Doppler evaluation of bioprosthetic and mechanical aortic valves: data from four models in 107 stable, ambulatory patients

Diagnostic evaluation of left-sided prosthetic heart valve dysfunction

Prosthetic heart valve (PHV) dysfunction is a rare, but potentially life-threatening, complication. In clinical practice, PHV dysfunction poses a diagnostic dilemma. Echocardiography and fluoroscopy are the imaging techniques of choice and are routinely used in daily practice. However, these techniques sometimes fail to determine the specific cause of PHV dysfunction, which is crucial to the selection of the appropriate treatment strategy. Multidetector-row CT (MDCT) can be of additional value in diagnosing the specific cause of PHV dysfunction and provides valuable complimentary information for surgical planning in case of reoperation. Cardiac magnetic resonance imaging (CMR) has limited value in the evaluation of biological PHV dysfunction. In this Review, we discuss the use of established imaging modalities for the detection of left-sided mechanical and biological PHV dysfunction and discuss the complementary role of MDCT in this context.

MP3 compression of Doppler ultrasound signals

The effect of lossy, MP3 compression on spectral parameters derived from Doppler ultrasound (US) signals was investigated. Compression was tested on signals acquired from two sources: 1. phase quadrature and 2. stereo audio directional output. A total of 11, 10-s acquisitions of Doppler US signal were collected from each source at three sites in a flow phantom. Doppler signals were digitized at 44.1 kHz and compressed using four grades of MP3 compression (in kilobits per second, kbps; compression ratios in brackets): 1400 kbps (uncompressed), 128 kbps (11:1), 64 kbps (22:1) and 32 kbps (44:1). Doppler spectra were characterized by peak velocity, mean velocity, spectral width, integrated power and ratio of spectral power between negative and positive velocities. The results suggest that MP3 compression on digital Doppler US signals is feasible at 128 kbps, with a resulting 11:1 compression ratio, without compromising clinically relevant information. Higher compression ratios led to significant differences for both signal sources when compared with the uncompressed signals.

Four year follow up of aortic valve replacement for isolated aortic stenosis: a link between reduction in pressure overload, regression of left ventricular hypertrophy, and diastolic function

OBJECTIVE

To evaluate changes in left ventricular function and the impact of ventricular hypertrophy and pressure gradient early and late after aortic valve replacement in patients with isolated aortic stenosis.

DESIGN

41 patients with isolated aortic stenosis and normal systolic function underwent cross sectional and Doppler echocardiography two months before and two weeks and four years after aortic valve replacement.

RESULTS

Early after the operation, left ventricular mass index (mean (SD)) decreased from 187 (44) g/m(2) to 179 (46) g/m(2), because of a reduction in end diastolic diameter (p < 0.05). Aortic pressure gradients were reduced, as expected. Isovolumic relaxation time was reduced from 93 (20) ms to 78 (12) ms, and deceleration time from 241 (102) ms to 205 (77) ms (p < 0.05). At four years, left ventricular mass index was further reduced to 135 (30) g/m(2) (p < 0.01) as a result of wall thickness reduction in the interventricular septum (from 14 (1.6) mm to 12 (1.4) mm, p < 0.01) and the posterior wall (from 14 (1.6) mm to 12 (1.3) mm, p < 0.01). Diastolic function, expressed by a reduction in isovolumic relaxation time from 93 (20) ms to 81 (15) ms (p < 0.01) and deceleration time from 241 (102) ms to 226 (96) ms (p < 0.05), remained improved. Prolonged isovolumic relaxation time was associated with significant septal and posterior wall hypertrophy (wall thickness > 13 mm) (p < 0.05), whereas prolonged deceleration time was related to high residual gradient (peak gradient > 30 mm Hg ) (p < 0.01).

CONCLUSIONS

Left ventricular diastolic function improves early after surgery for aortic stenosis in parallel with the reduction in the aortic gradient. However, prolongation of Doppler indices of myocardial relaxation and ventricular filling is observed in patients with significant left ventricular hypertrophy and a residual pressure gradient early after surgery. At four years postoperatively, diastolic function remains improved.

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.

Stentless or stented aortic valve implants in elderly patients?

OBJECTIVE

To assess differences in indication and mid-term results between stentless and stented procedures in elderly patients, we followed aortic valve patients over a period of 5 years.

