Doppler assessment of mechanical aortic valve prostheses: effect of valve design and size of the aorta

BACKGROUND AND AIM OF THE STUDY: Discrepancies between Doppler and catheter gradients have been reported for bileaflet aortic valve prostheses. Whether modifications in geometric design of newly developed bileaflet valves lead to a different Doppler-catheter gradient relationship has not been evaluated. Variable results have been reported for tilting-disc prostheses. In addition, the effect of aortic size on the Doppler-catheter gradient relationship remains unclear. METHODS: Various sizes of On-X and Edwards Mira (identical with Sorin Bicarbon) bileaflet valves and Sorin Allcarbon tilting-disc aortic valves (19-25 mm) were studied in a pulsatile flow model. Doppler and catheter gradients were measured simultaneously. Aortic diameters between 1.8 and 4 cm were evaluated. RESULTS: Correlation between Doppler and catheter gradients was excellent (r = 0.98-0.99 for peak and mean gradients), but in bileaflet valves Doppler significantly overestimated the corresponding catheter gradients as reflected by slopes of the regression lines (1.57-1.8). In the range of relevant gradients > or = 10 mmHg, Doppler exceeded catheter gradients by 40 +/- 17% (peak) and 39 +/- 16% (mean) in Mira valves, and by 46 +/- 19% (peak) and 43 +/- 14% (mean) in On-X valves. In the Sorin tilting-disc valve, Doppler accurately reflected catheter gradients (slopes of regression lines 1.05-1.14). The aortic diameter significantly influenced results in only tilting-disc valves, but in absolute terms the effect was clinically less relevant. CONCLUSION: Discrepancies between Doppler and catheter gradients are common to all bileaflet valves, regardless of their specific geometric design, whereas tilting-disc valves must be considered individually. The influence of aortic size on the Doppler-catheter gradient relationship appears clinically to be less relevant in prosthetic valves.     

The influence of prosthesis size and design on exercise dynamics after aortic valve replacement

BACKGROUND AND AIM OF THE STUDY: Residual gradient following aortic valve replacement (AVR) may adversely affect clinical outcome. The size and design of the valve may influence these characteristics. The study aim was to determine the influence of prosthesis physical size and leaflet design on hemodynamic performance after mechanical AVR. METHODS: After AVR, two patient groups with a range of valve sizes were studied. Group 1 patients (n=19) each received a monoleaflet valve; group 2 patients (n=18) each received a bileaflet valve. Transthoracic echocardiography was performed at rest and after graded bicycle ergometry to assess prosthetic valve parameters, including mean and peak transvalvular gradient and effective orifice area (EOA). RESULTS: Transprosthetic gradients (mean and peak) measured at rest, maximum exercise and 3-min recovery were related to indexed geometric orifice area (IGOA) by an exponential decay function, with no significant advantage for either valve design. However, in valve sizes < or =25 mm the bileaflet valves demonstrated lower gradients, both at rest and under exercise conditions (mean gradient during exercise, bileaflet versus monoleaflet 19.9 +/- 7.2 mmHg versus 25.6 +/- 6.3 mmHg, p = 0.01). Similarly, EOAs were larger in the bileaflet group when equivalent GOAs < or =2.5 cm2 were compared (EOA: bileaflet versus monoleaflet 1.51 +/- 0.33 cm2 versus 1.14 +/- 0.26 cm2, p = 0.018). The total work performed correlated with prosthesis diameter (r2 = 0.81, p = 0.037) and was not influenced by valve design. CONCLUSION: The hemodynamic performance of mechanical aortic valves, including transprosthetic gradient and maximum exercise work performed, related principally to the prosthesis physical size. However, within the smaller valve sizes, the bileaflet design appeared to offer hemodynamic advantages.     

