Current Status of Measurement Accuracy for Total Hemoglobin Concentration in the Clinical Context.

OBJECTIVE: The main objective of this investigation is to provide data about the accuracy of total hemoglobin concentration measurements with respect to clinical settings, and to devices within the categories of point-of-care and reference systems. In particular, tolerance of hemoglobin concentrations below 9 g/dL that have become common in clinical practice today determines the need to demonstrate the limits of measurement accuracy in patient care. METHODS: Samples extracted from six units of heparinized human blood with total hemoglobin concentrations ranging from 3 to 18 g/dL were assigned to the test devices in a random order. The pool of test devices comprised blood gas analyzers, an automatic hematology analyzer, a laboratory reference method, and the point-of-care system HemoCue. To reduce the pre-analytic error, each sample was measured three times. Due to the characteristics of the tested devices and methods, we selected the mean values of the data from all these devices, measured at the corresponding total hemoglobin concentrations, as the reference. MAIN RESULTS: The measurement results of the test devices overlap within strict limits (R2 = 0.999). Only the detailed analysis provides information about minor but systematic deviations. In the group of clinically relevant devices, which are involved in patient blood management decisions, the relative differences were within the limit of +/- 5 % for values down to 3 g/dL. CONCLUSIONS: A clinically relevant change of +/- 0.5 g/dL of total hemoglobin concentration can be detected with all selected devices and methods. Compliance with more stringent definitions-these are the relative differences of 5 % in relation to the corresponding reference values and the clinically adapted thresholds in the format of a tolerance level analysis-was achieved by the clinical devices assessed here.

Impact of high-pressure balloon aortic valvuloplasty on the hydrodynamic result after a transcatheter valve-in-valve procedure.

OBJECTIVES: The aim of this study was to investigate the degree of functional improvement of a transcatheter heart valve (THV) for valve-in-valve after bioprosthetic valve fracture (BVF) of three small surgical aortic valve bioprostheses (SAVBP) using high-pressure balloon aortic valvuloplasty (HP-BAV) under standardized ex-vivo-conditions. METHODS: A THV 26 mm (Evolut R) and SAVBP 21 mm (Perimount Magna Ease, Trifecta, and Epic supra [n = 4] were used. Mean pressure gradient (MPG), effective orifice area (EOA), geometric orifice area (GOA), minimal internal diameter (MID), and pinwheeling index (PWI) were analyzed before and after HP-BAV of the SAVBP using a noncompliant balloon. Fracturing of the SAVBP was done before implantation of the THV and the balloon pressures at the point of fracture were recorded. RESULTS: The Magna Ease and Epic fractured at balloon pressures of 18 and 8 atm, respectively. The Trifecta did not fracture up to a balloon pressure of 30 atm but was dilated. HP-BAV led to increased THV expansion as evident by straightened coaptation lines of the Evolut R 26 mm with reduced PWI, increased MID, and increased GOA in all 21 mm SAVBP. Evolut R showed significantly lower MPG and higher EOA as ViV in all prostheses after HP-BAV (p < 0.001). MPG and EOA of Evolut R differed regarding the SAVBP. Evolut R presented the lowest MPG and highest EOA in Magna Ease and the highest MPG and lowest EOA in Epic supra. CONCLUSIONS: The degree of function improvement of the same THV as ViV after HP-BAV depends on the surgical valve model. Functional improvement can also be achieved without valve fracture.

Functional performance of 8 small surgical aortic valve bioprostheses: an in vitro study.

OBJECTIVES: Selection of a surgical aortic valve (SAV) bioprosthesis model for the treatment of aortic valve disease remains controversial. The aim of this study was to characterize the functional performance of 8 SAV models in a standardized in vitro setting. METHODS: The hydrodynamic performance of 8 SAVs with labelled size 21 mm (Avalus™, Hancock® II, Mosaic® Ultra™, Perimount®, Perimount® Magna Ease, Epic™ Supra, Trifecta™ GT; Freestyle®), was investigated in a pulse duplicator. Transvalvular pressure gradients and effective orifice area (EOA) were recorded. The geometrical orifice area and physical dimensions of the valves were determined, and new functional dimensions were introduced. RESULTS: Mean pressure gradient (MPG) and EOA differed significantly between the analysed SAVs. The Epic presented with the lowest EOA and highest MPG, while the Trifecta showed the highest EOA and the lowest MPG. We introduce a useful way to determine the minimal internal diameter and a new measure termed 'relative orifice area' to characterize a valve's performance. CONCLUSIONS: SAVs showed significant differences in their hydrodynamic performance despite the same label size. This finding was related to the construction of the valves. We introduce a new measure that characterizes the functional performance of a valve model and size for the treatment of an aortic annulus of a specific size. Our data emphasize that SAV selection should carefully be done using an individual patient approach and that future research is necessary to improve the current generation of SAVs.

