- Email: [email protected]
Validation of applications of indexed aortic prosthetic valve areas calculated by Doppler echocardiography
JACC Vol. 16. Ma. 3 :$37-43 Sep?emberI
--
oppler echocardiogr es. The variables vasive evaluation of most often measured with this techn mean valve gradients and t tion of these variables has been derived from comparison with hemodynamic data in patients with native aortic valve disease, but to date t ere has been little actual validation in patients with an aortic valve The goals of the present st were to assess the validity of Doppler echocardiographic variables. particularly valve prosthesis area calculations, in patients with an aortic ation with and to determine the im lications of such i
From the Quebec Heart Institute. Lava1 University, Sainte-Foy. Quebec. Canada. anuscript received June 2. 1989: revised manuscript received March 7. 1990. accepted April 4, 1990. mress f r reg&& Jean G. Dumesnil. MD. Quebec Heart Institute. 2725 chemin &qte-Fey. Sainte-Foy. Quebec. Canada GIV 4GS. OWJO by the American College of Cardiology
purpose, aortic valve with Doppler echoca
between prcPsthetic valve size, body size and aortic pressure gradient were also evaluated in these patiects.
t ~ostit~tc
between
technically inadequate the remaining 31 patients ( age of 69 it 10 years (range $5 to 86). Indications
for surgery
0735.lO97/90/$3.S0
638
DIJMESNIL ET AL. DOPPLER ECHOCARDIOGRAPHY
OF AORTK BIOPROSTHETIC VALVE AREAS
were aortic stenosis (n = 23), aortic regurgitation(n = 4) or mixed aortic valve disease (n = 4). Nine patients had severe coronary artery disease and underwent concurrent coronary artery bypass graft surgery. Ail patients received a model 805 Medtronic Intact bioprosthesis, size 19(n = l), 21 (n = 6), 23 (n = 8), 25 (n = ii), 27 (n = 3) or 29 mm (n = 2). All patients gave: informed consent to the protocol, which was approved by the Ethics Committee of the Quebec Heart Institute and Laval Hospital. Doppler echocardiographic studies. Doppler echocardiographic examination was performed a mean of 20 + 4 months after surgery, Ail studies werr pgrformed by the same technician on a Hewlett-PackardSonos-500ultrasound SYStern and subsequently independently reviewed by the same investigator. Reasons for excluding the aforementioned four patients were inability to adequately measure left ventricular outflow tract diameter (n = 2). inability to obtain adequate pulsed Doppler signal in the outflow tract (n = I) or inability to obtain an adequate continuous wave Doppler signal of valve gradient (n = 1). In 21 cases the technician and investigator were in complete agreement on measurements; in 10 cases, after review, measurements were redone from stop frame analysis of the videotape. These 10cases were mostly from the earlier part of the study when the technician was uncertain of the left ventricular outflow tract measurement and had indicated more than one possibility. Measurements obtained in the 31 patients for the purpose of this study consisted of peak and mean aortic valve
gradients, stroke volume, cardiac output and prosthetic valve area. Peak and mean gradients were obtained with continuous wave Doppler recordings of the aortic jet veiocity from apical and right parastemai windows and appiication of the modified Bernoulli equation, as previously described and validated (4-10). Stroke volume was calculated from the left ventricular outflow tract area, as estimated from the corresponding internal diameter measured in the left parastemai long-axisview during systole, multiplied by the velocity-time integralof the left ventricular outflowtract pulsed Doppler signalrecorded from the apicalfour chamber view, as previously described (11-13). Cardiac output was equal to stroke volume multiplied by heart rate. Great care was taken to ensure that the diameter was measured perpendicularly to the left ventricular outflow tract, trailingedge to leadingedge just proximalto the prosthetic anulus; the angle between the Doppler cursor and the left ventricular outflow tract was as close to 0” as possible (always <20”);and the Dopplersignal was truly representative of the left ventricular outflowtract, as emphasized by Skjaerpe et al. (14).Multiple determinations were made in each patient to ensure reproducibility of measurements. ve area ~eu~at~s. Prosthetic valve area (PVA) was determined with the standard continuity equation: PVA = SVNTI,,, where SV is stroke volume and
JACC Vol. 16. No. 3 September 1 :637-43
VTl,, is the velocity-time integral of the colatinuous wave Doppler signal of the aortic jet (15-20).Valve area was also calculated using the previously proposed (1 continuity equation: PVA = (LVQT,,, Vmax,,, where LVQT,,, and LVGTvmaxare the left ventricular outflow tract area and peak jet velocity, tiveiy, and Vmax,, is the peak aortic jet velocity m with continuous wave In vitro valve area
bioprosthetic effective
model measures the transvaivular pressure 8rad~e~tsan pulsatiie flow rates at different cardiac outputs, with a puis rate of 70 beatslmin and systole accounting for approximately 35% of the cardiac cycle. From this information, effective valve orifice area was calculated using the formula proposed by Yoganathanet al. (22)and a range of values was tive obtained for each prosthesis size, suggesting that and orificearea increases as a function of the prevailing pressure gradient. The range of in vitro area values derive physicat a stroke volume (55 to ii 1 ml) approx~mati~ logic range of stroke volumes (46 to 118 ml) d in the present study patients was used for comparison purposes (Table 1) and the median value of each in vitro area range was used for linear regression analysis. The in vitro area data were not available to t her at the time of Doppler echocardiographic measure of the effective orifice area. Evaluation of aortic re~~~~t~tio~.Doppler color flow mappingwas performed in multiple views to interrogate for the presence of aortic regurgitation.This was visuallygraded as it when the jet was very narrow and extended only a short distance below the aortic valve and 2t when the jet was somewhat larger and longer but remained narrow at the level of the aortic anuius (~20% of the left ventricular outflowtract diameter) and did not extend beyond the tip of the anterior mitral valve leaflet. Significant3t or 4t aortic regurgitationwas not observed in our study patients. Statisticalanalysis. Continuous variables are expressed as the mean value + SD and the range. Statistical analysisof the association of continuous variables was performed using the Pearson linear correlation coefficient and graphs were constructed with the corresponding linear regression equation. For statistical inference, p values were obtained using the one-sided t test for directional association.