Long-Term Follow-Up and Dobutamine Stress Echocardiography of 19-mm Prosthetic Heart Valves

BACKGROUND: In patients with a small aortic root, the use of 19-mm valve prostheses for valve replacement is controversial because of the small orifice area of these valves. METHODS: To assess stress hemodynamics in patients with 19-mm valve prostheses, to find predictors of unfavorable hemodynamics, and to document the long-term follow-up, we examined 30 patients (age, 64 +/- 19 years; 27 women and 3 men; follow-up, 38 +/- 50 months) clinically and with the use of dobutamine stress echocardiography. A history was taken, and a physical examination was performed. At rest and during dobutamine stress, Doppler echocardiography was performed. RESULTS: At rest, transprosthetic gradients were moderately elevated with mean and peak gradients of 15 +/- 7 and 32 +/- 14 mmHg, and effective orifice areas were small (0.91 +/- 0.31 cm(2)). Gradients rose markedly during stress (mean, 37 +/- 14 mmHg; peak, 83 +/- 41 mmHg). Predictors of high transprosthetic gradients were larger body surface area, younger age, and valve type. Mean and peak gradients were lower with St. Jude Medical Hemodynamic Plus valves than with standard St. Jude Medical (P < 0.05) and other valves, and the effective orifice area was highest (1.07 +/- 0.29 cm(2); P < 0.05 versus standard St. Jude Medical) in this valve model. Sixty percent of patients developed significant dynamic subvalvular or intraventricular gradients (84 +/- 41 mmHg) during dobutamine stress. CONCLUSIONS: After aortic valve replacement with 19-mm prostheses in patients with a small aortic root, dobutamine stress leads to high transvalvular gradients, which are dependent on valve model, age, and body surface area. In addition, 60% of patients develop significant dynamic outflow obstructions. These findings and the persistence of some degree of exercise-induced symptoms in 70% of patients suggest that alternative surgical techniques should be considered if the size of the aortic annulus demands a 19-mm valve, especially if the patient seeks physical activity, is young, or is of larger body size.     

In-vitro testing of three totally supra-annular bileaflet mechanical valves: hydrodynamics in the Sheffield pulse duplicator

BACKGROUND AND AIM OF THE STUDY: In-vivo echocardiographic studies are limited by several confounding factors and technical pitfalls, and consequently the hypothetical differential hydraulic behavior between different prosthetic heart valves has not been identified. However, for surgeons it is essential to know the functional and geometric characteristics of the prostheses to be used. Herein, the in-vitro performance of two new supra-annular bileaflet prostheses--the Medtronic Advantage Supra and Sorin Bicarbon Overline--was compared with that of the 21-mm St. Jude Medical (SJM) Regent valve. METHODS: Three high-performance, production-quality prostheses, including the sewing-ring cuffs, were tested in the aortic chamber of a Sheffield pulse duplicator. The sizes of the prostheses which fitted the 21-mm valve holder were: 21 mm Advantage Supra Medtronic; 19 mm SJM Regent, and 18 mm Sorin Bicarbon Overline. The tests were carried out at a fixed pulse rate (70 beats/min), and at increasing cardiac output (CO) of 2, 4, 5, and 7 l/min. Forward-flow pressure drop, total regurgitant volume, closing and leakage volumes, effective orifice area (EOA) and stroke work loss (SWL) were recorded while the valve was operated at each CO. RESULTS: The SJM Regent and Sorin Bicarbon Overline valves each showed, at increasing CO, significantly lower mean and peak gradients. The calculated EOA and SWL were significantly better with the SJM Regent and Sorin Bicarbon Overline prostheses. The Medtronic Advantage Supra valve showed comparable results only while performing at 2 l/min CO. With regards to the regurgitant fraction, lowest values were observed with the Medtronic Advantage Supra valve. CONCLUSION: This hydrodynamic evaluation model allowed a comparison to be made of the efficiency of recently commercialized bileaflet prostheses, among which the older SJM Regent and the newer Sorin Bicarbon Overline valves demonstrated the best performances.     

Doppler-catheter discrepancies in patients with bileaflet mechanical prostheses or bioprostheses in the aortic valve position