METHODS

In a consecutive series of 154 elderly aortic patients in regular sinus rhythm from 1992 to 1997, we inserted 103 stentless (Toronto SPVTM, St Jude Medical Inc., St Paul, Minneapolis, MN) and 51 stented (Carpentier-Edwards supra annular porcine, Baxter Inc., Irvine, CA) bioprostheses in the aortic position.

RESULTS

All 154 patients seemed preoperatively eligible for a stentless procedure. Mean age was 74.8 years (range 67-86 years) with a majority of female patients. The surgeon's (in)experience, major dilatation or calcifications of the ascending aorta and aberrant coronary anatomy were the most common reasons for drawback from the stentless procedure (51/154 patients). Aortic clamp time was significantly higher in the stentless vs. stented group (70 vs. 57 min, P < 0.0001). The large average 25.3 mm size of the stentless prostheses (vs. 23.7 mm stented) stands in full contrast with the low mean body surface area of 1.68 m2 (vs. 1.70 m2) of the patients. We encountered. respectively. 5 and 2 hospital-deaths (P = n.s.). The follow-up period ranged from 6 to 66 months and was 97% complete, yielding, respectively, 302 and 139 patient-years. Survival (Kaplan-Meier method) was statistically higher in favor of the stentless procedures (log rank: P = 0.03). All survivors progressed markedly to a mean postoperative NYHA class 1.3 respectively, 1.4 (vs. preop. 3.3 and 3.2). Echocardiographic transvalvular gradients compared favorable for the stentless group in the small under 25 mm valves (P = 0.02 for 23 mm sized valves between groups) with improved left ventricular function and a significant decrease of left ventricular end diastolic diameter (LVEDD 48.0 vs. 56.5 mm) at 1 year follow-up. Cusp calcifications on control echocardiography were detected earlier (beyond 3 years) in the stented group, without signs of early significant regurgitation or dysfunction in both groups, except for one patient necessitating re-operation.

CONCLUSION

Although the implantation technique is much more demanding for stentless procedures, reflected by a longer aortic clamp-time, and remains impossible in some cases, elderly, small sized patients take full benefit of their large, non-obstructive prostheses.

Hemodynamic Comparison by Doppler Echocardiography of Valves in the Aortic Position: Value of the Continuity Equation to Assess Prosthetic Dysfunction

In 281 patients, we used Doppler echocardiography to compare the hemodynamic performance of different aortic prosthetic valves at three postoperative stages and investigated the value of the continuity equation in diagnosing aortic prosthetic obstruction. A baseline study was performed in 163 patients, a 5 +/- 2-month follow-up study was performed in 103 patients, and a 15 +/- 5-month follow-up study was performed in 65 patients. From baseline to the second study, left ventricular diastolic diameter, heart rate, and maximum (MG) and mean Doppler-derived gradient (MeG) decreased significantly, and left ventricular shortening fraction, systolic blood pressure, stroke volume, and prosthetic valvular area (PVA) increased significantly. No changes were found between the second and third studies. Thus, noninvasive hemodynamic values at the time of follow-up are reported in 171 patients: 86 with Björk-Shiley Monostrut, 27 with Carbomedics, 11 with Medtronic-Hall, 18 with Hancock modified, and 29 with Toronto valve bioprosthesis. Patients implanted with the Toronto had a larger prosthetic size (Monostrut 23 +/- 2 mm, Carbomedics 23 +/- 3 mm, Medtronic-Hall 23 +/- 2 mm, Hancock 23 +/- 2 mm, Toronto 25 +/- 2 mm, P < 0.01) despite a similar body surface area. MeG and MG were lower (MeG [in mmHg] Monostrut 12 +/- 5, Carbomedics 14 +/- 6, Medtronic-Hall 19 +/- 6, Hancock 11 +/- 4, Toronto 7 +/- 5; P < 0.01 between Toronto and all others), and PVA was greater (Monostrut 2.0 +/- 0.7 cm(2), Carbomedics 1.8 +/- 0.8 cm(2), Medtronic-Hall 1.6 +/- 0.7 cm(2), Hancock 1.7 +/- 0.5 cm(2), Toronto 2.2 +/- 0.9 cm(2); P < 0.01 between Toronto and Carbomedics, Medtronic-Hall, and Hancock), even compared with the same sizes in the other valves. A PVA of 0.9 cm(2) or less and MeG of 28 mmHg or more identified prosthetic obstruction with 100% sensitivity and 99% specificity. Hemodynamics change significantly from the early to the late postoperative state. The Toronto valve stentless porcine bioprostheses performs hemodynamically better than other valves. PVA measurement using the continuity equation may accurately identify prosthetic obstruction.