Valvearea and gradient ). For the b3 ( 31 patients, the peak gradient ranged from 10.8 to 75.0 mm Hg (mean 35 2 16)and the mean gradient ranged from 7.6 to
JACC Vol. 16. No. 3 September 1990~637-43
.5 + 9.5). Valve arearanged
fro
F@pnre 8. Correlation between Doppler echocardiographic eKective prosthetic aortic valve area (AVA) calculared with ~5 0. rhe Ah standard continuity equation (CE) and the same area calculak use of the simplified continuity equation.
we 2. CorreQatiw heWxn (cm’) for each valve size
r = 0.98 SEE .0.07 cm “~102ki.005 p~OOO05
22.
in vilro prosthetic
dele~rn~~ed by Doppler echocardiog~a~~y continuity equation KE).
valve area
with use of ahe standard
r
2.3 1
median
( ml and in vivo aortic valve area
a
20.
18.
0.0
3.0
1.2
1.4
1.6
1.B
20
22
24
IWITRO VALVE SIZE AYA BY STANDARDCE
(Cm’1
90
2,
23
PROSTHETIC AREA (cm*) 25
27
20
643
DUMESNIL ET AL. DOPPLER ECHOCARDIOGRAPHY
OF AORTIC
BIOPROSTHETIC
VALVE
AREAS
q
]
70
lACC Vol. 16. No. 3 September 199Q:h37-43
o
r = -0.72
1
D
m-l
,I
0
SEE * 11.72
mmUg
Y = ( -S.BX
+ 10.3 )’
P < D.oooS
\
so 0 40
0.8
,
1.E
I.1
I.2
2
1.B
2.2
““ 45
cl D
40
-0.48
SEE 0 IIS
1
Y = -ia.ou
0
P < o.oo3 0
r -
13
mm”g + 40.62
1.2
q
i
h2I
Y = ( -O.Ia!d
\
rnrn”~ + 7.15
)’
P < 0.0001 D
30 -
D
-0.70
SEE * 0
3!l cl
I
I
0
0.(1
0.a
Ll I -
:
D 2s -
20 -
15 -
a I
0.4
I
I
0.6
D.8 INCWZD
Figure 3. Correlation between prosthetic valve area determined by Doppler echocardiography (ECHO) with use of the standard continuity equation and peak (A) and mean (B) transprosthetic gradients derived from the modified Bernoulli equation.
prostheses. These correlations, however, improve when the valve area values are indexed for body surface area (r = -0.67 and r = -0.66 for peak and mean gradients, respectively) and are further enhanced (r = -0.72 and r = -0.70, respectively) when the gradient is considered to be a square function of the indexed prosthetic valve area, resulting in curvilinear relations (Fig. 4).
iscussiomr Validity of Dopplerechocardiographicvalve area measurements. These data indicate a good cnrrelatinn between the
aortic prosthetic valve area derived from in vitro variables and those calculated in vivo by Doppler echocardiography with the standard or simplified continuity equations, thus suggestingthat these two methods are valid for bioprosthesis assessment. To obtain the relation shown in Figure 2. we utilized the median in vitro valve area data because there is a range of area values for each prosthesis size, reflectingan
AREA by DOPPLER -
I
1
I
1
1.2
ECHO (cm’/m’)
Figure 4. Curvilinear relation between peak (A) and mean l transprosthetic valve gradients and indexed prosthetic area determined by Doppler echocardiography (ECHO) with use of the standard continuity equation. This relation is derived by considering the gradient as a square function of indexed prosthetic area.
