Validation of continuous-wave Doppler echocardiographic measurements of mitral and tricuspid prosthetic valve gradients: a simultaneous Doppler-catheter study

Echocardiographic Evaluation of Tricuspid Prosthetic Valves: An Update

This review focuses on the diagnostic value of novel echocardiographic techniques and the clinical application of recently described algorithms to assess tricuspid prosthetic valve function.

Successful fibrinolytic treatment of prosthetic heart valve thrombosis using streptokinase

OBJECTIVES

This study aims to evaluate the clinical outcome of fibrinolytic treatment of prosthetic valve thrombosis (PVT) with 'streptokinase' as a first line treatment for these cases.

METHODS

The study group was 20 consecutive patients (10 females) diagnosed with PVT. The protocol for streptokinase administration was either accelerated (intravenous infusion of 0.5 million IU over 30 minutes followed by 0.15 million IU/h) or conventional (intravenous infusion of 0.25 million IU over 30 minutes followed by 0.15 million IU/h). Success of fibrinolytic therapy was defined as complete restoration of valve function in the presence or absence of complications.

RESULTS

Eighteen patients (90%) had mitral PVT and two (10%) had aortic PVT. Thrombolytic therapy with streptokinase was successful in all but one case, with a total mortality of four cases (20%). In PVT episodes, before streptokinase therapy, the prosthetic valve areas (in all cases, mitral and aortic positions) were 0.82 ± 0.21, 0.83 ± 0.21, and 0.73 ± 0.18 cm²; and the peak and mean transvalvular gradients were 38.7 ± 16.7 and 25.4 ± 8.7, 34.1 ± 8.8 and 23.2 ± 5.4, and 80.0 ± 14.1 and 45.0 ± 7.1 mmHg, respectively. After streptokinase therapy, the prosthetic valve area and peak and mean transvalvular gradients improved significantly (for all cases, mitral and aortic positions: valve area 2.17 ± 0.58, 2.21 ± 0.61, and 1.85 ± 0.07 cm², peak gradient 18.7 ± 11.0, 16.4 ± 7.7, and 39.0 ± 18.4, and mean gradient 9.6 ± 7.1, 8.2 ± 5.3, and 22.0 ± 11.3 mmHg, respectively; paired t-test, P<0.001 for pre- versus post-streptokinase infusion for all variables).

CONCLUSION

Fibrinolytic therapy using streptokinase was an effective therapeutic strategy for the management of PVT and is a reasonable alternative to surgery.

Clinical and hemodynamic study of tilting disc heart valve: Single-center study

BACKGROUND

The TTK Chitra heart valve has been developed and widely used in India. This study aimed to evaluate its hemodynamics, complications, and event-free survival in comparison with other commonly used prosthetic valves. The role of color Doppler echocardiography in the follow-up of patients with prosthetic valves was also studied.

PATIENTS AND METHODS

Two hundred patients underwent 249 valve replacements (122 mitral, 29 aortic, 49 both). Total follow-up was 451 patient-years.

RESULTS

There were 18 late deaths (3.98% ± 0.92% per patient-year). One mitral valve replacement patient (0.36% ± 0.36% per patient-year) developed valve thrombosis. Two aortic valve replacement patients (2.74% ± 1.91% per patient-year), 2 double-valve replacement patients (1.95% ± 1.36% per patient-year) and 3 mitral valve replacement patients (1.08% ± 0.62% per patient-year) developed embolic complications. Freedom from all valve related mortality and morbidity at 4 years was 86% ± 4% for mitral valve replacement, 56% ± 10% for double-valve replacement, and 89% ± 6% for aortic valve replacement. The average peak gradient, mean gradient, and average peak velocity for the aortic and mitral positions were found to be comparable to those of other commonly used valves.

CONCLUSION

The performance of this valve in terms of hemodynamic complications, mortality, and morbidity is comparable to other valves in common use. Hemodynamic gradients are more reproducible than effective orifice area, hence more beneficial for follow-up.

A simplified model for mitral valve dynamics

Located between the left atrium and the left ventricle, the mitral valve controls flow between these two cardiac chambers. Mitral valve dysfunction is a major cause of cardiac dysfunction and its dynamics are little known. A simple non-linear rotational spring model is developed and implemented to capture the dynamics of the mitral valve. A measured pressure difference curve was used as the input into the model, which represents an applied torque to the anatomical valve chords. A range of mechanical model hysteresis states were investigated to find a model that best matches reported animal data of chord movement during a heartbeat. The study is limited by the use of one dataset found in the literature due to the highly invasive nature of getting this data. However, results clearly highlight fundamental physiological issues, such as the damping and chord stiffness changing within one cardiac cycle, that would be directly represented in any mitral valve model and affect behaviour in dysfunction. Very good correlation was achieved between modeled and experimental valve angle with 1-10% absolute error in the best case, indicating good promise for future simulation of cardiac valvular dysfunction, such as mitral regurgitation or stenosis. In particular, the model provides a pathway to capturing these dysfunctions in terms of modeled stiffness or elastance that can be directly related to anatomical, structural defects and dysfunction.

Real time triplane echocardiography in the assessment of the functional area of prosthetic aortic valves: reliability and feasibility

PURPOSE

Our study is aimed at evaluating the feasibility and reliability of a simple method for the measurement of the functional area of prosthetic aortic valves (EOA). Three-dimensional echocardiography has proven accurate for left ventricular volume, stroke volume, and aortic valve area measurement. We studied the feasibility and reliability of real time simultaneous triplane echocardiography (RT3P) for assessing the EOA with a fast formula based on the principle of continuity equation, in which we replaced Doppler-derived stroke volume (SV) with SV directly measured with RT3P.

METHODS AND RESULTS

EOA of prosthetic aortic valves were measured in 23 consecutive patients requiring periodical follow up. EOA was calculated using Doppler continuity equation (DCE) and the RT3P method by replacing Doppler-derived SV with SV measured with real time triplane echocardiography. We compared functional areas obtained with the two methods with the prosthetic area indicated in the manufacturer's specifications and with the mean transprosthetic gradient. Both methods had a good correlation with the area indicated by the manufacturer. RT3P revealed an inverse correlation between functional area and mean gradient that was better than DCE (P = 0.0359). Inter- and intraobserver variability was not different between the two methods. Execution time was significantly shorter for RT3P.

