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Hemodynamic evaluation of normally functioning sulzer carbomedics prosthetic valves
Ultrasound in Med. & Biol., Vol. 29, No. 5, pp. 649 – 657, 2003 Copyright © 2003 World Federation for Ultrasound in Medicine & Biology Printed in the USA. All rights reserved 0301-5629/03/$–see front matter
doi:10.1016/S0301-5629(02)00777-9
● Original Contribution HEMODYNAMIC EVALUATION OF NORMALLY FUNCTIONING SULZER CARBOMEDICS PROSTHETIC VALVES NURGU¨ L KESER,* NAVIN C. NANDA,* ANDREW P. MILLER,* SZILARD VOROS,* CAHIDE SOYDAS,* GOPAL AGRAWAL,* CHIARA LIGUORI,* DAVID NAFTEL,† ALBERT D. PACIFICO,† JAMES K. KIRKLIN,† DAVID C. MCGIFFIN† and WILLIAM L. HOLMAN† Divisions of *Cardiovascular Disease and †Cardiovascular and Thoracic Surgery, The University of Alabama at Birmingham, Birmingham, AL, USA (Received 19 August 2002; in final form 7 November 2002)
Abstract—The Sulzer Carbomedics prosthetic heart valve (CP) is a commonly used mechanical valve in clinical practice. In the present study, we used conventional and color Doppler echocardiography to assess the hemodynamics of normally functioning CP in the aortic (n ⴝ 73) and mitral (n ⴝ 127) positions. Our findings demonstrate no significant correlation of Doppler-measured peak and mean pressure gradients and effective orifice area with implanted valve size and actual orifice areas, measured directly by the manufacturer for CPs in both the mitral and aortic positions. However, it is still useful to measure effective orifice area by Doppler because a value in the normal or nonstenotic range points to an unobstructed prosthesis in the aortic or mitral position, in the absence of poor left ventricular ejection fraction. A value in the stenotic range could mean a normally functioning or obstructed prosthesis and, therefore, may need further investigation, such as assessment of valve leaflet motion by transthoracic or transesophageal echocardiography or fluoroscopy. Valve regurgitation as evaluated by color Doppler flow mapping was mild in practically all CPs in the aortic position, and in the majority of CPs in the mitral position. (E-mail: [email protected]) © 2003 World Federation for Ultrasound in Medicine & Biology. Key Words: Prosthetic heart valve, Echocardiography, Sulzer Carbomedics prosthetic heart valve.
ening ring and the high tungsten content of the leaflets provide the visibility for easy postoperative valve function assessment using fluoroscopy. The orientation of the valve can be adjusted at the time of implantation and the inner valve ring can be rotated within the valve housing. The patented valve pivot design provides thorough washing of the hinge mechanism to aid in the reduction of thrombus formation. The leaflets sit at a 25° angle to the plane of the valve ring and, on full excursion, open to 78°. The present study was undertaken to evaluate the hemodynamics of the normally functioning CP using both transesophageal (TEE) and transthoracic (TTE) echocardiographic modalities. The results were compared with data provided by the manufacturer and data in the published literature for a normally functioning CP.
INTRODUCTION Since the emergence of pyrolytic carbon as a suitable material for biologic implants, its use in the manufacture of mechanical heart valves has escalated tremendously. It was first used in clinical practice as a spherical poppet in the De Bakey ball-valve prostheses in 1969 and, since then, it has been used in tilting disk valves as well. The first bileaflet pyrolytic carbon mechanical valve to be developed for clinical use was the St. Jude Medical prosthetic heart valve, which was introduced in 1977 (Wang 1989). The Sulzer Carbomedics (Austin, Texas) prosthetic heart valve (CP) was developed in an attempt to improve an existing valve design, and was first utilized in clinical practice in 1986 (Richard et al. 1990). The circular configuration of the valve is maintained by a titanium stiffening band that provides added valve strength, to lessen the risk of leaflet dislodgement and impingement. The titanium stiff-
METHODS Patient population The study population included 128 consecutive patients (41 men, 87 women; mean age: 54.9 ⫾ 2.16 years)
Address correspondence to: Navin C. Nanda, M.D., The University of Alabama at Birmingham, Heart Station SW/S102, 619 South 19th Street, Birmingham, AL 35249 USA. E-mail: [email protected] 649
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with CP in the mitral position and 73 patients (49 men, 24 women; mean age: 52.1 ⫾ 2.58 years) with CP in the aortic position. Of these patients, 6 had both aortic and mitral valve replacement. A total of 13 patients with mitral valve replacement and 12 patients with aortic valve replacement also had coronary artery bypass surgery during the same operation. The criteria for inclusion in the present study were a clinically evaluated normal function of the prosthetic valve and a technically adequate ultrasonic examination. Only 5 patients with aortic prosthesis (AP) and 6 patients with mitral prosthesis (MP) had been excluded from the study population because of poor acoustic window; 2 patients with AP and 1 patient with MP were excluded because of obvious echocardiographic and clinical dysfunction of the prosthesis. Echocardiography TTEs were performed within 7 days of implantation using a Toshiba 140, Hewlett Packard 2500 or Acuson 128 XP US system and a 2.5-MHz transducer. TEEs were performed intraoperatively in the postbypass period using a Hewlett Packard 2500 or 1500 system and a 5-MHz multiplane transducer in all patients, except for 10 patients with MP in whom a biplane transducer was used. The usual examination was performed and left ventricular ejection fraction was calculated in all patients by a conventional method (Baran et al. 1983). Transvalvular pressure gradients, effective orifice area and insufficiency. Color Doppler-guided continuouswave Doppler was used to obtain maximum peak and mean velocities across the AP from the apical five-chamber view. The same view was utilized to obtain the maximum left ventricular outflow tract (LVOT) velocities using color Doppler-guided pulsed-wave Doppler. Peak and mean prosthetic pressure gradients were calculated by the modified Bernoulli equation (Wilkins et al. 1986; Holen et al. 1979). LVOT width was measured in the parasternal long axis view immediately proximal to the prosthesis and the LVOT cross-sectional area was calculated by assuming a circular outflow tract configuration, using the formula (r2) (Skjaserpe et al. 1985; Zoghbi et al. 1986). The effective AP orifice area was calculated by the simplified continuity equation in the standard manner (Skjaserpe et al. 1985). Using color Doppler flow imaging in multiple views, the percent ratio of maximal diameter of the aortic regurgitant (AR) jet width at its origin from the prosthesis to the maximal inner diameter of the LVOT taken at the same point was calculated, and AR severity graded as described previously for TTE and TEE (Perry et al. 1987; Sanyal et al. 1991). Maximal peak and mean pressure gradients across the MP were obtained in the apical four-chamber view utilizing color Doppler-guided continuous-wave Doppler and the modified Bernoulli equa-
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Fig. 1. Color Doppler-guided continuous-wave Doppler measurements of peak pressure gradient as calculated from the modified Bernoulli equation (mmHg) vs. actual implanted valve size.
tion (Wilkins et al. 1986; Zoghbi et al. 1986). The effective MP orifice area was estimated by the pressure half-time method (Hatle et al. 1979). Because no patient demonstrated mitral regurgitation (MR) by TTE, only TEE assessment was used. For TEE assessment, the maximal MR jet was used in multiple views to grade severity as described previously (Helmcke et al. 1987; Yoshida et al. 1990; Nanda and Domanski 1998). Statistical analysis Statistical analysis was done using a commercially available statistics software (SPSS version 10 for Microsoft). To assess the relationship between valvular size and transvalvular gradients, we used bivariate correlation analysis. Correlation coefficients were calculated by
Fig. 2. Color Doppler-guided continuous-wave Doppler measurements of mean pressure gradient (mmHg) vs. actual implanted valve size.