increase in effective orifice area as a function of gradient and flow. The latter is possibly related to greater leaflet inertia at low flow rates. The variability in the production of a bioprosthesis of a given size is also a factor that might influence results. Given the range of in vitro area values, the in vivo studies slightly overestimated the area in two patients (1.66 versus 1.55cm* and 1.44versus 1.38cm*), whereas underestimationswere observed in I5 patients. The latter might be due to deterioration of the effectiveorifice area during the 20 ? 4 months since implantationor to inherent errors in the in vitro or in vivo methods. Nonetheless, these deviations are quite small and it is somewhat reassuring that the in vivo method tends to underestimate rather than overestimate effective orifice area. evaluation of intrinsic prosthesis perfmnamce. Previous studies (23-28)have shown that there is only a weak relation between prosthesis size and transprosthetic gradient, with a tendency for higher gradients to be recorded with smaller
JAW Vol. 16. No. 3
SepIrmber 199O:M7-43
ts in assessing the i rosthetic
valve
area
t. As one would ex
hemodynamic pe~orma~ce and avoiding a mismatch between prosthesis size and body size. For native valves, generally agreed that severe aortic stenosis is present w the effective orifice area is CO.6 t area (31-33). The im (341, who described a group of prosthesis with an average calcul 1.7 cm*, which ranged form 0.9 o
&-T--7-. 0.4
present
study and suggested
that an effective
prosthettc
active individual and that “be replacement . . ., the cardiologist and the surgeon must attempt to project the postoperative result considering the patient’s hemodynamic state and the pe~orma~ce of the prosthesis that will be inserted.” Figure 5 attempts to show how the peak and mean pressure gradient would theoretically behave at different levels of exertion. The relations presented assume increases of 550% in stroke volume during maximal upright exercise, as described in untrained individuals (35-38). Pending further confirmation, it would appear th indexed prosthetic valve area Xt.9 to 1.0 cm’lm’ surface area would be a minimal requirement to minimtze a postoperative pressure gradient at rest or exercise. This ty of information should be helpful to the surge e and size of prosthesis to be insert as well as in considering alternat patients with a relatively small aortic anulus diameter. Such estimates, however, require precise information from the
IT_ lNDExe0
, ~___ T 0.8
0.0 iwE.
by DOPPLER -
~..7_ -.-l___._ 1
1.2
EC”0 (m%+)
petted behaviors of the peak (A) and mean ( ic gradients with a IQ% to 50% increase i s during upright exercise. Relations are obtained by increasing the square root of the peak pressure gradient obtained from the regression equathn given in Figure G by 10% to 500/o, in nce with the continuity and simplified Bernoulli equations. xc = echocardiography. EC
manufacturer and should also take into account that : vivo effective orifice area may be somewhat smaller that calculated in vitro. Further studies, including st during exercise, will be necessary to confirm these relations and to determine how they can be a prostheses.
similar sizes. The higher valve gradient re patients appears to be related mainly to a mi
642
DUMESNIL ET AL. DOPPLER ECHOCARDIOGRAPHY
9F AORTIC BIOPROSTHETIC VALVE AREAS
prosthesis size and body size and emphasizes the importance of taking the indexed prosthetic valve area into consideration before operation. Other factors such as deterioration of the prosthetic valve area over time and increased flow through the valve may also be implicated. Of the two patients with a peak gradient >70 mm Hg. one had a bmdycardia (heart rate 53 beatslmin) and 2+ aortic regurgitation and the other had a paced rhythm at 70 beatslmin, I + aofiic regurgitation and a valve area lower than the predicted range. Conclusions. We conclude that Doppler echocardiographic evaluation of aortic bioprosthetic valve area by the continuity equation is accurate and useful in evaluating prosthetic valve performance. The transprosthetic valve gradient is less useful to evaluate intrinsic prosthesis performance because it is influenced by both prosthetic valve area and cardiac output. On the basis of the relations demonstrated between gradient and indexed prosthetic valve area. some guidelines for appropriate preoperative prosthesis size selection can probably be derived to avoid mismatch between prosthesis size and body size.
I. Sagar KB. Wann S. Paulsen WHJ. Romhilt DW. Doppler echocardiographic evaluation of Hancock and Bjiirk-Shiley Coil Cardiol 1986;7:681-7.
prosthetic valves. J Am
2. Alam M. Rosman HS. Lakier JB. et al. Doppler and echocardiographic features of normal and dysfunctioning bioprosthetic valves. J Am Coll Cardiol 1987:10:851-8. 3. Williams GA, Labowitz AJ. Doppler hemodynamic evaluation of prosthetic (Starr-Edwards and Bjiirk-Shiley) and bioprosthetic (Hancock and Carpentier-Edwards) cardiac valves. Am J Cardiol 1985:56:325-32. 4. Hatle L. Angelsen BA. Tromsdal A. Non-invasive assessment of aortic stenosis by Doppler ultrasound. Br Heart J 1980;43:284-92. 5.
Slamm RB. Marlin RP. Quantification
of pressure gradients across stenotic valves by Doppler uhrdsound. J Am Coll Cardiol 1983:2:707-18.
6. Currie PJ. Seward JB. Reeder GS. et al. Continuous wave Doppler echocardiographic assessment of severity of calcific aortic stenosis: a SimUkaneOUS Doppler-catheter correlative study in 100 adult patients. Circulation 1985:76l:Il62-9. 7. Callahan MJ. Tajik AJ. SU-Fan Q, Bove AA. Validation of instantaneous pressure gradients measured by continuous-wave Doppler in experimentally induced aortic stenosis.Am J Cardiol 1985:56:989-93. 8. Smith MD. Dawson PL. Elion JL. et al. Correlation of continuous wave Doppler velocities with catheterization gradients: an experimental model of aortic stenosis. 3 Am Coll Cnrdiol 1985:6: 1306-14. 9. Kostumkis D. Allan HD. Goldberg SJ. Sahn DJ, Valdes-Cruz LM. Noninvasive quantification of stenotic semilunar valve areas by Doppler echocardiography. J Am Coll Cardiol 1984:3:1256-W. 10. Currie PJ. Hagler DJ. Seward JB, et al. Instantaneous pressure gndient: a ~~~UhneOUS kWkr and dual catheter correlative study. J Am Coll Cardiol 1986;7:800-6. ll.