CONCLUSIONS

RT3P is a simple method that can be performed quite rapidly, and can complement the overall assessment of prosthetic valve function. Further studies can confirm our technique.

Prosthetic heart valves: Types and echocardiographic evaluation

In the last five decades multiple different models of prosthetic valves have been developed. The purpose of this article is to provide a comprehensive source of information for the types and the echocardiographic evaluation of the prosthetic heart valves.

Assessment of hemodynamics properties of a new-type artificial heart valve prosthesis using catheterization and echocardiography

OBJECTIVE

The objectives of this study were to assess the hemodynamic properties of the newly developed artificial heart valve prosthesis experimentally in laboratory simulation, in an animal model, and clinically in a human model and to compare the results measured by catheterization and echocardiography.

METHODS

(1) Laboratory simulation. The prosthesis was tested using a pulsatile flow simulator in the aortic position. Hydrodynamics parameters were automatically analyzed through a custom-designed data processing program. (2) Animal experiment. Six sheep subjected to mitral replacement with 21-mm-valve prosthesis were measured by open cardiac catheterization intraoperatively. Doppler echocardiography and open cardiac catheterization under dobutamine stress were performed in two sheep subjected to implantation 2.5 years ago. (3) Clinical patient observation. Observations were carried out on 14 patients with aortas replacement and 10 patients with bicuspid replacement using both doppler echocardiography and open cardiac catheterization.

RESULTS

(1) Laboratory simulation. The results showed that the value of the transvalvular gradient (DeltaP) decreased with the increase of heart rate, and the values were not greater that 10 mm Hg at any given tissue annulus diameter. (2) Animal experiment. The mean DeltaP value of the six sheep was 5.2 +/- 1.7 mm Hg intraoperatively, while the corresponding DeltaP value of the two sheep 2.5 years after implantation was 6.1 +/- 0.3 mm Hg measured by open cardiac catheterization. (3) Clinical patient observation. The mean DeltaP values in the aortic position measured by catheterization and echocardiography were 6.26 approximately 4.10 and 9.42 approximately 7.48 mm Hg, respectively. The gradients in the mitral position were 2.10 approximately 1.9 and 5.28 approximately 4.10 mm Hg, respectively.

CONCLUSIONS

The results demonstrate that the new-type bileaflet heart valve prosthesis only generates a relatively low transvalvar gradient and thus has good hemodynamic properties.

In vivo short-term doppler hemodynamic profiles of 189 carpentier-edwards perimount pericardial bioprosthetic valves in the mitral position

We sought to determine the hemodynamic performance of the Carpentier-Edwards Perimount pericardial valve in the mitral position. We reviewed the Doppler echocardiographic data on 189 patients (110 women; 68 +/- 12 years of age) who were implanted with this valve (7.6 days +/- 13 postoperatively) at our institution between September 2000 and May 2002. The average ejection fraction was 47%. For all valves, the peak velocity was 1.9 +/- 0.3 m/s, peak gradient was 15 +/- 4.8 mm Hg, and mean gradient was 5.8 +/- 2 mm Hg. The pressure half-time was 93 +/- 24 milliseconds, with a calculated effective orifice area of 2.5 +/- 0.6 cm2. The average effective orifice area by continuity equation (83 valves) was 1.5 +/- 0.5 cm2. The mitral regurgitation was graded mild or less in 97.5% of all valves. This is the largest series establishing the favorable hemodynamic behavior of the different sizes of a new Perimount mitral valve, and the reported data could serve as a reference.

Hemodynamic evaluation of normally functioning Sulzer Carbomedics prosthetic valves

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 = 73) and mitral (n = 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.

Unsteady effects on the flow across tilting disk valves

The present study simulates numerically the flow across two-dimensional tilting disk models of mechanical heart valves. The time-dependent Navier-Stokes equations are solved to assess the importance of unsteady effects in the fully open position of the valve. Flow cases with steady or physiological inflow conditions and with fixed or moving valves are solved. The simulations lead into mixed conclusions. It is obvious that steady inflow cases that account for vortex shedding only cannot model realistic physiological cases. In cases with imposed physiological inflow, the details of the flow field for fixed and moving valves might differ in the fully open position as well, although the gross features are quite similar. The fixed valve case consistently results in safe estimations of several critical quantities such as the axial force, the maximal shear stress on the valve, or the transvalvular pressure drop. Thus, fixed valve simulations can provide useful information for the design of prosthetic heart valves, as long as the properties in the fully open position only are sought.

Doppler hemodynamics of 51 clinically and echocardiographically normal pulmonary valve prostheses

OBJECTIVE

To determine the normal Doppler hemodynamics of various pulmonary valve prostheses (PVPs).

PATIENTS AND METHODS

We retrospectively analyzed comprehensive Doppler echocardiographic examinations of 51 patients (mean age, 27.8 years; range, 1-59 years) with PVPs that were normal on clinical and 2-dimensional echocardiographic examinations to establish the normal hemodynamics of various types and sizes of PVPs. The earliest complete postoperative transthoracic echocardiogram was identified for each patient. Doppler examinations were analyzed for peak instantaneous velocity, right ventricular outflow tract velocity, and peak and mean systolic gradient. The frequency of prosthetic regurgitation was also noted.

RESULTS

The average +/- SD peak instantaneous velocity for all PVPs was 2.24+/-0.6 m/s, with an average peak systolic gradient of 20.4+/-10.4 mm Hg and an average mean systolic gradient of 11.0+/-5.1 mm Hg. The mean right ventricular outflow tract velocity was 1.0+/-0.2 m/s. Pulmonary homografts were found to have significantly lower peak velocities (average, 1.8+/-0.6 m/s) than all heterografts combined (average, 2.4+/-0.5 m/s; P=.002). Prosthetic regurgitation was more common in pulmonary homografts (88%) than in heterografts combined (29%; P<.001).