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Table 1. Average peak pressure gradients in Sulzer Carbomedics aortic prostheses (AP) (mmHg) AP size
18 mm
19 mm
21 mm
23 mm
25 mm
27 mm
Present study (4v2) Chambers et al. (1993) (4v2) Globits et al. (1992) (4v2) De Paulis et al. (1994) Chacrobarty et al. (1996) (4v2)
32.0 (n ⫽ 1)
27.1 ⫾ 21.5 (n ⫽ 8) 40.1 ⫾ 15.3 (n ⫽ 3) 43.4 ⫾ 8.9 (n ⫽ 16) 33.4 ⫾ 13.2 (n ⫽ 7) 30 ⫾ 6.3 (n ⫽ 11)
25.1 ⫾ 11.27 (n ⫽ 8) 28.2 ⫾ 10.2 (n ⫽ 11) 31.1 ⫾ 13.7 (n ⫽ 30) 25.4 ⫾ 5.2 (n ⫽ 7) 27.4 ⫾ 8.2 (n ⫽ 31)
24.2 ⫾ 10.37 (n ⫽ 82) 20 ⫾ 7.4 (n ⫽ 25) 28.7 ⫾ 7 (n ⫽ 57)
20.67 ⫾ 9.99 (n ⫽ 17) 16 ⫾ 7.9 (n ⫽ 22) 24.5 ⫾ 9.4 (n ⫽ 39)
22.5 ⫾ 14.4 (n ⫽ 7) 17.7 ⫾ 11.2 (n ⫽ 17) 24.1 ⫾ 6.3 (n ⫽ 21)
– 22.5 ⫾ 12.6 (n ⫽ 12)
– 22.1 ⫾ 3.8 (n ⫽ 6)
– 24.7 ⫾ 5.6 (n ⫽ 22)
29 mm
31 mm
–
17.0 (n ⫽ 1)
10.8 ⫾ 4.9
–
–
–
–
–
–
–
v2 ⫽ Square of peak velocity across the aortic prostheses.
Table 2. Average mean pressure gradients in Sulzer Carbomedics aortic prostheses (AP) (mmHg) AP size
18 mm
19 mm
21 mm
23 mm
25 mm
27 mm
Present study
12.0 (n ⫽ 1)
16.20 ⫾ 10.35 (n ⫽ 3) 19.4 ⫾ 5.6 (n ⫽ 3) 17.1 ⫾ 5.6 (n ⫽ 8) 17.3 ⫾ 4.2 (n ⫽ 11) 20.1 ⫾ 7.1 (n ⫽ 7)
12.5 ⫾ 6.7 (n ⫽ 8) 12.3 ⫾ 3.8 (n ⫽ 11) 12.1 ⫾ 3.6 (n ⫽ 14) 15.2 ⫾ 5.1 (n ⫽ 31) 12.3 ⫾ 3.4 (n ⫽ 7)
12.9 ⫾ 4.2 (n ⫽ 31) 9.8 ⫾ 3.8 (n ⫽ 25) 9.4⫾ 4 (n ⫽ 12) 14.4 ⫾ 3.7 (n ⫽ 22) –
11.6 ⫾ 6.1 (n ⫽ 17) 8.3 ⫾ 4.2 (n ⫽ 22) 9.1 ⫾ 3 (n ⫽ 22) 12.4 ⫾ 7.5 (n ⫽ 12) –
10 ⫾ 6.1 (n ⫽ 7) 8.8 ⫾ 3.3 (n ⫽ 10) 6.8 ⫾ 2.5 (n ⫽ 17) 12.1 ⫾ 2.6 (n ⫽ 6) –
Chambers et al. (1994) Ihlen et al. (1992) Chacrobarty et al. (1996) De Paulis et al. (1994)
29 mm – 5.8 ⫾ 3.2 (n ⫽ 3) – –
31 mm 8.0 (n ⫽ 1) – – –
–
–
Table 3. Average peak pressure gradients in Sulzer Carbomedics mitral prostheses (MP) (mmHg) MP size
18 mm
23 mm
25 mm
27 mm
29 mm
31 mm
33 mm
Present study (4v2) Chambers et al. (1993) (4v2) Soo et al. (1994) (4v2)
12.3 (n ⫽ 1) –
11.18 ⫾ 3.6 (n ⫽ 8) 18 (n ⫽ 2) –
11.63 ⫾ 4.8 (n ⫽ 51) 9.4 ⫾ 4.5 (n ⫽ 4) 10.3 ⫾ 2.3 (n ⫽ 2)
10.7 ⫾ 3.8 (n ⫽ 37) 10.5 ⫾ 4.4 (n ⫽ 28) 9.3 ⫾ 2.4 (n ⫽ 15)
10.3 ⫾ 4.9 (n ⫽ 18) 10.1 ⫾ 4.1 (n ⫽ 15) 9.6 ⫾ 2.2 (n ⫽ 10)
10.0 ⫾ 3.4 (n ⫽ 9) 8.6 ⫾ 5.6 (n ⫽ 14) 7.7 ⫾ 1.6 (n ⫽ 9)
10.1 ⫾ 2.5 (n ⫽ 3) 7.6 ⫾ 3.2 (n ⫽ 12) –
–
v2 ⫽ Square of peak velocity across the mitral prostheses.
Table 4. Average mean pressure gradients in Sulzer Carbomedics mitral prostheses (MP) (mmHg) MP size Present study Chambers et al. (1993) Soo et al. (1994)
18 mm
23 mm
25 mm
27 mm
29 mm
31 mm
33 mm
5.5 (n ⫽ 1) –
5.6 ⫾ 1.6 (n ⫽ 8) 7 (n ⫽ 2) –
4.8 ⫾ 2.03 (n ⫽ 51) 4.1 ⫾ 1.9 (n ⫽ 4) 3.6 ⫾ 0.6 (n ⫽ 2)
4.3 ⫾ 1.7 (n ⫽ 37) 3.9 ⫾ 2 (n ⫽ 28) 3.39 ⫾ 1.08 (n ⫽ 15)
4.1 ⫾ 1.9 (n ⫽ 18) 3.3 ⫾ 1.3 (n ⫽ 15) 3.37 ⫾ 0.89 (n ⫽ 10)
4.8 ⫾ 1.9 (n ⫽ 9) 3.3 ⫾ 1.2 (n ⫽ 14) 2.7 ⫾ 0.8 (n ⫽ 9)
4.2 ⫾ 0.8 (n ⫽ 3) 3.4 ⫾ 1.5 (n ⫽ 12) –
–
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Fig. 3. Color Doppler-guided continuous-wave Doppler measurements of peak pressure gradient as calculated from the modified Bernoulli equation (mmHg) vs. actual implanted valve size.
Spearman’s nonparametric test. Results were considered significant when the p value was less than 0.05. RESULTS Echocardiography The usual echocardiographic exam was performed in all patients. Left ventricular ejection fraction was measured in all patients and was greater than or equal to 25% in all but 3 patients. Complete Doppler studies were available for most patients (69 of 73 patients with AP and 127 of 128 with MP). Transvalvular pressure gradients Average peak and mean pressure gradients across the AP of various sizes calculated by the modified Bernoulli
Fig. 4. Color Doppler-guided continuous-wave Doppler measurements of mean pressure gradient (mmHg) vs. actual implanted valve size.
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Fig. 5. Measurement of effective orifice area by the simplified continuity equation (cm2) vs. actual implanted valve size.
equation are shown in Tables 1 and 2, respectively, with comparison to results from other investigators. Average peak and mean pressure gradients across the MP of various sizes are depicted in Table 3 and Table 4, respectively. Both the peak and mean gradients across both the AP and MP showed marked variability, and no correlation was found between pressure gradients and true valve size (Figs. 1 to 4). Effective valve orifice areas For AP, average effective orifice areas for various implanted CP sizes from the present study with comparison to those of other investigators and to the actual orifice areas obtained from the manufacturer are shown in Table 5. In general, Doppler measurements underestimated true valve area for AP for sizes 23, 25, 27 and 31, but there was a wide disparity of calculated effective orifice areas without correlation to actual implanted valve size and true orifice area (Fig. 5). Effective orifice
Fig. 6. Measurement of effective orifice area by the simplified continuity equation (cm2) vs. actual implanted valve size.
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Table 5. Effective orifice areas in Sulzer Carbomedics aortic prostheses (AP) (cm2) AP size Present study Chambers et al. (1993) Ihlen et al. (1992) Soo et al. (1994) DePaulis et al. (1994) Manufacturer
18 mm
19 mm
21 mm
23 mm
25 mm
27 mm
29 mm
31 mm
2 (n ⫽ 1) –
2.38 (n ⫽ 1) 1 ⫾ 0.4 (n ⫽3) 1.1 ⫾ 0.13 (n ⫽ 8) –
1.4 ⫾ 0.37 (n ⫽ 8) 1.54 ⫾ 0.31 (n ⫽ 16) 1.52 ⫾ 0.22 (n ⫽ 14) –
1.54 ⫾ 0.7 (n ⫽ 16) 1.98 ⫾ 0.41 (n ⫽ 30) 2.12 ⫾ 0.31 (n ⫽ 22) –
2.63 ⫾ 0.38 (n ⫽ 4) –
1.8 (n ⫽ 1) 3.9 (n ⫽ 1) –
–
–
1.38 ⫾ 0.2 (n ⫽ 7) 1.41
–
1.7 ⫾ 0.6 (n ⫽ 6) 2.41 ⫾ 0.46 (n ⫽ 13) 2.65 ⫾ 0.21 (n ⫽ 17) 2 ⫾ 0.4 (n ⫽ 5) –
–
1.02 ⫾ 0.2 (n ⫽ 7) 1.06
1.3 ⫾ 0.61 (n ⫽ 30) 1.63 ⫾ 0.3 (n ⫽ 29) 1.84 ⫾ 0.25 (n ⫽ 12) 2 ⫾ 0.6 (n ⫽ 6) –
–
–
1.75
2.19
2.63
3.07
3.07
– – – 1.06
area was greater than 1.0 cm2 for most patients. For MP, average Doppler-derived orifice areas for various implanted CP sizes are shown in Table 6, with comparison to other investigators and manufacturer specifications. Again, a wide range of values was obtained for MP effective orifice area and did not correlate to implanted valve size or actual orifice area as obtained from the manufacturer (Fig. 6). Most patients, though, had effective orifice areas greater than 1.5 cm2.