Huntsman LL. Stewart DK. Barnes SR. Franklin SB. Colocousis JS, Hes*l EA. Noninvasive Doppler determination ofcardiac output in man: clinical validation. Circulation 1983;67:593_602.
12. G&n JM. Tobis JM. Dabeslani A. et al. Superiority of two-dimensional measuremen of aortic vessel diameter in Doppler echacardiographic
JACC Vol. 16. No. 3 199&63?-43
September
eslimates of left ventricular stroke volume. J Am Coil Cardiol 1985:6:6674. 13. Gardin 91ti. E;rimation of volume flow by Doppler Echocardiography lY87;4: 16-28.
echocardiography.
14. Skjaerpe T. Hegrenaes L. Hatle L. Noninvasive estimation of valve area in patients with aortic stenosis by Doppler ultrasound and twodimensional echocardiography. Circulation 1985;72:810-8. 15. Warth C. Stewart W9, Block PC. Weyman AE. A new method lo calculate aortic valve area without left heart catheterization. Circulation 1984:70:978-83. 16. Zoghbi WA. Farmer KL. Soto JG, Nelson JG. Quinones MA. Accurate noninvasive quantificatks of stenotic aortic valve area by Doppler echocardiography. Circulalion 1986:73:4X!-9. 17. Richards KL. Cannon SR. Miller SC. Crawford MH. Calculation ofaortic valve area by Doppler echocardiography: a direct application of the continuity equation. Circulation 1986:73:964-9. 18. Otto CM. Pearhnan AS, Comcss KA. Reamer RP. Janko CL. Huntsmun LL. Determination of the stenolic aortic valve area in adults using Doppler echocardiography. J Am Coll Cardiol 1986;7:5OY-17. 19. Oh JK. Taliercio CP. Holmes DR Jr. et al. Prediction of the severity of aortic slenosis by Doppler aortic valve area determination: prospective Doppler-cathchcrization correlation in Iu(I patients. J Am Coll Cardiol 1988:l l:l??7-34. 20. Graybum PA. Smith MD. Harrison MR. Gurley JC. DeMaria AN. Pivotal role ofaortic valve area calculation by the continuity equation for Doppler assessment of aortic stenosis in patients with combined aortic stenosis and regurgitation. Am J Cardiol 1988:61:376-81. 21. Fujii K, Kitabake A. Asao M. et al. Noninvasive evaluation of valvular stenosis by a quantitative Doppler technique. J Cardiovasc Ultrason 1984:3:2Ol-8. 22. Yoganathan AP. Woo YR. Sung HW. Williams FP. Franch RH, Jones M. In vitro hemodynamic characteristics of tissue bioprosthesis in the aortic position. J Thorac Cardiavasc Surg 1986:92: l98-20Y. 23. Levine FH. Carter JE. Buckley MJ. Daggett WM. Akins CW. Auscen WG. Hemodvnamic evaluation of Hancock and Caroentier-Edwards bioprosthesis:Circulalion 1981:64(suppl 11):11-192-S. ’ 24. Morris DC. King SB 111, Douglas JS Jr, Wickliffe Hemodynamic results of aortic valvular replacement xenografi valve. Circulalion 1977:56:841-4.
CW, Jones EL. with the porcine
25. Rossiter 53. Miller DC. Stinson EB. et al. Hemodynamic and clinical comparison of the Hancock modified orifice and standard orifice bioprosthesis in the aorfic position. J Thorac Cardiovasc Surg 1980:80:54-60. 26. Becker RM. Strom J, Frishman W. et al. Hemodynamic performance of the IonescuShiley valve prosthesis. J Thorac Cardiovasc Surg 1980:80: 613-20. 27. Rothkopf M. qavidson T. Lipscomb K. et al. Hemodynamic evaluation of the Carpentier-Edwards bioprosthesis in the aortic position. Am J Cardiol 1979;44:209-14. 28. Cosgrove DM, Lythe BW. Williams GW. Hemodynamic performance of the Carpentier-Edwards pericardial valve in the aortic position in vivo. Circulation 1985:72(suppl H):il-146-52. 29. Thomasson B. Cardiac output in normal subjects under standard conditions: the reproducibility of measurements of the Fick method. Stand J Clio Lab Invest 1957:9:365-76. 30. Grossman W. Barry WH. Cardiac catheterization. In: Braunwald E. ed. Heart Disease: A Textbook of Cardiovascular Medicine. Philadelphia: WB Saunders, 1988:242-67. 31. Braunwald E. Roberts WC. Goldblatt A. Aygen MM. Rockoff SD, Gilbert JW. Aortic stenosis: physiological. pathological. and clinical concepts: combined clinical staff conference a( the National l&lutes of Health. Ann Intern Med 1%3:58:494-522. 32. Frank S. Johnson A. Ross J Jr. Natural history of valvular aortic stenosis. Br Heart J 1973;35:41-6.
