Evaluation of the hemodynamic performance of small CarboMedics aortic prostheses using dobutamine-stress Doppler echocardiography

Hemodynamic assessment of Perceval sutureless bioprosthesis by dobutamine stress echocardiography

OBJECTIVES

The aim of this study was to evaluate the hemodynamic performance of a sutureless bioprosthesis under high workload at mid-term follow-up.

METHODS

Thirty-two patients who underwent isolated aortic valve replacement with a Perceval sutureless bioprosthesis with a minimum follow-up of 1 year were enrolled in this study. S size prosthesis was deployed in 10 patients (31.3%), M size in 9 (28.1%), L size in 8 (25%) and XL size in 5 (15.6%). Effective orifice area (EOA), EOA index (EOAi), and transvalvular gradients were assessed at rest and during dobutamine stress echocardiography (DSE) a median of 19.5 months after surgery.

RESULTS

Dobutamine stress echocardiography (DSE) significantly increased heart rate, stroke volume, ejection fraction, and transvalvular gradients (peak gradient, 24.0 ± 7.6 vs 38.7 ± 13.6 mm Hg, P < .001; mean gradient, 12.6 ± 4.2 vs 19.8 ± 8.3, P < .001). When compared to baseline, estimated valve areas significantly increased at follow-up (EOA, 1.48 ± 0.46 vs 2.06 ± 0.67, P < .001; EOAi, 0.84 ± 0.26 vs 1.17 ± 0.37, P < .001). Mean percentage increase in EOAi was 40.3% ± 28.0%. S size prostheses had the highest increase in EOA1, but the difference was not significant (S 46.0% ± 27.5% vs M 45.4% ± 34.5% vs L 32.7% ± 26.4% vs XL 32.1% ± 20.5%, P = .66). Severe patient-prosthesis mismatch (EOAi ≤ 0.65 cm² /m² ) was present at rest in 8 patients (25%), but only in one patient (3.1%) during DSE.

CONCLUSIONS

The Perceval sutureless bioprosthesis demonstrated good hemodynamics at rest and under high workload. The significant increase in EOAi during DSE suggests the potential advantages of Perceval sutureless bioprostheses in case of small aortic annulus or when patient-prosthesis mismatch is anticipated.

The Scandinavian multicenter hemodynamic evaluation of the SJM Regent aortic valve

Background

112 patients who received small and medium sized St.Jude Regent heart valves (19-25 mm) at 7 Scandinavian centers were studied between January 2003 and February 2005 to obtain non-invasive data regarding the hemodynamic performance at rest and during Dobutamine stress echocardiography (DSE) testing one year after surgery.

Material and methods

46 woman and 66 men, aged 61.8 ± 9.7 (18-75) years, were operated on for aortic regurgitation (17), stenosis (65), or mixed dysfunction (30). Valve sizes were 19 mm (6), 21 mm (33), 23 mm (41), 25 mm (30). Two patients receiving size 27 valves were excluded from the hemodynamic evaluation. Pledgets were used in 100 patients, everted mattress in 66 and simple interrupted sutures in 21. Valve orientation varied and was dependent on the surgeons' choice. 34 patients (30.4%) underwent concomitant coronary artery surgery.

Results

There were two early deaths (1.8%) and three late deaths, one because of pancreatic cancer. Late events during follow-up were: non structural dysfunction (1), bleeding (2), thromboembolism (2). At one year follow up 93% of the patients were in NYHA classes 1-2 versus 47.8% preoperatively.

Dobutamine stress echocardiography (DSE) was performed in a total of 66 and maximal peak stress was reached in 61 patients.

During DSE testing, the following statistically significant changes took place: Heart rate increased by 73.0%, cardiac output by 85.5%, left ventriclular ejection fraction by 19.6%, and maximal mean prosthetic transvalvular gradient by 133.8%, whereas the effective orifice area index did not change.

Left ventricular mass fell during one year from 215 ± 63 to 197 ± 62 g (p < 0.05).

