Bileaflet Mechanical Prosthesis Research Articles

Platelet inhibition by aspirin after aortic valve replacement

Methods Subjects and drug administration. This study was conducted in agreement with the Declaration of Helsinki and was approved by the institutional ethics committee. Fifteen consecutive patients were included who underwent an elective aortic valve replacement with bileaflet mechanical prostheses (St Jude Medical). Informed consent was obtained from each participant. Drugs affecting hemostasis (including aspirin) had been terminated at least 7 days before surgical intervention. Antithrombotic therapy was initiated the first day after surgical intervention with heparin (3 10,000 IU administered subcutaneously). At day 3 after surgical intervention, anticoagulation with a vitamin K antagonist (phenprocoumon) was initiated, and heparin was terminated when a target international normalized ratio (INR) of 2.5 had been reached. Measurement of platelet function. One day before and at days 1, 5, and 10 after surgical intervention arachidonic acid (1 mmol/L)–induced aggregation and thromboxane formation were determined in venous blood samples. 2 Because thromboxane formation by platelet cyclooxygenase is the pharmacologic target of aspirin, the sensitivity of platelets to aspirin in vitro was determined by means of addition of aspirin (100 mol/L). Statistics. Data are presented as mean values the standard error of the mean. Statistical analyses were performed with 2-way analysis of variance for repeated measurements with the Tukey post-hoc test.

Characteristics of Pulsatile Blood Flow Through the Curved Bileaflet Mechanical Heart Valve Installed in Two Different Types of Blood Vessels: Velocity and Pressure of Blood Flow

The aim of this study was to investigate the flow fields of blood flowing through the curved bileaflet mechanical heart valve. A numerical analysis was carried out with the fluid-structure interaction between the blood flow and the motion of leaflets in two different types of blood vessels (type A, with sinus blood vessel, and type B, without sinus blood vessel). When the leaflet was fully opened, a fluttering phenomenon was detected in association with the blood flow, and recirculation flows were observed in the sinus region of the blood vessel for type A. During the closing phase, regurgitation was formed between the ring and the edge of the each leaflet for both types. When the leaflet came into contact with the valve ring at the end of the closing phase, rebound of the leaflet occurred. In consideration of the entire domain, the pressure drop occurs mainly in the valve region. The present results showed tendencies similar to those obtained by previous experiments for blood flow and contribute to the development of the curved bileaflet mechanical heart valve prostheses.

Tricuspid replacement and short-term follow-up: summary of 42 cases

To summarize the experience in tricuspid valve replacement (TVR). From March 1997 to June 2004, 42 patients underwent isolated or combined TVR. Of the cases, 20 cases had prior cardiac operation (tricuspid valve had been repaired in 8). Indication of TVR: (1) irreparable and/or progressive tricuspid lesions; (2) intolerable tricuspid dysfunction after tricuspid repair. Instead of tricuspid repair, TVR was preferred when one of the following co-existed: moderate to severe increase of pulmonary vascular resistance; residual left heart dysfunction; previously repaired tricuspid. Simultaneous replacement after unsuccessful tricuspid repair had to be done in 14 cases. Valve replacement combinations were isolated TVR in 30 cases, tricuspid and aortic and mitral in 8, tricuspid and mitral in 3, tricuspid and aortic in 1. Fourteen tissue and 28 bi-leaflet mechanical valve prostheses were used in the tricuspid position. Other simultaneous procedures included corrections of congenital anomalies in 10 patients, repair of peri-prosthetic leakage, resection of myxoma and coronary artery bypass grafting in 1 case each. The operative mortality was 17%, and mortality 31%. Four patients died of low cardiac output. Massive cerebral thromboembolism, renal failure and dyscrasia was the cause of death in 1 case each. Post-operative heart function NYHA classification: 21 cases in I, 10 in II, 1 in III and 1 in IV. Late death occurred in 2 cases. TVR is preferable for a severely damaged or deformed tricuspid valve if the possibility of successful repairing is small, especially when accompanied pulmonary vascular disease and uncorrected lesions and/or dysfunction of the left heart co-exists.