CONCLUSION

This study establishes the normal range for Doppler hemodynamics of various PVPs, specifically homografts and heterografts, in both pediatric and adult patients.

Noninvasive estimation of transmitral pressure drop across the normal mitral valve in humans: importance of convective and inertial forces during left ventricular filling

OBJECTIVES

We hypothesized that color M-mode (CMM) images could be used to solve the Euler equation, yielding regional pressure gradients along the scanline, which could then be integrated to yield the unsteady Bernoulli equation and estimate noninvasively both the convective and inertial components of the transmitral pressure difference.

BACKGROUND

Pulsed and continuous wave Doppler velocity measurements are routinely used clinically to assess severity of stenotic and regurgitant valves. However, only the convective component of the pressure gradient is measured, thereby neglecting the contribution of inertial forces, which may be significant, particularly for nonstenotic valves. Color M-mode provides a spatiotemporal representation of flow across the mitral valve.

METHODS

In eight patients undergoing coronary artery bypass grafting, high-fidelity left atrial and ventricular pressure measurements were obtained synchronously with transmitral CMM digital recordings. The instantaneous diastolic transmitral pressure difference was computed from the M-mode spatiotemporal velocity distribution using the unsteady flow form of the Bernoulli equation and was compared to the catheter measurements.

RESULTS

From 56 beats in 16 hemodynamic stages, inclusion of the inertial term ([deltapI]max = 1.78+/-1.30 mm Hg) in the noninvasive pressure difference calculation significantly increased the temporal correlation with catheter-based measurement (r = 0.35+/-0.24 vs. 0.81+/-0.15, p< 0.0001). It also allowed an accurate approximation of the peak pressure difference ([deltapc+I]max = 0.95 [delta(p)cathh]max + 0.24, r = 0.96, p<0.001, error = 0.08+/-0.54 mm Hg).

CONCLUSIONS

Inertial forces are significant components of the maximal pressure drop across the normal mitral valve. These can be accurately estimated noninvasively using CMM recordings of transmitral flow, which should improve the understanding of diastolic filling and function of the heart.

Transesophageal echocardiographic (TEE) evaluation of prosthetic valves

TEE overcomes many of the imaging constraints associated with transthoracic echocardiography for the assessment of valvular anatomy and function. Additional imaging artifacts and constraints associated with prosthetic valves are minimized or overcome with TEE. As such, TEE allows assessment of prosthetic valve anatomy and function and paraprosthetic anatomy, and serves as the diagnostic imaging modality of choice for patients with suspected prosthesis dysfunction or endocarditis.

Simultaneous Doppler and catheter transvalvular pressure gradients across St Jude bileaflet mitral valve prosthesis: in vivo study in a chronic animal model with pediatric valve sizes

A mixture of valve types has been used in previous in vivo studies to assess the accuracy of Doppler echocardiography compared with catheter-measured pressure gradients across prosthetic mitral valves. However, limited data exist regarding the most commonly used bileaflet mechanical valve. We studied 14 sheep with St Jude Medical mechanical mitral valves. Continuous wave Doppler data were obtained across each of the 3 valve orifices. Hemodynamic data were obtained simultaneously by direct measurements with catheters. Valve sizes commonly used in the pediatric population in the mitral position (23 mm, 25 mm, and 27 mm) were studied. Linear regression analyses of Doppler-predicted versus catheter-measured gradients provided correlation coefficients ranging from 0.75 to 0.91. Agreement analysis demonstrated a scatter of Doppler data about the regression line. Although a reasonably good correlation of Doppler-predicted peak and mean pressure gradients across bileaflet mechanical valves exists in the mitral position, caution is needed when this method is applied to patients. Doppler overestimation was greatest across the 23-mm valves. Analyses of the specific orifice interrogated demonstrated higher estimated pressure gradients across the central orifice compared with the side orifices.

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.

Differentiating thrombus from pannus formation in obstructed mechanical prosthetic valves: an evaluation of clinical, transthoracic and transesophageal echocardiographic parameters

OBJECTIVES

We sought to determine the clinical and echocardiographic parameters that differentiate thrombus from pannus formation as the etiology of obstructed mechanical prosthetic valves.

BACKGROUND

Distinction of thrombus from pannus on obstructed prosthetic valves is essential because thrombolytic therapy has emerged as an alternative to reoperation.

METHODS

We analyzed clinical, transthoracic and transesophageal echocardiography (TEE) data in 23 patients presenting with 24 obstructed prosthetic valves and compared the findings to pathology at surgery.

RESULTS

Fourteen valves had thrombus and 10 had pannus formation. Patients with thrombus had a shorter duration from time of valve insertion to malfunction, shorter duration of symptoms, but similar New York Heart Association functional class at the time of operation. Patients with thrombus had a lower rate of adequate anticoagulation (21% vs. 89%; p=0.0028). Pannus formation was more common in the aortic position (70% vs. 21%; p=0.035). Abnormal prosthetic valve motion was detected by TEE in all cases with thrombus formation but in 60% with pannus (p=0.0198). Thrombi were larger than pannuses (total length 2.8+/-2.47 cm vs. 1.17+/-0.43 cm; p=0.038). This was mostly due to extension of thrombi into the left atrium in prosthetic mitral valves. Thrombi appeared as a soft mass on the valve in 92% of cases, whereas 29% of pannuses had a soft echo density (p= 0.007). Ultrasound video intensity ratio, derived as the videointensity of the mass to that of the prosthetic valve, was lower in the thrombus group (0.46+/-0.14 vs. 0.71+/-0.17, p=0.006). A videointensity ratio of <0.70 had a positive predictive value of 87% and a negative predictive value of 89% for thrombus. Duration from onset of symptoms to reoperation of <1 month separated thrombus from pannus formation. The best objective clinical parameter for prediction of thrombus was inadequate anticoagulation, whereas the best TEE parameters were qualitative and quantitative ultrasound intensity of the mass. The presence of either inadequate anticoagulation or a soft mass by TEE improved the predictive power of either parameter alone and was similar to that of ultrasound videointensity ratio.