Echocardiography can detect cloth cover tears in fully covered Starr-Edwards valves: a long-term clinical and echocardiographic study

The incidence of cloth cover tears in fully covered Starr-Edwards valves, as assessed by autopsy or repeat surgery, is approximately 1% per patient-year. However, no echocardiographic study has explored this phenomenon. This study was designed as a one-time observational study and aimed to explore the ability of two-dimensional transthoracic echocardiography to identify cloth cover tears in 35 late survivors with 38 fully covered Starr-Edwards valves who had been operated on 20 to 24 years earlier. The hemodynamic profile, clinical status, and valve-related complications in this highly selected group of late survivors were also studied. Five patients also underwent transesophageal echocardiography. An elongated echogenic mass attached to the prosthetic valve cage and floating downstream was considered indicative of cloth tear. There were 16 patients with aortic valve prostheses, 16 with mitral valve prostheses, and three with double prosthetic valves. In six (17.1%) patients (four with aortic valve prostheses, two with mitral valve prostheses), an echogenic mass suggestive of cloth cover tear was detected, which was confirmed by transesophageal echocardiography in three patients. In two patients the echocardiographic finding was confirmed at surgery. The initial presentation of these six patients was endocarditis, possible embolism, unexplained dyspnea, and weakness in one patient each. Two patients were asymptomatic. There was no evidence of significant prosthetic valve malfunction in any patient. The transvalvular gradients were similar in patients with and without cloth cover tears. Echocardiographic findings highly suggestive of cloth cover tears are not uncommon and can be detected in the third postoperative decade in patients with fully covered Starr-Edwards valves. A prospective study to evaluate the clinical significance of an incidental echocardiographic finding suggestive of cloth cover tears in asymptomatic patients with these valve models is warranted.

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.

Clinical experience with the first 100 ATS heart valve implants

Between May 1992 and March 1994, 100 consecutive patients had 119 new ATS mechanical bileaflet valves inserted (61 aortic, 50 mitral, eight tricuspid). The mean age of the patients was 63.7 (range 13-82) years. The follow-up period ranged from 5 to 27 months and was complete in all cases. Before surgery, 53 aortic valve patients were in New York Heart Association functional class III or higher. This improved to a mean of 1.3 postoperatively, all patients being in classes I or II. One patient died in hospital, and another 3 months after implantation (actuarial survival rate 98%). One patient had an embolic event 9 days after an aortic valve reoperation which caused a parietal infarction. One tricuspid valve blocked in the open position 6 weeks after implantation as a result of inadequate anticoagulation and was successfully unblocked after 2 days of intensive thrombolytic therapy. Patients were treated by mild anticoagulation without developing bleeding complications. Echocardiographic, transoesophageal and transthoracic valvular gradients compared favourably with the gradients reported in other mechanical valves (including small aortic valves). The haemodynamics were excellent without evidence of significant regurgitation. This was confirmed by an in vitro hydrodynamic evaluation of the valve using a pulse duplicator system. The valve closure caused little noise and was as a result well tolerated.

Echocardiographic assessment of artificial heart valves: British Society of Echocardiography position paper

Images

Doppler hemodynamic profiles of 82 clinically and echocardiographically normal tricuspid valve prostheses

BACKGROUND

Normal Doppler hemodynamics for tricuspid prostheses have not been well characterized in a large group of patients. Therefore, we analyzed comprehensive Doppler echocardiographic examinations of 82 patients with tricuspid prostheses that were normal by clinical and two-dimensional echocardiographic examinations to establish the normal hemodynamics of various types and sizes of tricuspid prostheses.

METHODS AND RESULTS

The earliest complete postoperative echocardiographic study from each patient was chosen for analysis. Doppler examinations were analyzed on an off-line station from tapes or Doppler strip charts. Early velocity, atrial velocity, end-diastolic velocity, pressure half-time, and mean gradient were obtained by digitizing tricuspid velocity curves. The incidence of "physiological" tricuspid prosthetic regurgitation was noted. Ten Doppler cycles were measured for each patient, and maximal, minimal, and average measurements were recorded. The mean values +/- SD of early velocity, atrial velocity, end-diastolic velocity, mean gradient, and pressure half-time and incidence of mild prosthetic regurgitation were reported for each type of prosthesis, as were highest Doppler measurements for each valve type. Average pressure half-time was significantly lower for St Jude than for heterograft prostheses (P = .04). There were no significant differences between the valve types for mean gradient, early velocity, or incidence of prosthetic regurgitation. Increasing prosthesis size was associated with lower average pressure half-time for heterograft prostheses (P = .024). Average differences (respiratory- and cycle-length-dependent) between maximal and minimal values for 10 cardiac cycles were established for each prosthesis.