Conclusion

The Dobutamine test induces a substantial stress, well suitable for echocardiographic assessment of prosthesis valve function and can be performed in the majority of the patients. The changes in pressure gradients add to the hemodynamic characteristics of the various valve sizes.

In our patients the St. Jude Regent valve performed satisfactory at rest and under pharmacological stress situation.

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.

Aortic valve replacement with a 16-mm CarboMedics valve in adult patients

Management of the small aortic root is a significant problem for the surgeon with regard to operative technique and selection of the prosthesis. We report on four adults with a small aortic root who underwent aortic valve replacement with a 16-mm CarboMedics bileaflet valve. All patients now lead normal lives. Postoperative Doppler measurements demonstrated an acceptable transprosthetic gradient.

Evaluation of the hemodynamic performance of St. Jude mitral prostheses: a pilot study by dobutamine-stress Doppler echocardiography

In contrast to the widespread use of dobutamine stress Doppler echocardiography in the hemodynamic evaluation of the prosthetic valves in aortic position, it has been rarely, if ever, used for assessment of these valves in mitral position. Therefore, this pilot study was done to assess the hemodynamic performance of St. Jude prosthetic mitral valves (functional orifice area 25-31) with dobutamine-stress Doppler echocardiography. Twenty consecutive patients (13 women and 7 men, aged 23 to 42 years) who had undergone mitral valve replacement 6 to 4745 days previously and 16 healthy volunteers (5 women and 11 men, aged 18 to 42 years) underwent dobutamine-stress Doppler echocardiography. Dobutamine infusion was started at a rate of 5 microg/kg per minute and was increased by 5 microg increments at 3-minute intervals. Maximum and mean gradients as well as pressure halftime were measured at rest and at the end of each stage. The correlation between Doppler-derived variables versus the heart rate was assessed and a regression equation was obtained for each of them. A significant increase in blood pressure, heart rate, maximum and mean gradients was noted during dobutamine infusion in both groups. There was a significant positive linear correlation between the increasing transprosthetic mitral valvular maximum and mean gradients and the increments in the heart rate (G(max) = 4.47 + 0.093 [HR], r= 0.474, p<0.05) and (G(mean) = 3.0+0.003 [HR], r=0.2697, p<0.05), respectively, indicating the heart rate dependency of these parameters. Pressure halftime, on the other hand, had an inverse but linear relationship with the heart rate (PHT = 142 - 0.55 [HR], r= -0.577, p<0.05). Similar findings were found for the control group as well. Standard dobutamine-stress echocardiography can safely be performed in patients with St. Jude mitral valve prostheses. Single Doppler measurements of the pressure gradients and pressure halftime may yield erroneous conclusions regarding the function and size of these valves unless corrected for the patients simultaneous, online heart rate. The use of the regression equations obtained in this pilot study may help to partly overcome some of these difficult issues.

Hemodynamic performance of the 21-mm Sorin Bicarbon mechanical aortic prostheses using dobutamine Doppler echocardiography

BACKGROUND

Small-sized mechanical aortic prostheses are commonly associated with generation of high transvalvular gradients, particularly in patients with large body surface area, and can result in patient-prosthesis mismatch. This study evaluates the hemodynamic performance of 21-mm Sorin Bicarbon bileaflet mechanical prostheses using dobutamine stress echocardiography.

METHODS

Fourteen patients (7 women; mean age, 63+/-8 years) who had undergone aortic valve replacement with a 21-mm Sorin Bicarbon bileaflet mechanical prosthesis 32.4+/-5.1 months previously were studied. After a resting Doppler echocardiogram, a dobutamine infusion was started at a rate of 5 microg x kg(-1) x min(-1) and increased to 30 microg x kg(-1) x min(-1) at 15-minute intervals. Pulsed- and continuous-wave Doppler echocardiographic studies were performed at rest and at the end of each increment of dobutamine. Both peak and mean velocity and pressure gradient across the prostheses were measured, and effective orifice area, discharge coefficient, and performance index were calculated.