CONCLUSIONS

Duration of symptoms, anticoagulation status and qualitative and quantitative ultrasound intensity of the mass obstructing a mechanical prosthetic valve can help differentiate pannus formation from thrombus and may therefore be of value in refining the selection of patients for thrombolytic therapy of prosthetic valve obstruction.

Evaluation of prosthetic valve function and associated complications

Significant advances in imaging modalities have occurred to evaluate prosthetic valve function and associated complications. These developments involve predominantly the introduction of Doppler technology for the non-invasive determination of gradients and valve areas and TEE for an improved assessment of valve structure, function, and associated complications. The current role of cinefluoroscopy is mostly to complement TEE in the evaluation of motion of mechanical prosthetic valves in the aortic position. Cardiac catheterization is now rarely needed to assess valve function. Diagnosis of prosthetic valve obstruction can be performed in the majority of cases with transthoracic Doppler echocardiography. Differentiation of valve obstruction from normal valve function in small valves with high flow conditions, however, may be difficult. Because of this and the variability in normal valves among different prostheses, knowledge of the type and size of the implanted valve is essential. Patients and ultrasound laboratories are encouraged to seek and provide this information on a routine basis. Although transthoracic echocardiography is the main diagnostic modality for the serial evaluation of prosthetic valve function, it is important to recognize its limitations in assessing prosthetic mitral regurgitation and evaluating structural abnormalities of prosthetic valves. These are the situations in which TEE has the most impact. A summary of general indications of TEE in prosthetic valves is provided in Table 6. Finally, a baseline transthoracic Doppler study is essential in the overall follow-up and serial evaluation of valve function. For future comparisons, the best indices of valve functions are those obtained for patients as their own control, from a baseline Doppler echocardiographic study performed early after the operation.

Overestimation of flow velocity through leaks in mechanical valve prostheses and through small orifices by continuous-wave Doppler

The reliability of continuous-wave Doppler flow velocity measurements through small regurgitant lesions, such as in prosthetic leakage, has not been systematically analyzed. To evaluate the accuracy of continuous-wave Doppler in prosthetic valve leakage and small orifices in an in vitro, steady-flow model-flow velocities through the leaks of twelve intact mechanical prostheses and through six circular nozzles (area 0.5 to 20 mm2) were measured at pressure drops between 30 and 105 mm Hg. These results were compared with those predicted by the modified Bernoulli equation. Laser Doppler anemometry of flow velocities through the nozzles was also performed. Despite high correlation, there was substantial overestimation of Bernoulli predicted velocities by echo Doppler in the prosthetic leaks (mean +12.3% +/- 9.4%; range 90.3% to 143.4%). In the nozzles < or = 10 mm2, but not in the largest (20 mm2) nozzle, there was also overestimation of the Bernoulli predicted velocities (mean +6.2% +/- 2%). Laser Doppler anemometry of flow velocities through the nozzles showed slightly lower values than predicted by the Bernoulli equation. Thus, continuous-wave echo Doppler overestimates flow velocities through small orifices. This apparently is, at least in part, due to transit time effects and should be taken into account when using echo Doppler in small (< 10 mm2) orifices, such as in mild to moderate regurgitant lesions and prosthetic valve leakage.

Thrombolytic therapy for obstruction of mechanical prosthetic valves

This report describes two patients who were treated for obstruction of St. Jude tricuspid valve prostheses. In the patient with the hypereosinophilic syndrome, right heart failure developed 15 days after valve replacement. The other patient had symptoms of right heart failure for 8 weeks; these occurred 15 months after valve implantation. In both patients, thrombolytic therapy was successful and without major sequelae. Herein we review the literature on the use of thrombolysis for obstructed mechanical prosthetic valves and completely summarize the English literature; the efficacy of thrombolysis for obstructed prosthetic valves and the associated morbidity and mortality are emphasized. Recommendations for thrombolysis in clinical practice are provided.

Serial doppler echocardiographic evaluation of bioprosthetic valves in the tricuspid position

OBJECTIVES

This study sought to evaluate bioprosthetic valve dysfunction in the tricuspid position by serial Doppler echocardiography.

BACKGROUND

Few reports on the long-term results of tricuspid valve replacement with bioprosthetic valves are evaluated by serial Doppler echocardiography.

METHODS

Between September 1979 and December 1993, 95 patients underwent tricuspid valve replacement with bioprosthetic valves at our facility. Sixty patients who underwent serial Doppler echocardiographic examination at intervals of at least 2 years after operation were included in the final analysis. These patients were followed up from 1.5 to 13.0 years (mean 5.8 +/- 2.5).

RESULTS

The actuarial rates of freedom from bioprosthetic valve stenosis and regurgitation at 10 years were 46% and 51%, respectively. The prevalence of bioprosthetic valve stenosis and regurgitation increased progressively in a linear manner beginning 1 or 2 years after tricuspid valve replacement. Right heart failure developed during follow-up in 20 of the 25 patients with bioprosthetic valve dysfunction.

CONCLUSIONS

The long-term durability of bioprosthetic valves in the tricuspid position was substantially lower in our study than that reported in previous studies. Tricuspid bioprosthetic valve dysfunction increased progressively in a linear manner beginning 1 to 2 years after tricuspid valve replacement.

Doppler echocardiographic assessment of normally functioning Starr-Edwards, carbomedics and Carpentier-Edwards valves in aortic position

Doppler echocardiography was performed in 168 normally functioning aortic prostheses to determine acceptable pressure gradients across the commonly used valves and to establish the relationship between valve size and gradients. There were 82 Carbomedics (C), 63 Starr-Edwards (SE), and 23 Carpentier-Edwards (CE) valves. Peak and mean gradients across the prostheses were measured by use of the simplified Bernoulli equation. CarboMedics valve had a lower peak and mean gradient than Starr-Edwards and Carpentier-Edwards valve (P < 0.05 when compared with Starr-Edwards). The authors observed a weak inverse correlation between valve size and peak and mean gradients in CarboMedics and Carpentier-Edwards valves but not in the Starr-Edwards valve. For the CarboMedics valve the peak pressure gradient (PPG) was 26.1 +/- 8.2 mm Hg and the mean pressure gradient (MPG) was 14.7 +/- 5.1 mm Hg; in Starr-Edwards valve the PPG was 32.8 +/- 9.1 mm Hg and the MPG was 19.5 +/- 5.6 mm Hg; in the Carpentier-Edwards valve the PPG was 28.7 +/- 10.1 mm Hg and the MPG was 16.1 +/- 5.2 mm Hg when size was not specified. The CarboMedics valves were noted to have a better hemodynamic profile in comparison with Starr-Edwards and Carpentier-Edwards prostheses.

