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Sensor-Enabled 3D Printed Tissue-Mimicking Phantoms: Application in Pre-Procedural Planning for Transcatheter Aortic Valve Replacement
Published in Ayman El-Baz, Jasjit S. Suri, Cardiovascular Imaging and Image Analysis, 2018
Kan Wang, Chuck Zhang, Ben Wang, Mani A Vannan, Zhen Qian
The 3D model of the aortic valve should be reconstructed at a late systolic cardiac phase, in which the aortic valve has the maximum annular diameter. Therefore, the pre-TAVR CT images at peak aortic valve opening are identified and used to produce the 3D model of the aortic root. A research software (CT Auto Valve, Siemens Corporate Technology, Princeton, NJ) is used to semi-automatically segment the images and produce a single-layer 3D model of the aortic root, which consists of the arterial wall and the valvular leaflets, as shown in Figure 13.9. Proprietary in-house software has been further developed to refine the 3D model by extending the model into the ascending aorta and the left ventricular outflow tract (LVOT). The lowest level of the model was empirically set to 10 mm below the aortic valve annulus. In addition, our software empirically adds a 2.0-mm wall thickness to the aortic root and a 0.5-mm thickness to the leaflets.
Aortic Valve Mechanics
Published in Michel R. Labrosse, Cardiovascular Mechanics, 2018
J. Dallard, M. Boodhwani, M. R. Labrosse
The AV is classically divided into different structures to make the description easier (Berdajs, 2015). The so-called aortic root is the biological structure at the transition between the left ventricular outflow tract and the ascending aorta. This transition is a complex and mixed structure, both part of the left ventricle from a physiological point of view and part of the aorta from a morphological point of view. The aortic root is mainly composed of the three sinuses of Valsalva located between the ventriculoaortic junction (VAJ) and the sinotubular junction (STJ). The three sinuses of Valsalva are outwardly ballooned regions of the aortic wall (Figure 9.1a), with an approximately hemispherical shape (Thubrikar, 1989). Two of these sinuses include orifices for the coronary arteries. There is a leaflet or cusp inside each sinus of Valsalva (Sauren et al., 1980).
SPECT Imaging of Cardiac Adrenergic Receptors
Published in Robert J. Gropler, David K. Glover, Albert J. Sinusas, Heinrich Taegtmeyer, Cardiovascular Molecular Imaging, 2007
In patients presenting with idiopathic ventricular tachycardia and fibrillation, no structural or functional abnormalities of the myocardium can be demonstrated by conventional imaging and clinical testing. Early diagnosis and treatment are of clinical importance because ventricular fibrillation is the most common arrhythmia at the time of sudden death (7). Typical arrhythmias in these patients can be provoked by physical or mental stress or by catecholamine application. Schaffers et al. (8), using 123I-MIBG, 11C-hydroxyephedrine and 11C-CGP, have demonstrated that in patients with idiopathic right ventricular outflow tract tachycardia, both the presynaptic myocardial catecholamine reuptake and the postsynaptic myocardial β-adrenoceptors density are reduced despite normal blood catecholamine levels. These scintigraphic findings represent the only demonstrable myocardial abnormality in patients with idiopathic tachycardia and fibrillation, and suggest that myocardial β-adrenoceptor downregulation in these patients occurs subsequently to increased local synaptic catecholamine levels caused by impaired catecholamine reuptake (9).
Comparison of patients with bicuspid and tricuspid aortic valve in transcatheter aortic valve implantation
Published in Expert Review of Medical Devices, 2023
Zhongkai Zhu, Tianyuan Xiong, Mao Chen
BAV is independently associated with an increased risk of THV malpositioning or embolism (OR 3.43, 95% CI 2.03–5.82) [73], either a ‘pop-up’ into the ascending aorta or ‘slip’ into the left ventricular outflow tract. Maintaining the position of the prosthesis at the target landing zone during deployment can be challenging, and up to 30% of patients with BAV require repositioning when using SEV [16]. Moreover, an extensive retrospective analysis showed that 1.7% of patients with BAV and 1.2% of those with tricuspid anatomy (P = 0.002) required a second valve during TAVI procedures to reduce severe PVL after slipping into the left ventricular outflow tract and avoid the need for conversion to open surgery [6]. Intraprocedural use of snare catheters may aid deployment and positioning for improved alignment and unsatisfactory outcomes. Moreover, the final valve position can be suboptimal when repositioning is not feasible or successful, resulting in residual high transvalvular gradients or PVL. Balloon postdilatation is mostly required to improve the hemodynamic outcome in both situations but exacerbates the risk of further valve migration or annular rupture.
Ablation for the treatment of Brugada syndrome: current status and future prospects
Published in Expert Review of Medical Devices, 2020
Alessandro Rizzo, Carlo de Asmundis, Pedro Brugada, Mark La Meir, Gian-Battista Chierchia
The repolarization hypothesis suggests that an outward shift in the balance of currents in the right ventricular epicardium can result in repolarization abnormalities. These abnormalities can facilitate the development of phase 2 reentry generating closely coupled premature beats that can precipitate ventricular tachycardia (VT) or ventricular fibrillation (VF) [9–11]. According to this theory, a reduced inward sodium current (INa) and prominent outward current lead to the accentuation of the action potential notch in the right ventricular epicardium relative to the endocardium, producing a transmural voltage gradient which manifests electrocardiographically as the characteristic ST-segment elevation seen in patients with Brugada syndrome. The depolarization hypothesis claims that slow conduction in the right ventricular outflow tract (RVOT) has a primary role in the development of the electrocardiographic and arrhythmic manifestations of Brugada syndrome [12]. According to this hypothesis, ST-segment elevation is caused by a conduction delay in the RVOT, and ventricular arrhythmias associated with Brugada syndrome are induced by the abnormal current created by delayed depolarization of this area [13,15].
The Visible Heart® project and methodologies: novel use for studying cardiac monophasic action potentials and evaluating their underlying mechanisms
Published in Expert Review of Medical Devices, 2018
Megan M. Schmidt, Paul A. Iaizzo
As previously mentioned, due to their ability to represent the underlying TAPs, MAP recordings in novel groups of patients may provide unique insights relative to abnormal myocyte repolarizations (also known as repolarization syndromes). While other mapping technologies, such as optical mapping, may be able to record repolarization patterns from more points at any given time, the undetected morphology focal waveforms can be altered due to the use of paralytic drugs (thus the underutilization of stretch-activated channels) required for such techniques [42–45]. For example, Blana et al. conducted studies with mice genetically modified to express long QT syndrome type 3; they concluded that this model for long QT demonstrated both structural and electrophysiologic changes in atrial substrates [46]. Similarly, Shimizu et al. conducted some early studies on long QT syndrome and, through the study of afterdepolarizations, concluded that both verapamil and propranolol could help improve these abnormalities [47]. Interestingly, verapamil and propranolol have also been studied by other researchers, focusing on the ability to recreate a Brugada-like action potential [48–51]. Recently, using Visible Heart methodologies, we have initiated similar studies to generate Brugada-like action potentials in the right ventricular outflow tract of reanimated large mammalian hearts. This model allows us to monitor the focal and global applications of a variety of current and novel therapies for the treatment of early repolarization diseases.