Time-resolved particle image velocimetry and laser doppler anemometry study of the turbulent flow field of bileaflet mechanical mitral prostheses

Dynamic particle image velocimetry (PIV) was applied to the study of the flow field associated with prosthetic heart valves. The results were compared with those of laser Doppler anemometry (LDA). Anatomically and antianatomically oriented Jyros (JR) and St. Jude Medical (SJM) valves were compared in the mitral position to study the effects of valve design on the downstream flow field. The experimental program used a dynamic PIV system utilizing high-speed, high-resolution video to map the true time-resolved velocity field inside the simulated ventricle. This system was complemented by a study using the more traditional LDA system for comparison. Based on the experimental data, the following general conclusions can be made. High-resolution dynamic PIV can capture true chronological changes in the velocity and turbulence fields. It also produces very detailed velocity and turbulence information comparable to the LDA results. In the vertical measuring plane that passes both the center of the aortic and mitral valves (A-A section), the two valves (the SJM and the JR) show distinct circulatory flow patterns when the valve is installed in the antianatomical orientation. Small differences in valve design can generate noticeable differences, particularly during the accelerating flow phase. The SJM valve maintains a relatively high velocity through the central orifice; the curved leaflets of the JR valve generate higher velocities with a divergent flow during the accelerating and peak flow phases. In the velocity field directly below the mitral valve and normal to the previous measuring plane (B-B section), where characteristic differences in valve design will be visible, symmetrical twin circulations were observed because of the divergent nature of the flow generated by the two inclined half-disks installed in the antianatomical orientation. The SJM valve, with a central downward flow near the valve, is contrasted with the JR valve, which has a peripheral downward circulation with higher, turbulent stresses.

Changes in aortic root function after valve replacement in patients with aortic stenosis

Background Aortic elastic properties are compromised in various states that induce functional and histological changes in the aortic wall. Aortic stenosis is frequent and often requires replacement of the stenotic valve. The purpose of this study was to examine the effect of aortic valve replacement on the aortic root function. Methods 31 patients, mean ± SD age 67.2 ± 9.1 years with severe aortic stenosis, who underwent aortic valve replacement with a bileaflet mechanical prosthesis, were studied. Aortic root function indices such as aortic cross-sectional compliance (CSC), aortic root distensibility (ARD), and aortic stiffness index (ASI) were calculated with the use of M-mode echocardiography in three sessions: one preoperatively (pre-op), one on day 7 postoperatively (early post-op), and one 6 months postoperatively (late post-op). Results Aortic root function deteriorated early post-op ( p < 0.001 for all) and returned towards pre-op levels late post-op ( p = NS for all). CSC changed from 2.84 ± 1.98 to 1.37 ± 0.92, and 2.30 ± 1.11 cm 2/mmHg, ARD from 2.21 ± 5.60 to 1.01 ± 0.67, and 1.79 ± 0.96 cm 2/dyne, and ASI from 9.72 ± 5.60 to 24.65 ± 19.10, and 11.51 ± 7.85, respectively. Correlations were found between early changes in some aortic root indices and the degree of aortic stenosis, denoting that aortic function deteriorated less in more severe cases of aortic stenosis. None of the late changes were related to aortic valve or left ventricular indices. Conclusions Aortic valve replacement with a mechanical valve results in a significant but transient impairment of aortic distensibility.

Design and in Vitro Performance of a Novel Bileaflet Mechanical Heart Valve Prosthesis

Design and in vitro performance of a novel bileaflet mechanical heart valve prosthesis are presented. The novel heart valve exhibits three main design characteristics: (i) The leaflets form a Venturi passage in open position. Thus, a beneficial pressure distribution is obtained and the leaflets are stabilised in opened position. (ii) The orifice inlet is nozzle-shaped. Flow is convectively accelerated and flow separation at the orifice inlet is avoided. (iii) The hinge design facilitates an additional axial movement of the leaflets and leads to a self cleaning effect and enhances washout of the hinges. The design of the leaflet hinges is of main importance for the functional reliability and durability of mechanical heart valves. After manufacturing first prototypes from titanium and polymeric materials the hydrodynamic performance was evaluated according to ISO 5840 and FDA guidelines. Hydrodynamic performance is comparable with the results of commonly available bileaflet mechanical heart valve prostheses. Initial durability tests showed suitable material couples for further long term studies.