RESULTS

Dobutamine stress increased heart rate and cardiac output by 83% and 81%, respectively (both p < 0.0001), and mean transvalvular gradient increased from 15.6+/-5.5 mm Hg at rest to 35.4+/-11.9 mm Hg at maximum stress (p < 0.0001). Although the indexed effective orifice area was significantly lower in patients with a larger body surface area, this was not associated with any significant pressure gradient. The performance index of this valve was unchanged throughout the study. Regression analyses demonstrated that the mean transvalvular gradient at maximum stress was independent of all variables except resting gradient (p = 0.05). Body surface area had no association with the changes in cardiac output, transvalvular gradient at maximum stress, and effective orifice area.

CONCLUSIONS

These data show that the 21-mm Sorin Bicarbon bileaflet mechanical prosthesis offers an excellent hemodynamic performance with full utilization of its available orifice when implanted in the aortic position. The lack of significant transvalvular gradient in patients with a larger body surface area suggests that patient-prosthesis mismatch is highly unlikely when this prosthesis is used.

Left ventricular architecture after valve replacement due to critical aortic stenosis: an approach to dis-/qualify the myth of valve prosthesis-patient mismatch?

OBJECTIVES

Left ventricular hypertrophy in patients with critical aortic stenosis (AS) is an adaptive process that compensates for high intracavitary pressure and reduces systolic wall stress followed by an increase in myocardial masses. In the present prospective clinical trial, we investigated long-term compensatory changes in left ventricular geometry and function after aortic valve replacement using mechanical bileaflet prostheses with the main emphasis on the small-sized aortic annulus and valve prosthesis-patient mismatch.

METHODS

A total of 58 patients with critical AS were assigned to the following groups according to the predictive value of prosthetic valve area index (VAI): group EXMIS: 29 patients (VAI < or =0.99), expected mismatch; group NOMIS: 29 patients (VAI < or =0.99), no mismatch. At controls T(0) (before operation/operation (OP), T(1) and T(2) (4 and 20 months after OP) the left ventricular geometry was recorded by means of Imatron electron beam tomography and the transprosthetic velocities were measured by echocardiography.

RESULTS

Statistical analysis showed a consistent reduction in the absolute (P=0.04) and indexed (P=0.04) left ventricular myocardial mass for both cohorts; furthermore, there was a significant difference between EXMIS and NOMIS patients concerning the factors, time and mass reduction (P=0.005), because of distinct baselines. A logistic regression report revealed preoperative cardiac output, absolute left ventricular myocardial mass, perfusion, body surface area and the native valve orifice area as predicting coefficients and factors for a minimum mass reduction of 25%. We explain a mathematical formula that turned out to be the most sensitive for correctly classified factors.

CONCLUSIONS

The left ventricular geometry and transprosthetic velocities resulted in the same postoperative recovery for both EXMIS and NOMIS patients. The presented data showed that valve prosthesis-patient mismatch had no influence in several stepwise logistic regression models. We conclude that modern mechanical bileaflet prostheses allow both acceptable hemodynamics and recovery of left ventricular hypertrophy, even in small aortic annuli.

An evaluation of prosthetic aortic valves using transesophageal echocardiography: the double-envelope technique

The conventional continuity equation uses nonsimultaneous measurements of blood flow velocities through the left ventricular outflow tract and across the aortic valve to calculate aortic valve area (AVA). We have noted that both velocities can be simultaneously obtained from continuous wave (CW) Doppler analysis (double-envelope [DE]). We hypothesize that prosthetic AVA can be calculated by using the DE technique, during transesophageal echocardiography (TEE). Prosthetic AVA was calculated in 41 of 45 patients immediately after aortic valve replacement by using the DE/AVA technique. Left ventricular outflow tract diameter was obtained from an esophageal view, while subvalvular (V(1)) and valvular (V(2)) peak velocities were simultaneously obtained from transgastric views by using CW Doppler. Prosthetic AVA and V(1)/V(2) ratio (Doppler velocity index) were calculated. V(1) was also measured by using pulse wave Doppler, as is conventionally done. Twenty-three Carbomedic (CM) and 18 Carpentier-Edwards (CE) AVA were evaluated. DE/AVAs for CM and CE valves correlated and agreed with that reported by the manufacturer (CM r(2) = 0.91, mean bias -0.25 cm(2) [SD 0.18]; CE r(2) = 0.73, mean bias -0.02 cm(2) [SD 0.27]). Calculated Doppler velocity index values agree with available data (mean bias 0.03 [SD 0.05]). The V(1) obtained by using the DE method was nearly identical to the V(1) obtained by using pulse wave (r(2) = 0.95, mean bias 0.02 m/s [SD 0.04 m/s]). TEE assessment of prosthetic AVA using the DE technique agrees with data reported by the manufacturer. Obtaining subvalvular and valvular velocities from the same CW Doppler trace may simplify the continuity equation and help avoid errors caused by beat-to-beat changes in blood flow. Quantitative prosthetic aortic valve assessment can be performed, on-line, with TEE by using the DE technique.