Ex vivo evaluation of the Ozaki procedure in comparison with the native aortic valve and prosthetic valves.

OBJECTIVES: We investigated the hydrodynamic performance and cusp kinematics of the Ozaki neocuspidized aortic valve in comparison with the native aortic and prosthetic valves in an ex vivo study. METHODS: Native aortic valves of swine hearts were replaced by aortic valve substitutes, and their hydrodynamic performance (effective orifice area and mean pressure gradient) was evaluated in a mock circulation under defined conditions. The following aortic valve substitutes were investigated: native aortic valve, Ozaki valve, Perimount Magna Ease, Trifecta and St. Jude Medical Masters. All prosthetic valves had a labelled size of 21 mm. RESULTS: The Ozaki valve and native aortic valve showed a similar and significantly larger orifice area than all investigated prosthetic valves particularly at high flow rates. There was no significant difference between the Ozaki valve and the native aortic valve. The native aortic valve and Ozaki valve showed a similar increase in orifice area with increasing flow through the valve while prosthetic valves showed a markedly weaker increase. Similarly, the native and Ozaki valve showed a similar increase in mPG with forward flow which was weaker than prosthetic valves. Cusp kinematics were similar between the native and Ozaki valve, whilst prosthetic valves were clearly distinguishable from them. CONCLUSIONS: The Ozaki procedure showed excellent hydrodynamic performance compared to prosthetic valves and showed similar cusp motion characteristics to the native aortic valve. Our results suggest that the Ozaki neocuspidized valve behaves physiologically in many aspects, which may contribute to beneficial clinical outcomes.

The figure-of-8 aortic valve suturing technique optimizes the effective orifice area of a small aortic annulus-an ex vivo study.

OBJECTIVES: Surgical aortic valve replacement (SAVR) in small annuli carries an elevated risk for the patient-prosthesis mismatch. In this study, we systematically investigated the influence of different implantation techniques including annular enlargement (AE) on the functional result after SAVR in small annuli using a standardized ex vivo model. METHODS: SAVR using the PERIMOUNT Magna Ease® (PME) 21 mm was performed in small porcine aortic roots using 4 implantation techniques: non-everting pledgeted (NE) suture, single interrupted (SI) suture, continuous suture (CS), figure-of-8 (F8) suture, as well as the PME 23 mm after AE using the Nunez method and the NE suture technique (PME23 AE). The effective orifice area (EOA), mean pressure gradient and leakage volume were evaluated using a mock circulation loop in accordance with ISO regulations. RESULTS: Experiments were conducted on 31 porcine aortic roots. PME21 using F8 and PME23 after AE achieved a significantly larger EOA than using NE. PME23 after AE showed a larger EOA than the PME21 using any suture technique, except the F8 [for stroke volume of 74 ml: PME21 NE: 1.68 (1.63-1.72) cm2, PME21 SI: 1.76 (1.68-1.81) cm2 (P = 0.17), PME21 CS: 1.76 (1.65-1.79) cm2 (P = 0.14), PME21 F8: 1.81 (1.70-1.85) cm2 (P = 0.005); PME23 AE: 1.83 (1.73-1.92) cm2 (P < 0.001)]. SI and CS did not result in larger EOA compared with the NE technique. PME21 using SI had a significantly larger leakage volume than using NE and there was no significant difference between other techniques [for stroke volume of 74 ml: PME21 NE: 3.51 (1.85-4.53) ml/stroke, PME21 SI: 6.00 (4.02-7.06) ml/stroke (P < 0.001), PME21 CS: 4.04 (3.60-4.49) ml/stroke (P = 0.10), PME21 F8: 3.16 (1.99-3.62) ml/stroke (P = 0.74), PME23 NE: 2.89 (2.45-4.72) ml/stroke (P = 0.51)]. CONCLUSIONS: The F8 technique with the PME21 achieved a similar EOA as the 1 size larger PME23 using NE after AE. These results suggest that the F8 technique may be an effective surgical modification to improve the haemodynamic result in a small annulus without additional AE.

Impact of different valve-in-valve positions on the hydrodynamic performance of the newest-generation self-expanding transcatheter heart valve.

