In vitro study of the aortic interleaflet triangle reshaping

Aortic interleaflet triangle reshaping (AITR) is a surgical approach to aortic valve incontinence that involves placing three stitches at half of the interleaflet triangles height. In this work, the relationship between the actual stitch height and valve functioning, and the safety margin that the surgeon can rely on in applying the stitches were systematically investigated in vitro. AITR surgery was applied to six swine aortic roots placing the stitches empirically at 50%, 60% and 75% of the triangle heights. Then the actual stitch heights were measured and the hydrodynamic performances were evaluated with a pulsatile hydrodynamic mock loop. Actual stitch heights were 45\ub12%, 61\ub14% and 79\ub16%. As compared to untreated conditions, the 50% configuration induced a significant variation in the effective orifice area. With stitches placed at 60%, the mean systolic pressure drop increased significantly with respect to the untreated case, but no significant changes were recorded with respect to the 50% configuration. At 75%, all the hydrodynamic parameters of systolic valve functioning worsened significantly. Summarizing, the AITR technique, when performed in a conservative manner did not induce significant alterations in the hydrodynamics of the aortic root in vitro, while more aggressive configurations did. The absence of a statistically significant difference between the 50% and 60% configurations suggests that there is a reasonably limited risk of inducing valve stenosis in the post-op scenario due to stitch misplacement

Aortic interleaflet triangles reshaping : hydrodynamic, kinematic and morphological effects in in-vitro analysis

BACKGROUND AND AIM OF THE STUDY: Subcommissural triangles reshaping is a reparative technique used to remodel the ventriculo-aortic junction. The study aim was to evaluate, by means of in-vitro testing, the effects of this technique on hemodynamics, leaflet kinematics and aortic root functional unit morphology. METHODS: Twenty-one porcine aortic roots were tested in a pulsatile mock loop under basal conditions and after subcommissural triangles reshaping performed at 50% of the interleaflet triangles height. During each test, hydrodynamic quantities, high-speed digital videos and echocardiographic images were recorded. RESULTS: The comparison between pre- and post-surgery data showed a statistically significant increase in coaptation height (p < 0.01) and length (p < 0.01). Significant reductions were found in the virtual basal ring diameter (p < 0.01), sinus of Valsalva diameters (p < 0.01), maximum leaflet opening (p < 0.01), leaflet opening before rapid valve closing time (p < 0.01) and maximum opening area (p < 0.01). An opened valve time reduction (p <0.01) was observed due to an opening time reduction (p < 0.01), offset by a closed valve time increase (p < 0.01). A slow closing period increase (p < 0.07) and a rapid closing phase reduction (p < 0.01), were also highlighted without influence on the total closing time. A statistical, but not clinically significant, increase in pressure drop across the valve (p < 0.01) and an effective orifice area reduction (p < 0.01) were observed. CONCLUSION: Subcommissural triangles reshaping performed at 50% of the interleaflet triangles' height determines an increase in leaflet coaptation by remodeling the ventriculo-aortic junction. Some hydrodynamic and kinematic changes also occur, without any acute clinically threatening alterations

In vitro study of a standardized approach to aortic cusp extension

Purpose: Cusp extension technique (CET) is a reparative surgical procedure for restoring aortic valve function by suturing patches to the compromised native leaflets. Its outcomes are strongly dependent on the ability of the surgeon. We proposed and tested a novel approach on an in vitro model, aimed at standardizing and simplifying the surgical procedure. Methods: A set of standard pre-cut bovine pericardium patches, available in different sizes, was developed. The surgeon can choose the leaflet-specific patches to be implanted according to the patient anatomy, using a geometrical model of the aortic valve whose inputs are the measured intercommissural distances. The hemodynamic performance of this approach was evaluated on porcine aortic roots in a pulsatile mock loop. Hydrodynamic and kinematic evaluation of the samples was provided. Results: After CET, mean and maximum pressure drops were 3.1 \ub1 1.3 mmHg and 25.4 \ub1 5.0 mmHg respectively, and EOA was 3.8 \ub1 0.8 cm2. Static regurgitant fraction and closing volumes were 6.9 \ub1 2.7% and 7.0 \ub1 1.5 mL, respectively. All the hemodynamics changes induced by the surgery were statistically significant yet clinically irrelevant as compared to baseline. The treatment also induced a statistically significant alteration in the closing time of the valve. Conclusions: Our approach to cusp extension proved to be reliable and effective in restoring valve functioning, without significantly altering the physiological kinematics. The use of pre-cut patches considerably simplified the surgery, increasing standardization and repeatability

A novel passive left heart platform for device testing and research

Integration of biological samples into in vitro mock loops is fundamental to simulate real device's operating conditions. We developed an in vitro platform capable of simulating the pumping function of the heart through the external pressurization of the ventricle. The system consists of a fluid-filled chamber, in which the ventricles are housed and sealed to exclude the atria from external loads. The chamber is connected to a pump that drives the motion of the ventricular walls. The aorta is connected to a systemic impedance simulator, and the left atrium to an adjustable preload.The platform reproduced physiologic hemodynamics, i.e. aortic pressures of 120/80mmHg with 5L/min of cardiac output, and allowed for intracardiac endoscopy. A pilot study with a left ventricular assist device (LVAD) was also performed. The LVAD was connected to the heart to investigate aortic valve functioning at different levels of support. Results were consistent with the literature, and high speed video recordings of the aortic valve allowed for the visualization of the transition between a fully opening valve and a permanently closed configuration.In conclusion, the system showed to be an effective tool for the hemodynamic assessment of devices, the simulation of surgical or transcatheter procedures and for visualization studies