IMPLICATIONS

Quantitative assessment of prosthetic aortic valve area can be performed on-line by using transesophageal echocardiography using the double envelope technique.

Patient-prosthesis mismatch is negligible with modern small-size aortic valve prostheses

BACKGROUND

Concern has been raised about residual significant gradients when small aortic prostheses are used, particularly in patients with large body surface areas. We studied the performance of six types of small aortic prostheses using dobutamine stress echocardiography.

METHODS

Sixty-three patients (mean age, 67 +/- 7 years) who had undergone aortic valve replacement 17 +/- 6 months previously were studied. Two bileaflet mechanical prostheses (St. Jude Medical and CarboMedics: sizes, 19 mm and 21 mm) and two biological prostheses (Medtronic Intact and St. Jude BioImplant: size, 21 mm) were evaluated. A graded infusion of dobutamine was given and Doppler studies of valve performance were carried out.

RESULTS

All prostheses except one biological valve had acceptable hemodynamic performance under stress. Using regression modeling, gradient at rest was the only variable found to predict gradient under stress (p < 0.001). Moreover, the most important predictor of gradient at rest was valve design, which accounted for 72% of the variance (p < 0.001). This relationship was independent of valve size (19 mm or 21 mm) or material (ie, mechanical or biological). Body surface area accounted for 4% of the variance in gradient only.

CONCLUSIONS

The main predictor of transprosthetic gradient is the inherent characteristics of each particular prosthesis, with relatively insignificant contribution from variations in body surface area. Patient-prosthesis mismatch is not a problem of clinical significance when certain modern valve prostheses are used.

Stress echocardiography in valvular heart disease

Stress echocardiography has been widely accepted as an important diagnostic and prognostic tool in the assessment of known or suspected coronary artery disease. Its use in valvular heart disease, to date, has been more limited, but is continuing to grow as the technology and the understanding of valvular disorders progress. In this article, we will review the current literature regarding the use of both exercise and pharmacological stress testing in conjunction with echocardiography in the settings of native and prosthetic mitral and aortic valve disease. We will also discuss the limitations of this modality and touch upon possible future areas of investigation.

Temporal variability of exercise Doppler echocardiography in patients with nonstented aortic bioprostheses

Temporal variability and reproducibility of Doppler-derived variables obtained during supine symptom-limited exercise was investigated in 26 patients who were in clinically and hemodynamically stable condition with normally functioning nonstented aortic bioprostheses (stentless porcine, n = 13; cryopreserved homografts, n = 13). All patients had normal systolic left ventricular function and underwent 2 similar exercise tests within 12 months (mean time interval 7.2 +/- 1.9 months). The coefficient of variation was 8% to 9% for primary Doppler-derived variables (ie, velocities and velocity time integrals) at rest and during exercise. The coefficient of variation for calculated maximal pressure difference was 16% at rest and 15% at peak exercise. Measurement variability assessed from repeated measurements from the same videotaped recording was approximately 2%. High reproducibility was shown for most variables with intraclass correlation coefficients of 0.85 or more. We conclude that Doppler echocardiography can be used in patients with nonstented aortic bioprostheses with the same high reproducibility during exercise as at rest. The results provide clinically useful information regarding temporal variability for Doppler-derived variables.