OBJECTIVES: Transcatheter aortic valve-in-valve (ViV) procedures are increasingly performed for the treatment of degenerated surgical aortic valves with a high risk for a redo operation. For an optimal functional result, precise positioning of the transcatheter heart valve (THV) inside the SHV is crucial. The aim of this study was to systematically investigate the impact of implantation depth on the functional result after a ViV procedure in a standardized in vitro setting. METHODS: A THV 23 mm (Evolut PRO) and 3 SHV 21 mm (Perimount Magna Ease, Trifecta and Hancock II) were used for hydrodynamic testing with a constant heartbeat 64/min and a range of 55-105 ml of stroke volume in 5 different positions of the THV. The following parameters were analysed: mean pressure gradient (MPG), effective orifice area (EOA), geometric orifice area, minimal internal diameter and pin-wheeling index. RESULTS: MPG and EOA differed significantly regarding the position of the THV in the same SHV. The highest EOA and the lowest MPG were recorded for Evolut PRO with significance for both parameters in Hancock II at 4 vs 5 mm (P < 0.001), in Magna Ease at 2 mm (vs 3 mm and vs 6 mm, P < 0.001) and in Trifecta at 4 mm (vs 5 and 6 mm, P < 0.001). Leaflet coadaptation, minimal internal diameter and maximal geometric orifice area of the same TAV differ regarding the position of the TAV. CONCLUSIONS: The optimal position for hydrodynamic performance of the THV as ViV differs among specific SHV models. The findings may be useful for planning a ViV procedure using the Evolut PRO THV.

An ex vivo evaluation of two different suture techniques for the Ozaki aortic neocuspidization procedure.

OBJECTIVES: We investigated the Ozaki procedure using a single interrupted suture technique (SST) and compared this with the standard continuous suture technique (CST) with regard to hydrodynamic valve performance. In addition, both techniques were compared with the native aortic valve (NAV). METHODS: Effective orifice area, mean pressure gradient and leakage volume were evaluated in the NAV as well as after an Ozaki procedure using SST or CST in fresh swine aortic roots using a mock circulation loop. The NAV, SST and CST were evaluated under 4 defined hydrodynamic conditions. RESULTS: Both suture techniques resulted in a similar effective orifice area under all conditions [for stroke volume of 70 ml: SST: 1.50 (1.35-1.87) vs CST: 1.57 (1.41-1.72) cm2, P = 0.8] and there were no significant differences between both suture techniques and the NAV (P > 0.05). Regarding mean pressure gradient, the Ozaki procedure with SST and CST showed no significant differences [7.23 (5.53-8.91) vs 7.04 (6.65-7.60) mmHg, P = 0.72] and there was no significant difference between both suture techniques and the NAV (P > 0.1). In leakage volume, there was no significant difference between SST and CST [4.49 (3.91-4.99) vs CST: 4.23 (3.58-4.87) ml/stroke, P = 0.34]. CONCLUSIONS: The Ozaki procedure with SST performed similarly to that with CST with regard to hydrodynamic performance. Our results suggest that the Ozaki procedure can be performed with SST instead of CST, which may be useful in patients with limited surgical exposure, such as a small annulus.

Aortic valve replacement in sheep with a novel trileaflet mechanical heart valve prosthesis without anticoagulation.

Background: Even after decades of intensive research, an ideal heart valve prosthesis remains elusive. Shortcomings of conventional devices include reduced durability of bioprostheses and the thrombogenicity of mechanical substitutes, necessitating anticoagulation and resulting in imperfect hemodynamics. Here we present in vivo results of a novel mechanical heart valve prosthesis aiming for freedom from anticoagulation. Methods: Four female sheep had their aortic valves replaced using the novel mechanical heart valve (size 21 mm), with no postoperative anticoagulation treatment. This trileaflet heart valve was designed with the pivots in the systolic central flow. Hemodynamics, biochemistry, hematology, and macroscopy and microscopy were studied at 90 days in 2 sheep and at 1 year in the other 2 sheep. Results: Mean (<6 mm Hg) and peak (<10 mm Hg) aortic transvalvular gradients remained low during the study period. Aortic regurgitation was trivial, and central traces were only rarely observed. The rate of thrombotic events was very low, with none macroscopically and microscopically visible thrombotic material on the device. Biochemistry and hemotology were unchanged without hemolysis. In 3 sheep, the fibrous pannus and mitral leaflet were partially folded over the edge of the annular body. Apart from organic/inorganic deposits on the leaflets after 1 year, the ultrastructurally evaluated leaflets were similar to those of nonimplanted controls. Conclusions: The preliminary in vivo results of this novel anticoagulation-free aortic mechanical heart valve are promising with excellent hemodynamics and a very low risk of thrombotic events.