The aims of the present study were to investigate in vivo Doppler-catheter discrepancies in aortic bileaflet mechanical and stented biologic valves and evaluate whether these can be predicted using Doppler echocardiography. Results of in vitro studies of bileaflet mechanical valves suggested overestimation using Doppler gradients. Findings in stented biologic valves were conflicting. Patients who underwent valve replacement with a St. Jude Medical mechanical (n = 14, size 19 to 29) or a St. Jude Medical Biocor (Biocor, n = 13, size 21 to 25) valve were included. Simultaneous continuous Doppler recordings (transesophageal transducer) and left ventricular and aortic pressure measurements were performed using high-fidelity catheters. Gradients after pressure recovery were predicted from Doppler using a validated equation. Doppler overestimated catheter gradients in both the mechanical and Biocor. Mean Doppler catheter differences for the mechanical/Biocor were for mean gradients of 4 +/- 3 (SD; p = 0.002)/6 +/- 4 mm Hg (p = 0.002). There was a strong relation between catheter and Doppler gradients (r = 0.85 to 0.92). Doppler catheter discrepancy as a percentage of the Doppler mean gradient for the mechanical was median 41% (range -30% to 76%) and for the Biocor was median 35% (range -7% to 75%). The catheter-Doppler discrepancy was not significant using the predicted net gradient from Doppler. In conclusion, this was the first in vivo investigation of prosthetic valves using simultaneous Doppler and high-fidelity catheters. Doppler overestimated catheter gradients in both mechanical and stented biologic valves. However, the discrepancy can be predicted considering pressure recovery in the aorta.     

Early postoperative outcome and hemodynamic performance of the sorin pericarbon stentless aortic valve

BACKGROUND AND AIMS OF THE STUDY: Stentless aortic bioprostheses offer potential advantages in terms of durability and hemodynamic performance. The study aim was to evaluate the early postoperative performance of the Sorin Pericarbon stentless bioprosthesis. METHODS: Between November 1999 and December 2000, 34 patients (12 males, 22 females; mean age 71.2 +/- 4.8 years; range: 48-85 years) underwent aortic valve (AV) replacement with the Sorin Pericarbon stentless bioprosthesis. Twenty-two patients were in NYHA classes III-IV, and 12 were in classes I-II. Twenty-one patients had AV stenosis, nine AV regurgitation, and four mixed pathology. Doppler-echocardiography was performed before surgery, at hospital discharge and at six-month follow up. At this time, 20 patients also underwent echo-Doppler stress testing, with peak transvalvular gradient measured at rest and during exercise. RESULTS: There were two hospital deaths (not valve-related). No significant perioperative complications were recorded. At hospital discharge, the aortic peak gradient was 15.7 +/- 10.6 mmHg; nil or trivial aortic regurgitation was found in three patients. During six months follow up no endocarditis or thromboembolic events were registered. At six months postoperatively, the transvalvular peak gradient showed a small but significant decrease (11.3 +/- 3.5 mmHg at six months, p = 0.036). Mean left ventricular mass index was also decreased significantly (118.4 +/- 28.5 versus 98.4 +/- 17.8 g/m2, p = 0.024). Left ventricular ejection fraction and effective orifice area were not changed significantly during follow up. In patients undergoing exercise testing (mean maximal workload 96 +/- 48 W), the peak aortic gradient was increased (not significantly) at exercise peak (from 14.7 +/- 6.5 to 17.2 +/- 6.7 mmHg, p = 0.086). CONCLUSION: The excellent early postoperative outcome of this experience with the Sorin Pericarbon stentless valve encourages the use of this prosthesis. Long-term follow up and further evaluations are required with regard to hemodynamic performance and durability.     

Hemodynamic performance of the Ultracor and Carpentier-Edwards aortic prostheses using exercise and dobutamine stress echocardiography

BACKGROUND AND AIM OF THE STUDY: The study aim was to compare the hemodynamic profiles of the aortic standard porcine Carpentier-Edwards (C-E) and Ultracor (tilting-disc) valve using exercise and dobutamine stress. METHODS: A total of 36 patients was examined, 18 for each valve type. When analyzing the data, valve types were matched for valve size, which ranged from 21 to 25 mm. All patients were analyzed within an 18-month period after implantation. Hemodynamic variables, two-dimensional echocardiography and Doppler flows were recorded at rest. These were repeated during bicycle ergometry, performed for a maximum of four, 3-min stages, with each stage increasing in workload by 20 W. After resting, patients were subjected to dobutamine stress, administered up to a maximum 40 microg/kg/min, dependent upon heart rate. RESULTS: Mean (+/- SD) resting pressure drops across the C-E and Ultracor valves were comparable (maximum drop 19.4 +/- 8.6 versus 22.9 +/- 12.2 mmHg; mean drop 9.96 +/- 3.8 versus 11.83 +/- 6.6 mmHg, respectively). During exercise, the maximum cardiac flow rate attained was approximately 400 ml/s for both valve types. At this flow rate, the maximum and mean pressure differences between valve types were 6.2 mmHg and 4.4 mmHg, respectively (p = NS). During dobutamine stress, the maximum cardiac flow attained was approximately 500 ml/s, which resulted in significant differences between valve types of 11.6 and 7.3 mmHg, for maximum and mean pressure drops, respectively. When slopes of the mean pressure drop/cardiac flow were calculated for individual valves, a difference was observed between the two valve types (p = 0.02 and p = 0.039 for dobutamine and exercise, respectively). CONCLUSION: Both prostheses demonstrated significant increases in pressure drop under stress conditions. The standard porcine C-E valve had a statistically better hemodynamic profile than the Ultracor prosthesis at higher flow rates. When a study cohort of patients is small, these differences will only be evident at optimal flow rates. The higher flow rates seem most easily obtained when using pharmacological stress.     