[Hemodynamic evaluations of patients with small aortic annulus with St. Jude Medical prosthetic heart valve]

As the elderly population in Japan increases, senile degenerative aortic valvular disease also tends to increase. These patients often have a small aortic annulus. The problem of "valve-patient-mismatch" occurs when a small prosthesis is inserted into a patient with a small aortic annulus. To avoid annular enlargement after aortic valve replacement (AVR), we tried to use a small-sized St. Jude Medical (SJM) valve. From September 1988 through November 1996, 110 AVR were performed in our institution. In these cases, 30 underwent AVR with a small sized SJM valve (male < or = 21 mm, female < or = 19 mm). Dobutamine stress echocardiography was performed in 19 patients who had undergone AVR with a small-sized SJM valve. Surgical results were also compared between patients with small aortic annulus and those with normal-sized aortic annulus. Using Doppler echocardiography, pressure gradients (PG), cardiac index (CI), effective orifice area (EOA), and performance index (PI) were calculated at rest and during stress. The mean body surface area (BSA) of patient who had undergone AVR with SJM19A, 19HP and 21A was 1.40, 1.42 and 1.56 m2, respectively. With dobutamine stress, heart rates, PG and CI increased significantly. Mean and maximum PG of patients with 19HP (8.0 and 15.4 mmHg at rest, 12.9 and 28.0 mmHg under stress, respectively) and 21A (9.5 and 19.1 mmHg at rest, 16.5 and 35.3 mmHg under stress, respectively) were relatively low. EOA index (EOAI) of patient with 19HP showed the highest values mean 0.93 cm2/m2. PIs tended to be higher with HP models than with standard models. The tests were completed without significant side effects such as frequent ventricular arrhythmias. Among the cases with small aortic annulus, there were no operative deaths or hospital deaths. There were also no late deaths, episodes of hemorrhage or thrombosis. Conclusions. In our institution, AVR was performed safely without any aortic annular enlargement with a small aortic anulus in small BSA patients. Postoperative hemodynamic data obtained by echocardiography were satisfactory for all patients at rest and even during maximum dobutamine stress test.

Functional evaluation of the bileaflet mechanical valve in the aortic position using dobutamine-stress echocardiography: is a 23-mm prosthetic valve adequately large enough?

The issue of valve prosthesis-patient mismatch in small annular patients is still controversial. The hemodynamic function of bileaflet mechanical valves in the aortic position was examined using dobutamine-stress echocardiography. Forty-four patients were enrolled in the study and divided into 5 groups, according to prosthesis size, from 21 mm to 29 mm. The aortic peak pressure gradient (APG) increased significantly in all groups with dobutamine-stress and exceeded 50 mmHg in 83% of the 21-mm group, in 64% of the 23-mm group, and in 33% of the 25-mm group. The APG even exceeded 80 mmHg in 22% and 18% of the 21-mm and 23-mm groups, respectively. In these cases, the potential of 'valve prosthesis-patient mismatch' was considered. From the relationship between the APG and the prosthesis valve area index (VAI), 'critical VAIs' were found where patients were likely to enter the 'mismatch' status; that is, 1.22 and 1.77 cm2/m2, respectively, for the 5 and 10 microg/kg per min stages of dobutamine stress. This critical VAI range is useful in predicting the 'mismatch' patients preoperatively. Alternative procedures or prostheses should then be selected for them.

Dobutamine Stress Test to Evaluate Different Sizes of Prosthetic Aortic Valves

Dobutamine stress testing and Doppler echocardiography were used to assess hemodynamics in 27 patients aged 16 to 54 years with various sizes and types of aortic valve prosthesis. All patients underwent a symptom-limited treadmill exercise test within two days of the dobutamine test. There was no significant difference in ejection fractions and transvalvular gradients at rest and during dobutamine stress between St. Jude Medical, Medtronic-Hall, and Carbomedics valves. Exercise duration did not differ significantly among the different types of valve. When patients were classified by their underlying lesion, those with aortic stenosis and those with aortic insufficiency had similar ejection fractions and transvalvular gradients at rest and during dobutamine stress. The mean and peak transvalvular gradients at rest and during dobutamine stress were significantly different in patients with different valve sizes but the extent of the increase in gradients during stress was not significant. Linear regression analysis revealed that both peak and mean gradients during dobutamine stress could be predicted by the resting gradients. There was a negative correlation between valve size and gradients at rest and during stress, while there was a significant correlation between exercise duration and valve size. Dobutamine stress echocardiography was useful for studying hemodynamics in patients with aortic valve prostheses and the findings show that valvular size was the main determinant of exercise capacity.