Small aortic annulus: The hydrodynamic performances of 5 commercially available bileaflet mechanical valves

ObjectiveHemodynamic performances of mechanical valve prostheses in patients with aortic valve stenosis and a small aortic annulus are crucial. We analyzed the in vitro hydrodynamics of 5 currently available bileaflet mechanical prostheses that fitted a 21-mm-diameter valve holder of a Sheffield pulse duplicator. MethodsThree samples of 5 high-performance production-quality prostheses, including the sewing ring cuffs, were tested in the aortic chamber of a Sheffield pulse duplicator. Sizes of the prostheses fitting the 21-mm valve holder were as follows: 18-mm ATS, 19-mm SJM Regent, 19-mm Sorin Bicarbon Slimline, 19-mm On-X, and 21-mm Carbomedics Top Hat. The tests were carried out at a fixed pulse rate (70 beats/min) and at increasing cardiac outputs of 2, 4, 5, and 7 L/min. Each valve was tested 10 times for each different cardiac output. This resulted in a total of 40 tests for each valve and 120 tests for each valve model. The aortic pressure was set at 120/80 mm Hg (mean pressure, 100 mm Hg) throughout the experiment for all cardiac outputs. Forward flow pressure decrease, total regurgitant volume, closing and leakage volumes, effective orifice area, and stroke work loss were recorded while the valve operated under each cardiac output. ResultsThe SJM Regent valve and the Sorin Bicarbon Slimline prosthesis showed the lowest mean and peak gradients at increasing cardiac outputs. The closure volume was higher for the SJM Regent and Sorin Bicarbon Slimline prostheses, unlike with the ATS prosthesis at 7 L/min of cardiac output. The ATS and SJM Regent prostheses showed the largest regurgitant volume, whereas the Sorin Bicarbon Slimline prosthesis showed the lowest regurgitant volume. The calculated effective orifice area and stroke work loss were significantly better with the SJM Regent and Sorin Bicarbon Slimline prostheses. ConclusionAssuming that the 21-mm valve holder in which all the tested prostheses were accommodated is comparable with a defined aortic valve size, this hydrodynamic evaluation model allowed us to compare the efficiency of currently available valve prostheses, and among these, the SJM Regent and the Sorin Bicarbon Slimline exhibited the best performances.

Particle image velocimetry for flow analysis in longitudinal planes across a mechanical artificial heart valve.

In the last decades a great number of in vitro studies have been conducted to improve the design and to understand the transvalvular flow patterns under steady-state and pulsating flow conditions. Steady-state tests are useful for studying the flow established upstream and downstream of the valve prosthesis in different flow conditions and, in particular, at the peak flow rate. In the present study, the particle image velocimetry (PIV) technique is employed to visualize the flow patterns in a precommercial model of a bi-leaflet mechanical heart valve prosthesis in a steady-state flow regime. The use of the PIV technique and a convenient test rig provide good conditions with which to investigate the whole flow field upstream and downstream of the valve. Velocity and vorticity maps are obtained for the flow passing through the prosthesis in different axial planes. A new and simple solution for the measurement test chamber is proposed. This innovative approach of observing the flow in staggered planes (other than diametrical planes) allows a flow analysis to be performed upstream and downstream of the valve in regions near the tube wall where it has the maximum potential for injury of the vessel's inner cell layer.