~M~~e~~PE. Swan HJC, Percemage of lefa imtoola S 33. Tobin % Jr. ventricuk;: stroke work loss: a simple hemodynamic concept for estimatioa d severity in valvular aortic stenosis. Circmlntion l%9;3WiM-99. e problem ~~r~M~a~~0~ w%:S8:20-4. Robinson . #a card ockade on exercise in man. J Clin Invest 1 36. Robinson RF. Epst.zin SE, Kak
of valve
prosthesis-patiena
rniw~ahh.
ald E. EtTecis of beteaximal and s~~~~~~~~~
--
oppler echocardiogr es. The variables vasive evaluation of most often measured with this techn mean valve gradients and t tion of these variables has been derived from comparison with hemodynamic data in patients with native aortic valve disease, but to date t ere has been little actual validation in patients with an aortic valve The goals of the present st were to assess the validity of Doppler echocardiographic variables. particularly valve prosthesis area calculations, in patients with an aortic ation with and to determine the im lications of such i
From the Quebec Heart Institute. Lava1 University, Sainte-Foy. Quebec. Canada. anuscript received June 2. 1989: revised manuscript received March 7. 1990. accepted April 4, 1990. mress f r reg&& Jean G. Dumesnil. MD. Quebec Heart Institute. 2725 chemin &qte-Fey. Sainte-Foy. Quebec. Canada GIV 4GS. OWJO by the American College of Cardiology
purpose, aortic valve with Doppler echoca
between prcPsthetic valve size, body size and aortic pressure gradient were also evaluated in these patiects.
t ~ostit~tc
between
technically inadequate the remaining 31 patients ( age of 69 it 10 years (range $5 to 86). Indications
for surgery
0735.lO97/90/$3.S0
638
DIJMESNIL ET AL. DOPPLER ECHOCARDIOGRAPHY
OF AORTK BIOPROSTHETIC VALVE AREAS
were aortic stenosis (n = 23), aortic regurgitation(n = 4) or mixed aortic valve disease (n = 4). Nine patients had severe coronary artery disease and underwent concurrent coronary artery bypass graft surgery. Ail patients received a model 805 Medtronic Intact bioprosthesis, size 19(n = l), 21 (n = 6), 23 (n = 8), 25 (n = ii), 27 (n = 3) or 29 mm (n = 2). All patients gave: informed consent to the protocol, which was approved by the Ethics Committee of the Quebec Heart Institute and Laval Hospital. Doppler echocardiographic studies. Doppler echocardiographic examination was performed a mean of 20 + 4 months after surgery, Ail studies werr pgrformed by the same technician on a Hewlett-PackardSonos-500ultrasound SYStern and subsequently independently reviewed by the same investigator. Reasons for excluding the aforementioned four patients were inability to adequately measure left ventricular outflow tract diameter (n = 2). inability to obtain adequate pulsed Doppler signal in the outflow tract (n = I) or inability to obtain an adequate continuous wave Doppler signal of valve gradient (n = 1). In 21 cases the technician and investigator were in complete agreement on measurements; in 10 cases, after review, measurements were redone from stop frame analysis of the videotape. These 10cases were mostly from the earlier part of the study when the technician was uncertain of the left ventricular outflow tract measurement and had indicated more than one possibility. Measurements obtained in the 31 patients for the purpose of this study consisted of peak and mean aortic valve
gradients, stroke volume, cardiac output and prosthetic valve area. Peak and mean gradients were obtained with continuous wave Doppler recordings of the aortic jet veiocity from apical and right parastemai windows and appiication of the modified Bernoulli equation, as previously described and validated (4-10). Stroke volume was calculated from the left ventricular outflow tract area, as estimated from the corresponding internal diameter measured in the left parastemai long-axisview during systole, multiplied by the velocity-time integralof the left ventricular outflowtract pulsed Doppler signalrecorded from the apicalfour chamber view, as previously described (11-13). Cardiac output was equal to stroke volume multiplied by heart rate. Great care was taken to ensure that the diameter was measured perpendicularly to the left ventricular outflow tract, trailingedge to leadingedge just proximalto the prosthetic anulus; the angle between the Doppler cursor and the left ventricular outflow tract was as close to 0” as possible (always <20”);and the Dopplersignal was truly representative of the left ventricular outflowtract, as emphasized by Skjaerpe et al. (14).Multiple determinations were made in each patient to ensure reproducibility of measurements. ve area ~eu~at~s. Prosthetic valve area (PVA) was determined with the standard continuity equation: PVA = SVNTI,,, where SV is stroke volume and
JACC Vol. 16. No. 3 September 1 :637-43
VTl,, is the velocity-time integral of the colatinuous wave Doppler signal of the aortic jet (15-20).Valve area was also calculated using the previously proposed (1 continuity equation: PVA = (LVQT,,, Vmax,,, where LVQT,,, and LVGTvmaxare the left ventricular outflow tract area and peak jet velocity, tiveiy, and Vmax,, is the peak aortic jet velocity m with continuous wave In vitro valve area
bioprosthetic effective
model measures the transvaivular pressure 8rad~e~tsan pulsatiie flow rates at different cardiac outputs, with a puis rate of 70 beatslmin and systole accounting for approximately 35% of the cardiac cycle. From this information, effective valve orifice area was calculated using the formula proposed by Yoganathanet al. (22)and a range of values was tive obtained for each prosthesis size, suggesting that and orificearea increases as a function of the prevailing pressure gradient. The range of in vitro area values derive physicat a stroke volume (55 to ii 1 ml) approx~mati~ logic range of stroke volumes (46 to 118 ml) d in the present study patients was used for comparison purposes (Table 1) and the median value of each in vitro area range was used for linear regression analysis. The in vitro area data were not available to t her at the time of Doppler echocardiographic measure of the effective orifice area. Evaluation of aortic re~~~~t~tio~.Doppler color flow mappingwas performed in multiple views to interrogate for the presence of aortic regurgitation.This was visuallygraded as it when the jet was very narrow and extended only a short distance below the aortic valve and 2t when the jet was somewhat larger and longer but remained narrow at the level of the aortic anuius (~20% of the left ventricular outflowtract diameter) and did not extend beyond the tip of the anterior mitral valve leaflet. Significant3t or 4t aortic regurgitationwas not observed in our study patients. Statisticalanalysis. Continuous variables are expressed as the mean value + SD and the range. Statistical analysisof the association of continuous variables was performed using the Pearson linear correlation coefficient and graphs were constructed with the corresponding linear regression equation. For statistical inference, p values were obtained using the one-sided t test for directional association.