Rest and exercise hemodynamics after the Ross procedure: an echocardiographic study

BACKGROUND

Aortic prosthetic valves with superior hemodynamic performance are associated with more complete regression of left ventricular hypertrophy and better left ventricular function postoperatively. The near normal function of the pulmonary autografts at rest is well documented, however, exercise data has been seldom reported. The purpose of this study is to evaluate the hemodynamic performance of pulmonary autografts in the aortic position and the homografts used to reconstruct the right ventricular outflow tract during conditions of high cardiac output by means of dobutamine stress echocardiography.

METHODS

Between May 1995 and February 1998, 67 patients were submitted to a Ross operation at our institution. Twenty of these patients had a mean age of 28.6+/-8.3 years and a mean follow-up time of 15.7+/-5.9 months. They were studied by dobutamine stress echocardiography to evaluate rest and exercise hemodynamics of the pulmonary autografts as well as of the aortic and pulmonary homografts used to reconstruct the right ventricular outflow tract. Dobutamine infusion was started at 5 microg/kg with incremental doses up to 40 microg/kg in every case.

RESULTS

With dobutamine infusion, heart rate increased from 71+/-10 to 142+/-11 beats/min, left ventricular systolic volume from 86.8+/-33.9 mL to 115.9+/-52.6 mL, and cardiac output from 6.3+/-2.9 L/min to 16.8+/-7.4 L/min. Left ventricular function was considered satisfactory at rest and during exercise in all patients. The mean gradient across the autograft increased from 1.03+/-0.95 mmHg to 4.03+/-2.05 mmHg and maximal instantaneous gradient from 2.45+/-2.21 mmHg to 9.54+/-4.85 mmHg. The mean effective orifice area for the autografts were 3.5+/-1.3 cm2 at rest and 3.3+/-1.4 cm2 during exercise. The patients with mild aortic insufficiency at rest had no increase in the degree of regurgitation with exercise. In the right ventricular outflow tract, the mean gradient across the homograft increased from 9.06+/-5.29 mmHg to 17.55+/-9.76 mmHg and maximal instantaneous gradient from 21.4+/-12.5 mmHg to 41.5+/-23.1 mmHg.

CONCLUSIONS

Pulmonary autografts exhibit normal hemodynamic performance at rest and during exercise after the Ross operation. However, mild-to-moderate gradients are common at the right ventricular outflow tract and should be carefully monitored.

Functional hemodynamic assessment of the 21-mm and 23-mm CarboMedics Top Hat aortic prosthetic valve

Between 1993 and 1996 the CarboMedics Top Hat supraannular aortic valve was implanted in 41 patients at the Wessex Cardiothoracic Centre (age, 39 to 74 years; mean, 61.3+/-8.9 years). Comparisons of annular dimensions made at surgery indicate that conventional annular valve replacement would have required at least a size smaller valve. This was particularly marked when a prosthetic mitral valve was in place. Operative mortality was 2.4%. There were also three late deaths. Echocardiography before and after symptom-limited treadmill testing has been performed in 21 patients. The mean time to follow-up was 16.1 months. The Doppler-derived indices of forward flow pre- and postexercise were expressed as mean+/-standard deviation. For 23-mm valves the values were: peak valve gradient 21.43+/-7.46 mm Hg and 35.86+/-14.4 mm Hg, aortic valve area 1.13+/-0.39 cm2 and 1.24+/-0.54 cm2. For 21-mm valves the values were: peak valve gradient 24.84+/-8.2 mm Hg and 31.29+/-5.84 mm Hg, aortic valve area 1.08+/-0.44 cm2 and 0.95 +/-0.2 cm2. The Top Hat valve has a good hemodynamic profile at rest and during exercise. Surgical considerations make it particularly useful in patients with a small aortic annulus and in patients undergoing combined aortic and mitral valve replacement.