In vitro 4D Flow MRI evaluation of aortic valve replacements reveals disturbed flow distal to biological but not to mechanical valves.

BACKGROUND AND AIM OF THE STUDY: Aortic hemodynamics influence the integrity of the vessel wall and cardiac afterload. The aim of this study was to compare hemodynamics distal to biological (BV) and mechanical aortic valve (MV) replacements by in vitro 4D Flow MRI excluding confounding factors of in-vivo testing potentially influencing hemodynamics. METHODS: Two BV (Perimount MagnaEase [Carpentier-Edwards], Trifecta [Abbott]) and two MV (On-X [CryoLife], prototype trileaflet valve) were scanned in a flexible aortic phantom at 3T using a recommended 4D Flow MR sequence. A triphasic aortic flow profile with blood-mimicking fluid was established. Using GTFlow (Gyrotools), area and velocity of the ejection jet were measured. Presence and extent of sinus vortices and secondary flow patterns were graded on a 0 to 3 scale. RESULTS: A narrow, accelerated central ejection jet (Area = 27 ± 7% of vessel area, Velocity = 166 ± 13 cm/s; measured at sinotubular junction) was observed in BV as compared to MV (Area = 53 ± 13%, Velocity = 109 ± 21 cm/s). As opposed to MV, the jet distal to BV impacted the outer curvature of the ascending aorta and resulted in large secondary flow patterns (BV: n = 4, grades 3, 3, 2, 1; MV: n = 1, grade 1). Sinus vortices only formed distal to MV. Although physiologically configured, they were larger than normal (grade 3). CONCLUSIONS: In contrast to mechanical valves, biological valve replacements induced accelerated and increased flow patterns deviating from physiological ones. While it remains speculative whether this increases the risk of aneurysm formation through wall shear stress changes, findings are contrasted by almost no secondary flow patterns and typical, near-physiological sinus vortex formation distal to mechanical valves.

A novel trileaflet mechanical heart valve: first in vitro results.

OBJECTIVES: Heart valve prostheses are the therapy of choice for patients with severe heart valve diseases. Two types of prostheses that can be implanted in patients are available: biological and mechanical. Though mechanical heart valves have some disadvantages like necessity of life-long anticoagulation, biological heart valve prostheses often necessitate reinterventions due to limited durability. Therefore, a new trileaflet mechanical heart valve was developed, featuring hinges in the systolic flow with the aim of function and thrombogenicity. METHODS: We first compared the new trileaflet mechanical heart valve to conventional bileaflet heart valves (St. Jude Medical and On-X valves) in vitro. Haemodynamic measurements were performed in a pulse duplicator system, and clot formation was examined with an implemented method using enzyme-activated milk as the test medium. RESULTS: Haemodynamic measurements showed the largest effective orifice areas and smallest pressure gradients for the trileaflet prosthesis compared to the bileaflet valve. Opening and closing characteristics of the trileaflet valve and of the St. Jude Medical valve were comparable. Clotting tests depicted only minor isolated deposits for the new trileaflet valve whereas the bileaflet valves showed distinct clots in the area of the hinge in all experiments. CONCLUSIONS: Haemodynamic and clotting tests showed improvements for the new trileaflet valve compared to common bileaflet valves. The off-wall systolic position of the hinges, which eluded adverse flow areas, was a major advantage of the new valve.

Novel stent design for transcatheter mitral valve implantation.

OBJECTIVES: In this study, results of a functional in vitro study of 2 newly developed valved stents for transcatheter mitral valve implantation are presented. METHODS: Two novel stent designs, an oval-shaped and a D-shaped stent with a strut fixation system were developed. The fixation force of the novel stents were tested in vitro in porcine hearts with a tensile test set-up. In further experiments, the stents were equipped with a circular valved stent, and the valve performances were investigated in a pulsatile heart valve tester. RESULTS: Sufficient mean stent fixation forces in the range of 24.2 ± 0.9 N to 28.6 ± 1.9 N were measured for the different stent models. The novel valved stents showed good performance in an in vitro pulsatile heart valve tester. A sufficient opening area and low opening pressures were measured for all tested mitral valved stents. Compared with an established reference valve, the D-shaped stent and the oval-shaped valved stent showed a lower systolic transvalvular pressure gradient, which indicates slightly greater extent of valvular leakage of the closed valved stents. However, the mitral nitinol valved stents demonstrated adequate durability. CONCLUSIONS: This study indicates a sufficient annular fixation force of the tested transcatheter mitral valve implantation valved stent prototypes. Therefore, these mitral valved stents demonstrate a new type of mitral valved stent design.