Valvearea and gradient ). For the b3 ( 31 patients, the peak gradient ranged from 10.8 to 75.0 mm Hg (mean 35 2 16)and the mean gradient ranged from 7.6 to
JACC Vol. 16. No. 3 September 1990~637-43
.5 + 9.5). Valve arearanged
fro
F@pnre 8. Correlation between Doppler echocardiographic eKective prosthetic aortic valve area (AVA) calculared with ~5 0. rhe Ah standard continuity equation (CE) and the same area calculak use of the simplified continuity equation.
we 2. CorreQatiw heWxn (cm’) for each valve size
r = 0.98 SEE .0.07 cm “~102ki.005 p~OOO05
22.
in vilro prosthetic
dele~rn~~ed by Doppler echocardiog~a~~y continuity equation KE).
valve area
with use of ahe standard
r
2.3 1
median
( ml and in vivo aortic valve area
a
20.
18.
0.0
3.0
1.2
1.4
1.6
1.B
20
22
24
IWITRO VALVE SIZE AYA BY STANDARDCE
(Cm’1
90
2,
23
PROSTHETIC AREA (cm*) 25
27
20
643
DUMESNIL ET AL. DOPPLER ECHOCARDIOGRAPHY
OF AORTIC
BIOPROSTHETIC
VALVE
AREAS
q
]
70
lACC Vol. 16. No. 3 September 199Q:h37-43
o
r = -0.72
1
D
m-l
,I
0
SEE * 11.72
mmUg
Y = ( -S.BX
+ 10.3 )’
P < D.oooS
\
so 0 40
0.8
,
1.E
I.1
I.2
2
1.B
2.2
““ 45
cl D
40
-0.48
SEE 0 IIS
1
Y = -ia.ou
0
P < o.oo3 0
r -
13
mm”g + 40.62
1.2
q
i
h2I
Y = ( -O.Ia!d
\
rnrn”~ + 7.15
)’
P < 0.0001 D
30 -
D
-0.70
SEE * 0
3!l cl
I
I
0
0.(1
0.a
Ll I -
:
D 2s -
20 -
15 -
a I
0.4
I
I
0.6
D.8 INCWZD
Figure 3. Correlation between prosthetic valve area determined by Doppler echocardiography (ECHO) with use of the standard continuity equation and peak (A) and mean (B) transprosthetic gradients derived from the modified Bernoulli equation.
prostheses. These correlations, however, improve when the valve area values are indexed for body surface area (r = -0.67 and r = -0.66 for peak and mean gradients, respectively) and are further enhanced (r = -0.72 and r = -0.70, respectively) when the gradient is considered to be a square function of the indexed prosthetic valve area, resulting in curvilinear relations (Fig. 4).
iscussiomr Validity of Dopplerechocardiographicvalve area measurements. These data indicate a good cnrrelatinn between the
aortic prosthetic valve area derived from in vitro variables and those calculated in vivo by Doppler echocardiography with the standard or simplified continuity equations, thus suggestingthat these two methods are valid for bioprosthesis assessment. To obtain the relation shown in Figure 2. we utilized the median in vitro valve area data because there is a range of area values for each prosthesis size, reflectingan
AREA by DOPPLER -
I
1
I
1
1.2
ECHO (cm’/m’)
Figure 4. Curvilinear relation between peak (A) and mean l transprosthetic valve gradients and indexed prosthetic area determined by Doppler echocardiography (ECHO) with use of the standard continuity equation. This relation is derived by considering the gradient as a square function of indexed prosthetic area.
