Limitations and pitfalls in the assessment of prosthetic valves with Doppler ultrasonography

Echocardiographically derived effective valve opening area in mitral prostheses: a comparative analysis of various calculations using continuity equation and pressure half time method

Detection of dysfunctional mitral valve prostheses (MP) remains complex even though being optimized by considering echocardiographically derived prosthetic effective orifice area (VA). The purpose was to compare VA in MP, calculated by the continuity equation (CE) using peak velocities (CEVpeak), mean velocities (CEVmean), velocity-time integrals (CEVTI) and the pressure half time method using 220 ms as constant first (PHT220) as well as optimized constants. In 267 consecutive patients with normally functioning MP, we investigated VA within the first postoperative month. With increasing prosthetic sizes, mean VA values also increase in all calculations. The statistical curves demonstrate no significant difference in graphical steepness but show different levels. Comparison of mean VA showed the known systematic higher values of PHT220 and significantly decreased results when using CEVTI. This systematic difference between mean VA applying PHT220 versus CEVTI is approximately 1.0 cm(2) for all prosthetic sizes. Calculations via CEVpeak were close to the results of CEVTI. CEVmean produced values, which graphically correspond to the PHT220 curve. Only PHT220 detected the constructional equal prosthetic inner ring width between 29 and 31 mm. To compensate the systematic difference between CEVTI and PHT220, an optimized constant of 140 ms was calculated to be applied in PHT (PHT140). VA is a robust and, therefore, preferable parameter for investigating MP. If needed, both CE and PHT are applicable with a systematical difference between CEVTI and PHT220. An optimized constant of 140 ms (PHT140) should be applied when calculating VA of mitral valve prostheses via PHT.

Effective valve opening area in the detection of dysfunctional aortic valve prostheses: a differentiated statistical analysis of this parameter including the introduction of minimal expected normal values as borderline to dysfunctional stenotic prostheses

BACKGROUND

Dysfunction of heart valve prostheses (VP) is a life-threatening complication and the diagnosis remains difficult. The motivation for this study was to improve the detection of dysfunctional VP by optimizing application of the prosthetic effective orifice area (VA). For this reason the minimal expected normal VA (VA(expected)) was introduced.

METHODS

We investigated echocardiographically 1,369 normally functioning aortic valve prostheses (AVP). Mean VA, transprosthetic peak (PPG) and mean pressure gradients (MPG) were evaluated to gain reference values depending on prosthetic size and construction principle. Mean VA(expected) was calculated by applying a simple formula that was developed empirically using statistical analyses. The results were compared with those of 65 dysfunctional AVPs.

RESULTS

VA(expected) can be applied as a threshold between normal and dysfunctional stenotic AVP and showed a correct estimation in 87% of all normally functioning and 100% of dysfunctional stenotic VPs. The sensitivity for all prosthetic sizes is 1.0, independently of the constructional principle of the VP. Specificity ranged between 0.8 and 1.0, dependent on VP size. The formula representing VA(expected) is simple and can be executed easily.

CONCLUSION

As nearly independent of stroke volume and in consideration of VA(expected), VA seems to have become one of the preferable parameters for detecting pathological stenotic AVPs echocardiographically. The additional application of PPG/MPG and other parameters permits prostheses with relevant isolated regurgitation and patient-prosthesis-mismatch to be distinguished.

The measurement of opening angle and orifice area of a bileaflet mechanical valve using multidetector computed tomography

BACKGROUND AND OBJECTIVES

The aim of this study was to assess mechanical valve function using 64-slice multidetector computed tomography (MDCT).

SUBJECTS AND METHODS

In 20 patients (mean age, 50+/-12 years; male-to-female ratio, 10:10), 30 St. Jude bileaflet mechanical valves (15 aortic and 15 mitral valves) were evaluated using MDCT. We selected images vertical and parallel to the mechanical valve. The valve orifice area (OA) and valve length were determined by manual tracing and the opening and closing angles were measured using a protractor. The OA and length of the mechanical valves were compared with the manufacturer's values.