Late results after mitral valve replacement with bileaflet mechanical prosthesis in children: evaluation of prosthesis-patient mismatch

Background Mechanical prosthesis is the choice of valve at the mitral position in children, although re-replacement of prostheses because of prosthesis-patient mismatch is almost inevitable when prostheses were implanted in small children. The methods to predict prosthesis-patient mismatch as a result of patients' somatic growth or pannus formation in children by noninvasive methods have not been well established. Methods Thirty-two children underwent mitral valve replacement with 37 bileaflet mechanical prostheses (26 St. Jude Medical prosthetic valves, and 11 CarboMedics prosthetic valves) and were followed up a mean of 6.8 years (maximum 18.3 years) with a complete follow-up rate of 94%. Results There were no operative deaths and 5 late deaths. Re-replacement of mitral valve because of prosthesis-patient mismatch was required in 5 patients. Freedom from valve-related events and re-replacement of mitral valve at 15 years were 32% ± 23% and 54% ± 18%, respectively. Actuarial survival rate was 63% ± 19% at 15 years. Prosthetic valve orifice area index (manufactured geometric prosthetic valve area divided by patient's body surface area) was well correlated with maximum transprosthesis flow velocity estimated by Doppler echocardiography during follow-up, whereas valve orifice area index had no significant correlation with pulmonary artery wedge pressure assessed by cardiac catheterization. Maximum transprosthesis flow velocity had a significant correlation with pulmonary artery wedge pressure. Conclusions Valve orifice area index itself was not a reliable index to predict prosthesis-patient mismatch. Maximum transprosthesis flow velocity was a useful index to predict pulmonary artery wedge. Invasive cardiac catheterization to determine re-replacement of the prosthesis should be considered when maximum transprosthesis flow velocity exceeds 270 cm/s.

An unusual complication after chordal sparing mitral valve replacement

J Thorac Cardiovasc Surg 2004;127:599-600 Miomir Dj. Jovic and Miroslav M. Jakovljevic Dusko G. Nezic, Milan M. Vukovic, Milan V. Cirkovic, Aleksandar M. Knezevic,An unusual complication after chordal sparing mitral valve replacement http://jtcs.ctsnetjournals.org/cgi/content/full/127/2/599 located on the World Wide Web at: The online version of this article, along with updated information and services, is

Development of an animal experimental model for a bileaflet mechanical heart valve prosthesis.

The objective of this study was to develop a pre-clinical large animal model for the in vivo hemodynamic testing of prosthetic valves in the aortic position without the need for cardiopulmonary bypass. Ten male pigs were used. A composite valved conduit was constructed in the operating room by implanting a prosthetic valve between two separate pieces of vascular conduits, which bypassed the ascending aorta to the descending aorta. Prior to applying a side-biting clamp to the ascending aorta for proximal grafting to the aortic anastomosis, an aorta to femoral artery shunt was placed just proximally to this clamp. The heart rate, cardiac output, Vmax, transvalvular pressure gradient, effective orifice area and incremental dobutamine stress response were assessed. A dose dependant increase with dobutamine was seen in terms of cardiac output, Vmax, and the peak transvalvular pressure gradient both in the native and in the prosthetic valve. However, the increment was much steeper in the prosthetic valve. No significant differences in cardiac output were noted between the native and the prosthetic valves. The described pre-clinical porcine model was found suitable for site-specific in-vivo hemodynamic assessment of aortic valvular prosthesis without cardiopulmonary bypass.

A structural analysis on the leaflet motion induced by the blood flow for design of a bileaflet mechanical heart valve prosthesis

This paper presents a structural analysis on the rigid and deformed motion of the leaflet induced by the blood flow required in the design of a bileaflet mechanical heart valve (MHV) prosthesis. In the study on the design and the mechanical characteristics of a bileaflet mechanical heart valve, the fluid mechanics analysis on the blood flow passing through leaflets, the kinetodynamics analysis on the rigid body motion of the leaflet induced by the pulsatile blood flow, and the structural mechanics analysis on the deformed motion of the leaflet are required sequentially and simultaneously. Fluid forces computed in the previous hemodynamics analysis on the blood flow are used in the kinetodynamics analysis on the rigid body motion of the leaflet. Thereafter, the structural mechanics analysis on the deformed motion of the leaflet follows to predict the structural strength variation of the leaflet as the leaflet thickness changes. Analysis results show that structural deformations and stresses increase as the fluid pressure increases and the leaflet thickness decreases. Analysis results also show that the leaflet becomes structurally weaker and weaker as the leaflet thickness becomes smaller than 0.6 mm.

