Biomedical subjects

Martin Heidt

Publications and source records attributed to Martin Heidt.

5 recordsLinked to original sources

PubMed2006

Comparison between pulsed and continuous radiofrequency delivery.

INTRODUCTION: Potentials arising in the pulmonary veins (PV) have been proposed to be a trigger of atrial fibrillation. Percutaneously, the best results for curative treatment of atrial fibrillation have been achieved by segmental or circumferential isolation of the PV. The purpose of our study was to determine the feasibility of ostial pulmonary vein isolation and to compare continuous radiofrequency (RF) with pulsed RF concerning homogeneity and transmurality of produced lesions. MATERIALS AND METHODS: In vivo tests were performed in seven anesthetized and ventilated pigs. Under fluoroscopy and guided by intracardiac electrograms each of the 28 pulmonary veins was targeted for circumferential isolation near its ostium. After the continuous energy application in one PV-ostium the catheter was placed into the next PV-ostium and the same procedure was repeated using pulsed energy. The ablations were performed with an octapolar circumferential ablation catheter, with either continuous RF energy delivery to each electrode for 120 s or pulsed energy delivery to four electrodes simultaneously with a 5 ms duty cycle. Lesion diameter was measured with a microcaliper and homogeneity classified from 1 (highest) to 4 (least). RESULTS: More homogeneous lesions were produced in significantly less time with pulsed rather than with continuous energy delivery. There were no significant differences in impedance or temperature of the electrodes. We did not observe tissue carbonization or "popping," pulmonary vein stenosis, pericardial effusion/perforation at any time. CONCLUSION: Ostial ablation of the PV with pulsed energy delivery proved feasible. It was the faster and more reliable method of creating linear circumferential lesions with a maximum amount of homogeneity and transmurality. We observed no elevated risk of PV stenosis during our experiments.

Animals↗

PubMed2004

Comparison of interventional versus conservative treatment of isolated ostial lesions of coronary diagonal branch arteries.

This study compares percutaneous coronary intervention of isolated ostial stenosis of diagonal branches with a luminal diameter >/=2.0 mm with medical treatment with regard to cardiac events during hospitalization and follow-up. Medical treatment is an alternative to percutaneous intervention without a greater incidence of death or myocardial infarction at 12-month follow-up. Interestingly, patients with isolated ostial stenosis of diagonal branches who were treated interventionally showed a significantly greater probability of rehospitalization for severe angina, recatheterization, and reintervention compared with medically treated patients.

Adrenergic beta-Antagonists↗

PubMed2004

Use of gadobutrol in coronary angiography.

Gadobutrol was used in coronary angiography in three patients. All three patients had a substantially increased risk of developing renal complications with iodinated contrast agents. Gadobutrol was well tolerated in all three patients without any complications. The quality of the coronary angiograms was good.

Adult↗

PubMed2003

Increased expression of disintegrin-metalloproteinases ADAM-15 and ADAM-9 following upregulation of integrins alpha5beta1 and alphavbeta3 in atherosclerosis.

Regulation of alphavbeta3 and alpha5beta1 integrin function plays a crucial role in atherosclerosis. Possible regulators of integrin-matrix interactions are integrin-binding ADAMs (proteins with a disintegrin- and metalloproteinase-domain), like ADAM-15 and ADAM-9. Molecular interactions between ADAM-15, alpha5beta1, and alphavbeta3 have been demonstrated. ADAM-9 and ADAM-15 were found to be interdependently regulated. This study, therefore, investigated whether the upregulation of integrins alpha5beta1 and alphavbeta3 was correlated with the expression of integrin-binding ADAMs in atherosclerotic processes. Human arterial and venous vascular smooth muscle cells (VSMCs) were incubated with PDGF over different time intervals up to a 3-day culture period. mRNA concentrations, quantified by real-time RT-PCR and normalized to PBGD, of integrins alphavbeta3 and alpha5beta1 were strongly increased after a 12-h PDGF-incubation in arterial and venous VSMC. ADAM-15 and ADAM-9 mRNA production showed a corresponding increase following integrin upregulation after a 24-h incubation period. Western blot anaylsis revealed an increased protein expression of integrins and ADAMs in PDGF-stimulated VSMC. Additionally, mRNA concentrations of atherosclerotic and normal human specimens were quantified by real-time RT-PCR. mRNA of ADAMs and integrins was significantly increased in atherosclerotic arteries compared to normal arteries. Immunohistochemistry of these specimens showed an increased expression and codistribution of both ADAMs and integrins in atherosclerosis. In conclusion, upregulation of ADAM-15 and ADAM-9 in atherosclerosis appears to follow an increase in alpha5beta1 and alphavbeta3 integrins. Since alpha5beta1 and alphavbeta3 are known to promote smooth muscle cell migration and proliferation, upregulation of ADAM-15 and ADAM-9 could balance integrin-matrix interactions and cell migration, thus modulating neointima progression.

ADAM Proteins↗

PubMed2002

Insulin and local growth factor PDGF induce intimal hyperplasia in bypass graft culture models of saphenous vein and internal mammary artery.

OBJECTIVE: In arteriosclerosis and bypass graft stenosis, intimal proliferation is controlled by local and systemic growth factors, such as platelet derived growth factor (PDGF) or insulin. Intimal hyperplasia can be produced in organ culture models. Our aim was to compare neointima formation in two organ culture models of internal mammary artery (IMA) and saphenous vein (SV), with special reference to the influence of systemic and local growth stimuli. METHODS: Rings of freshly isolated human SV and IMA were cultured over a 3-, 6- or 8-day period. They were distributed into five groups of incubation protocols: incubation with 10% serum; insulin 50 ng/ml and 100 ng/ml; PDGF-BB 5 ng/ml and 10 ng/ml. Frozen sections of cultured rings and pre-culture segments were subjected to elastic stain and immunohistochemistry. Antibodies directed against beta-actin and smooth muscle alpha-actin were used to characterize smooth muscle cell phenotype and against proliferating cell nuclear antigen (PCNA) to demonstrate proliferating cells. RESULTS: Growth factor incubation caused massive intimal hyperplasia with increased elastic fibers in SV and intimal smooth muscle cell as well as matrix accumulation in IMA. Intimal thickening, PCNA and beta-actin expression reached their maximum on day 6 of culture. In both culture models, serum, insulin and PDGF caused increasing intimal thickening, with more pronounced effects in SV. CONCLUSIONS: These organ culture models demonstrate the effects of insulin and PDGF on intimal hyperplasia in IMA and SV representing models for arteriosclerosis and bypass graft stenosis and stressing the role of insulin and growth factors for neointima development.

Aged↗