RESULTS

The geometric orifice areas (GOAs) based on the manufacturer's values and the OAs determined by MDCT were 3.4+/-0.2 cm(2) and 3.4+/-0.3 cm(2) for the mitral valves and 2.1+/-0.3 cm(2) and 2.1+/-0.4 cm(2) for the aortic valves, respectively. The correlation coefficients between the OA measures were 0.433 for the mitral valves and 0.874 for the aortic valves (both p<0.001). The lengths based on the manufacturer's values and determined by MDCT were 29.3+/-1.99 mm and 29.6+/-1.65 mm for the mitral valves and 21.5+/-2.1 mm and 20.7+/-2.3 mm for the aortic valves, respectively. The correlation coefficients between the measures were 0.651 for the mitral valve and 0.846 for the aortic valve (both p<0.001). The opening and closing angles determined by MDCT were 10.9+/-0.6 degrees and 131.1+/-3.2 degrees for the mitral valves and 11.1+/-0.9 degrees and 120.6+/-1.7 degrees for the aortic valves, respectively.

CONCLUSION

MDCT is an accurate modality with which to assess the function and morphology of bileaflet mechanical valves.

Use of the Ejection Fraction-Velocity Ratio in the Hemodynamic Assessment of Aortic Bioprosthetic Valves

BACKGROUND

A new echocardiographic severity index of aortic valve stenosis has been recently introduced: the ejection fraction-velocity ratio (EFVR), which is a simple ratio ejection fraction/4Vmax2. This nonflow corrected index demonstrated an excellent accuracy in quantifying the effective orifice area (EOA) in native aortic valves. There is no information about the reliability of EFVR in assessing aortic EOA in patients with bioprostheses.

METHODS

In 141 consecutive patients with aortic bioprostheses (85 males, mean age 74 +/- 9 years), EOA was calculated by both continuity equation (CE) and EFVR.

RESULTS

The correlation between CE and EFVR was highly significant (r = 0.88; P < 0.0001). The area under the receiver operating characteristic (ROC) curve was 0.97 (considering a positive case CE < 1.0 cm2, best cutoff of EFVR was <1.06). Using CE as gold standard and a cutoff of 1.0 for both indexes, EFVR showed good sensitivity (80%) and specificity (98%). Also in a subgroup of 46 patients with moderate or severe mitral regurgitation, the EFVR had a good diagnostic accuracy (sensitivity 89%, specificity 97%). In 91 patients with ejection fraction < or = 50%, the EFVR confirmed good sensitivity (79%) and specificity (97%).

CONCLUSIONS

The EFVR, a simple and not time-consuming index, demonstrated a good diagnostic accuracy in assessing EOA also in patients with aortic bioprostheses. The presence of moderate to severe mitral regurgitation or left ventricular dysfunction does not reduce significantly the reliability of this new index. The EFVR can be taken into consideration in the clinical practice, at least when CE measurements are technically difficult.

Quantitative assessment of mechanical prosthetic valve area by 3-dimensional transesophageal echocardiography

OBJECTIVE

The goal of this study was to assess the geometric orifice area of mechanical valve prostheses by transesophageal 3-dimensional echocardiographic planimetry.

METHODS AND RESULTS

Currently used Doppler methods for prosthetic assessment (orifice area-Doppler) were compared with 3D planimetry for orifice area (orifice area-3D) and with manufacturer's values (orifice area-manufacturer) for the corresponding prosthesis types and sizes and with historical controls provided by Doppler literature (orifice area-literature). Twenty-four mechanical valve prostheses (in 22 patients) were studied: 13 in mitral position and 11 in aortic position. Orifice area-manufacturer, orifice area-Doppler, orifice area-literature, and orifice area-3D were 3.6 +/- 1.1 cm(2), 2.3 +/- 0.9 cm(2), 2.4 +/- 0.9 cm(2), and 2.6 +/- 0.7 cm(2), respectively. Orifice area-manufacturer values were significantly larger. Correlation coefficients between orifice area-3D and orifice area-manufacturer, and between orifice area-3D and orifice area-Doppler and orifice area-literature were 0.83, 0.90, and 0.73, respectively (all P < .0001).

CONCLUSION

Three-dimensional transesophageal echocardiography is feasible and has good correlation with orifice area-Doppler (in aortic position) and good correlation with orifice area-manufacturer (in aortic and mitral positions) methods.

Hemodynamic performance of four mechanical bileaflet prosthetic valves in the mitral position: an echocardiographic study

OBJECTIVES

The CarboMedics, Duromedics, Sorin Bicarbon and the St. Jude Medical valves are bileaflet mechanical prostheses of modern but different design. Choosing a valve with the best hemodynamic profile is of clinical importance in patients with small ventricles and a small mitral annulus.