The Carbomedics Top Hat supraannular aortic valve: a multicenter study

Background Introduced in 1993, the Carbomedics Top Hat (Sulzer, Carbomedics, Austin, TX) valve is a bileaflet mechanical aortic prosthesis designed to be placed in a supraannular position. Five institutions pooled their clinical experiences to evaluate early outcome in patients with this prosthesis. Methods From 1994 to 2000, 639 patients underwent aortic valve replacement with Top Hat (Sulzer Carbomedics) valves at 5 institutions. Mean age was 60 ± 13 years. In this heterogeneous population, 28% of patients had previous cardiac operations and 64% had concomitant procedures, including procedures involving more than 1 heart valve in 32%. Implanted prostheses sizes included the 19 mm (15%), 21 mm (37%), 23 mm (33%), 25 mm (13%), and 27 mm (2%). Mean follow-up was 2.0 ± 1.5 years, and there were 1,206 patient-years of follow-up available for analysis. Results Thirty-day mortality was 5.3%. Five-year survival was 74%. Risk factors for death included older age ( p = 0.01), decreased ejection fraction ( p = 0.007), and increased New York Heart Association functional class ( p = 0.003). Five-year freedoms from thromboembolism and hemorrhage were 90% and 85%, respectively. Five-year freedoms from explant and endocarditis were both 99%. There were no structural valve failures. Conclusions The Top Hat valve outcomes have been similar to those of the standard Carbomedics intraannular prostheses. The unique design of the Top Hat valve, with all its components in the aortic sinuses, has particular advantages in the small aortic root, in settings where leaflet entrapment may occur, and in multiple valve replacement.

Impact of high intensity transient signals on the choice of mechanical aortic valve substitutes.

High intensity transient signals (HITS) observed during extracorporeal circulation and following mechanical valve replacement are suspected of causing cognitive dysfunction (deterioration of episodic and working memory). This study evaluates the role played by valve design (bileaflet versus tilting disc) and other parameters in the incidence of HITS. Thirty patients were selected for the study as follows: 18 males, 58-78 years of age; ten St. Jude Medical, ten CarboMedics, ten Medtronic Hall (MH); all size 23, in optimum orientation (Ann Thorac Surg 68 (1999) 1069); all in sinus rhythm; no coronary or carotid artery disease; all in sinus rhythm, international normalized ratio greater than 2.5 and all at least 9 months postoperative. All patients had bilateral HITS measurement in both middle cerebral arteries via transcranial doppler for 30 min. If five HITS or more were observed during the initial 10 min, patients were subjected to 100% oxygen breathing followed by 10 min of normal air breathing. Simultaneously, HITS were measured in the right radial and femoral arteries. Patients with bileaflet valve substitutes revealed HITS rates varying from 32 to 108 counts/h. There was only one HITS observed in the MH valve group during the 5h observation period (0.2 HITS/h). There were no HITS detected in either the radial or the femoral arteries in any patient. After breathing 100% oxygen, HITS significantly decreased or completely disappeared (0-30 HITS/h). When normal air breathing was resumed HITS reappeared or increased. With an intravenous infusion of 100 mg of lysine acetylsalicylate (Aspisol, Bayer Leverkusen, Germany), HITS decreased by 16 to 41%. We conclude that bileaflet mechanical valve prostheses produce HITS even in their optimum orientation. HITS following bileaflet valve replacement have an unstable nature and might be composed of nitrogen and platelets. Tilting disc valves in their optimum orientation provide almost physiological conditions with HITS measured in the same range as bioprosthesis.

Modified button-Bentall operation for aortic root replacement: the miniskirt technique