Echocardiography and Doppler assessment of prosthetic heart valves with transesophageal echocardiography

This article examines the use of transesophageal echocardiography (TEE) in the assessment of prosthetic heart valves. A summary of the commonly used artificial valves and their physiologic regurgitant flow patterns, as identified by color Doppler imaging, is presented. The hemodynamic evaluation of prosthetic valve stenosis using Doppler techniques is reviewed, and the diagnostic utility of TEE in identifying the complications of cardiac prostheses is discussed.

Comparison of hemodynamic performances of St. Jude Medical and CarboMedics 21 mm aortic prostheses by means of dobutamine stress echocardiography

Dobutamine stress Doppler echocardiography was used to compare the hemodynamic performance of two small aortic bileaflet prostheses. Nineteen patients (14 female, mean age 64 years) who had undergone aortic valve replacement with 21 mm bileaflet valve prostheses (St. Jude Medical valve, n = 9, or CarboMedics valve, n = 10) were studied. Dobutamine infusion was started at a rate of 5 micrograms.kg-1.min-1 and increased to 10 and 20 micrograms.kg-1.min-1 at 15-minute intervals. Under maximum stress, heart rate and cardiac output increased by 70% and 120%, respectively, and mean arterial blood pressure decreased by 9%. Pulsed-wave and continuous-wave Doppler studies were performed at rest and at the end of each stage. Velocity ratio, effective orifice area, performance index, and discharge coefficient of the valve were calculated, and peak and mean velocities and pressure drops across the prostheses were measured. Dobutamine infusion produced similar increases in cardiac output in all patients. Effective orifice areas, discharge coefficients, and performance indexes were comparable for the two valve groups both at rest and maximum stress. Transvalvular velocities and pressure drops were also similar in the two valve groups. Transvalvular pressure drops were also comparable in patients with large body surface area. Dobutamine stress echocardiography is useful in the evaluation of the hemodynamic performance of prosthetic heart valves. St. Jude Medical and CarboMedics 21 mm prostheses have equally favorable hemodynamic performances in most patients under conditions of high cardiac output.

Doppler echocardiographic assessment with the continuity equation of St. Jude Medical mechanical prostheses in the mitral valve position

Evaluation of the St. Jude Medical (SJM) valve in the mitral position with Doppler echocardiography has usually involved the use of gradients across the valve and the application of the pressure half-time (PHT) method to derive a mitral valve area. The purpose of this study was, first, to determine the normal values of effective orifice areas for the SJM valve in the mitral position using the continuity equation, and second, to evaluate whether this parameter provides an improved assessment of valve function. Accordingly, Doppler echocardiography was performed in 40 patients within 6 weeks after valve replacement. All patients were clinically stable, without evidence of valvular dysfunction or aortic insufficiency. Valve size ranged from 23 to 33 mm and ventricular ejection fraction averaged 54 +/- 13%. Effective orifice area was derived by the continuity equation using stroke volume measured in the ventricular outflow tract, divided by the time-velocity integral of the SJM valve jet, and by PHT. Doppler-derived SJM valve mean gradient averaged 4 +/- 2 mm Hg. Effective area by the continuity equation averaged 1.82 +/- 0.36 cm2 (range 1.03 cm2 for a 23 mm valve to 2.63 cm2 for a 31 mm valve) and was smaller than by PHT (mean 3.10 +/- 0.65 cm2, p = 0.0001; range 1.38 to 4.78 cm2). Areas by both methods were smaller than the actual valve orifice area provided by the manufacturer (4.53 +/- 0.80 cm2, p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Recombinant tissue-type plasminogen activator therapy in prosthetic mitral valve thrombosis: assessment by transthoracic and transesophageal echocardiography

Prosthetic cardiac thrombosis is a life-threatening complication that needs prompt diagnosis and therapy. We used recombinant tissue-type plasminogen activator (rT-PA), followed by heparin, in three patients with mitral prosthetic thrombosis, which was evident in two and suspect in one. Transthoracic and transesophageal echocardiography were employed in the diagnosis of both thrombosis and its resolution. No complications occurred. Immediately after the end of treatment with rT-PA, clinical status and echocardiographic data improved in all cases: transthoracic echocardiography showed the normalization of prosthetic function and transesophageal echocardiography showed resolution of thrombosis. One patient needed reoperation for rethrombosis due to the presence of prosthetic fibrous clot. rT-PA, followed by heparin, led to a good clinical result without bleeding and embolic complications in selected patients with mitral prosthetic thrombosis. Transthoracic and transesophageal echocardiography are complementary diagnostic tools in the diagnosis and management of patients with prosthetic thrombosis.

Is cardiac catheterization necessary in the era of echocardiography? Cost-effective approach combining echocardiography and cardiac catheterization

Definitive evaluation of cardiovascular disease is traditionally accomplished by cardiac catheterization. Advances in transthoracic and transesophageal Doppler echocardiography provides an accurate and cost-effective approach when compared to cardiac catheterization. Recent data suggests that for most adult patients with aortic or mitral valve disease, Doppler echocardiographic data enables the clinician to make the same decision reached with catheterization data. Echo and Doppler studies are useful in guiding certain therapeutic interventional procedures, and in the diagnosis of aortic dissection, mechanical complications of myocardial infarction, and in identifying aortic atheromas as a potential source of embolism. Future research will need to demonstrate that not only is echocardiography cost-effective, but that it will change the outcome of the patient.