METHODS

The hemodynamic performance of these valves in the mitral position was compared in 76 asymptomatic, ambulatory patients with normally functioning prosthesis and left ventricle, using Doppler echocardiography. Of the 76 patients studied, 22 had the CarboMedics, 16 had the Duromedics, 17 had the Sorin Bicarbon and 21 had the St. Jude prosthesis. The patients ages ranged from 18 to 81 years. There were 44 women and 32 men. The time from implantation to echocardiographic study ranged from 1 to 55 months.

RESULTS

The echocardiographic study was performed earlier after surgery in the Sorin Bicarbon group. There was no significant difference in women/man ratio, incidence of atrial fibrillation, left ventricular or left atrial diameters between the four groups. The mean prosthesis size was significantly smaller for Sorin Bicarbon and Duromedics valves compared to the CarboMedics and the St. Jude valves (mean+/-SD, 27.2+/-1.3, 27.1+/-1.1 and 30.0+/-1.9 and 30.0+/-2.7 mm, respectively, P<0.001). Despite its smaller size the Sorin Bicarbon valve had significantly larger effective valve area by Doppler compared to the CarboMedics valve (290+/-40 vs 250+/-60 mm2, respectively, P=0.014). The ratio of effective valve area to prosthesis size was significantly larger for the Sorin Bicarbon valve when compared with any other type of prosthesis.

CONCLUSIONS

(1) The Sorin Bicarbon bileaflet valve offered the best hemodynamic results that may be explained by the valve's large leaflet opening angle and small thickness of the leaflets. (2) Since the Sorin Bicarbon is the newest bileaflet valve, durability of this valve remains uncertain.

Doppler Hemodynamics of CarboMedics Prosthetic Valves in Aortic Position at Rest and Exercise

To evaluate the size adequacy of CarboMedics prosthetic heart valves, Doppler pressure gradients after aortic valve replacement were determined at rest and immediately after exercise in 83 patients, at a mean time of 18.8 days after aortic valve replacement with CarboMedics prosthetic heart valves (31 standard and 52 R-series). There were 54 males and 29 females, average age 55 years; 12 had pure aortic stenosis, 47 had aortic regurgitation, and 24 had combined lesions. Exercise significantly increased (p < 0.01) the peak velocity (from 2.50 to 2.88 m/sec), the peak pressure gradient (from 25.9 to 34.6 mm Hg), and the mean pressure gradient (from 13.9 to 18.4 mm Hg). Significant differences were observed even in patients with seemingly large valve sizes. Significant correlation (p < 0.0001) was observed between pressure gradients at rest and immediately after exercise, as well as between pressure gradients and theoretical performance index. A theoretical performance index larger than 1.0 cm2/m2 was needed to obtain a postexercise Doppler peak pressure gradient of less than 60 mm Hg early after aortic valve replacement using either the Carbomedics standard or R-series prosthetic heart valves.

Influence of the size of aortic valve prostheses on hemodynamics and change in left ventricular mass: implications for the surgical management of aortic stenosis

Discussion of aortic valve replacement has primarily concerned the choice between tissue and mechanical prostheses. Less emphasis has been placed on prosthesis size. Despite technical advances increasing prosthesis orifice area, small valves implanted in the unenlarged aortic root may not be significantly less obstructive than the stenotic native valves they replace.

METHODS

In this work we studied 52 patients (31 women, 21 men; mean age 59.2 years) in whom valve prostheses sized 19, 21, 23, or 25 mm (30 bioprostheses and 22 tilting disc valves) had been implanted to replace stenotic aortic valves. Most patients with 19 or 21 mm prostheses were women. Doppler and conventional echocardiographic studies were performed in the 10 days preceding the operation and between 10 and 40 months (mean 18 months) after the operation. The patients receiving larger valve sizes had significantly larger body surface areas than those receiving smaller valve sizes (mainly women).

RESULTS

No significant differences were observed between preoperative and postoperative diameters or left ventricular systolic function parameters, but left ventricular mass and mass index decreased in all four groups (albeit nonsignificantly in the 19 mm group, and with less statistical significance in the 21 mm group than in the 23 and 25 mm groups). Postoperative peak and mean transvalvular pressure drops were significantly greater in the 19 mm group than in the other groups, and the 21 mm group had significantly greater transvalvular pressure drops than the 25 mm group. Postoperative effective valve area was significantly smaller in the 19 mm group than in the 21 mm group, and significantly smaller in the 21 mm group than in the 23 and 25 mm groups.