The CP has been used successfully at our institution for the past several years. In the present study, we used Doppler echocardiography to evaluate the hemodynamic features of the normally functioning CP, which provides important quantitative information regarding the flow characteristics, pressure gradients and effective valve orifice areas of various types of prosthetic valves (Panidis et al. 1986; Labovitz 1989).
Prosthetic regurgitation The maximum AR jet widths/LVOT widths (AR%) by both TTE and TEE are given in Table 7. The AR% was 25% or less by TTE in all patients except 1, in whom it was 34%, and was less than 25% by TEE in all except 1 patient, in whom it was 27% (Figs. 7 and 8). These findings indicated the presence of mild AR in most patients. In patients with MP, no regurgitation was detected by TTE, probably due to reverberations from the prostheses. The maximum MR jet areas seen in Table 8 were calculated based on TEE measurements. The maximum area was found to be ⬍ 4 cm2 in 79% of patients, indicating the presence of mild MR. In the remaining patients, the maximum MR area was less than 8 cm2, consistent with moderate MR (Fig. 9).
Transvalvular pressure gradients The transvalvular gradient is a frequently used parameter to characterize prosthetic heart valves. Several echocardiographic studies have suggested that the Doppler technique is reliable in determining the pressure gradient in both tissue and mechanical valves (Holen et al. 1979, 1981; Gross and Wann 1984; Gibbs et al. 1988). However, because transprosthetic pressure gradients are determined by the cardiac output, as well as by the type and size of the prostheses, relatively high gradients have been obtained even with clinically normal prosthetic valve function (Nanda and Domanski 1998; Williams and Labovitz 1985; Cooper et al. 1987). This is because Doppler is extremely sensitive and will detect even localized high velocities originating from the metallic/ carbon prosthetic components. These high velocities do
DISCUSSION
Table 6. Effective orifice areas in Sulzer Carbomedics mitral prostheses (MP) (cm2) MP size Present study Chambers et al. (1993) Soo et al. (1994) Globitz et al. (1992) Manufacturer
18 mm
23 mm
25 mm
27 mm
29 mm
31 mm
33 mm
3.25 (n ⫽ 1) –
2.2 ⫾ 0.74 (n ⫽ 7) 1.3 (n ⫽ 1) –
2.2 ⫾ 0.68 (n ⫽ 50) 2.23 ⫾ 0.48 (n ⫽ 4) 2.9 ⫾ 0.8 (n ⫽ 2) 2.3 ⫾ 0.2 (n ⫽ 10) 2.19
2.49 ⫾ 0.59 (n ⫽ 36) 2.08 ⫾ 0.58 (n ⫽ 19) 2.9 ⫾ 0.75 (n ⫽ 15) 2.2 ⫾ 0.5 (n ⫽ 36) 2.63
2.3 ⫾ 0.68 (n ⫽ 18) 2.06 ⫾ 0.46 (n ⫽ 8) 2.3 ⫾ 0.4 (n ⫽ 10) 2.4 ⫾ 0.3 (n ⫽ 7) 3.07
2.1 ⫾ 1.06 (n ⫽ 9) 1.85 ⫾ 0.9 (n ⫽ 6) 2.8 ⫾ 1.14 (n ⫽ 9) 2.1 ⫾ 0.5 (n ⫽ 17) 3.07
1.8 ⫾ 0.6 (n ⫽ 2) 2.27 ⫾ 0.67 (n ⫽ 10) –
– – 1.06
1.7 ⫾ 0.3 (n ⫽ 2) 1.75
– 3.07
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Table 7. Evaluation of Sulzer Carbomedics aortic prosthetic (AP) regurgitation (AR) No
18 mm
19 mm
21 mm
23 mm
25 mm
27 mm
29 mm
31 mm
AR% (TTE)
10 (n ⫽ 1) 20 (n ⫽ 1)
25 (n ⫽ 1) 19 (n ⫽ 1)
10.12 ⫾ 0.83 (n ⫽ 8) 17.5 ⫾ 3.53 (n ⫽ 2)
13.2 ⫾ 5.5 (n ⫽ 31) 18.8 ⫾ 4.3 (n ⫽ 21)
16.2 ⫾ 6.1 (n ⫽ 16) 20.7 ⫾ 4.0 (n ⫽ 14)
14.1 ⫾ 6.6 (n ⫽ 7) 17.1 ⫾ 7.5 (n ⫽ 6)
16 (n ⫽ 1) 0
9 (n ⫽ 1) 0
AR% (TEE)
AR% ⫽ Maximum diameter of AR jet at its origin/maximum inner diameter of the left ventricular outflow tract at the same point ⫻ 100; TTE ⫽ transthoracic echocardiography; TEE ⫽ transesophageal echocardiography.
not reflect the true pressure gradients across the prosthesis, which are much lower (Gibbs et al. 1988). In the present study, the average peak gradients across different CP sizes in the aortic position as calculated by the modified Bernoulli equation ranged between 17 mmHg and 32 mmHg, and the average mean pressure gradients ranged from 8 mmHg to 16 mmHg, both with wide confidence intervals. Likewise, Chambers et al. (1993), Globits et al. (1992), De Paulis et al. (1994) and Chacrobarty et al. (1996) recorded pressure gradients in this range with generous SDs. As for MP, the average peak gradients were around 11 mmHg and the average mean gradients were around 4 to 5 mmHg but, again, with significant ranges. These values are similar to those previously described by Chambers et al. (1993) and Soo et al. (1994). One possible interpretation of this data would be to utilize Doppler-measured pressure gradients cautiously in the evaluation of prosthetic valves. Although a normal gradient, in the absence of poor left ventricular ejection fraction, is reassuring, an abnormal gradient may not necessarily indicate a malfunctioning or stenotic valve. For example, one normally functioning AP demonstrated
a peak pressure gradient of 56 mmHg and one normally functioning MP had a peak gradient of 28 mmHg. Other parameters may be needed to evaluate true valve function.
Fig. 7. Measurement of percent aortic regurgitation jet width/ left ventricular outflow tract width by Doppler color flow mapping (transthoracic echocardiography, TTE) vs. actual implanted valve size.
Fig. 8. Measurement of percent aortic regurgitation jet width/ left ventricular outflow tract width by Doppler color flow mapping (transesophageal echocardiography, TEE) vs. actual implanted valve size.
