Ryuichi Yoneyama

Funnel-Tipped Aortic Cannula for Reduction of Atheroemboli

BACKGROUND Atheroemboli caused by aortic manipulation poses a risk for stroke in patients undergoing cardiopulmonary bypass (CPB) surgery. One potential cause is the high velocity jet from aortic perfusion cannulae. This study describes the flow patterns of a novel funnel-tip cannula designed to reduce emboli by decreasing fluid velocity and resultant shear force on the aortic wall. METHODS A funnel-tip cannula was constructed and compared with standard straight-tip cannulae and the Dispersion (Research Medical Inc, Midvale, UT) and Sarns Soft Flow (Terumo Cardiovascular Systems Corp, Ann Arbor, MI) cannulae. Pressure drop measurements were collected at 1 to 6 L/minute flows. Velocity flow profiles were created using phase contrast magnetic resonance imaging. Absolute velocity was measured in a phantom aorta at 5 L/minute flow. Each cannula was further studied in a synthetic model of an atherosclerotic aorta to determine the mass of dislodged particulate matter generated at 2, 3, and 5 L/minute flows. RESULTS The funnel-tip cannula demonstrated significantly lower values (p < 0.05) in pressure drop (55 mm Hg), exit velocity (309 cm/second, 167 cm/second for center axis and wall, respectively), and particulate dislodgement (0.15 +/- 0.05 g) than other tested cannulae. The Soft Flow cannula generated the next lowest pressure drop but exhibited twice the exit velocity and particulate dislodgement of the funnel-tip cannula. The Dispersion cannula did not demonstrate a reduction in velocity or particulate dislodgement compared with the standard straight-tip cannulae. CONCLUSIONS The results of this study suggest that a low-angled funnel-tip cannula has favorable flow characteristics warranting further investigation. Design development may reduce the risk of atheroemboli generation during CPB surgery.

3D coronary motion tracking in swine models with MR tracking catheters

To develop MR‐tracked catheters to delineate the three‐dimensional motion of coronary arteries at high spatial and temporal resolution.

Tracking Stem Cells In Vivo

Stem cells have been targeted to many organ systems specifically to replace scarred organs and to rejuvenate diseased organs. Even though our understanding of the versatility of stem cells is slowly unraveling, tracking these cells as they enter the body has become a very important field of study. In this chapter, we review various modalities for imaging stem cells and assess the advantages and shortcomings of each technique.

Catheter-based ventricle-coronary vein bypass.

The goal of this study was to investigate the feasibility of a catheter‐based ventricle‐to‐coronary vein bypass (VPASS) in order to achieve retrograde myocardial perfusion by a conduit (VSTENT) from the left ventricle (LV) to the anterior interventricular vein (AIV). Percutaneous coronary venous arterialization has been proposed as a potential treatment strategy for otherwise untreatable coronary artery disease. In an acute setting, the VSTENT implant was deployed percutaneously using the VPASS procedure in five swine. Coronary venous flow and pressure patterns were measured before and after VSTENT implant deployment with and without AIV and left anterior descending artery (LAD) occlusion. In a separate chronic pilot study, the VPASS procedure was completed on two animals that had a mid‐LAD occlusion or LAD stenosis. At day 30 post‐VPASS procedure, left ventriculography and magnetic resonance imaging (MRI) were performed to assess the patency and myocardial viability of the VSTENT implants. Pre‐VSTENT implantation, the mid‐AIV systolic wedge pressure was significantly lower than LV systolic pressure during AIV blockage (46 ± 19 vs. 90 ± 16 mm Hg; P < 0.01). The VSTENT implant deployment was performed without complication and achieved equalization of the AIV and LV systolic pressures and creation of retrograde flow in the distal AIV (maximal flow velocity: 37 ± 7 cm/sec). At day 30 post‐VPASS procedure, left ventriculography showed VSTENT implant patency. MRI perfusion images demonstrated myocardial viability even with an LAD occlusion. Coronary retrograde perfusion using the VPASS procedure is feasible and may represent a potential technique for end‐stage myocardial ischemia. Catheter Cardiovasc Interv 2005.

Magnetic resonance assessment of myocardial perfusion via catheter-based ventricle-coronary vein bypass in porcine myocardial infarction model.

Objective: The goal of this study was to investigate the efficacy of VPASS with physiological measurements, magnetic resonance imaging (MRI), and histology in a porcine model of myocardial infarction. Background: A catheter‐based ventricle‐to‐coronary vein bypass (VPASS™) has been proposed as a potential treatment strategy for refractory coronary artery disease patients. Methods: In an acute setting, the VPASS implant was deployed percutaneously in three swine. The partial pressure of oxygen (PO2) in the anterior interventricular vein (AIV) and left ventricle (LV) were measured before and after VPASS implant with various combinations of balloon occlusion in the AIV and left anterior descending artery (LAD). In a separate chronic study, the VPASS procedure was completed on three swine with a mid‐LAD occlusion. Thirty days post‐VPASS procedure, angiography, contrast‐enhanced MRI, and histology were performed to assess myocardial viability. Perfusion was analyzed using the average percent signal intensity change (APSIC) in the anterior walls (AW) and inferior walls (IW). Results: The VPASS implant was performed without complication. Post‐VPASS implantation, the distal AIV PO2 increased up to the LV PO2 level during simultaneous AIV and LAD blockage (432 ± 24 mmHg). At day 30, quantitative perfusion analysis demonstrated no difference in APSIC between AW and IW (125 ± 26% vs. 137 ± 38%, P = 0.46). Delayed enhancement and histology showed focal subendomyocardial infarction. Conclusions: VPASS implant with simultaneous AIV and LAD occlusion allows perfusion of oxygenated blood to the distal AIV, which in the setting of an acute myocardial infarction model was capable of rescuing most of the myocardium at risk.