CONCLUSION

We conclude that despite undeniable recent improvements in the design of artificial heart valves, 19 mm aortic prostheses continue to create significant obstruction of the left ventricular outflow tract and, possibly as a consequence of this, fail to bring about significant reduction in left ventricular hypertrophy.

Doppler echocardiographic assessment of prosthetic aortic valve area: estimation with the continuity equation compared to the Gorlin formula

Effective orifice area of 3 different designs of prosthetic valves implanted in the aortic position was determined by the continuity equation and the Gorlin formula using Doppler hemodynamic data. The orifice area by the two methods correlated well in the case of tilting disc prostheses (r = 0.75, P = 0.0001, n = 37, SEE = 0.17 cm2) but poorly in the case of bileaflet mechanical valves (r = 0.40, P = 0.17, n = 13) and ball-in-cage prostheses (r = 0.58, P = 0.06, n = 11). Estimation of prosthetic aortic valve area by the Gorlin formula is inappropriate in the latter two types of prostheses because of design-related variable empiric constant.

Doppler-derived gradients in normally functioning Monostrut Björk-Shiley prostheses

In summary, reference values of Doppler gradients obtained in a large number of patients with normal-functioning mitral and aortic Monostrut Björk-Shiley prostheses are reported. It is shown that the value of the transprosthetic gradient increases with decreasing valve size in patients with aortic prostheses. No individual significant variations of the transprothetic Doppler gradient during a 3-year follow-up were observed.

Doppler echocardiographic comparison of small (19 mm) bileaflet and pericardial heart valve prostheses in aortic position

The resting haemodynamics of five types of small (19 mm) aortic valve prosthesis (2 bileaflet, 3 pericardial) were evaluated with Doppler echocardiography in 43 patients. Two received St Jude Medical and six CarboMedics bileaflet valves and 35 were given bioprostheses--16 Ionescu-Shiley, four Mitroflow and 15 Labcor-Santiago. No significant differences in peak or mean transvalvular pressure drop or in effective valve area were found between the bileaflet and the pericardial valves or among the three types of bioprosthesis. All but one of the bileaflet prostheses showed a characteristic regurgitation pattern, with two lateral and one central jet, and 16 (46%) of the bioprostheses showed central regurgitation, but in no case were these jets haemodynamically significant. Thus the 19 mm bileaflet and the studied pericardial prostheses all have satisfactory resting haemodynamics, and all are suitable for implanting in small aortic roots.

Improved Doppler assessment of the Bjork-Shiley mitral prosthesis using the continuity equation

To assess whether derivation of an effective mitral prosthetic valve area using the continuity equation provides an improved functional assessment of the Bjork-Shiley mitral prosthesis over the pressure half-time method, Doppler echocardiographic studies were performed in 43 patients 12 +/- 7 months following the valve replacement. Effective valve orifice area used as the standard for comparison was determined by a hydraulic formula validated in vitro over a wide range of flow rates. All patients were clinically stable, without evidence of prosthetic dysfunction or aortic regurgitation. Prosthetic mitral valve orifice area determined by the hydraulic formula, by the continuity equation and by pressure half-time method for all prostheses sizes averaged 1.6 +/- 0.46 cm2, 1.83 +/- 0.56 cm2 and 2.34 +/- 0.48 cm2, respectively. Effective valve orifice area by the hydraulic formula had a strong correlation with that derived by the continuity equation (r = 0.86; P < 0.0001; standard error of estimate (S.E.E.), 0.12 cm2), but an insignificant correlation with the area calculated by the pressure half-time method (r = 0.24). Prosthetic mitral valve areas determined by the continuity equation and by pressure half-time method also correlated poorly (r = 0.24). Pressure half-time was affected by heart rate, diastolic filling period, left ventricular fractional shortening and presence of atrial fibrillation (P < 0.001). Thus, using the standard continuity equation to determine the orifice area of the Bjork-Shiley prosthesis in the mitral position provides improved assessment compared with the pressure half-time method.