Background. The aim of this study was to evaluate the midterm results of a modified button-Bentall operation (modified-bB) specifically designed to incorporate any type of prosthetic valve in composite conduit aortic root replacement. Methods. Between 1991 and 2000, a total of 135 patients underwent modified-bB for annuloaortic ectasia (74 patients), type A dissection (31), or aortic aneurysm without dissection (30). Of these, 34 were emergencies (25.2%). A total of 50 bioprostheses (study group 1) and 85 bileaflet mechanical prostheses (study group 2) were implanted. Group 1 mean age was 66.9 ± 7.4 years versus 51.5 ± 12.1 years in group 2 ( p < 0.001). Composite-conduit creation occurred during proximal suture line construction as a single-step maneuver. Interrupted extracardiac polyester mattress sutures sequentially entered the aortic annulus, the prosthetic valve ring, and the vascular graft 7 mm from its free edge (miniskirt). Running monofilament suture line secured proximal hemostasis, buttressing aortic remnants and graft edge. Coronary reimplantation was accomplished in all cases by the button technique. Concomitant procedures were performed in 51 patients (37.8%). Results. The 30-day mortality was 5.18% (7/135 patients). Eight patients (5.9%) required revision for proximal (1 patient), coronary button (3), or distal (4) anastomosis leakage. Three patients (2.2%) perioperatively developed nonfatal inferior myocardial infarction. Kaplan-Meier 9-year survival is 91.8% ± 0.026 SE with 88.1% (95% confidence limits 71.7% to 95.5%) reoperation freedom. According to the Cox proportional hazard method, stratification of the risk for death according to prosthesis type indicates previous operation ( p = 0.001) and emergency ( p = 0.0465) as independent predictors of hospital mortality. Associated procedures to modified-bB increased risk of reoperation ( p = 0.031). Conclusions. Modified-bB was associated with low mortality, excellent midterm survival, and freedom from reoperation. Absence of valve-to-graft tapering, reduced coronary button anastomosis tension, and prosthesis selection according to patient profile, are apparent advantages of modified-bB.

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 μg · kg −1 · min −1 and increased to 30 μg · kg −1 · 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.

Severe intermittent intraprosthetic regurgitation after mitral valve replacement with subvalvular preservation

Preservation of the subvalvular apparatus during mitral valve replacement preserves left ventricular function and improves long-term survival. Complications of subvalvular preservation include left ventricular outflow tract obstruction and prosthesis impingement. We report a case of severe intermittent intraprosthetic mitral regurgitation detected by transesophageal echocardiography after mitral valve replacement by a bileaflet mechanical prosthesis with subvalvular preservation. Intravalvular prosthetic valve regurgitation was caused by remnants of the subvalvular apparatus, which were shown at reoperation to interfere with prosthetic leaflet motion and which were excised. Postoperative transesophageal echocardiography showed neither abnormal mitral regurgitation nor residual mass. The use of intraoperative transesophageal echocardiography could enable the detection of this rare complication. (J Am Soc Echocardiogr 2001;14:314-6.)

Gradiente residual em operação de valva aórtica

OBJECTIVES: Evaluate residual pressure gradients after aortic valve replacement surgery in our Institution. MATERIAL AND METHODS: Between January 1988 and December 1998, 44 patients with isolated aortic stenosis underwent surgery and received a valve prosthesis size 23 or smaller. Echocardiographic studies were performed at our Institution before surgery and six months postoperatively. There were 28(63.6%) males, with an average age of 53.9, and an average body surface area of 1.67 m2. Preoperative average transvalvar pressure gradient was 95.8 mmHg. Twelve patients were in functional class II, 28 in class III, and 4 in class IV. Bioprostheses were implanted in 25 patients, and mechanic prostheses in the other 19, 11 of which received a bileaflet prostheses. RESULTS: Six months after surgery 35 (79.5%) patients were in functional class I, and 9 (20.5%) in class II. Average gradient variation was 62.9 mmHg. The average residual postoperative gradient was 32.9 mmHg. The gradient reduction was not influenced by sex, age, body surface area, or size of the valve prosthesis. The gradient variation was directly proportional to the preoperative gradient. Regarding type of valve prosthesis, the average residual gradient was 24.3 mmHg for the bileaflet mechanical prosthesis, 33.7 mmHg for the bioprosthesis, and 42.3 mmHg for the single leaflet mechanical prosthesis. CONCLUSION: Gradient variation was directly influenced by the preoperative gradient. The best results regarding residual gradients were achieved with bileaflet mechanical prostheses, followed by bioprostheses and single leaflet mechanical prostheses. Use of a smaller than recommended for body surface area prosthesis, avoiding aortic annulus enlargement procedures, was not related to higher residual gradients in this group of patients.