Effective orifice areas AP areas can be potentially measured noninvasively using the simplified continuity equation (Gupta et al. 1988), which has been found to be more accurate than data obtained from invasive measurements, where valve areas in one study were found to be more than twice the theoretical orifice area (Ihlen et al. 1992). Dumesnil et al. (1990) showed excellent correlation between the standard and simplified continuity equation, the derived aortic valve area, and in vitro prosthetic valve area. However, Chambers et al. (1991) suggested that the continuity equation might be inaccurate in assessing the valve area in bileaflet aortic prostheses, because of the difficulties in estimating subaortic cross-sectional area and subaortic velocity. In the current study, measurements of effective orifice area of AP by the simplified continuity equation showed a tendency to underestimate, but did not corre-
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Table 8. Maximum Sulzer Carbomedics mitral prosthetic (MP) regurgitation jet area MP size
18 mm
23 mm
25 mm
27 mm
29 mm
31 mm
33 mm
Max. MR jet area (TEE) ⬍ 4 cm2 4–5 cm2 5–5.5 cm2 5.5–7 cm2
– (n ⫽ 1) – –
(n ⫽ 6) – – –
(n ⫽ 34) (n ⫽ 10) (n ⫽ 2) (n ⫽ 1)
(n ⫽ 24) (n ⫽ 4) (n ⫽ 1) (n ⫽ 1)
(n ⫽ 14) (n ⫽ 3) – –
(n ⫽ 7) (n ⫽ 1) – –
(n ⫽ 3) – – –
TEE ⫽ Transesophageal echocardiography.
late with the true valve size as obtained from the manufacturer. A wide disparity was, again, produced with large confidence intervals, and some valve areas were calculated as significantly stenotic. These data conflict somewhat with the findings of Chambers et al. (1993), De Paulis et al. (1994), Soo et al. (1994), and Ihlen et al. (1992), who obtained values closer to the manufacturer specifications. For CP in the mitral position, Thomas and Weyman (1987) and Bjornerheim et al. (1997) demonstrated a shortened pressure half time compared to other valve designs, indicating a larger orifice size. In the present study, no correlation was found between the effective orifice area calculated by Doppler using the pressure half time method and the actual size of the implanted CP in the mitral position. There was a tendency toward underestimation of actual orifice area by Doppler for the larger CP sizes (Chambers et al. 1991; Bjornerheim et al. 1997; Dellsperger et al. 1983). However, overall, our data would suggest that Doppler interrogation of normally functioning mitral CP yields nonstenotic orifice areas. Our findings were similar to those of other authors (Chambers et al. 1993; Globits et al. 1992; Soo et al. 1994). In our experience, Doppler yields a wide range of
Fig. 9. Measurement of maximal mitral regurgitation area (cm2) by Doppler color flow mapping vs. actual implanted valve size.
velocities and pressure gradients that do not correlate with actual orifice or implant sizes. Because Doppler calculation of effective orifice area takes into account the stroke volume, one would expect this parameter to be more valuable than velocities or gradients. However, in our study, Doppler-calculated effective orifice area did not show significant correlation with actually measured orifice area for both MP and AP. All but 3 patients in the present report had a left ventricular ejection fraction greater than 25%; thus, a very low cardiac output was not a significant factor for lower than expected effective orifice areas obtained by Doppler in a number of patients with both AP and MP. Despite this, it is clinically useful to measure this parameter because a value in the normal or nonstenotic range points to an unobstructed prosthesis in the aorta or mitral position, in the absence of poor left ventricular ejection fraction. However, if the orifice area calculates to a stenotic value then the valve may or may not be functioning properly. Further parameters may be used then to evaluate valve function, such as valve motion by TTE, TEE and fluoroscopy. Regurgitation Mild degrees of regurgitation in both AP and MP have been found during catheterization in many normally functioning valves (Bjork and Henze 1979). The presence of such minimal regurgitant jets is clinically insignificant. Dellsperg et al. (1983) and other investigators also concluded that there is an obligatory closing backflow in mechanical prosthetic valves. Furthermore, echocardiographic evaluation of regurgitant jets is complicated by artefactual reverberations from the metallic/carbon components of prosthetic valves. These reverberations make the assessment of MR especially difficult during TTE because these can mask the regurgitant jet in the left atrium. It is, therefore, not surprising that, in the present study, we could not detect MR by color Doppler flow mapping in any MP using TTE, although all CPs showed MR with TEE. Both TTE and TEE were found useful in detecting AR by color Doppler for CPs in the aortic position. In the patients described by us, all but 2 normally functioning CP placed in the aortic position and most (79%)
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CP in the mitral position demonstrated no or mild insufficiency. In 20% of patients with CP in the mitral position, moderate MR was noted. These results are similar to those of previous investigators who have evaluated the St. Jude MP (Lange et al. 1991). Limitations The current study is limited by our choice of a clinically defined normal population that does not allow application of our findings to abnormal valves. We demonstrated a wide range in Doppler characteristics of these normal valves with several values clearly falling in the stenotic range for effective orifice area. We expect that malfunctioning or stenotic valves would all produce pathologic effective orifice areas, but a cohort of abnormal valves would be needed in further investigation to prove this point. Another limitation of the study is that patients were examined only at rest and not during stress such as exercise. In all patients, TTEs were performed within 7 days of valve implantation and, hence, it was not felt prudent to have them undergo stress echocardiography. CONCLUSION The CP has been used extensively in clinical practice due to its excellent hemodynamic profile. In the present study, we employed Doppler echocardiography to assess the hemodynamic function of normally functioning prostheses, both in the aortic and mitral positions. Our findings demonstrate no significant correlation of Doppler measured peak and mean pressure gradients and effective orifice area with implanted valve size and actual orifice areas measured directly by the manufacturer for CPs in both the mitral and aortic positions. However, it is still useful to measure effective orifice area by Doppler because a value in the normal or nonstenotic range points to an unobstructed prosthesis in the aortic or mitral position, in the absence of poor left ventricular ejection fraction. A value in the stenotic range could mean a normally functioning or obstructed prosthesis and, therefore, may need further investigation, such as assessment of individual valve leaflet motion by TTE/TEE or fluoroscopy. Valve regurgitation as evaluated by color Doppler flow imaging was mild in practically all CPs in the aortic position and the majority of CPs in the mitral position. Both TTE and TEE were found useful in assessing AR in CPs in the aortic position, but only TEE detected MR in CPs in the mitral position. The inability of TTE to detect MR in CPs in the mitral position could be due to the presence of reverberatory artefacts from the metallic/carbon components of the prosthesis cluttering the left atrium and masking the MR jet.
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REFERENCES Baran A, Rogal G, Nanda NC. Ejection fraction determination without planimetry by two-dimensional echocardiography: A new method. J Am Coll Cardiol 1983;1:1471–1478. Bjork VO, Henze A. Ten years’ experience with the Bjork Shiley tilting disk valve. J Thorac Cardiovasc Surg 1979;78:331–342. Bjornerheim R, Ihlen H, Simonsen S, et al. Hemodynamic characterization of the Carbomedics mitral valve prosthesis. J Heart Valve Dis 1997;6:115–122. Chacrobarty B, Quek S, Pin DZ, et al. Doppler echocardiographic assessment of normally functioning Starr-Edwards, Carbomedics and Carpentier Edwards valves in aortic position. Angiology 1996; 47:481–488. Chambers J, Cappock F, Deverall P, et al. The continuity equation tested in a bileaflet aortic prostheses. Int J Cardiol 1991;31:149– 154. Chambers J, Cross J, Deverall P, et al. Echocardiographic description of the Carbomedics Bileaflet prosthetic heart valve. J Am Coll Cardiol 1993;21:398–405. Cooper DM, Stewart WJ, Schiavone WA, et al. Evaluation of normal prosthetic valve function by Doppler echocardiography. Am Heart J 1987;114:576–582. De Paulis R, Sommariva L, Russo F, et al. Doppler echocardiographic evaluation of the Carbomedics valve in patients with small aortic annulus and valve prosthesis-body surface area mismatch. J Thorac Cardiovasc Surg 1994;108:57–62. Dellsperger KL, Wieting DW, Baehr DA, et al. Regurgitation of prosthetic heart valves dependence on heart rate and cardiac output. Am J Cardiol 1983;51:321–328. Dumesnil JG, Honos GN, Lemieux M. Validation and applications of indexed aortic prosthetic valve areas calculated by Doppler echocardiography. J Am Coll Cardiol 1990;16:637–643. Gibbs JL, Wharton GA, Williams GJ. Doppler ultrasound of normally functioning mechanical mitral and aortic valve prostheses. Int J Cardiol 1988;18:391–398. Globits S, Rodler S, Mayr H, et al. Doppler sonographic evaluation of the carbomedics bileaflet valve prostheses: One year experience. J Cardiac Surg 1992;7:9–16. Gross CM, Wann LS. Doppler echocardiographic diagnosis of porcine bioprosthetic cardiac valve malfunction. Am J Cardiol 1984;53: 1203–1205. Gupta A, Helmcke F, Pandey BJ, et al. Color guided continuous wave Doppler assessment of effective prosthetic valve area (Abst). J Am Coll Cardiol 1988;2:177A. Hatle L, Angelsen B, Tromsdal A. A non-invasive assessment of atrioventricular pressure half-time by Doppler ultrasound. Circulation 1979;60:1096–1104. Helmcke F, Nanda NC, Hsiung MC, et al. Color Doppler assessment of mitral regurgitation with orthogonal planes. Circulation 1987;75: 175–183. Holen J, Simonsen S, Froysaker T. An ultrasound Doppler technique for the noninvasive determination of the pressure gradient in the Bjork-Shiley mitral valve. Circulation 1979;59:436–442. Holen J, Simonsen S, Fraysaker T. Determination of pressure gradient in the Hancock mitral valve from non-invasive ultrasound Doppler data. Scand J Clin Lab Invest 1981;41:177–183. Ihlen H, Molstad P, Simonsen S, et al. Hemodynamic evaluation of the Carbomedics prosthetic heart valve in the aortic position: Comparison of non-invasive and invasive techniques. Am Heart J 1992; 123:151–159. Labovitz AJ. Assessment of prosthetic heart valve function by Doppler echocardiography (A decade of experience). Circulation 1989;80: 707. Lange H, Olson J, Pedersen W, et al. Transesophageal color Doppler echocardiography of the normal St Jude Medical mitral valve prosthesis. Am Heart J 1991;122:489–494. Nanda NC, Domanski M. Atlas of transesophageal echocardiography. Baltimore: Williams and Wilkins, 1998:181–250.