CONCLUSIONS

This study establishes normal ranges for Doppler hemodynamics of various tricuspid prostheses and emphasizes the importance of measuring multiple cycles for each tricuspid prosthesis, regardless of cardiac rhythm.

Doppler-derived pressure differences in normally functioning aortic valve prostheses. Studies in Björk-Shiley monostrut and Biocor porcine prostheses

To determine the normal range of maximum and mean Doppler-derived pressure differences for mechanical and bioprosthetic valves in the aortic position, Doppler echocardiography was performed on 239 stable patients with normally functioning Björk-Shiley monostrut (BSM, n = 185) or Biocor porcine (n = 54) prostheses. The interval from aortic valve replacement to echocardiography was 3-9 days. Maximum and mean pressure differences were significantly greater in 21 mm than in 25 or 27 mm BSM prostheses. The pressure differences in 23 mm BSM valves did not diverge significantly from those in 21, 25 or 27 mm valves. The mean pressure difference did not exceed 30 mm Hg in any type or size of studied prosthesis. No significant differences were found in pressure gradients in comparisons between BSM and Biocor prostheses of corresponding sizes. The calculated velocity ratio for BSM prostheses was not significantly influenced by the valve size. We suggest that the normal range of Doppler-derived maximum and mean pressure differences determined in this study be adopted as reference in evaluations of aortic BSM and Biocor valve prostheses.

Assessment of spatial and temporal velocity profiles distal of normally functioning Björk-Shiley prosthesis by the Doppler method

By Doppler echocardiography, the performance of heart valve prostheses is assessed with the aid of maximal transprosthetic velocities, which, however, may not be representative for the full spatial velocity profile in the vicinity of mechanical valve substitutes due to flow separation by the open occluder. The purpose of this study was to determine characteristics of velocity profiles downstream of a normally functioning Björk-Shiley prosthesis. In a pulsatile flow apparatus, different flow rates of 6.3 and 8.4 l/min were delivered. Using a spatially and temporally resolving ultrasonic Doppler method, velocity profiles 20 and 30 mm distal from the prosthesis were registered and displayed in a three-dimensional grid. The spatial velocity profile was found to deviate substantially from a flat profile at these transducer positions at the two flow conditions. Distal to the minor orifice, velocities measured only 70 and 80% of those downstream of the major orifice. In between, a region of relatively slow moving flow was present. The shape of the profiles remained essentially unchanged during acceleration and deceleration of flow. Thus, spatially resolved velocity profiles downstream of mechanical prostheses can be registered by an ultrasonic Doppler device. These findings may be useful for the detection of beginning malfunction both in the experimental and the clinical setting.

Assessing prosthetic heart valve function. Value of Doppler echocardiography and patient/prosthetic valve identity and follow-up card

Doppler echocardiography is being used increasingly in the follow-up of patients with valvular heart prostheses because it provides unique hemodynamic information about flow through prosthetic valves. A baseline checkup about 3 months after implantation is now recommended. We therefore now supply each patient with an identity and follow-up card for each particular prosthesis.

Long-term reproducibility of conventional Doppler analysis in patients with prosthetic valves

Long-term reproducibility of Doppler recordings made by the same investigator using the same ultrasound equipment was determined in 50 clinically stable patients. The mean interval between the first and second examination was 16 +/- 7 months. In 90% of the 33 patients with aortic prostheses, the relative difference between the first and second examination was less than 16% (mean value 9.1%) for the maximum instantaneous gradient and less than 17% (mean value 7.4%) for the mean gradient; the relative difference was less than 20% (mean value 8.5%) for the maximum flow velocity in the left ventricular outflow tract and less than 24% (mean value 10.8) for the maximum flow velocity ratio. In 90% of the 25 patients with mitral prostheses, the absolute difference between the first and second examination was less than 3 mmHg for the maximum instantaneous gradient, less than 2.5 mmHg for the mean gradient, and less than 20 msec for the pressure half-time. We conclude that long-term reproducibility of Doppler echocardiographic characteristics of prosthetic valve function is good as far as transprosthetic gradients or pressure half-time are concerned but is less so for maximum flow velocity in the left ventricular outflow tract and the maximum flow velocity ratio. Changes beyond the aforementioned values may represent a real change in prosthetic valve function.