Ten-year outcome with the sorin bicarbon and Baxter Mira bileaflet prostheses in the aortic position

BACKGROUND AND AIM OF THE STUDY: Sorin Bicarbon (SB) and Baxter Mira (BM) are almost identical bileaflet prostheses that share the same mechanical design, the only difference being in the sewing cuff. Hence, the long-term clinical performance of the two prostheses, when implanted in the aortic position, was evaluated in a combined population of patients. METHODS: Between January 1992 and December 2002, 714 patients (454 males, 260 females; mean age 60 +/- 13 years) underwent single aortic valve replacement with SB (n = 392) or BM (n = 322) valves. Concomitant non-valve procedures were performed in 64 patients (9.5%). Follow up was 95.7% complete, with a mean of 3.1 +/- 2.4 years. RESULTS: Operative mortality was 5.4% (39/714). Overall patient survival at five and 10 years was 89.3 +/- 1.4% and 77.7 +/- 4.3%, respectively; the linearized rate was 3.37% per pt-yr. Overall freedoms from complications at 10 years and valve group freedoms at four years were: thromboembolism 92.9 +/- 3.6% (SB 96.8 +/- 1.2% versus BM 98.4 +/- 0.8%); bleeding 94.5 +/- 3.5% (SB 97.5 +/- 1.1% versus BM 98.5 +/- 0.5%); nonstructural dysfunction 85.8 +/- 7.5% (SB 97.1 +/- 1.2% versus BM 99.3 +/- 0.07%); endocarditis 98.0 +/- 1.2% (SB 98.6 +/- 0.9% versus BM 100%); reoperation 95.1 +/- 3% (SB 98.6 +/- 0.9% versus BM 100%). Neither structural dysfunction nor valve thrombosis were observed. At the end of follow up, 78.3% of survivors were in NYHA class I, 17.3% in class II, 3.6% in class III, and 0.8% in class IV. CONCLUSION: Experience with Sorin Bicarbon and Baxter Mira valve prostheses shows that these valves, when implanted in the aortic position, provide a satisfactory clinical performance, with low complication rates.     

Quantitative assessment of regional left ventricular motion using endocardial landmarks

Doppler echocardiography was performed in 136 patients with a normally functioning prosthetic valve in the aortic (n = 59), mitral (n = 74) and tricuspid (n = 3) positions. These included patients with St. Jude (n = 82), Bj?rk-Shiley (n = 18), Beall (n = 13), Starr-Edwards (n = 7) or tissue (n = 16) valves. Peak and mean pressure gradients across the prostheses were measured using the simplified Bernoulli equation. The prosthetic valve orifice (PVO, in square centimeters), only in the mitral position, was calculated by the equation: PVO = 220/pressure half-time. In the aortic position, the St. Jude valve had a lower peak velocity (2.3 +/- 0.6 m/s, range 1.0 to 3.9), peak gradient (22 +/- 12 mm Hg, range 4 to 61) and mean gradient (12 +/- 7 mm Hg, range 2 to 32) than the other valves (p less than 0.05) when compared with Starr-Edwards). In the mitral position, the St. Jude valve had the largest orifice (3.0 +/- 0.6 cm2, range 1.8 to 5.0) (p less than 0.0001 compared with all other valves). Insignificant regurgitation was commonly found by pulsed mode Doppler technique in patients with a St. Jude or Bj?rk-Shiley valve in the aortic or mitral position and in patients with a Starr-Edwards or tissue valve in the aortic position. In 17 other patients with a malfunctioning prosthesis (four St. Jude, two Bj?rk-Shiley, four Beall and seven tissue valves) proven by cardiac catheterization, surgery or autopsy, Doppler echocardiography correctly identified the complication (significant regurgitation or obstruction) in all but 2 patients who had a Beall valve. It is concluded that 1) the St. Jude valve appears to have the most optimal hemodynamics; mild regurgitation can be detected by the Doppler technique in normally functioning St. Jude and Bj?rk-Shiley valves in the aortic or mitral position and in Starr-Edwards and tissue valves in the aortic position, and 2) Doppler echocardiography is a useful method for the detection of prosthetic valve malfunction, especially when the St. Jude, Bj?rk-Shiley and tissue valves are assessed.     