Detection of "pathologic" prosthetic valve stenosis via exercise Doppler echocardiography

To detect borderline mitral valve dysfunction in asymptomatic patients, with Björk-Shiley valves, we studied the patients' hemodynamics at rest and during exercise by Doppler echocardiography. Supine bicycle exercise was performed by 65 patients. The patients were divided into two groups according to the measurements of the exercise Doppler echocardiography: a normally functioning group (n = 45) and a borderline group (n = 20). The valve area at rest was 2.0 +/- 0.6, 2.1 +/- 0.7, and 2.3 +/- 0.5 cm2 with valve sizes of 25, 27, and 29 mm, respectively, in the normal group and 1.9 +/- 0.5, 1.9 +/- 0.4, and 2.1 +/- 0.3 cm2 in the borderline group. The mitral valve area did not significantly change with exercise in either group. In the normal group, peak gradients increased from 9.9 +/- 3.5, 9.7 +/- 1.1, and 9.5 +/- 1.6 mmHg with valve sizes of 25, 27, and 29 mm, respectively, at rest to 15.1 +/- 3.1, 14.0 +/- 3.3, and 14.8 +/- 2.6 mmHg with exercise. Mean gradients increased from 5.2 +/- 1.2, 5.9 +/- 1.3, and 5.8 +/- 1.8 mmHg with valve sizes of 25, 27, and 29 mm, respectively, at rest to 8.0 +/- 2.5, 9.1 +/- 2.0, and 8.8 +/- 1.6 mmHg with exercise. In the borderline group, peak gradients increased from 10.5 +/- 3.1, 10.1 +/- 2.1, and 10.8 +/- 1.7 mmHg with valve sizes of 25, 27, and 29 mm, respectively, at rest to 24.5 +/- 4.2, 23.6 +/- 4.4, and 22.4 +/- 3.2 mmHg with exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of Björk-Shiley Mitral Valve Dysfunction via Doppler Echocardiography

Fifty-eight patients with a Björk-Shiley (B-S) mitral valve were examined to study applicability of Doppler echocardiography in diagnosing and predicting the severity of prosthetic valve dysfunction. The effect of valve replacement on the hemodynamic performance at rest and during bicycle exercise was determined from serial echocardiographic data. The high pressure gradient group in which peak pressure gradients were assumed to be more than 15mmHg at rest, showed negative values of percent change in both stroke volume index (%ΔSVI) and left ventricular end-diastolic volume index (%ΔEDVI). All patients with high pressure gradients had poor exercise response of the left ventricle, whereas most patients with low pressure gradients showed good exercise response. The high pressure gradient group had significantly smaller mitral valve area than did the low pressure group. This suggests that impairment of inflow caused by the artificial valve, namely, prosthetic valve stenosis, is possibly a significant factor causing left ventricular dysfunction—notably a decrease in stroke volume during exercise. Reoperation was performed with good results in 5 of 58 patients because of high pressure gradients across the mitral valve prosthesis caused by tissue overgrowth. We conclude the high pressure gradient group is considered to be a reserved cohort of reoperation and periodical measurement of the pressure gradient via Doppler echocardiography can predict prosthetic valve dysfunction before it deteriorates significantly.

Tricuspid valve replacement with the St. Jude Medical valve

A study was conducted on 20 patients who underwent tricuspid valve replacement (TVR) with the St. Jude Medical (SJM) valve. Isolated TVR was performed on 9 patients, and additional mitral, or mitral and aortic valve replacements were performed on 11 patients. Four patients (20%) died in the early postoperative period, but there were no deaths related to the SJM valve in the tricuspid position. The mean follow-up period of the 16 survivors was 74.4 months, and there have been no deaths during the follow-up period. The postoperative actuarial survival rate was 80%, 10 years after surgery. Three patients, representing 0.25%/patient-months, developed valve thrombosis, the valve thrombosis-free rate being 72.8%, 10 years after surgery, while entrapment of a leaflet by endothelial pannus was found in one patient, representing 0.08%/patient-months. Thus, the incidence of all prosthetic valve-related complications was 0.34%/patient-months, and the postoperative complication-free rate was 65.3%, 10 years after surgery. The medium-term follow-up study of TVR with the SJM valve revealed no prosthetic valve-related deaths and a relatively low incidence of prosthetic valve-related complications. However, as with other mechanical valves, valve thrombosis was a major risk posed by the SJM valve in the tricuspid position.

Quantitative hemodynamics by Doppler echocardiography: a noninvasive alternative to cardiac catheterization

Doppler echocardiography has greatly enhanced the information provided by two-dimensional echocardiography. By providing information concerning pressure gradients, intracardiac pressures, volumetric flow, and diastolic filling of the heart, most hemodynamic information that in the past could be obtained only from cardiac catheterization can now be provided accurately and noninvasively by Doppler echocardiography. Future developments in instrument technology and understanding of the various Doppler velocity curves should further aid in the ability to obtain a complete, noninvasive hemodynamic assessment of the patient with cardiac disease.

Effect of stenosis geometry on the Doppler-catheter gradient relation in vitro: a manifestation of pressure recovery

OBJECTIVES

This study investigated the effect of stenosis geometry on the Doppler-catheter gradient relation.

BACKGROUND

Although gradient estimation by Doppler ultrasound has been shown to be accurate in various clinical and in vitro settings, there have also been reports of substantial discrepancies between Doppler and catheter gradients. These conflicting results may be due to differences in geometry and hemodynamic characteristics of flow obstructions.

METHODS

Stenoses of various geometry were simultaneously studied with continuous wave Doppler and catheter technique in a well controlled pulsatile flow model.