increase in effective orifice area as a function of gradient and flow. The latter is possibly related to greater leaflet inertia at low flow rates. The variability in the production of a bioprosthesis of a given size is also a factor that might influence results. Given the range of in vitro area values, the in vivo studies slightly overestimated the area in two patients (1.66 versus 1.55cm* and 1.44versus 1.38cm*), whereas underestimationswere observed in I5 patients. The latter might be due to deterioration of the effectiveorifice area during the 20 ? 4 months since implantationor to inherent errors in the in vitro or in vivo methods. Nonetheless, these deviations are quite small and it is somewhat reassuring that the in vivo method tends to underestimate rather than overestimate effective orifice area. evaluation of intrinsic prosthesis perfmnamce. Previous studies (23-28)have shown that there is only a weak relation between prosthesis size and transprosthetic gradient, with a tendency for higher gradients to be recorded with smaller
JAW Vol. 16. No. 3
SepIrmber 199O:M7-43
ts in assessing the i rosthetic
valve
area
t. As one would ex
hemodynamic pe~orma~ce and avoiding a mismatch between prosthesis size and body size. For native valves, generally agreed that severe aortic stenosis is present w the effective orifice area is CO.6 t area (31-33). The im (341, who described a group of prosthesis with an average calcul 1.7 cm*, which ranged form 0.9 o
&-T--7-. 0.4
present
study and suggested
that an effective
prosthettc
active individual and that “be replacement . . ., the cardiologist and the surgeon must attempt to project the postoperative result considering the patient’s hemodynamic state and the pe~orma~ce of the prosthesis that will be inserted.” Figure 5 attempts to show how the peak and mean pressure gradient would theoretically behave at different levels of exertion. The relations presented assume increases of 550% in stroke volume during maximal upright exercise, as described in untrained individuals (35-38). Pending further confirmation, it would appear th indexed prosthetic valve area Xt.9 to 1.0 cm’lm’ surface area would be a minimal requirement to minimtze a postoperative pressure gradient at rest or exercise. This ty of information should be helpful to the surge e and size of prosthesis to be insert as well as in considering alternat patients with a relatively small aortic anulus diameter. Such estimates, however, require precise information from the
IT_ lNDExe0
, ~___ T 0.8
0.0 iwE.
by DOPPLER -
~..7_ -.-l___._ 1
1.2
EC”0 (m%+)
petted behaviors of the peak (A) and mean ( ic gradients with a IQ% to 50% increase i s during upright exercise. Relations are obtained by increasing the square root of the peak pressure gradient obtained from the regression equathn given in Figure G by 10% to 500/o, in nce with the continuity and simplified Bernoulli equations. xc = echocardiography. EC
manufacturer and should also take into account that : vivo effective orifice area may be somewhat smaller that calculated in vitro. Further studies, including st during exercise, will be necessary to confirm these relations and to determine how they can be a prostheses.
similar sizes. The higher valve gradient re patients appears to be related mainly to a mi
642
DUMESNIL ET AL. DOPPLER ECHOCARDIOGRAPHY
9F AORTIC BIOPROSTHETIC VALVE AREAS
prosthesis size and body size and emphasizes the importance of taking the indexed prosthetic valve area into consideration before operation. Other factors such as deterioration of the prosthetic valve area over time and increased flow through the valve may also be implicated. Of the two patients with a peak gradient >70 mm Hg. one had a bmdycardia (heart rate 53 beatslmin) and 2+ aortic regurgitation and the other had a paced rhythm at 70 beatslmin, I + aofiic regurgitation and a valve area lower than the predicted range. Conclusions. We conclude that Doppler echocardiographic evaluation of aortic bioprosthetic valve area by the continuity equation is accurate and useful in evaluating prosthetic valve performance. The transprosthetic valve gradient is less useful to evaluate intrinsic prosthesis performance because it is influenced by both prosthetic valve area and cardiac output. On the basis of the relations demonstrated between gradient and indexed prosthetic valve area. some guidelines for appropriate preoperative prosthesis size selection can probably be derived to avoid mismatch between prosthesis size and body size.
I. Sagar KB. Wann S. Paulsen WHJ. Romhilt DW. Doppler echocardiographic evaluation of Hancock and Bjiirk-Shiley Coil Cardiol 1986;7:681-7.
prosthetic valves. J Am
2. Alam M. Rosman HS. Lakier JB. et al. Doppler and echocardiographic features of normal and dysfunctioning bioprosthetic valves. J Am Coll Cardiol 1987:10:851-8. 3. Williams GA, Labowitz AJ. Doppler hemodynamic evaluation of prosthetic (Starr-Edwards and Bjiirk-Shiley) and bioprosthetic (Hancock and Carpentier-Edwards) cardiac valves. Am J Cardiol 1985:56:325-32. 4. Hatle L. Angelsen BA. Tromsdal A. Non-invasive assessment of aortic stenosis by Doppler ultrasound. Br Heart J 1980;43:284-92. 5.
Slamm RB. Marlin RP. Quantification
of pressure gradients across stenotic valves by Doppler uhrdsound. J Am Coll Cardiol 1983:2:707-18.
6. Currie PJ. Seward JB. Reeder GS. et al. Continuous wave Doppler echocardiographic assessment of severity of calcific aortic stenosis: a SimUkaneOUS Doppler-catheter correlative study in 100 adult patients. Circulation 1985:76l:Il62-9. 7. Callahan MJ. Tajik AJ. SU-Fan Q, Bove AA. Validation of instantaneous pressure gradients measured by continuous-wave Doppler in experimentally induced aortic stenosis.Am J Cardiol 1985:56:989-93. 8. Smith MD. Dawson PL. Elion JL. et al. Correlation of continuous wave Doppler velocities with catheterization gradients: an experimental model of aortic stenosis. 3 Am Coll Cnrdiol 1985:6: 1306-14. 9. Kostumkis D. Allan HD. Goldberg SJ. Sahn DJ, Valdes-Cruz LM. Noninvasive quantification of stenotic semilunar valve areas by Doppler echocardiography. J Am Coll Cardiol 1984:3:1256-W. 10. Currie PJ. Hagler DJ. Seward JB, et al. Instantaneous pressure gndient: a ~~~UhneOUS kWkr and dual catheter correlative study. J Am Coll Cardiol 1986;7:800-6. ll.
