Kenichiro Hanawa

Low-Intensity Pulsed Ultrasound Induces Angiogenesis and Ameliorates Left Ventricular Dysfunction in a Porcine Model of Chronic Myocardial Ischemia

Background Although a significant progress has been made in the management of ischemic heart disease (IHD), the number of severe IHD patients is increasing. Thus, it is crucial to develop new, non-invasive therapeutic strategies. In the present study, we aimed to develop low-intensity pulsed ultrasound (LIPUS) therapy for the treatment of IHD. Methods and Results We first confirmed that in cultured human endothelial cells, LIPUS significantly up-regulated mRNA expression of vascular endothelial growth factor (VEGF) with a peak at 32-cycle (P<0.05). Then, we examined the in vivo effects of LIPUS in a porcine model of chronic myocardial ischemia with reduced left ventricular ejection fraction (LVEF) (n = 28). The heart was treated with either sham (n = 14) or LIPUS (32-cycle with 193 mW/cm2 for 20 min, n = 14) at 3 different short axis levels. Four weeks after the treatment, LVEF was significantly improved in the LIPUS group (46±4 to 57±5%, P<0.05) without any adverse effects, whereas it remained unchanged in the sham group (46±5 to 47±6%, P = 0.33). Capillary density in the ischemic region was significantly increased in the LIPUS group compared with the control group (1084±175 vs. 858±151/mm2, P<0.05). Regional myocardial blood flow was also significantly improved in the LIPUS group (0.78±0.2 to 1.39±0.4 ml/min/g, P<0.05), but not in the control group (0.84±0.3 to 0.97±0.4 ml/min/g). Western blot analysis showed that VEGF, eNOS and bFGF were all significantly up-regulated only in the LIPUS group. Conclusions These results suggest that the LIPUS therapy is promising as a new, non-invasive therapy for IHD.

Association of Adventitial Vasa Vasorum and Inflammation With Coronary Hyperconstriction After Drug-Eluting Stent Implantation in Pigs In Vivo

BACKGROUND The importance of adventitial inflammation has been implicated for the pathogenesis of coronary artery disease. However, the roles of adventitial changes in drug-eluting stent (DES)-induced coronary hyperconstriction remain largely unknown. In the present study, this issue in pigs in vivo with a special reference to adventitial vasa vasorum (VV) formation and Rho-kinase activation, a central mechanism of coronary vasospasm, was examined. METHODS AND RESULTS Each animal received a sirolimus-eluting stent (SES) and a biolimus A9-eluting stent (BES), one in the left anterior descending and another in the left circumflex coronary arteries in a randomized manner (n=18). After 1, 3 and 6 months, coronary vasomotion was examined. At 1 month, coronary vasoconstriction to serotonin was significantly enhanced at the SES edges as compared with the BES edges (SES, 52±7% vs. BES, 22±3%, P<0.01), which was equally prevented by a selective Rho-kinase inhibitor, hydroxyfasudil. A significant difference in vasoconstriction between SES and BES was sustained for 6 months. A micro-CT showed VV augmentation at the SES site, extending to the proximal and distal edges. Immunostainings demonstrated that VV formation, macrophage infiltration in the adventitia and Rho-kinase expressions/activation were significantly enhanced at the SES edges as compared with the BES edges. CONCLUSIONS The DES with durable polymers enhances VV formation and inflammation in the adventitia, associating with the pathogenesis of DES-induced coronary hyperconstriction through Rho-kinase activation in pigs in vivo.

Accuracy of Optical Frequency Domain Imaging for Evaluation of Coronary Adventitial Vasa Vasorum Formation After Stent Implantation in Pigs and Humans – A Validation Study –

BACKGROUND Coronary adventitia harbors a wide variety of components, such as inflammatory cells and vasa vasorum (VV). Adventitial VV initiates the development of coronary artery diseases as an outside-in supply route of inflammation. We have recently demonstrated that drug-eluting stent implantation causes the enhancement of VV formation, with extending to the stent edges in the porcine coronary arteries, and also that optical frequency domain imaging (OFDI) is capable of visualizing VV in humans in vivo. However, it remains to be fully validated whether OFDI enables the precise measurement of VV formation in pigs and humans. METHODS AND RESULTS In the pig protocol, a total of 6 bare-metal stents and 12 drug-eluting stents were implanted into the coronary arteries, and at 1 month, the stented coronary arteries were imaged by OFDI ex vivo. OFDI data including the measurement of VV area at the stent edge portions were compared with histological data. There was a significant positive correlation between VV area on OFDI and that on histology (R=0.91, P<0.01). In the human protocol, OFDI enabled the measurement of the VV area at the stent edges after coronary stent implantation in vivo. CONCLUSIONS These results provide the first direct evidence that OFDI enables the precise measurement of the VV area in coronary arteries after stent implantation in pigs and humans.