RESULTS

Doppler and catheter gradients correlated very well regardless of stenosis geometry and site of distal catheter measurement (r = 0.98 to 0.99, SEE = 1.8 to 5.3 mm Hg). When the catheter was pulled back through the stenosis, the highest gradients were found in or close to the stenosis. When these catheter gradients were compared with Doppler gradients, the agreement between the two techniques was excellent regardless of stenosis geometry (slope 0.97; mean difference 0.6 +/- 2.0 mm Hg). However, when distal pressures were measured 10 cm downstream from the stenotic segment, the slope of the regression line, and therefore the agreement between Doppler and catheter gradients, differed for the different stenosis types (slopes from 0.98 to 1.69). In stenoses with abrupt narrowing and abrupt expansion, agreement was acceptable. Doppler gradients were only slightly greater than catheter gradients (mean difference 4.5 +/- 5.2 mm Hg). In stenoses with a gradually tapering inlet and outlet, the Doppler-catheter gradient relation was dependent on the outflow angle. Good agreement was found for an angle of 60 degrees (mean difference 0.6 +/- 1.8 mm Hg). In stenoses with a 40 degrees outflow angle, Doppler gradients exceeded the catheter gradients by 13% on average; for stenoses with a 20 degrees outflow angle, Doppler gradients exceeded catheter gradients by 46 +/- 11.4%, with differences as great as 65 mm Hg. These results were identical for stenoses gradually tapering outward to the distal tubing diameter and those with abrupt expansion after 2 cm of gradual expansion. The results were also not affected by changing the inflow angle from 20 degrees to 60 degrees. However, an abrupt narrowing instead of a tapering inlet significantly altered the Doppler-catheter gradient relation (p < 0.001); Doppler gradients exceeded the catheter gradients by 34 +/- 10% for this stenosis type.

CONCLUSIONS

Doppler gradients accurately reflect the highest gradients across flow obstructions that occur in the vena contracta. However, these gradients may be significantly greater than catheter gradients that are measured farther downstream, as is usually the case in clinical catheterization studies. These discrepancies are due to pressure recovery. The magnitude of pressure recovery is highly dependent on the stenosis geometry, which therefore significantly affects the Doppler-catheter gradient relation. It is the outflow geometry that predominantly influences this relation, but the shape of the inlet may affect the results as well. Although pressure recovery occurs even in stenoses with abrupt narrowing and abrupt expansion, the phenomenon is most likely to become clinically relevant in stenoses with a gradually tapering inlet and outlet with an outflow angle < or = 20 degrees.

An unusual Doppler-echocardiographic finding in case of a Björk-Shiley mitral prosthetic valve thrombosis

We report a patient in whom the commonly accepted Doppler echocardiographic findings failed to suggest prosthetic valve dysfunction. This was diagnosed by M-mode technique. We therefore feel that M-mode echocardiography still has its place in the complete evaluation of patients with suspected prosthetic valve dysfunction.

Doppler sonographic evaluation of mechanical and bioprosthetic mitral valve prostheses during exercise with a rate corrected pressure half time

OBJECTIVE

To compare the effect of exercise on pressure half time in patients with mechanical or bioprosthetic mitral valves. A relative pressure half time (pressure half time as a percentage of RR interval) was used in an attempt to correct for the shortening of the diastolic time interval caused by the increase in heart rate during exercise and thus to uncover the effects of valve design on pressure half time during exercise.

PATIENTS

Twenty clinically stable (New York Heart Association grade I-II) patients with mechanical (n = 12) or bioprosthetic (n = 8) mitral valves (median age 51) years. The median time since valve replacement was 42 months.

METHODS

Continuous wave Doppler echocardiography from the apical view at rest and during moderate supine bicycle exercise (50 W).

RESULTS

During exercise the mean (SD) heart rate increased from 79 (12) to 101 (12) beats per minute (95% confidence interval (95% CI) of difference, 15 to 29/min) and the peak pressure gradient from 11 (5) to 18 (6) mm Hg (95% CI of difference 5 to 9 mm Hg). The pressure half time decreased from 114 (30) to 78 (26) ms (95% CI of difference (30-42 ms). There was no difference between the valve types. The relative pressure half time remained unchanged in patients with mechanical valves during exercise (13 (4) rest and 13 (5)% exercise, respectively) and decreased in patients with bioprostheses (17 (3) and 12 (3)%, respectively (95% CI of difference 2 to 8%, p = 0.025).

CONCLUSIONS

In patients with mechanical mitral valves the decrease in the pressure half time during exercise is probably mostly the result of the shortening of the diastolic time interval with increasing heart rate whereas in patients with bioprosthetic valves an increase in functional valve area may contribute to the shortening of pressure half time during exercise.

The Hatle orifice area formula tested in normal bileaflet mechanical mitral prostheses

The Hatle formula was derived empirically in native mitral stenosis and may not be valid for normal prosthetic valves. Bileaflet mechanical prostheses open fully at low flows and have minimal interindividual variation in orifice area. In these valves effective area and measured manufacturer's area should be similar. We studied 60 patients aged 58 +/- 12 yr at a mean of 5 months after implantation with a CarboMedics prosthesis. There was a coexistent aortic prosthesis in 21. All diastolic measurements were averaged over 5 beats and stroke volume was calculated from the integral of the subaortic velocity trace and the cross-sectional area of the left ventricular outflow tract. For the whole group, area by the Hatle formula was 3.1 +/- 0.7 cm2 and measured area was 2.8 +/- 0.4 cm2. There was no significant correlation between these values (p = 0.329). Pressure half-time was more closely correlated with peak transmitral velocity (p = 0.012), RR interval (p = 0.015), diastolic time interval (p = 0.062) and stroke volume (p = 0.074). We conclude that the Hatle formula should not be applied to normal bileaflet mitral prostheses where pressure half-time reflects nonprosthetic factors more closely than orifice area.

Thrombolytic therapy for prosthetic valve thrombosis: a study based on serial Doppler echocardiographic evaluation

Sixteen patients with echocardiographic and cinefluoroscopic evidence of Björk-Shiley prosthetic valve obstruction (13 mitral valves and 3 aortic valves) were treated with intravenous streptokinase. Streptokinase was administered as an initial bolus of 250,000 units for 30 minutes, followed by an infusion of 100,000 units/hr. Serial cinefluoroscopy and echocardiography (M-mode, two-dimensional, and Doppler) were performed at 0, 24, 48, and 72 hours of treatment. The end point of treatment was defined as near normalization of clinical, echocardiographic, and fluoroscopic parameters. Successful thrombolysis was achieved in all patients. The average duration of streptokinase therapy was 43 hours (range 2 to 72 hours). Two of 16 patients had minor systemic embolism during therapy. Short-term follow-up has shown sustained benefit in 14 of 16 patients. Two patients have had rethrombosis of the mitral prosthetic valves and have undergone thrombectomy. Our study demonstrates the feasibility, safety, and efficacy of thrombolytic therapy in the treatment of prosthetic valve thrombosis. It also emphasizes the role of serial Doppler echocardiography in guiding the duration of therapy and assessing its efficacy.