Doppler evaluation of the Sorin and Medtronic-Hall prostheses in the aortic position

Doppler characteristics of normally functioning tilting disk prostheses in aortic position were studied in 55 patients (30 Medtronic-Hall and 25 Sorin) whose valvular function was considered normal using clinical and echocardiographic evaluation. Peak gradients, mean gradients and effective orifice area were estimated for different sizes of prostheses. The peak gradient calculated from maximal aortic velocity was 27.3 +/- 11.1 mmHg in Sorin and 21.1 +/- 9.7 mmHg in Medtronic-Hall valves; the mean gradients were 12.9 +/- 6.2 mmHg and 10.8 +/- 5.7 mmHg in Sorin and Medtronic-Hall valves respectively. The effective orifice area calculated by the continuity equation was 1.4 +/- 0.5 cm2 in Sorin and 1.5 +/- 0.57 cm2 in Medtronic-Hall prostheses; the performance index calculated as the ratio between functional area and manufactured area was 0.4-0.6 for Medtronic-Hall and 0.45-0.52 for Sorin prostheses. Prosthetic regurgitation was found in 64% of Sorin valves and 80% of Medtronic-Hall valves; prosthetic regurgitation was mild in 81% and moderate in 19% of cases. Doppler echocardiography is a reliable method for the characterization of the normal function of prosthetic aortic valves and provides information similar to cardiac catheterization.     

A single-center experience of the Sorin Bicarbon heart valve prosthesis: long-term clinical, hematological and hemodynamic results

BACKGROUND AND AIM OF THE STUDY: The Sorin Bicarbon (SB) bileaflet valve, available since 1990, has a good clinical safety profile. The study aim was to assess the long-term clinical results following implantation, plus hemodynamic and hematological aspects of the valve. METHODS: A total of 195 SB prostheses (100 aortic, 67 mitral, 14 double valve replacements) was implanted in 181 patients (108 males, 73 females) since 1991. RESULTS: Mean age at implantation was 60.5 +/- 10.8 years. Actuarial analysis at 9.0 years showed an overall survival of 63.9 +/- 5.5%; 28.2% of deaths were early (n = 11), and 71.8% late (n = 28). Freedom from thrombosis was 99.4 +/- 0.6% (one early event, successfully reoperated on), and from embolic events was 86.3 +/- 4.7%. Freedom from endocarditis and hemorrhagic complications were respectively 98.1 +/- 1.1% and 98.6 +/- 0.9%. No occurrence of hemolysis was reported. Freedom from non-structural valve dysfunction was 98.7 +/- 0.9%, and from reoperation was 96.1 +/- 1.6%. Hemodynamic evaluation by echocardiography and hematological testing was performed at 7.0 +/- 1.3 years (range 5-9 years) in a subset of 31 patients (20 males, 11 females). Mean valve size was 23.9 mm for aortic mitral. Echocardiography showed that aortic valves had a mean effective orifice area (EOA) of 2.26 +/- 1.28 cm2, with peak and mean pressure gradients of 23.6 +/- 14.6 and 12.9 +/- 8.1 mmHg, respectively. The mean EOA of mitral valve prostheses was 2.67 +/- 0.66 cm2, with peak and mean pressure gradients of 12.2 +/- 4.5 and 3.8 +/- 1.6 mmHg, respectively. Overall mean hemoglobin was 13.4 +/- 1.35 g/dl, and serum lactate dehydrogenase 630 +/- 13 IU/l. Serum haptoglobin was detectable in one patient only, and the mean reticulocyte count was 1.24 +/- 0.51%. CONCLUSION: In the present authors' experience, the Sorin Bicarbon prosthesis has low complication rates and maintains an excellent hemodynamic function over time. Hemolytic potential is insignificant with this valve.     