Low-Intensity Pulsed Ultrasound Enhances Angiogenesis and Ameliorates Left Ventricular Dysfunction in a Mouse Model of Acute Myocardial Infarction

Objective— Left ventricular (LV) remodeling after acute myocardial infarction still remains an important issue in cardiovascular medicine. We have recently demonstrated that low-intensity pulsed ultrasound (LIPUS) therapy improves myocardial ischemia in a pig model of chronic myocardial ischemia through enhanced myocardial angiogenesis. In the present study, we aimed to demonstrate whether LIPUS also ameliorates LV remodeling after acute myocardial infarction and if so, to elucidate the underlying molecular mechanisms involved in the beneficial effects of LIPUS. Approach and Results— We examined the effects of LIPUS on LV remodeling in a mouse model of acute myocardial infarction, where the heart was treated with either LIPUS or no-LIPUS 3 times in the first week (days 1, 3, and 5). The LIPUS improved mortality and ameliorated post–myocardial infarction LV remodeling in mice. The LIPUS upregulated the expression of vascular endothelial growth factor, endothelial nitric oxide synthase, phosphorylated ERK, and phosphorylated Akt in the infarcted area early after acute myocardial infarction, leading to enhanced angiogenesis. Microarray analysis in cultured human endothelial cells showed that a total of 1050 genes, including those of the vascular endothelial growth factor signaling and focal adhesion pathways, were significantly altered by the LIPUS. Knockdown with small interfering RNA of either &bgr;1-integrin or caveolin-1, both of which are known to play key roles in mechanotransduction, suppressed the LIPUS-induced upregulation of vascular endothelial growth factor. Finally, in caveolin-1–deficient mice, the beneficial effects of LIPUS on mortality and post–myocardial infarction LV remodeling were absent. Conclusions— These results indicate that the LIPUS therapy ameliorates post–myocardial infarction LV remodeling in mice in vivo, for which mechanotransduction and its downstream pathways may be involved.

Development of a Novel Shock Wave Catheter Ablation System -The First Feasibility Study in Pigs-

Introduction Radio-frequency catheter ablation (RFCA) using Joule heat has two fundamental weaknesses: the limited depth of treatment and the risk of thrombus formation. In contrast, focused shock wave (SW) therapy could damage tissues at arbitrary depths without heat generation. Thus, we aimed to develop a SW catheter ablation (SWCA) system that could compensate for the weaknesses of RFCA therapy. Methods and Results We developed a SWCA system where the SW generated by a Q-switched Holmium: yttrium aluminum garnet (YAG) laser beam was reflected by a reflector attached to 14-Fr catheter tip and then was converged onto the focus. We examined the feasibility of our system on pigs in vivo. When applied using the epicardial approach, the SWCA caused persistent spheroidal lesions with mild superficial injury than the RFCA. The lesions were created to a depth based on the focal length (2.0 mm) [2.36 ± 0.45 (SD) mm immediately after procedure, n = 16]. When applied to the atrioventricular (AV) node using the endocardial approach, the SWCA caused junctional escape rhythms in 2 pigs and AV block in 12 pigs (complete AV block in 9) in acute phase (n = 14). Nine of the 14 pigs survived with pacemakers for the long-term study, and the AV block persisted for 12.6 ± 3.9 (SD) days in all surviving pigs. Histological examination showed AV nodal cell body atrophy in the acute phase and fibrotic lesions in the chronic phase. Importantly, no acute or chronic fatal complications were noted. Conclusions Our novel SWCA system could be a promising modality as a non-thermal ablation method to compensate for the weaknesses of RFCA therapy. However, further research and development will be necessary as the current prototype still exhibited the presence of micro-thrombus formation in the animal studies.

Successful recanalization of chronic total occlusion using retrograde approach in a patient with acute coronary syndrome due to aortosaphenous vein graft occlusion

Although percutaneous coronary intervention (PCI) is one of the most suitable treatment options in patients with acute coronary syndrome (ACS), PCI for ACS patients with occluded saphenous vein graft (SVG) remains challenging. An 80-year-old man with previous coronary artery bypass grafting (CABG) was admitted with the diagnosis of ACS. Emergent coronary angiography showed a total occlusion of SVG to the left circumflex coronary artery (LCx) with large thrombus burden. Because of concern about serious distal embolization, we subsequently performed primary PCI for the occluded native LCx using a combined antegrade and retrograde approach with the SVG as an access conduit. Successful crossing of the native LCx was achieved by retrograde wire through the SVG, and finally recanalization and stent placement was done. A retrograde approach for chronic total occlusion of coronary artery has become more popular during recent years with encouraging results. This novel technique may provide an additional therapeutic option even in ACS patients with previous CABG.