Hemodynamic performance of the 21-mm St. Jude BioImplant prosthesis using dobutamine Doppler echocardiography

This study examines the hemodynamic performance of small size St. Jude BioImplant aortic prostheses using dobutamine echocardiography. Eleven patients (3 women, mean age 75 years) who had undergone aortic valve replacement with a size 21-mm St. Jude BioImplant aortic prostheses at 10.8 +/- 5.1 months (SD) previously were studied. Dobutamine infusion was started at a rate of 5 microg/kg/min and increased to 10 microg/kg/min, and subsequently to 20 microg/kg/min at 15-minute intervals. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Effective orifice area, mean gradient, and the performance index across each prosthesis were calculated and cardiac output was determined by Doppler measurement of flow in the left ventricular outflow tract. Stress dobutamine increased heart rate and cardiac output by 51% and 56%, respectively (both p <0.0001), and the mean transvalvular gradient increased from 30.1 +/- 7.5 mm Hg at rest to 49.3 +/- 11.5 mm Hg at maximum stress (p <0.0005). The performance index increased progressively from 0.29 +/- 0.05 at rest to 0.40 +/- 0.10 at maximum stress (p <0.0005). Regression modeling analyses demonstrated that the maximum stress gradient was independent of all variables except the resting gradient (p = 0.03). Body surface area had no effect on the changes in cardiac output, effective orifice area, or transprosthetic gradient at maximum stress. Thus, these data demonstrate that the size 21-mm St. Jude BioImplant prosthesis exhibits suboptimal hemodynamic performance with transvalvular gradients consistent with mild to moderate aortic stenosis, both at rest and under stress conditions.

Usefulness of dobutamine echocardiography in the hemodynamic assessment of mechanical prostheses in the aortic valve position

Dobutamine stress echocardiography is a simple, safe, and readily available method to evaluate prosthetic valve hemodynamics under various flow conditions. A normal response of aortic valve prostheses to dobutamine infusion is a 100% increment in transprosthetic pressure gradients with an unchanged valve area.

Long-term follow-up of small (size 20 and 21) Medtronic-Hall aortic valve prostheses

BACKGROUND

Our goal was to study the long-term follow-up of patients having aortic valve replacement and to focus particularly on the patients receiving small prostheses.

METHODS

Four hundred twenty-eight Medtronic-Hall valves were implanted (156 size 20 or 21 mm, 149 size 22 or 23 mm, and 123 size 25 or 27 mm). Group 20-21 had a higher number of female patients, more associated coronary lesions, and more patients with aortic stenosis.

RESULTS

The actuarial survival rate at 8 years was 80% for group 20-21, 80% for group 22-23, and 76% for group 25-27 (p = not significant). In group 20-21, the actuarial event-free rates at 8 years were as follows: thromboembolic complications, 94%; prosthetic valve endocarditis, 99%; reoperation, 98%; and hemorrhagic complications, 78%. The only factors of prognostic value in this group were age and associated coronary lesions.

CONCLUSIONS

The durable nature of the results obtained with the Medtronic-Hall 20- and 21-mm prostheses compared with large-diameter prostheses allows the use of a simple and reliable surgical technique and should mean that indications for ring enlargement become rare.

Haemodynamic performance of a 16-mm Carbomedics aortic prosthesis

A 55-year-old lady underwent repeat aortic valve replacement using a 16-mm Carbomedics prosthesis. She made an uneventful postoperative recovery and now leads an unrestricted life. Doppler echocardiography reveals a 21-mm Hg gradient across the valve at rest. This did not increase with an infusion of 30 mcg/kg per min of dobutamine, which resulted in an increase in the cardiac output from 1.96 to 5.46 l/min.