Comparison of On-X and SJM HP bileaflet aortic valves

BACKGROUND AND AIM OF THE STUDY: The study aim was to evaluate the hemodynamic function after aortic valve replacement (AVR) using the On-X valve, in comparison with St. Jude Medical (SJM) HP bileaflet valves. METHODS: Patients received either the On-X (n = 20) or SJM HP prosthesis (n = 20) for AVR. The control (SJM HP) group was computer-matched with the On-X group for age, gender, aortic stenosis as underlying disease, body surface area, NYHA functional class, left ventricular size, mass and function, transvalvular pressure gradients and cardiac index. Mean implanted valve size was 23.5 mm (three 21 mm, ten 23 mm, six 25 mm, one 27 mm) in both groups. All patients underwent postoperative, and six- and 12-month follow up echocardiography. RESULTS: The intra- and postoperative course was uneventful in all patients. There were no significant differences in cross-clamp and cardiopulmonary bypass times, intensive care unit stay, in-hospital stay and postoperative NYHA functional class. Two patients (both On-X) had paravalvular leakage postoperatively and at follow up. Five patients in the control group had additional myocardial revascularization. Transvalvular flow velocities were 2.38 +/- 0.3 versus 2.38 +/- 0.4 m/s (p = NS) postoperatively, and 2.08 +/- 0.2 versus 2.22 +/- 0.3 m/s (p = NS) at one year follow up for On-X and SJM HP valves, respectively. Maximum pressure gradients were 16.9 +/- 6.0 versus 18.5 +/- 8.0 mmHg (p = NS) postoperatively and 14.0 +/- 3.7 versus 16.5 +/- 5.7 mmHg (p = NS) at one year for the two valve types, respectively. A relatively pronounced transvalvular reflux was diagnosed for On-X valves. CONCLUSION: At one year after implantation, the On-X bileaflet prosthesis is equally suited for AVR in comparison with the 'standard' therapy (SJM HP). Exact sizing requires some experience. There were no significant differences between the two prostheses with regard to hemodynamic parameters either postoperatively or at one-year follow up. Long-term prospective randomized studies yet have to be carried out.     

Contribution of Doppler echocardiography in the evaluation of normal and pathologic aortic valve prosthesis

Doppler echocardiography was performed in 112 patients with normal aortic valve prostheses and 13 patients with dysfunction (3 obstructions, 10 regurgitations) confirmed at catheterisation and/or surgery. The maximum and mean transprosthetic pressure gradients were measured in all patients by continuous wave Doppler. The prosthetic valve surface area was calculated by applying the continuity equation in the last 67 patients and compared with the effective surface area deduced from hemodynamic studies in the literature: --There was a great variability in the values of mean pressure gradient and prosthetic valve area within each group and with each size of prosthesis in patients with normal valves. No significant difference was observed between the gradients of different prostheses. However, for a given size, the St Jude Medical prosthesis had larger calculated surface areas than the other prostheses. The Doppler valve surface area did not differ significantly from the area measured invasively for the different categories of prostheses, and it increased with the size of the prosthesis. Mild aortic regurgitation was observed in 16 per cent of bioprostheses and 30 per cent of mechanical prostheses. The three cases of obstruction were characterised by a high mean pressure gradient (59 +/- 16 mmHg, p less than 0.01 vs normal prostheses) and a reduced Doppler surface area (0.7 +/- 0.2 cm2, p less than 0.005 vs normal prostheses) and were correctly diagnosed by Doppler echocardiography. Eight of the ten prosthetic regurgitations were correctly quantified by Doppler. Cardiac Doppler coupled with echocardiography is a very valuable method of non-invasive assessment of aortic valve prostheses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dobutamine stress echocardiography and left ventricular mass changes of mechanical aortic valve replacement in four years follow-up

