1 is the diameter of the mitral valve annulusmeasured at the base of the leaflets from inner edge toinner edge in the apical four-chamber view; d 2 is the diameterof the mitral valve annulus measured at the base of theleaflets from inner edge to inner edge in the apical twochamberview; and TVI MV is the time–velocity integral(in cm) measured by PWD with the sample volume inthe center of the mitral valve annulus, tracing the modal(most dense) velocity on the Doppler signal envelope.In the case of isolated aortic valve regurgitation, theaortic regurgitant volume is given by the followingequation:Aortic Regurgitant Volume ¼ SV LVOT SV MV(5:52)In isolated mitral valve regurgitation, the mitral regurgitantvolume is given by following equation:Mitral Regurgitant Volume ¼ SV MV SV LVOT(5:53)Note that in both situations, the SV obtained by the differencebetween left ventricular end-diastolic and end-systolicvolume measured by 2D echocardiography corresponds tothe sum of the forward SV and the regurgitant volume,and can be substituted to the first SV of the equation.In the case of combined significant aortic and mitralvalve regurgitation, respective aortic and mitral regurgitantvolumes cannot be determined by the preceding continuityequation applied to the mitral and aortic flow alone. In theabsence of intracardiac shunt and pulmonary valve regurgitation,the forward SV can be obtained from the RVOT,considered as the competent valve. Mitral regurgitantvolume can alternatively be obtained from the convergence(PISA) method, as it invokes the continuity equation at themitral valve only and is not affected by the presence ofaortic regurgitation. Once the mitral effective regurgitantorifice is calculated, the regurgitant volume is obtained bythe following equation:Mitral Regurgitant Volume ¼ ERO MV TVI MR(5:54)where ERO is the effective regurgitant orifice (in cm 2 )andTVI MR is the time–velocity integral (in cm) of the mitralregurgitant signal obtained by CWD, tracing the peak(outer edge) of the Doppler signal envelope.The regurgitant fraction is defined as the ratio of thetotal volume ejected being regurgitated through the incompetentvalve. This is mathematically expressed as follows:RF ¼Reg VolSV Total 100 (5:55)where RF is the regurgitant fraction (in %); Reg Vol is theregurgitant volume (in mL); and SV Total is the total strokevolume (in mL), given by the Doppler-stroke volumeacross the incompetent valve or the stroke volumeobtained by 2D methods.H. Shunt FractionsAccording to the principle of conservation of mass(volume), the volumetric flow through the right heartshould be equal to that through the left heart. However, inthe presence of an intracardiac shunt, the SV will begreater on the side receiving the additional shunt volumetricflow. Because the left-sided intracardiac pressures areusually greater than on the right, intracardiac shunts aremost often from left to right, and the pulmonary bloodflow will be greater than the systemic blood flow. The magnitudeof systemic-to-pulmonary intracardiac shunt can bequantitated by determining the ratio of pulmonary blood