Normally functioning prosthetic valves ● N. KESER et al. Panidis IP, Ross J, Mintz GS. Normal and abnormal prosthetic valve function as assessed by Doppler echocardiography. J Am Coll Cardiol 1986;8:317. Perry GJ, Helmcke F, Nanda NC, et al. Evaluation of aortic insufficiency by Doppler color flow mapping. J Am Coll Cardiol 1987; 9:952–959. Richard G, O’Bannon W, More RB. An in vitro comparison of 29 mm mitral Carbomedics and St Jude medical artificial heart valves. In: Bodnar E, ed. Surgery for heart valve disease, proceedings of the 1989 symposium. London: ICR Publications, 1990:628. Sanyal RS, Pizzano N, Fan P, et al. Assessment of aortic regurgitation severity by transesophageal color Doppler echocardiography. J Am Coll Cardiol 1991;17:370A. Skjaserpe T, Hegrenaes L, Hatle L. Noninvasive estimation of valve area in patients with aortic stenosis by Doppler ultrasound and two-dimensional echocardiography. Circulation 1985;12:810– 818. Soo CS, Ca M, Tay M, et al. Doppler echocardiographic assessment of Carbomedics prosthetic valves in the mitral position. J Am Soc Echo 1994;7:159–164.
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Thomas JD, Weyman AE. Doppler mitral pressure half-time: A clinical tool in search of theoretical justification. J Am Coll Cardiol 1987; 10:923. Wang JH. The design, simplicity and clinical elegance of the St Jude Medical Heart Valve. Ann Thorac Surg 1989;48:55–56. Wilkins GT, Gillam LD, Kritzer GL, et al. Validation of continuous wave Doppler echocardiographic measurements of mitral and tricuspid prosthetic valve gradients: A simultaneous Doppler-catheter study. Circulation 1986;74:786–795. Williams GA, Labovitz AJ. Doppler hemodynamic evaluation of prosthetic (Starr Edwards and Bjork Shiley) and bioprosthetic (Hancock and Carpentier-Edwards) cardiac valves. Am J Cardiol 1985;56: 325–332. Yoshida K, Yoshikawa J, Yamaura Y, et al. Assessment of mitral regurgitation by biplane transesophageal color Doppler flow mapping. Circulation 1990;82:1121–1126. Zoghbi WA, Former KL, Soto JG, et al. Accurate noninvasive quantification of stenotic aortic valve area by Doppler echocardiography. Circulation 1986;73:452–459.
doi:10.1016/S0301-5629(02)00777-9
● Original Contribution HEMODYNAMIC EVALUATION OF NORMALLY FUNCTIONING SULZER CARBOMEDICS PROSTHETIC VALVES NURGU¨ L KESER,* NAVIN C. NANDA,* ANDREW P. MILLER,* SZILARD VOROS,* CAHIDE SOYDAS,* GOPAL AGRAWAL,* CHIARA LIGUORI,* DAVID NAFTEL,† ALBERT D. PACIFICO,† JAMES K. KIRKLIN,† DAVID C. MCGIFFIN† and WILLIAM L. HOLMAN† Divisions of *Cardiovascular Disease and †Cardiovascular and Thoracic Surgery, The University of Alabama at Birmingham, Birmingham, AL, USA (Received 19 August 2002; in final form 7 November 2002)
Abstract—The Sulzer Carbomedics prosthetic heart valve (CP) is a commonly used mechanical valve in clinical practice. In the present study, we used conventional and color Doppler echocardiography to assess the hemodynamics of normally functioning CP in the aortic (n ⴝ 73) and mitral (n ⴝ 127) positions. Our findings demonstrate no significant correlation of Doppler-measured peak and mean pressure gradients and effective orifice area with implanted valve size and actual orifice areas, measured directly by the manufacturer for CPs in both the mitral and aortic positions. However, it is still useful to measure effective orifice area by Doppler because a value in the normal or nonstenotic range points to an unobstructed prosthesis in the aortic or mitral position, in the absence of poor left ventricular ejection fraction. A value in the stenotic range could mean a normally functioning or obstructed prosthesis and, therefore, may need further investigation, such as assessment of valve leaflet motion by transthoracic or transesophageal echocardiography or fluoroscopy. Valve regurgitation as evaluated by color Doppler flow mapping was mild in practically all CPs in the aortic position, and in the majority of CPs in the mitral position. (E-mail: [email protected]) © 2003 World Federation for Ultrasound in Medicine & Biology. Key Words: Prosthetic heart valve, Echocardiography, Sulzer Carbomedics prosthetic heart valve.
ening ring and the high tungsten content of the leaflets provide the visibility for easy postoperative valve function assessment using fluoroscopy. The orientation of the valve can be adjusted at the time of implantation and the inner valve ring can be rotated within the valve housing. The patented valve pivot design provides thorough washing of the hinge mechanism to aid in the reduction of thrombus formation. The leaflets sit at a 25° angle to the plane of the valve ring and, on full excursion, open to 78°. The present study was undertaken to evaluate the hemodynamics of the normally functioning CP using both transesophageal (TEE) and transthoracic (TTE) echocardiographic modalities. The results were compared with data provided by the manufacturer and data in the published literature for a normally functioning CP.
INTRODUCTION Since the emergence of pyrolytic carbon as a suitable material for biologic implants, its use in the manufacture of mechanical heart valves has escalated tremendously. It was first used in clinical practice as a spherical poppet in the De Bakey ball-valve prostheses in 1969 and, since then, it has been used in tilting disk valves as well. The first bileaflet pyrolytic carbon mechanical valve to be developed for clinical use was the St. Jude Medical prosthetic heart valve, which was introduced in 1977 (Wang 1989). The Sulzer Carbomedics (Austin, Texas) prosthetic heart valve (CP) was developed in an attempt to improve an existing valve design, and was first utilized in clinical practice in 1986 (Richard et al. 1990). The circular configuration of the valve is maintained by a titanium stiffening band that provides added valve strength, to lessen the risk of leaflet dislodgement and impingement. The titanium stiff-
METHODS Patient population The study population included 128 consecutive patients (41 men, 87 women; mean age: 54.9 ⫾ 2.16 years)
Address correspondence to: Navin C. Nanda, M.D., The University of Alabama at Birmingham, Heart Station SW/S102, 619 South 19th Street, Birmingham, AL 35249 USA. E-mail: [email protected] 649
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with CP in the mitral position and 73 patients (49 men, 24 women; mean age: 52.1 ⫾ 2.58 years) with CP in the aortic position. Of these patients, 6 had both aortic and mitral valve replacement. A total of 13 patients with mitral valve replacement and 12 patients with aortic valve replacement also had coronary artery bypass surgery during the same operation. The criteria for inclusion in the present study were a clinically evaluated normal function of the prosthetic valve and a technically adequate ultrasonic examination. Only 5 patients with aortic prosthesis (AP) and 6 patients with mitral prosthesis (MP) had been excluded from the study population because of poor acoustic window; 2 patients with AP and 1 patient with MP were excluded because of obvious echocardiographic and clinical dysfunction of the prosthesis. Echocardiography TTEs were performed within 7 days of implantation using a Toshiba 140, Hewlett Packard 2500 or Acuson 128 XP US system and a 2.5-MHz transducer. TEEs were performed intraoperatively in the postbypass period using a Hewlett Packard 2500 or 1500 system and a 5-MHz multiplane transducer in all patients, except for 10 patients with MP in whom a biplane transducer was used. The usual examination was performed and left ventricular ejection fraction was calculated in all patients by a conventional method (Baran et al. 1983). Transvalvular pressure gradients, effective orifice area and insufficiency. Color Doppler-guided continuouswave Doppler was used to obtain maximum peak and mean velocities across the AP from the apical five-chamber view. The same view was utilized to obtain the maximum left ventricular outflow tract (LVOT) velocities using color Doppler-guided pulsed-wave Doppler. Peak and mean prosthetic pressure gradients were calculated by the modified Bernoulli equation (Wilkins et al. 1986; Holen et al. 1979). LVOT width was measured in the parasternal long axis view immediately proximal to the prosthesis and the LVOT cross-sectional area was calculated by assuming a circular outflow tract configuration, using the formula (r2) (Skjaserpe et al. 1985; Zoghbi et al. 1986). The effective AP orifice area was calculated by the simplified continuity equation in the standard manner (Skjaserpe et al. 1985). Using color Doppler flow imaging in multiple views, the percent ratio of maximal diameter of the aortic regurgitant (AR) jet width at its origin from the prosthesis to the maximal inner diameter of the LVOT taken at the same point was calculated, and AR severity graded as described previously for TTE and TEE (Perry et al. 1987; Sanyal et al. 1991). Maximal peak and mean pressure gradients across the MP were obtained in the apical four-chamber view utilizing color Doppler-guided continuous-wave Doppler and the modified Bernoulli equa-
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Fig. 1. Color Doppler-guided continuous-wave Doppler measurements of peak pressure gradient as calculated from the modified Bernoulli equation (mmHg) vs. actual implanted valve size.