AIM: The aim of this study was to investigate the differences in cardiac response to stress according to the size of the prosthetic valve in patients who underwent aortic valve replacement (AVR) and to evaluate the relationship between the size of the prosthetic valve and cardiac recovery-remodeling after the operation. METHODS: Thirty patients who had undergone AVR (12 patients) or double valve replacement (18 patients) underwent dobutamine-stress echocardiography 4.2 years after the operation to evaluate response to stress . They were divided into 2 groups according to valve prosthesis size. The small-size AVR group (group 1, n=17) had prosthetic aortic valves 21 pounds mm; the large-size AVR group (group 2, n=13) had valves >21 mm. Response to stress and preoperative and postoperative echocardiographic findings were compared. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Peak and mean aortic gradients, left ventricular diastolic and systolic functions were measured for each group. RESULTS: Dobutamine stress increased heart rate and blood pressure in both groups. Peak pressure gradient across the aortic valve prostheses was 42.1 mm Hg in group 1 and 20.9 mm Hg in group 2 (P<0.05) at rest. After dobutamine infusion, the peak pressure gradient across the aortic valve prostheses increased to 85.1 mm Hg in group 1 and 54 mm Hg in group 2 (P<0.05). Isovolumetric relaxation time returned to normal in both groups following dobutamine infusion; this decrease was significant only in group 1. Patients achieved a decrease in left atrium and left ventricular diameters and volumes, as evidence of remodeling following AVR. Left ventricular mass index (LVMI) decreased from 127.6+/-47.6 to 98.1+/-36.9 and from 159.9+/-16.1 to 125.3+/-10.1 in groups 1 and 2, respectively, but this decline was not statistically significant. CONCLUSIONS: Smaller valves have higher gradients and this significant difference increases under stress. Significant improvement in echocardiographic diameters, cardiac filling volumes and LVMI reflects the benefit of the operation. Cardiac remodeling is independent of valve size, although high transprosthetic gradients occur during stress conditions.     

Usefulness of the indexed effective orifice area at rest in predicting an increase in gradient during maximum exercise in patients with a bioprosthesis in the aortic valve position

This study examines the hemodynamic behavior of aortic bioprosthetic valves during maximum exercise. Nineteen patients with a normally functioning stented bioprosthetic valve and preserved left ventricular function were submitted to maximum ramp bicycle exercise. In 14 of the 19 patients, valve effective orifice area and mean gradient were measured at rest and during exercise using Doppler echocardiography. At peak exercise (mean maximal workload 118 +/- 53 W), the cardiac index increased by 122 +/- 34% (+3.18 +/- 0.71 L/min/ m2, p <0.001), whereas mean gradient increased by 94 +/- 49% (+12 +/- 8 mm Hg, p <0.001), and effective orifice area by 9 +/- 13% (+0.15 +/- 0.22 cm2, p = 0.02). A strong correlation was found between the increase in mean gradient during maximum exercise and the valve area at rest indexed for body surface area (r = 0.84, p <0.0001). Due to the increase in valve area, the increase in gradient was less (-9 +/- 7 mm Hg, -41 +/- 33%, p = 0.0006) than theoretically predicted assuming a fixed valve area. These results suggest that the effective orifice area of the bioprostheses has the capacity to increase during exercise; therefore, limiting the increase in gradient. The relation found between the indexed effective orifice area at rest and the increase in gradient during exercise should be useful in predicting the hemodynamic behavior of a stented bioprosthesis during exercise.     

Noise levels of closing sounds in vivo are equal for different bileaflet mechanical heart valves

BACKGROUND AND AIM OF THE STUDY: Patients with mechanical heart valves must endure the valve's closing sounds for the rest of their life. Sound pressure levels (SPLs) recorded show wide patient-to-patient variation, even for the same type of valve. The variation was attributed to body constitution variability and differences in hemodynamic status. It was hypothesized that aortic mechanical valves generate closing clicks which correlate in magnitude with hemodynamic parameters, such as the rate of relaxation of the left ventricle (dp/dt) and potential energy stored in the aortic windkessel. METHODS: Three different aortic mechanical heart valves were investigated in a porcine model (n = 9), namely St. Jude Medical, CarboMedics and ATS. Closing sounds were measured with a microphone placed in a portable anechoic chamber 10 cm above the exposed heart. Left ventricular pressure (LVP) and cardiac output were also measured. Different hemodynamic conditions were produced by intravenous infusion of isotonic saline and dobutamine. Volume regulation and atrial pacing were also applied. RESULTS: Different hemodynamic situations were established (cardiac output, 1.2-6.5 l/min; heart rate, 99-171 bpm). The measured mean SPLs were 49.5-53.9 dB(A), and there were no statistically significant differences in noise between the valves (p = 0.8; one-way ANOVA). Likewise, only a weak relationship was identified between different hemodynamic parameters and the SPLs recorded. CONCLUSION: The SPLs of the investigated bileaflet mechanical heart valves did not differ significantly. Moreover, the SPL was only weakly related to LVP during closure and estimated stroke work.     

