JACC Vol. 16. Ma. 3 Sep?ember I :$37-43

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oppler echocardiogr vasive evaluation of es. The variables

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 area calculations, in patients with an aortic prosthesis

and to determine the im lications of such i ation with

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.

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 OWJO by the American College of Cardiology

638 DIJMESNIL ET AL. DOPPLER ECHOCARDIOGRAPHY OF AORTK BIOPROSTHETIC VALVE AREAS

JACC Vol. 16. No. 3 September 1 :637-43

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 echocardio- graphic examination was performed a mean of 20 + 4 months after surgery, Ail studies werr pgrformed by the same technician on a Hewlett-Packard Sonos-500 ultrasound SYS- tern and subsequently independently reviewed by the same investigator. Reasons for excluding the aforementioned four patients were inability to adequately measure left ven- tricular 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 measure- ments; in 10 cases, after review, measurements were redone from stop frame analysis of the videotape. These 10 cases 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 possi- bility.

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 veioc- ity from apical and right parastemai windows and appiica- tion of the modified Bernoulli equation, as previously de- scribed 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-axis view during systole, multiplied by the velocity-time integral of the left ventricular outflow tract pulsed Doppler signal recorded from the apical four 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 perpen- dicularly to the left ventricular outflow tract, trailing edge to leading edge just proximal to 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 Doppler signal was truly representative of the left ventricular outflow tract, as emphasized by Skjaerpe et al. (14). Multiple determinations were made in each patient to ensure repro- ducibility of measurements.

ve area ~eu~at~s. Prosthetic valve area (PVA) was determined with the standard continuity equa- tion: PVA = SVNTI,,, where SV is stroke volume and

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 LVGTvmax are the left ven- tricular 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~ts an pulsatiie flow rates at different cardiac outputs, with a puis rate of 70 beatslmin and systole accounting for approxi- mately 35% of the cardiac cycle. From this information, effective valve orifice area was calculated using the formula proposed by Yoganathan et al. (22) and a range of values was obtained for each prosthesis size, suggesting that tive orifice area increases as a function of the prevailing and pressure gradient. The range of in vitro area values derive at a stroke volume (55 to ii 1 ml) approx~mati~ physic- 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 mapping was performed in multiple views to interrogate for the presence of aortic regurgitation. This was visually graded 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 outflow tract diameter) and did not extend beyond the tip of the anterior mitral valve leaflet. Significant 3t or 4t aortic regurgitation was not observed in our study patients.

Statistical analysis. Continuous variables are expressed as the mean value + SD and the range. Statistical analysis of the association of continuous variables was performed using the Pearson linear correlation coefficient and graphs were constructed with the corresponding linear regression equa- tion. For statistical inference, p values were obtained using the one-sided t test for directional association.

Valve area and gradient b3 ( ). For the 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 area ranged fro

F@pnre 8. Correlation between Doppler echocardiographic eKective prosthetic aortic valve area (AVA) calculared with ~5 0. rhe standard continuity equation (CE) and the same area calculak Ah

use of the simplified continuity equation.

2.3 1 r = 0.98

22.

20.

18.

SEE .0.07 cm a “~102ki.005 p~OOO05

0.0 3.0 1.2 1.4 1.6 1.B 20 22 24

AYA BY STANDARDCE (Cm’1

we 2. CorreQatiw heWxn median in vilro prosthetic valve area

(cm’) for each valve size ( ml and in vivo aortic valve area dele~rn~~ed by Doppler echocardiog~a~~y with use of ahe standard continuity equation KE).

r

IWITRO PROSTHETIC AREA (cm*) VALVE SIZE 90 2, 23 25 27 20

643 DUMESNIL ET AL. DOPPLER ECHOCARDIOGRAPHY OF AORTIC BIOPROSTHETIC VALVE AREAS

lACC Vol. 16. No. 3 September 199Q:h37-43

0.8 , I.2 I.1 1.E 1.B 2 2.2

Ll

cl I - -0.48

D SEE 0 IIS mm”g

cl Y = -ia.ou + 40.62

P < o.oo3

0 D

Figure 3. Correlation between prosthetic valve area determined by Doppler echocardiography (ECHO) with use of the standard conti- nuity 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, respec- tively) 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 Doppler echocardiographic valve area measure-

ments. 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 suggesting that 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, reflecting an

70 ] q o r = -0.72

1 SEE * 11.72 mmUg

m-l D 0 Y = ( -S.BX + 10.3 )’

I \ P < D.oooS , so

40 :

0

““ 0 I I

0.a 0.(1 1.2

45

40 1 q

0 r - -0.70

13 SEE * h2I rnrn”~

3!l

i

30 -

2s -

20 -

15 -

0 Y = ( -O.Ia!d + 7.15 )’

\ P < 0.0001 D

D

a I I I I 1 I 0.4 0.6 D.8 1 1.2

INCWZD AREA by DOPPLER - ECHO (cm’/m’)

Figure 4. Curvilinear relation between peak (A) and mean l transprosthetic valve gradients and indexed prosthetic area deter- mined 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 bio- prosthesis 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 1.55 cm* and 1.44 versus 1.38 cm*), whereas under- estimations were observed in I5 patients. The latter might be due to deterioration of the effective orifice area during the 20 ? 4 months since implantation or 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 be- tween 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

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 theoreti-

cally 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

o &-T--7-. IT_ , ~_ __ T ~. .7_ -.-l___._ 0.4 0.0 0.8 1 1.2

lNDExe0 iwE. by DOPPLER - 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 xc nce with the continuity and simplified Bernoulli equations. EC = echocardiography.

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

JACC Vol. 16. No. 3 September 199&63?-43

prosthesis size and body size and emphasizes the importance of taking the indexed prosthetic valve area into consider- ation 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 regurgi- tation 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 echocardio-

graphic 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 perfor- mance because it is influenced by both prosthetic valve area and cardiac output. On the basis of the relations demon- strated between gradient and indexed prosthetic valve area. some guidelines for appropriate preoperative prosthesis size selection can probably be derived to avoid mismatch be-

tween prosthesis size and body size.

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