Dynamic evaluation of the 21-mm Medtronic Intact aortic bioprosthesis by dobutamine echocardiography

BACKGROUND

High residual transvalvular gradients have been reported with the use of small Medtronic Intact aortic valve prostheses. The aim of this study was to evaluate the hemodynamic performance of 21-mm prostheses using dobutamine Doppler echocardiography.

METHODS

Ten patients (7 women; mean age, 79 years) who had undergone aortic valve replacement with 21-mm Medtronic Intact prostheses 19.1 +/- 9.9 (standard deviation) months previously were studied. Dobutamine infusion was started at a rate of 5 microg x kg(-1) x min(-1) and increased to 10 and 20 microg x kg(-1) x min(-1) at 15-minute intervals. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Effective orifice area, performance index, and discharge coefficient of each valve were calculated, and peak and mean velocity and pressure drop across the prostheses were measured. Cardiac output was determined by Doppler measurement of flow in the left ventricular outflow tract.

RESULTS

Dobutamine stress increased heart rate and cardiac output by 68% and 65%, respectively (both p < 0.005), and mean transvalvular gradient increased from 19.1 +/- 5.1 mm Hg at rest to 33.2 +/- 7.7 mm Hg at maximum stress (p < 0.0001). Regression analyses demonstrated that maximum-stress gradient was independent of all variables except resting gradients (p < 0.004). Body surface area had no effect on the changes in cardiac output, effective orifice area, or transprosthetic gradient at maximum stress.

CONCLUSIONS

These data show that the 21-mm Medtronic Intact aortic prosthesis exhibits acceptable hemodynamic performance. Transvalvular gradients remained within a clinically acceptable range, both at rest and at maximum stress. Moreover, overall hemodynamic performance suggests that patient-prosthesis mismatch is unlikely to be a problem of clinical importance when this prosthesis is used.

Early in vivo experience with the Hemodynamic Plus St. Jude Medical heart valves in patients with narrowed aortic annulus

BACKGROUND

Small aortic orifice primarily resulted in heart prosthesis mismatch in a significant number of patients. The Hemodynamic Plus (HP) series of St. Jude Medical heart valves represents an interesting innovation, allowing a larger valve orifice area with an equivalent tissue annulus diameter.

METHODS

Hemodynamic characteristics of the 21-mm HP St. Jude Medical valve were prospectively compared with those of the standard 21-mm and 23-mm St. Jude Medical valves in three groups of 22 patients. Patients were selected from a database to be rigorously matched for age, sex, body surface area, functional class, underlying lesion, native valve opening area, left ventricular function, and preoperative peak and mean valve gradients. Postoperative evaluation (follow-up ranging from 3 to 24 months; mean, 11.5 months) included clinical examination and echocardiographic studies.

RESULTS

There was no operative mortality or significant perioperative complications. Short-term clinical follow-up was marked by a complete absence of valve-related complications. Presently, all but 1 patient in the 21-mm HP group and 2 in the 21-mm standard group are in New York Heart Association functional class I. Doppler echocardiography-derived mean and maximal pressure gradients were significantly lower in the 21-mm HP group (8.1 +/- 1.9 and 16.4 +/- 3.4 mm Hg) than in the 21-mm standard group (13.4 +/- 3.9 and 21.2 +/- 4.3 mm Hg; p = 0.002 and p = 0.0004, respectively), confirming the better hemodynamic performance already described in in vitro studies. Pressure gradients did not differ significantly between the 21-mm HP and the 23-mm standard groups. The 21-mm HP valve demonstrated the highest performance index; 0.66 +/- 0.08, compared with 0.49 +/- 0.09 for the 21-mm standard valve (p < 0.001) and 0.59 +/- 0.07 for the 23-mm standard valve (p < 0.001).

CONCLUSIONS

In vivo hemodynamic performance of the 21-mm HP valve corresponds closely to that of the 23-mm standard valve and is substantially better than that of the 21-mm standard valve. The 21-mm HP St. Jude Medical valve demonstrates excellent hemodynamic characteristics and can be recommended in normal-sized adult patients with narrow aortic root. This valve will minimize the need for aortic annulus enlargement.