Doppler echocardiography in 180 normally functioning St. Jude Medical aortic valve prostheses. Early and late postoperative assessments

Limited Doppler echocardiographic data are available regarding velocities and gradients across normally functioning St. Jude Medical valves in the aortic position. To establish a standard reference for Doppler characteristics of normal aortic St. Jude Medical prostheses, we recorded continuous-wave Doppler measurements of peak and mean velocities and peak and mean gradients in 180 patients with normally functioning St. Jude aortic valves. There were 119 men and 61 women in the study; the mean age was 57 years. Minimal valvular regurgitation was present in 56 patients (31 percent). Velocities and gradients were reported in five patient groups according to valve sizes of 19 mm, 21 mm, 23 mm, 25 mm, and 27 mm; the mean gradients were 16 +/- 6, 16 +/- 6, 14 +/- 5, 12 +/- 5, and 12 +/- 6, respectively. Differences in velocities and gradients among the five valve sizes were not statistically significant (p = 0.05). Velocities and gradients were also analyzed in three patient groups according to time intervals after valve replacement. The first group (n = 64) underwent Doppler evaluation one to seven days postoperatively (mean, six days); the second group (n = 60) was evaluated after 8 to 30 days postoperatively (mean, 12 days); and the third group (n = 56) was evaluated after more than 30 days postoperatively (mean, 691 days). There were no significant differences in measurements for the three groups.     

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)     

Aortic valve repair versus replacement in bicuspid aortic valve disease

BACKGROUND AND AIM OF THE STUDY: The study aim was to compare the results of aortic valve repair and replacement with biological valves in adult patients with aortic insufficiency (AI) caused by congenital bicuspid aortic valve (BAV) METHODS: Forty-four patients who had aortic valve repair were matched for age and left ventricular function to 44 patients who had aortic valve replacement (AVR) with biological valves. Patients were followed annually using echocardiography. The mean follow up was 2.6 +/- 2.1 years for the repair group, and 3.5 +/- 2.1 years for the replacement group. Follow up was complete. RESULTS: There was no operative or late death in either group. Early postoperative echocardiography showed trace or no AI in 35 patients and mild AI in nine who had repair, and trace or no AI in 38 patients and mild AI in five who had AVR. The mean peak systolic gradient was 16.2 +/- 7.6 mmHg for repair and 13.2 +/- 7.2 mmHg for AVR. Four patients who had valve repair and two who had AVR, needed repeat aortic valve surgery because of progressive AI or endocarditis. Freedom from reoperation at five years was 91 +/- 5% for repair and 94 +/- 6% for replacement (p = 0.2), while freedom from moderate or severe AI at five years was 79 +/- 8% for repair and 94 +/- 6% for replacement (p = 0.024). The peak systolic gradient at follow up was 11.7 +/- 6.8 mmHg after repair and 13.3 +/- 9.6 mmHg after AVR (p = 0.4). There were no thromboembolic complications in either group. CONCLUSION: Repair of BAV is feasible in certain patients with AI, but the hemodynamics and clinical outcomes do not appear to be superior to AVR with biological valves during the first five years of follow up.     

Heart valve replacement with the St. Jude medical prosthesis -- first clinical results --.

Starting in February 1978 52 St. Jude Medical Prostheses have been implanted in 47 patients (age 13--73 years) in aortic, mitral and tricuspid positions. Perioperative death occurred in 3 cases. Post mortem examination of these patients showed unimpaired valvular function. There were no other complications in an accumulated total valve time of approximately 300 months. Prior to surgery and post-operatively, several hemolytic parameters were analyzed. There was only a mild elevation in Serum LDH (285 +/- 10 iV/L). Fifteen patients underwent recatheterization 3 months postoperatively. The mitral valves did not reveal an enddiastolic gradient at rest, while the aortic valves had a peak to peak gradient of 8 +/- 2.1 mmHg. A standardized stress consisting of an infusion of isoproterenol was used. The results were compared to results obtained in patients with Bj?rk-Shiley prostheses under identical conditions and did not show a significant difference. The preliminary hemodynamic findings correlate with preceding in vitro results and preclinical data, and the first clinical experience is promising.