Validity of an early postoperative baseline Doppler recording after aortic valve replacement

In 131 patients undergoing aortic valve replacement (53 bioprostheses, 78 mechanical), the pressure decrease across the prosthesis was recorded with Doppler ultrasound at a baseline study early postoperatively (mean 11 +/- 5 days) and compared with a repeat measurement 3 to 5 months later. At baseline the hemodynamic state was markedly different, with increased heart rate (89 +/- 14 vs. 74 +/- 13 beats/min, p less than 0.001) and decreased left ventricular ejection time index (367 +/- 21 vs 390 +/- 22, p less than 0.001). A minor and clinically insignificant decrease in pressure decrease with time was found. The 95% confidence interval for the difference was 0.2 to 3.0 and 0.2 to 1.7 mm Hg for the peak and the mean pressure decrease, respectively. The change in pressure decrease was statistically significant for bioprostheses (mean 16 +/- 5 vs 14 +/- 4 mm Hg, p less than 0.01) and smaller (less than or equal to 23 mm) valves (mean 17 +/- 4 vs 15 +/- 4 mm Hg, p less than 0.01), whereas no significant changes were found for mechanical valves or valves of a larger size. The change in mean pressure decrease from baseline to the second examination was within +/- 5 mm Hg for 82% of patients. It is concluded that despite a different hemodynamic state in the early postoperative period, the pressure decrease across aortic valve prostheses obtained at this time can be used as a reference for later comparison.

Doppler echocardiographic assessment of prosthetic aortic valve function. Findings in normal valves

To determine the Doppler-derived aortic flow velocity profiles in relation to type of prosthetic valve and left ventricular function, 70 patients with normal functioning aortic prosthetic valves (group 1 = 44 patients with low-profile mechanical valves and group 2 = 26 patients with high-profile mechanical valves) were evaluated. Peak flow velocity and mean systolic gradient were inversely related to valve size (r = -0.72; r = -0.76) in group 1. On the other hand, aortic flow velocity profiles had significant correlations with left ventricular end-systolic dimension (r = 0.75; r = 0.76) and left ventricular fractional shortening (r = -0.69; r = -0.66) in group 2. Thus, aortic flow velocity profiles in the low-profile mechanical valve were affected by pressure gradient caused by the valve size, whereas the hydromechanical disadvantage of the high profile mechanical valve affected the left ventricular pump function and Doppler-derived flow velocity profiles.

Effect of depressed left ventricular function on hemodynamics of normal St. Jude Medical prosthesis in the aortic valve position

To evaluate the effect of left ventricular (LV) dysfunction on Doppler-derived transprosthetic hemodynamic indexes in patients with normally functioning St. Jude aortic valve prostheses, 74 consecutive patients were studied. LV ejection fraction was assessed by using Simpson's biplane rule. The 34 patients with normal ejection fraction (greater than or equal to 0.51) (group A) generally had the highest values of peak (31 +/- 13 mm Hg) and mean (16 +/- 6 mm Hg) gradients, whereas 19 patients with moderate to severe reduction of ejection fraction (less than or equal to 0.31) (group C) had the lowest values (17 +/- 6 and 9 +/- 3 mm Hg, respectively) (p less than 0.05). Significant decreases (p less than 0.05) for acceleration and corrected (for heart rate) velocity time integral in group C were noted compared to group A, and group B (21 patients with mild to moderately reduced ejection fraction [0.50 to 0.32]). A significant inverse correlation for Doppler-derived peak and mean gradients and corrected velocity time integral was demonstrated with increasing aortic valve prosthetic sizes from 19 to 29 mm in group A patients (r = -0.41 to -0.71) but less so in group B or C. Thus, in addition to valve size, LV function should be considered an important factor in detecting prosthetic valvular flow characteristics and dysfunction. A normal derived velocity and gradient in patients with moderately to severely depressed LV function may not rule out significant valvular stenosis.