Postoperative Doppler echocardiographic evaluation in different sizes of Medtronic-Hall, Biocor and Carpentier-Edwards S.A.V. prosthetic aortic valves

Doppler echocardiography was performed on 108 patients 4-15 days after implantation of a Medtronic-Hall, Biocor or Carpentier-Edwards S.A.V. prosthetic aortic valve because of aortic stenosis. Significant correlation was found between the in vitro (maker-declared) and the Doppler-estimated effective prosthetic valve orifice area (r = 0.70, p < 0.01). Doppler-estimated prosthetic valve orifice area, but not transprosthetic blood velocities, discriminated between different sizes of Medtronic-Hall and Biocor valves. The effective orifice area in these valves was 57% of the in vitro area, but in Carpentier-Edwards valves it was only 43%. Transprosthetic blood velocity was inversely related to orifice area in men, but not in women, who also had longer duration of systole and better preservation of systolic left ventricular function. The data suggest that the effective prosthetic valve areas found in patients are significantly smaller than the experimental in vitro areas. Prosthesis size and type, anatomic and hemodynamic variables and gender are important in Doppler estimation of effective valve area.

St. Jude prosthesis for aortic and mitral valve replacement: a ten-year experience

From January 1, 1979 through December 1990, 456 adult patients underwent isolated aortic (AVR) (254) or mitral (MVR) (202) valve replacement with the St. Jude prosthesis at the Medical University of South Carolina. Age ranged from 21 to 84 years (mean: 54 +/- 15 years for AVR; 51 +/- 13 years for MVR). Male sex predominated in the AVR group (66%) and female sex in the MVR group (64%). Ninety-two patients (20%) had associated coronary artery bypass grafting (AVR, 25%; MVR, 14%). There were 17 deaths (3.7%) occurring during the same hospitalization or within 30 days (AVR, 10/254 [3.9%]; MVR, 7/202 [3.5%]). Follow-up is 94.5% complete and ranges from 1.0 to 131 months (mean, 55 +/- 37 months; total, 2,073 patient-years). In the AVR group, 53 late deaths have occurred and actuarial survival is 80% +/- 3% at 5 years and 47% +/- 9% at 10 years. Twenty-one patients have sustained thromboembolic episodes (1.8%/patient-year), and the probability of remaining free of thromboembolism at 10 years is 67% +/- 13%. The mean improvement in New York Heart Association functional class from preoperative to postoperative is 3.1 +/- 0.76 to 1.6 +/- 0.84 (p < 0.0001). In the MVR group, there have been 41 late deaths, and the actuarial survival was 80% +/- 3% at 5 years and 63% +/- 5% at 10 years. Twenty-eight patients have sustained thromboembolic complications (2.9%/patient-year), and the probability of remaining free of thromboembolism at 10 years is 77% +/- 5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic description of the CarboMedics bileaflet prosthetic heart valve

OBJECTIVES

The aim of this study was to describe the echocardiographic appearance of the normal CarboMedics prosthesis in the aortic and mitral positions.

BACKGROUND

Echocardiography is the standard method of assessing prosthetic valves. However, new valve designs may still be marketed without an accompanying echocardiographic description. The CarboMedics prosthesis is in widespread use, but few noninvasive hemodynamic data have been published.

METHODS

Echocardiography was performed in 147 patients with a total of 96 normally functioning CarboMedics prostheses in the aortic position and 75 in the mitral position; in 24 patients, valves were implanted in both positions. The following variables were measured: peak and mean transvalvular velocities, peak and mean instantaneous gradient estimated from the modified Bernoulli equation, aortic acceleration slope, pressure half-time, transvalvular flow and effective orifice area using the continuity equation. Patterns of regurgitation were observed by transthoracic study in all valves and by transesophageal study in selected mitral valve prostheses.

RESULTS

For the aortic valve prostheses, estimated mean gradient ranged between 6 and 19 mm Hg. Effective area differed markedly among the anulus diameters (p < 0.001), with a mean value of 1 cm2 for the 19-mm valve and 2.6 cm2 for the 29-mm valve. For the mitral valve prostheses, mean gradient ranged from 3 to 7 mm Hg. There were a total of four washing leaks, one on either side of each pivotal point, and these lasted throughout systole or diastole. One jet was commonly more prominent than the other three.

CONCLUSIONS

The CarboMedics prosthesis offered relatively little resistance to forward flow except at small anulus diameters. The washing jets were prominent and would be easy to misdiagnose as a sign of paraprosthetic regurgitation.