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Biomedical subjects

Eugene K W Sim

Publications and source records attributed to Eugene K W Sim.

27 records · Page 2Linked to original sources
PubMed2003

Comparison of human and porcine aortic valves.

We compared the anatomy of human and porcine aortic valves. Porcine hearts were collected from the abattoir. Human hearts from patients who had died of non-cardiac causes were examined in the mortuary; only undamaged and anatomically normal hearts were used. Silicon casts were prepared by injecting engineering silicon at 80 mm Hg into the aortic arch. Various features of the aortic valve were measured: circumference, length between the commissural end point and central point of coaptation, surface diameter, and surface area. In total, 12 porcine and 12 human aortic valves were studied. The average circumferences of the human and porcine aortic valves were 8.00 +/- 0.2 (SD) cm and 7.90 +/- 1.0 cm, respectively. The central point of coaptation in human valves was skewed toward the left coronary cusp, whereas in porcine valves it was skewed toward the non-coronary cusp. In human aortic valves, the non-coronary cusp had the largest surface diameter and surface area with mean measurements of 3.6 +/- 0.2 cm and 1.230 +/- 0.228 cm(2), respectively; the left coronary cusp was smallest for the same variables with measurements of 3.1 +/- 0.3 cm and 0.898 +/- 0.357 cm(2). In porcine valves, the right coronary cusp had the largest surface diameter and surface area with mean measurements of 3.9 +/- 0.7 cm and 1.716 +/- 0.81 cm(2), respectively; the non-coronary cusp was the smallest for the same variables with measurements of 2.9 +/- 0.5 cm and 1.023 +/- 0.659 cm(2). These differences suggest that when using porcine valves as transplant material (e.g., stentless valves), geometric considerations, such as commissural length, may be important.

Anatomy, Comparative↗
PubMedDate not supplied

Skeletal myoblast transplant in heart failure.

Despite recent advances in the prevention and treatment of ischemic heart disease (IHD), treatment of patients with heart failure secondary to myocardial infarction remains a therapeutic challenge. Heart transplantation has emerged as a viable option but is fraught with problems of supply. Mechanical assist devices are extremely expensive and dynamic cardiomyoplasty has shown only limited success in the clinical setting. Recent insights into the pathogenesis of myocardial diseases and the progress made in the field of molecular biology have resulted in the development of new strategies at molecular as well as cellular levels for cardiac muscle repair. One such strategy is to augment ventricular function by means of cellular cardiomyoplasty through intracardiac cell grafting using adult and fetal cardiomyocytes, stem cells, and autologous skeletal myoblasts.

Animals↗
PubMedDate not supplied

Chronic effects of transmyocardial laser revascularization in the nonischemic myocardium: a word of caution.

BACKGROUND: Transmyocardial laser revascularization (TMLR) has been shown to induce angiogenesis and improve regional myocardial blood flow. However, the biological response to laser of different energy doses in nonischemic myocardium has not been well studied. We study the time course of histological appearance following high- and low-energy TMLR in a rodent model of normal myocardium. METHODS: The animals were randomized to two groups (high-energy (1.4 J/pulse) TMLR group and low-energy (0.6 J/ pulse) TMLR group). TMLR was applied to the anterolateral wall of the left ventricle. Then the animals were sacrificed (one every 2 or 3 days up to 6 weeks, then one every week) to give a series of hearts from 1 week to 12 weeks following TMLR. RESULTS: No patent laser channels were identified. All laser channel remnants were composed of granulation tissue, fibrosis, and various amounts of vascular structures. Changes in vascular density demonstrated a similar pattern in both groups over time. The initial increase in vascular density within the laser channel remnants and the surrounding areas was more marked in group I than in group II. Gradual decline of vascular density occurred during a later follow-up. More fibrosis and less vasculature were demonstrated 12 weeks after laser therapy in group I. CONCLUSION: Angiogenic response to the Holmium:YAG laser in the nonischemic myocardium is nonspecific and unsustainable. TMLR might chronically impair the myocardium function by enhancing regional scar formation. Therefore, we should clearly identify the ischemic area for laser therapy. Reduction of laser energy might prevent this potential complication.

Animals↗
PubMedDate not supplied

Therapeutic angiogenesis for coronary artery disease.

Therapeutic angiogenesis may be a realistic approach in treating ischemic heart disease. VEGF is a major angiogenic factor involved in physiological as well as pathological angiogenesis. The ability of VEGF to promote angiogenesis in animal and clinical studies has been studied extensively. However, it is becoming clear that VEGF alone may not be sufficient to effectively complete the angiogenesis process. The use of more than one growth factor may be more pertinent in creating a sustainable angiogenic effect with clinically significant outcome. The challenge is to find complementary partners in angiogenesis to better affect the outcome of the process. To this end, we have been studying the effects of other angiogenic factors such as angiopoietin-1 (Ang-1) in a chronic ischemic porcine model. Single intramyocardial introduction of adenovirus-mediated gene transfer of Ang-1 into the left ventricle free wall has been found to enhance angiogenesis by augmenting the formation of new capillaries that manifested in improved total blood flow in the myocardium. A combined therapeutic angiogenesis study involving VEGF and Ang-1 is currently underway. Due to their unique complementary properties, it is expected that the combination will not merely enhance angiogenesis but will also lead to healthy and mature vascular network in the ischemic myocardium.

Angiogenesis Inducing Agents↗
PubMedDate not supplied

Myoblast transplantation on the beating heart.

Cellular cardiomyoplasty using various types of donor cells is now validated by a large number of experimental studies. We report a case of cellular cardiomyoplasty performed on a beating heart using autologous skeletal myoblasts, thus combining the efficacy of both procedures. Approximately 2.5 g of rectus femoris muscle tissue biopsy was taken from the patient and cultured using a patented procedure to generate human myoblasts. The cell type and the purity of the cell culture were ascertained by immunostaining for human desmin expression. Under direct vision and stabilization with the Octopus III tissue stabilizer, 3.70 x 10(8) myoblasts in 3 ml of the patient's own serum were injected into the myocardium in 20 sites on the anterior wall and near the apex on the posterior wall, in and around the infarcted areas. In this case report, this procedure was found to be a safe and viable option, with improvement in cardiac function.

Cardiomyoplasty↗