tion (Wilkins et al. 1986; Zoghbi et al. 1986). The effective MP orifice area was estimated by the pressure half-time method (Hatle et al. 1979). Because no patient demonstrated mitral regurgitation (MR) by TTE, only TEE assessment was used. For TEE assessment, the maximal MR jet was used in multiple views to grade severity as described previously (Helmcke et al. 1987; Yoshida et al. 1990; Nanda and Domanski 1998). Statistical analysis Statistical analysis was done using a commercially available statistics software (SPSS version 10 for Microsoft). To assess the relationship between valvular size and transvalvular gradients, we used bivariate correlation analysis. Correlation coefficients were calculated by
Fig. 2. Color Doppler-guided continuous-wave Doppler measurements of mean pressure gradient (mmHg) vs. actual implanted valve size.
Normally functioning prosthetic valves ● N. KESER et al.
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Table 1. Average peak pressure gradients in Sulzer Carbomedics aortic prostheses (AP) (mmHg) AP size
18 mm
19 mm
21 mm
23 mm
25 mm
27 mm
Present study (4v2) Chambers et al. (1993) (4v2) Globits et al. (1992) (4v2) De Paulis et al. (1994) Chacrobarty et al. (1996) (4v2)
32.0 (n ⫽ 1)
27.1 ⫾ 21.5 (n ⫽ 8) 40.1 ⫾ 15.3 (n ⫽ 3) 43.4 ⫾ 8.9 (n ⫽ 16) 33.4 ⫾ 13.2 (n ⫽ 7) 30 ⫾ 6.3 (n ⫽ 11)
25.1 ⫾ 11.27 (n ⫽ 8) 28.2 ⫾ 10.2 (n ⫽ 11) 31.1 ⫾ 13.7 (n ⫽ 30) 25.4 ⫾ 5.2 (n ⫽ 7) 27.4 ⫾ 8.2 (n ⫽ 31)
24.2 ⫾ 10.37 (n ⫽ 82) 20 ⫾ 7.4 (n ⫽ 25) 28.7 ⫾ 7 (n ⫽ 57)
20.67 ⫾ 9.99 (n ⫽ 17) 16 ⫾ 7.9 (n ⫽ 22) 24.5 ⫾ 9.4 (n ⫽ 39)
22.5 ⫾ 14.4 (n ⫽ 7) 17.7 ⫾ 11.2 (n ⫽ 17) 24.1 ⫾ 6.3 (n ⫽ 21)
– 22.5 ⫾ 12.6 (n ⫽ 12)
– 22.1 ⫾ 3.8 (n ⫽ 6)
– 24.7 ⫾ 5.6 (n ⫽ 22)
29 mm
31 mm
–
17.0 (n ⫽ 1)
10.8 ⫾ 4.9
–
–
–
–
–
–
–
v2 ⫽ Square of peak velocity across the aortic prostheses.
Table 2. Average mean pressure gradients in Sulzer Carbomedics aortic prostheses (AP) (mmHg) AP size
18 mm
19 mm
21 mm
23 mm
25 mm
27 mm
Present study
12.0 (n ⫽ 1)
16.20 ⫾ 10.35 (n ⫽ 3) 19.4 ⫾ 5.6 (n ⫽ 3) 17.1 ⫾ 5.6 (n ⫽ 8) 17.3 ⫾ 4.2 (n ⫽ 11) 20.1 ⫾ 7.1 (n ⫽ 7)
12.5 ⫾ 6.7 (n ⫽ 8) 12.3 ⫾ 3.8 (n ⫽ 11) 12.1 ⫾ 3.6 (n ⫽ 14) 15.2 ⫾ 5.1 (n ⫽ 31) 12.3 ⫾ 3.4 (n ⫽ 7)
12.9 ⫾ 4.2 (n ⫽ 31) 9.8 ⫾ 3.8 (n ⫽ 25) 9.4⫾ 4 (n ⫽ 12) 14.4 ⫾ 3.7 (n ⫽ 22) –
11.6 ⫾ 6.1 (n ⫽ 17) 8.3 ⫾ 4.2 (n ⫽ 22) 9.1 ⫾ 3 (n ⫽ 22) 12.4 ⫾ 7.5 (n ⫽ 12) –
10 ⫾ 6.1 (n ⫽ 7) 8.8 ⫾ 3.3 (n ⫽ 10) 6.8 ⫾ 2.5 (n ⫽ 17) 12.1 ⫾ 2.6 (n ⫽ 6) –
Chambers et al. (1994) Ihlen et al. (1992) Chacrobarty et al. (1996) De Paulis et al. (1994)
29 mm – 5.8 ⫾ 3.2 (n ⫽ 3) – –
31 mm 8.0 (n ⫽ 1) – – –
–
–
Table 3. Average peak pressure gradients in Sulzer Carbomedics mitral prostheses (MP) (mmHg) MP size
18 mm
23 mm
25 mm
27 mm
29 mm
31 mm
33 mm
Present study (4v2) Chambers et al. (1993) (4v2) Soo et al. (1994) (4v2)
12.3 (n ⫽ 1) –
11.18 ⫾ 3.6 (n ⫽ 8) 18 (n ⫽ 2) –
11.63 ⫾ 4.8 (n ⫽ 51) 9.4 ⫾ 4.5 (n ⫽ 4) 10.3 ⫾ 2.3 (n ⫽ 2)
10.7 ⫾ 3.8 (n ⫽ 37) 10.5 ⫾ 4.4 (n ⫽ 28) 9.3 ⫾ 2.4 (n ⫽ 15)
10.3 ⫾ 4.9 (n ⫽ 18) 10.1 ⫾ 4.1 (n ⫽ 15) 9.6 ⫾ 2.2 (n ⫽ 10)
10.0 ⫾ 3.4 (n ⫽ 9) 8.6 ⫾ 5.6 (n ⫽ 14) 7.7 ⫾ 1.6 (n ⫽ 9)
10.1 ⫾ 2.5 (n ⫽ 3) 7.6 ⫾ 3.2 (n ⫽ 12) –
–
v2 ⫽ Square of peak velocity across the mitral prostheses.
Table 4. Average mean pressure gradients in Sulzer Carbomedics mitral prostheses (MP) (mmHg) MP size Present study Chambers et al. (1993) Soo et al. (1994)
18 mm
23 mm
25 mm
27 mm
29 mm
31 mm
33 mm
5.5 (n ⫽ 1) –
5.6 ⫾ 1.6 (n ⫽ 8) 7 (n ⫽ 2) –
4.8 ⫾ 2.03 (n ⫽ 51) 4.1 ⫾ 1.9 (n ⫽ 4) 3.6 ⫾ 0.6 (n ⫽ 2)
4.3 ⫾ 1.7 (n ⫽ 37) 3.9 ⫾ 2 (n ⫽ 28) 3.39 ⫾ 1.08 (n ⫽ 15)
4.1 ⫾ 1.9 (n ⫽ 18) 3.3 ⫾ 1.3 (n ⫽ 15) 3.37 ⫾ 0.89 (n ⫽ 10)
4.8 ⫾ 1.9 (n ⫽ 9) 3.3 ⫾ 1.2 (n ⫽ 14) 2.7 ⫾ 0.8 (n ⫽ 9)
4.2 ⫾ 0.8 (n ⫽ 3) 3.4 ⫾ 1.5 (n ⫽ 12) –
–
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Fig. 3. Color Doppler-guided continuous-wave Doppler measurements of peak pressure gradient as calculated from the modified Bernoulli equation (mmHg) vs. actual implanted valve size.