Huntsman LL. Stewart DK. Barnes SR. Franklin SB. Colocousis JS, Hes*l EA. Noninvasive Doppler determination ofcardiac output in man: clinical validation. Circulation 1983;67:593_602.
12. G&n JM. Tobis JM. Dabeslani A. et al. Superiority of two-dimensional measuremen of aortic vessel diameter in Doppler echacardiographic
JACC Vol. 16. No. 3 199&63?-43
September
eslimates of left ventricular stroke volume. J Am Coil Cardiol 1985:6:6674. 13. Gardin 91ti. E;rimation of volume flow by Doppler Echocardiography lY87;4: 16-28.
echocardiography.
14. Skjaerpe T. Hegrenaes L. Hatle L. Noninvasive estimation of valve area in patients with aortic stenosis by Doppler ultrasound and twodimensional echocardiography. Circulation 1985;72:810-8. 15. Warth C. Stewart W9, Block PC. Weyman AE. A new method lo calculate aortic valve area without left heart catheterization. Circulation 1984:70:978-83. 16. Zoghbi WA. Farmer KL. Soto JG, Nelson JG. Quinones MA. Accurate noninvasive quantificatks of stenotic aortic valve area by Doppler echocardiography. Circulalion 1986:73:4X!-9. 17. Richards KL. Cannon SR. Miller SC. Crawford MH. Calculation ofaortic valve area by Doppler echocardiography: a direct application of the continuity equation. Circulation 1986:73:964-9. 18. Otto CM. Pearhnan AS, Comcss KA. Reamer RP. Janko CL. Huntsmun LL. Determination of the stenolic aortic valve area in adults using Doppler echocardiography. J Am Coll Cardiol 1986;7:5OY-17. 19. Oh JK. Taliercio CP. Holmes DR Jr. et al. Prediction of the severity of aortic slenosis by Doppler aortic valve area determination: prospective Doppler-cathchcrization correlation in Iu(I patients. J Am Coll Cardiol 1988:l l:l??7-34. 20. Graybum PA. Smith MD. Harrison MR. Gurley JC. DeMaria AN. Pivotal role ofaortic valve area calculation by the continuity equation for Doppler assessment of aortic stenosis in patients with combined aortic stenosis and regurgitation. Am J Cardiol 1988:61:376-81. 21. Fujii K, Kitabake A. Asao M. et al. Noninvasive evaluation of valvular stenosis by a quantitative Doppler technique. J Cardiovasc Ultrason 1984:3:2Ol-8. 22. Yoganathan AP. Woo YR. Sung HW. Williams FP. Franch RH, Jones M. In vitro hemodynamic characteristics of tissue bioprosthesis in the aortic position. J Thorac Cardiavasc Surg 1986:92: l98-20Y. 23. Levine FH. Carter JE. Buckley MJ. Daggett WM. Akins CW. Auscen WG. Hemodvnamic evaluation of Hancock and Caroentier-Edwards bioprosthesis:Circulalion 1981:64(suppl 11):11-192-S. ’ 24. Morris DC. King SB 111, Douglas JS Jr, Wickliffe Hemodynamic results of aortic valvular replacement xenografi valve. Circulalion 1977:56:841-4.
CW, Jones EL. with the porcine
25. Rossiter 53. Miller DC. Stinson EB. et al. Hemodynamic and clinical comparison of the Hancock modified orifice and standard orifice bioprosthesis in the aorfic position. J Thorac Cardiovasc Surg 1980:80:54-60. 26. Becker RM. Strom J, Frishman W. et al. Hemodynamic performance of the IonescuShiley valve prosthesis. J Thorac Cardiovasc Surg 1980:80: 613-20. 27. Rothkopf M. qavidson T. Lipscomb K. et al. Hemodynamic evaluation of the Carpentier-Edwards bioprosthesis in the aortic position. Am J Cardiol 1979;44:209-14. 28. Cosgrove DM, Lythe BW. Williams GW. Hemodynamic performance of the Carpentier-Edwards pericardial valve in the aortic position in vivo. Circulation 1985:72(suppl H):il-146-52. 29. Thomasson B. Cardiac output in normal subjects under standard conditions: the reproducibility of measurements of the Fick method. Stand J Clio Lab Invest 1957:9:365-76. 30. Grossman W. Barry WH. Cardiac catheterization. In: Braunwald E. ed. Heart Disease: A Textbook of Cardiovascular Medicine. Philadelphia: WB Saunders, 1988:242-67. 31. Braunwald E. Roberts WC. Goldblatt A. Aygen MM. Rockoff SD, Gilbert JW. Aortic stenosis: physiological. pathological. and clinical concepts: combined clinical staff conference a( the National l&lutes of Health. Ann Intern Med 1%3:58:494-522. 32. Frank S. Johnson A. Ross J Jr. Natural history of valvular aortic stenosis. Br Heart J 1973;35:41-6.
~M~~e~~PE. Swan HJC, Percemage of lefa imtoola S 33. Tobin % Jr. ventricuk;: stroke work loss: a simple hemodynamic concept for estimatioa d severity in valvular aortic stenosis. Circmlntion l%9;3WiM-99. e problem ~~r~M~a~~0~ w%:S8:20-4. Robinson . #a card ockade on exercise in man. J Clin Invest 1 36. Robinson RF. Epst.zin SE, Kak
of valve
prosthesis-patiena
rniw~ahh.
ald E. EtTecis of beteaximal and s~~~~~~~~~