Transesophageal echocardiography

Transesophageal echocardiography has provided a new acoustic window to the heart, the great vessels, and the mediastinum. It provides anatomical, functional hemodynamic, and blood flow information. High-quality visualization of left atrial appendage, thoracic aorta, atrial septum, and mitral valvular apparatus can be obtained readily. We discuss historical and technical aspects of transesophageal echocardiography, anatomical views, and major clinical indications for this procedure. These indications include intracardiac masses, thoracic aortic dissection, endocarditis, prosthetic and native cardiac valve function assessment, as well as its value in the detection of intracardiac source of systemic emboli. Furthermore, the role of transesophageal echocardiography in the assessment of coronary artery and congenital heart disease and as an intraoperative diagnostic and monitoring technique is discussed.

Use of transesophageal echocardiography during thrombolysis with tissue plasminogen activator of a thrombosed prosthetic mitral valve

Inadequate anticoagulation in patients with mechanical prosthetic heart valves can result in a significant incidence of thromboembolic complications. An even more life-threatening complication is massive thrombosis of the valve itself. Thrombolytic therapy was given to a moribund 22-year-old woman with intractable heart failure caused by a thrombosed St. Jude prosthetic mitral valve (St. Jude Medical, Inc., St. Paul, Minn.). Although this form of therapy has been used before, this is the first report of a case in which transesophageal echocardiography was performed during thrombolytic therapy to continually record successful thrombolysis of the clotted prosthetic valve. Serial imaging during thrombolysis displayed progressive dissolution of the thrombus and progressive improvement in valve function. Transesophageal echocardiography is helpful in the diagnosis of prosthetic valve thrombosis and has the ability to monitor continually the effect of treatment with thrombolysis. Although thrombolytic therapy with recombinant tissue plasminogen activator is effective in treating prosthetic valve thrombosis, it carries a high risk for serious thromboembolic complications and thus should be reserved for critically ill patients who are too sick to undergo immediate surgery.

Exercise evaluation of prosthetic heart valves by Doppler echocardiography: comparison with catheterization studies

Although valve replacement remains the cornerstone of treatment for critical heart valve dysfunction, problems including thromboembolism, infection, and primary failure of the prosthesis remain. Resting studies of valve hemodynamics are sometimes insufficient to reveal valve dysfunction. Early studies using cardiac catheterization focused on changes in prosthetic function seen with various types of exercise or drug-induced stress. These studies suffered from an inability to adequately stress catheterized patients and were cumbersome to the patient and the investigator. With the introduction of Doppler echocardiography, however, studies could be performed after significant exercise with low risk and increased ease. Using echocardiography, reports of exercise-induced changes in aortic and mitral valve hemodynamics have appeared. Over 600 patients have been studied using Doppler echocardiography. In the aortic position, all prostheses studied have a mild peak instantaneous gradient (18-26 mmHg) at rest, which increases with exercise (35-63 mmHg). No significant differences between the four models of mechanical prostheses studied are found. The gradients achieved with exercise do not appear to be related to the heart rate achieved or duration of exercise. Smaller prostheses are associated with larger gradients; however, the correlation was not strong. All mitral valve prostheses studied are also mildly stenotic at rest (range of mean gradients 2.3-7.1 mmHg) and become moderately stenotic with exercise (range 5.1-16.5). Although the lowest gradients are seen with St. Jude Medical and Medtronic Hall prostheses, their gradients are not significantly less than with other valves.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of prosthetic aortic valve design on the Doppler-catheter gradient correlation: an in vitro study of normal St. Jude, Medtronic-Hall, Starr-Edwards and Hancock valves

To evaluate the normal range of Doppler-derived velocities and gradients, their relation to direct flow measurements and the importance of prosthetic valve design on the relation between Doppler and catheter-derived gradients, five sizes of normal St. Jude bileaflet, Medtronic-Hall tilting disc, Starr-Edwards caged ball and Hancock bioprosthetic aortic valves were studied with use of a pulsatile flow model. A strong linear correlation between peak velocity and peak flow, and mean velocity and mean flow, was found in all four valve types (r = 0.96 to 0.99). In small St. Jude and Hancock valves, Doppler velocities and corresponding gradients increased dramatically with increasing flow, resulting in velocities and gradients as high as 4.7 m/s and 89 mm Hg, respectively. The ratio of velocity across the valve to velocity in front of the valve (velocity ratio) was independent of flow in all St. Jude, Medtronic-Hall, Starr-Edwards and Hancock valves when the two lowest flow rates were excluded for Hancock valves. Although Doppler peak and mean gradients correlated well with catheter peak and mean gradients in all four valve types, the actual agreement between the two techniques was acceptable only in Hancock and Medtronic-Hall valves. For St. Jude and Starr-Edwards valves, Doppler gradients significantly and consistently exceeded catheter gradients with differences as great as 44 mm Hg. Thus, Doppler velocities and gradients across normal prosthetic heart valves are highly flow dependent. However, the velocity ratio is independent of flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical assessment of prosthetic valve function

The advent of high-quality ultrasound technology has made the assessment of prosthetic valve function quicker, easier, and more accurate than ever before. By using cross-sectional imaging, colour flow mapping, and spectral Doppler techniques from both the precordium and the oesophagus, it is possible to assess a prosthetic valve fully. Cardiac catheterization with its attendant risks can be avoided. Echocardiography gives detailed morphological information, and it can be used for routine serial follow-up of individual patients. Using the patient as his or her own control avoids the problems caused by poorly-defined 'normal ranges' for prosthetic function.