Doppler echocardiography assessment of prosthetic heart valves

Transthoracic Doppler echocardiography is an accurate noninvasive method for the evaluation of prosthetic valve function. The flow characteristics and pressure gradients of normally functioning mechanical and bioprosthetic valves have been, in general established. Normal functioning mitral valve prostheses have a valve area greater than 1.8 cm 2 with the St. Jude valve having the largest effective valve area and normally functioning aortic prosthetic valves have a peak instantaneous gradient of less than 45 mmHg, with the Starr-Edwards valves (Starr-Edwards, Irvine CA) showing the highest gradients. The incidence of minimal or mild regurgitation is approximately 15% to 30% in the mitral position and 25% to 50% in the aortic position, with the higher incidence of regurgitation seen with mechanical compared to bioprosthetic valves. Transthoracic Doppler echocardiography can accurately detect patients with prosthetic valvular stenosis. The presence of prosthetic aortic regurgitation can also generally be accurately assessed, except in the presence of both prosthetic aortic and mitral valves. Assessment of prosthetic mitral regurgitation remains limited due to significant attenuation of the ultrasound beam by the prosthesis and the frequent underestimation of severity of regurgitation. Other limitations of transthoracic studies include assessment of leaflet morphology, detection of vegetations and valve abscesses, and differentiation between valvular and paravalvular regurgitation.

Colour flow Doppler mapping in the assessment of prosthetic valve regurgitation

Two hundred Carpentier-Edwards, Björk-Shiley, and Starr-Edwards prostheses in 173 patients were examined. Sixteen (16%) in the aortic and 24 (25%) in the mitral position were associated with clinical signs of regurgitation. A phased array system (Hewlett-Packard A77020A) with a 2.5 MHz duplex and 1.9 MHz continuous wave transducer was used. Colour flow mapping showed trivial transvalvar regurgitation in 23 (53%) metal aortic prosthesis, and only nine (20%) metal mitral prostheses. This difference was probably attributable to shielding of the left atrium by the metal components. Colour mapping confirmed abnormal regurgitation in all aortic prostheses with early diastolic numbers, but regurgitation was also shown in 25 (29%) with no diastolic murmur. Abnormal mitral regurgitation was found in 13 (54%) patients with a pansystolic murmur, but also in six (8%) with no systolic murmur. Two patients, thought on clinical grounds to have mild mitral regurgitation, had unexpectedly large jets on colour flow mapping. About one in three prostheses had paraprosthetic leaks, 65 (79%) of which were small with a jet area less than 20% of the area of the receiving chamber. The development of new paraprosthetic leaks led to the diagnosis of bacterial endocarditis in two patients. In eight patients regurgitation was first diagnosed with continuous wave Doppler, but was afterwards shown with colour mapping and in a further 10 regurgitation could only be shown by continuous wave Doppler. Colour flow mapping was less sensitive than continuous wave Doppler in detecting regurgitation,but seemed able to distinguish normal transvalvar from paraprosthetic regurgitation. Further studies in the natural course of paraprosthetic leaks and a comparison of the transoesophageal and transthoracic approaches in the assessment of mitral prostheses are needed.

Doppler echocardiographic evaluation of tilting-disc prosthetic heart valves in children

To determine the Doppler characteristics of tilting-disc prosthetic heart valves in children, 22 children with mitral prostheses were studied 8 +/- 2 months after surgery, and 10 children with aortic prostheses were studied 37 +/- 26 months after surgery. All valves were thought to be functioning normally by clinical examination. Valve competence was interrogated and peak and mean velocities were measured by standard pulsed wave, continuous wave and color Doppler techniques. Prosthetic valve area was calculated and compared to the known valve area. Mild prosthetic valve regurgitation was present in 8 of 22 mitral and 7 of 10 aortic prostheses. For mitral prostheses, peak velocity was 192 +/- 41 cm/s, mean velocity was 118 +/- 37 cm/s and mean gradient was 7 +/- 4 mm Hg. For aortic prostheses, peak velocity was 287 +/- 88 cm/s, mean velocity was 197 +/- 59 cm/s, peak gradient was 36 +/- 21 mm Hg and mean gradient was 19 +/- 11 mm Hg. Prosthetic mitral valve area, calculated by the pressure half-time and modified Gorlin methods, correlated well with the known valve area (r = 0.89, standard error of the estimate = 0.29 and r = 0.95, standard error of the estimate = 0.21, respectively). Prosthetic aortic valve area, calculated by the modified Gorlin method, correlated well with the known valve area (r = 0.89, standard error of the estimate = 0.18). Residual valvular abnormalities are common after prosthetic valve insertion in children. Doppler estimates of prosthetic valve area correlate well with the known valve area but have a large standard error of the estimate.