Spearman’s nonparametric test. Results were considered significant when the p value was less than 0.05. RESULTS Echocardiography The usual echocardiographic exam was performed in all patients. Left ventricular ejection fraction was measured in all patients and was greater than or equal to 25% in all but 3 patients. Complete Doppler studies were available for most patients (69 of 73 patients with AP and 127 of 128 with MP). Transvalvular pressure gradients Average peak and mean pressure gradients across the AP of various sizes calculated by the modified Bernoulli
Fig. 4. Color Doppler-guided continuous-wave Doppler measurements of mean pressure gradient (mmHg) vs. actual implanted valve size.
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Fig. 5. Measurement of effective orifice area by the simplified continuity equation (cm2) vs. actual implanted valve size.
equation are shown in Tables 1 and 2, respectively, with comparison to results from other investigators. Average peak and mean pressure gradients across the MP of various sizes are depicted in Table 3 and Table 4, respectively. Both the peak and mean gradients across both the AP and MP showed marked variability, and no correlation was found between pressure gradients and true valve size (Figs. 1 to 4). Effective valve orifice areas For AP, average effective orifice areas for various implanted CP sizes from the present study with comparison to those of other investigators and to the actual orifice areas obtained from the manufacturer are shown in Table 5. In general, Doppler measurements underestimated true valve area for AP for sizes 23, 25, 27 and 31, but there was a wide disparity of calculated effective orifice areas without correlation to actual implanted valve size and true orifice area (Fig. 5). Effective orifice
Fig. 6. Measurement of effective orifice area by the simplified continuity equation (cm2) vs. actual implanted valve size.
Normally functioning prosthetic valves ● N. KESER et al.
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Table 5. Effective orifice areas in Sulzer Carbomedics aortic prostheses (AP) (cm2) AP size Present study Chambers et al. (1993) Ihlen et al. (1992) Soo et al. (1994) DePaulis et al. (1994) Manufacturer
18 mm
19 mm
21 mm
23 mm
25 mm
27 mm
29 mm
31 mm
2 (n ⫽ 1) –
2.38 (n ⫽ 1) 1 ⫾ 0.4 (n ⫽3) 1.1 ⫾ 0.13 (n ⫽ 8) –
1.4 ⫾ 0.37 (n ⫽ 8) 1.54 ⫾ 0.31 (n ⫽ 16) 1.52 ⫾ 0.22 (n ⫽ 14) –
1.54 ⫾ 0.7 (n ⫽ 16) 1.98 ⫾ 0.41 (n ⫽ 30) 2.12 ⫾ 0.31 (n ⫽ 22) –
2.63 ⫾ 0.38 (n ⫽ 4) –
1.8 (n ⫽ 1) 3.9 (n ⫽ 1) –
–
–
1.38 ⫾ 0.2 (n ⫽ 7) 1.41
–
1.7 ⫾ 0.6 (n ⫽ 6) 2.41 ⫾ 0.46 (n ⫽ 13) 2.65 ⫾ 0.21 (n ⫽ 17) 2 ⫾ 0.4 (n ⫽ 5) –
–
1.02 ⫾ 0.2 (n ⫽ 7) 1.06
1.3 ⫾ 0.61 (n ⫽ 30) 1.63 ⫾ 0.3 (n ⫽ 29) 1.84 ⫾ 0.25 (n ⫽ 12) 2 ⫾ 0.6 (n ⫽ 6) –
–
–
1.75
2.19
2.63
3.07
3.07
– – – 1.06
area was greater than 1.0 cm2 for most patients. For MP, average Doppler-derived orifice areas for various implanted CP sizes are shown in Table 6, with comparison to other investigators and manufacturer specifications. Again, a wide range of values was obtained for MP effective orifice area and did not correlate to implanted valve size or actual orifice area as obtained from the manufacturer (Fig. 6). Most patients, though, had effective orifice areas greater than 1.5 cm2.
The CP has been used successfully at our institution for the past several years. In the present study, we used Doppler echocardiography to evaluate the hemodynamic features of the normally functioning CP, which provides important quantitative information regarding the flow characteristics, pressure gradients and effective valve orifice areas of various types of prosthetic valves (Panidis et al. 1986; Labovitz 1989).
Prosthetic regurgitation The maximum AR jet widths/LVOT widths (AR%) by both TTE and TEE are given in Table 7. The AR% was 25% or less by TTE in all patients except 1, in whom it was 34%, and was less than 25% by TEE in all except 1 patient, in whom it was 27% (Figs. 7 and 8). These findings indicated the presence of mild AR in most patients. In patients with MP, no regurgitation was detected by TTE, probably due to reverberations from the prostheses. The maximum MR jet areas seen in Table 8 were calculated based on TEE measurements. The maximum area was found to be ⬍ 4 cm2 in 79% of patients, indicating the presence of mild MR. In the remaining patients, the maximum MR area was less than 8 cm2, consistent with moderate MR (Fig. 9).
Transvalvular pressure gradients The transvalvular gradient is a frequently used parameter to characterize prosthetic heart valves. Several echocardiographic studies have suggested that the Doppler technique is reliable in determining the pressure gradient in both tissue and mechanical valves (Holen et al. 1979, 1981; Gross and Wann 1984; Gibbs et al. 1988). However, because transprosthetic pressure gradients are determined by the cardiac output, as well as by the type and size of the prostheses, relatively high gradients have been obtained even with clinically normal prosthetic valve function (Nanda and Domanski 1998; Williams and Labovitz 1985; Cooper et al. 1987). This is because Doppler is extremely sensitive and will detect even localized high velocities originating from the metallic/ carbon prosthetic components. These high velocities do
DISCUSSION
Table 6. Effective orifice areas in Sulzer Carbomedics mitral prostheses (MP) (cm2) MP size Present study Chambers et al. (1993) Soo et al. (1994) Globitz et al. (1992) Manufacturer
18 mm
23 mm
25 mm
27 mm
29 mm
31 mm
33 mm
3.25 (n ⫽ 1) –
2.2 ⫾ 0.74 (n ⫽ 7) 1.3 (n ⫽ 1) –
2.2 ⫾ 0.68 (n ⫽ 50) 2.23 ⫾ 0.48 (n ⫽ 4) 2.9 ⫾ 0.8 (n ⫽ 2) 2.3 ⫾ 0.2 (n ⫽ 10) 2.19
2.49 ⫾ 0.59 (n ⫽ 36) 2.08 ⫾ 0.58 (n ⫽ 19) 2.9 ⫾ 0.75 (n ⫽ 15) 2.2 ⫾ 0.5 (n ⫽ 36) 2.63
2.3 ⫾ 0.68 (n ⫽ 18) 2.06 ⫾ 0.46 (n ⫽ 8) 2.3 ⫾ 0.4 (n ⫽ 10) 2.4 ⫾ 0.3 (n ⫽ 7) 3.07
2.1 ⫾ 1.06 (n ⫽ 9) 1.85 ⫾ 0.9 (n ⫽ 6) 2.8 ⫾ 1.14 (n ⫽ 9) 2.1 ⫾ 0.5 (n ⫽ 17) 3.07
1.8 ⫾ 0.6 (n ⫽ 2) 2.27 ⫾ 0.67 (n ⫽ 10) –
– – 1.06
1.7 ⫾ 0.3 (n ⫽ 2) 1.75
– 3.07
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Table 7. Evaluation of Sulzer Carbomedics aortic prosthetic (AP) regurgitation (AR) No
18 mm
19 mm
21 mm
23 mm
25 mm
27 mm
29 mm
31 mm
AR% (TTE)
10 (n ⫽ 1) 20 (n ⫽ 1)
25 (n ⫽ 1) 19 (n ⫽ 1)
10.12 ⫾ 0.83 (n ⫽ 8) 17.5 ⫾ 3.53 (n ⫽ 2)
13.2 ⫾ 5.5 (n ⫽ 31) 18.8 ⫾ 4.3 (n ⫽ 21)
16.2 ⫾ 6.1 (n ⫽ 16) 20.7 ⫾ 4.0 (n ⫽ 14)
14.1 ⫾ 6.6 (n ⫽ 7) 17.1 ⫾ 7.5 (n ⫽ 6)
16 (n ⫽ 1) 0
9 (n ⫽ 1) 0
AR% (TEE)
AR% ⫽ Maximum diameter of AR jet at its origin/maximum inner diameter of the left ventricular outflow tract at the same point ⫻ 100; TTE ⫽ transthoracic echocardiography; TEE ⫽ transesophageal echocardiography.