Assessment of prosthetic aortic valve performance by magnetic resonance velocity imaging

Objectives: Magnetic resonance (MRI) velocity mapping was used to evaluate non-invasively the flow profiles of the ascending aorta in normal volunteers and in patients with an aortic (mechanical) valve prosthesis. Background: In patients with artificial aortic valves the flow profile in the ascending aorta is severely altered. These changes have been associated with an increased risk of thrombus formation and mechanical hemolysis. Methods: Velocity profiles were determined 30 mm distal to the aortic valve in six healthy volunteers and seven patients with aortic valve replacement (replacement within the last 2 years) using ECG triggered phase contrast MRI. Peak flow, mean flow and mean reverse flow were measured in intervals of 25 ms during the entire heart cycle. Systolic reverse flow, end-systolic closing and diastolic leakage volume were calculated for all subjects. Results: Peak flow velocity during mid-systole was significantly higher in patients with valvular prosthesis than in normals (mean±SD, 1.9 ±0.4 m/s vs. 1.2±0.03 m/s, P <0.001) with a double peak and a zone of reversed flow close to the inner (left lateral) wall of the ascending aorta of the patients. Closing volume was significantly larger in patients than in controls (−3.3±1.2 ml/beat vs. −0.9±0.5 ml/beat; P <0.001). There was reverse flow during systole in valvular patients amounting to 15.7±6.7% of total cardiac output compared to 2.3±1.2% in controls ( P <0.001). Diastolic mean flow was negative in patients after valve replacement but not in controls (−11.0±15.2 ml/beat vs. 6.8±3.2 ml/beat; P <0.01). Conclusions: The following three major quantitative observations have been made in the present study: (1) Mechanical valve prostheses have an increased peak flow velocity with a systolic reverse flow at the inner (left lateral) wall of the ascending aorta. (2) A double peak flow velocity pattern can be observed in patients with bileaflet (mechanical) prosthesis. (3) The blood volume required for leaflet closure and the diastolic leakage blood volume are significantly higher for the examined bileaflet valve than for native heart valves.

Assessment of prosthetic aortic valve performance by magnetic resonance velocity imaging.

Magnetic resonance (MRI) velocity mapping was used to evaluate non-invasively the flow profiles of the ascending aorta in normal volunteers and in patients with an aortic (mechanical) valve prosthesis. In patients with artificial aortic valves the flow profile in the ascending aorta is severely altered. These changes have been associated with an increased risk of thrombus formation and mechanical hemolysis. Velocity profiles were determined 30 mm distal to the aortic valve in six healthy volunteers and seven patients with aortic valve replacement (replacement within the last 2 years) using ECG triggered phase contrast MRI. Peak flow, mean flow and mean reverse flow were measured in intervals of 25 ms during the entire heart cycle. Systolic reverse flow, end-systolic closing and diastolic leakage volume were calculated for all subjects. Peak flow velocity during mid-systole was significantly higher in patients with valvular prosthesis than in normals (mean + SD, 1.9 +/- 0.4 m/s vs. 1.2 +/- 0.03 m/s, P < 0.001) with a double peak and a zone of reversed flow close to the inner (left lateral) wall of the ascending aorta of the patients. Closing volume was significantly larger in patients than in controls (-3.3 +/- 1.2 ml/beat vs. -0.9 +/- 0.5 ml/beat; P < 0.001). There was reverse flow during systole in valvular patients amounting to 15.7 +/- 6.7% of total cardiac output compared to 2.3 +/- 1.2% in controls (P < 0.001). Diastolic mean flow was negative in patients after valve replacement but not in controls (-11.0 +/- 15.2 ml/beat vs. 6.8 +/- 3.2 ml/beat; P < 0.01). The following three major quantitative observations have been made in the present study: (1) Mechanical valve prostheses have an increased peak flow velocity with a systolic reverse flow at the inner (left lateral) wall of the ascending aorta. (2) A double peak flow velocity pattern can be observed in patients with bileaflet (mechanical) prosthesis. (3) The blood volume required for leaflet closure and the diastolic leakage blood volume are significantly higher for the examined bileaflet valve than for native heart valves.