not reflect the true pressure gradients across the prosthesis, which are much lower (Gibbs et al. 1988). In the present study, the average peak gradients across different CP sizes in the aortic position as calculated by the modified Bernoulli equation ranged between 17 mmHg and 32 mmHg, and the average mean pressure gradients ranged from 8 mmHg to 16 mmHg, both with wide confidence intervals. Likewise, Chambers et al. (1993), Globits et al. (1992), De Paulis et al. (1994) and Chacrobarty et al. (1996) recorded pressure gradients in this range with generous SDs. As for MP, the average peak gradients were around 11 mmHg and the average mean gradients were around 4 to 5 mmHg but, again, with significant ranges. These values are similar to those previously described by Chambers et al. (1993) and Soo et al. (1994). One possible interpretation of this data would be to utilize Doppler-measured pressure gradients cautiously in the evaluation of prosthetic valves. Although a normal gradient, in the absence of poor left ventricular ejection fraction, is reassuring, an abnormal gradient may not necessarily indicate a malfunctioning or stenotic valve. For example, one normally functioning AP demonstrated
a peak pressure gradient of 56 mmHg and one normally functioning MP had a peak gradient of 28 mmHg. Other parameters may be needed to evaluate true valve function.
Fig. 7. Measurement of percent aortic regurgitation jet width/ left ventricular outflow tract width by Doppler color flow mapping (transthoracic echocardiography, TTE) vs. actual implanted valve size.
Fig. 8. Measurement of percent aortic regurgitation jet width/ left ventricular outflow tract width by Doppler color flow mapping (transesophageal echocardiography, TEE) vs. actual implanted valve size.
Effective orifice areas AP areas can be potentially measured noninvasively using the simplified continuity equation (Gupta et al. 1988), which has been found to be more accurate than data obtained from invasive measurements, where valve areas in one study were found to be more than twice the theoretical orifice area (Ihlen et al. 1992). Dumesnil et al. (1990) showed excellent correlation between the standard and simplified continuity equation, the derived aortic valve area, and in vitro prosthetic valve area. However, Chambers et al. (1991) suggested that the continuity equation might be inaccurate in assessing the valve area in bileaflet aortic prostheses, because of the difficulties in estimating subaortic cross-sectional area and subaortic velocity. In the current study, measurements of effective orifice area of AP by the simplified continuity equation showed a tendency to underestimate, but did not corre-
Normally functioning prosthetic valves ● N. KESER et al.
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Table 8. Maximum Sulzer Carbomedics mitral prosthetic (MP) regurgitation jet area MP size
18 mm
23 mm
25 mm
27 mm
29 mm
31 mm
33 mm
Max. MR jet area (TEE) ⬍ 4 cm2 4–5 cm2 5–5.5 cm2 5.5–7 cm2
– (n ⫽ 1) – –
(n ⫽ 6) – – –
(n ⫽ 34) (n ⫽ 10) (n ⫽ 2) (n ⫽ 1)
(n ⫽ 24) (n ⫽ 4) (n ⫽ 1) (n ⫽ 1)
(n ⫽ 14) (n ⫽ 3) – –
(n ⫽ 7) (n ⫽ 1) – –
(n ⫽ 3) – – –
TEE ⫽ Transesophageal echocardiography.
late with the true valve size as obtained from the manufacturer. A wide disparity was, again, produced with large confidence intervals, and some valve areas were calculated as significantly stenotic. These data conflict somewhat with the findings of Chambers et al. (1993), De Paulis et al. (1994), Soo et al. (1994), and Ihlen et al. (1992), who obtained values closer to the manufacturer specifications. For CP in the mitral position, Thomas and Weyman (1987) and Bjornerheim et al. (1997) demonstrated a shortened pressure half time compared to other valve designs, indicating a larger orifice size. In the present study, no correlation was found between the effective orifice area calculated by Doppler using the pressure half time method and the actual size of the implanted CP in the mitral position. There was a tendency toward underestimation of actual orifice area by Doppler for the larger CP sizes (Chambers et al. 1991; Bjornerheim et al. 1997; Dellsperger et al. 1983). However, overall, our data would suggest that Doppler interrogation of normally functioning mitral CP yields nonstenotic orifice areas. Our findings were similar to those of other authors (Chambers et al. 1993; Globits et al. 1992; Soo et al. 1994). In our experience, Doppler yields a wide range of
Fig. 9. Measurement of maximal mitral regurgitation area (cm2) by Doppler color flow mapping vs. actual implanted valve size.
velocities and pressure gradients that do not correlate with actual orifice or implant sizes. Because Doppler calculation of effective orifice area takes into account the stroke volume, one would expect this parameter to be more valuable than velocities or gradients. However, in our study, Doppler-calculated effective orifice area did not show significant correlation with actually measured orifice area for both MP and AP. All but 3 patients in the present report had a left ventricular ejection fraction greater than 25%; thus, a very low cardiac output was not a significant factor for lower than expected effective orifice areas obtained by Doppler in a number of patients with both AP and MP. Despite this, it is clinically useful to measure this parameter because a value in the normal or nonstenotic range points to an unobstructed prosthesis in the aorta or mitral position, in the absence of poor left ventricular ejection fraction. However, if the orifice area calculates to a stenotic value then the valve may or may not be functioning properly. Further parameters may be used then to evaluate valve function, such as valve motion by TTE, TEE and fluoroscopy. Regurgitation Mild degrees of regurgitation in both AP and MP have been found during catheterization in many normally functioning valves (Bjork and Henze 1979). The presence of such minimal regurgitant jets is clinically insignificant. Dellsperg et al. (1983) and other investigators also concluded that there is an obligatory closing backflow in mechanical prosthetic valves. Furthermore, echocardiographic evaluation of regurgitant jets is complicated by artefactual reverberations from the metallic/carbon components of prosthetic valves. These reverberations make the assessment of MR especially difficult during TTE because these can mask the regurgitant jet in the left atrium. It is, therefore, not surprising that, in the present study, we could not detect MR by color Doppler flow mapping in any MP using TTE, although all CPs showed MR with TEE. Both TTE and TEE were found useful in detecting AR by color Doppler for CPs in the aortic position. In the patients described by us, all but 2 normally functioning CP placed in the aortic position and most (79%)
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CP in the mitral position demonstrated no or mild insufficiency. In 20% of patients with CP in the mitral position, moderate MR was noted. These results are similar to those of previous investigators who have evaluated the St. Jude MP (Lange et al. 1991). Limitations The current study is limited by our choice of a clinically defined normal population that does not allow application of our findings to abnormal valves. We demonstrated a wide range in Doppler characteristics of these normal valves with several values clearly falling in the stenotic range for effective orifice area. We expect that malfunctioning or stenotic valves would all produce pathologic effective orifice areas, but a cohort of abnormal valves would be needed in further investigation to prove this point. Another limitation of the study is that patients were examined only at rest and not during stress such as exercise. In all patients, TTEs were performed within 7 days of valve implantation and, hence, it was not felt prudent to have them undergo stress echocardiography. CONCLUSION The CP has been used extensively in clinical practice due to its excellent hemodynamic profile. In the present study, we employed Doppler echocardiography to assess the hemodynamic function of normally functioning prostheses, both in the aortic and mitral positions. Our findings demonstrate no significant correlation of Doppler measured peak and mean pressure gradients and effective orifice area with implanted valve size and actual orifice areas measured directly by the manufacturer for CPs in both the mitral and aortic positions. However, it is still useful to measure effective orifice area by Doppler because a value in the normal or nonstenotic range points to an unobstructed prosthesis in the aortic or mitral position, in the absence of poor left ventricular ejection fraction. A value in the stenotic range could mean a normally functioning or obstructed prosthesis and, therefore, may need further investigation, such as assessment of individual valve leaflet motion by TTE/TEE or fluoroscopy. Valve regurgitation as evaluated by color Doppler flow imaging was mild in practically all CPs in the aortic position and the majority of CPs in the mitral position. Both TTE and TEE were found useful in assessing AR in CPs in the aortic position, but only TEE detected MR in CPs in the mitral position. The inability of TTE to detect MR in CPs in the mitral position could be due to the presence of reverberatory artefacts from the metallic/carbon components of the prosthesis cluttering the left atrium and masking the MR jet.
Volume 29, Number 5, 2003
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