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M H Keelan

Publications and source records attributed to M H Keelan.

At least 19 recordsLinked to original sources
PubMed2001

Effect of short pulsed nonablative infrared laser irradiation on vascular cells in vitro and neointimal hyperplasia in a rabbit balloon injury model.

BACKGROUND: Neointimal hyperplasia after PTCA is an important component of restenosis. METHODS AND RESULTS: Cultures of rabbit endothelial cells and smooth muscle cells (SMCs) were irradiated with different doses of nonablative infrared (1064-nm) radiation. Normalized viability index detected with nondestructive Alamar Blue assay and direct cell count were studied. Our experiments demonstrated dose-dependent cytostatic or cytotoxic effects of laser irradiation. We also evaluated the long-term effect of endoluminal nonablative infrared laser irradiation on neointimal hyperplasia in a rabbit balloon injury model. PTCA of both iliac arteries of 23 New Zealand White rabbits was performed. One iliac artery was subjected to intra-arterial subablative infrared irradiation via a diffuse tip fiber. The contralateral vessel served as control. The diet was supplemented with 0.25% cholesterol and 2% peanut oil for 10 days before and 60 days after PTCA. Morphometry after 60 days showed that intimal areas were 0.76+/-0.18 and 1.85+/-0.30 mm(2) in the laser and control arteries, respectively (P=2.2x10(-11)). CONCLUSIONS: We conclude that nonablative infrared laser inhibited neointimal hyperplasia after PTCA in cholesterol-fed rabbits for up to 60 days.

Angioplasty, Balloon, Coronary↗
PubMed2001

Local delivery of c-myc neutrally charged antisense oligonucleotides with transport catheter inhibits myointimal hyperplasia and positively affects vascular remodeling in the rabbit balloon injury model.

Myointimal hyperplasia after percutaneous transluminal coronary angioplasty (PTCA) is a key component of the process of restenosis. The c-myc is a critical cell-cycle division protein involved in the formation of neointima. We evaluated the long-term impact of local delivery of c-myc neutrally charged antisense oligonucleotides (Resten-NG) on myointimal hyperplasia after PTCA in a rabbit model. PTCA was performed in the iliac arteries of 25 New Zealand white rabbits, using a Transport catheter at 8 atm for 30 sec, three times; 500 microg Resten-NG (n = 11) or saline (n = 14) was delivered to the PTCA site at 2 atm with the outer balloon for 2 min. The diet was supplemented with 0.25% cholesterol for 10 days before and 60 days after PTCA. Angiography was performed at harvest, and vessels were fixed in formalin, processed, and stained with hematoxylin and eosin (H&E) and Movat. Quantitative angiography showed that local delivery of antisense c-myc at PTCA reduced late luminal loss from 1.8 +/- 0.30 mm in control animals to 0.90 +/- 0.30 mm in the treatment group (P = 0.001). Histological analysis by planimetry showed that intimal areas were 1.67 +/- 0.44 mm(2) and 0.82 +/- 0.32 mm(2) in the control and antisense delivery groups, respectively (P < 0.05). We conclude that local delivery of Resten-NG inhibited myointimal hyperplasia after PTCA in cholesterol-fed rabbits for up to 60 days.

Angioplasty, Balloon, Coronary↗
PubMed2001

Intravascular low-power laser irradiation after coronary stenting: long-term follow-up.

BACKGROUND AND OBJECTIVE: A high restenosis rate remains a limiting factor for percutaneous transluminal coronary angioplasty and stenting. The objective of this study was to evaluate the effect of intravascular red laser therapy (IRLT) on restenosis after stenting procedures in de novo lesions. STUDY DESIGN/MATERIALS AND METHODS: A total of 68 consecutive patients were treated with IRLT in conjunction with coronary stenting procedures. Mean lesion length was 16.5 +/- 2.4 mm. Reference vessel diameter (RVD) and pre-minimal lumen diameter (MLD) were 2.90 +/- 0.15 mm and 1.12 +/- 0.26 mm, respectively. RESULTS: After treatment, MLD was 2.76 +/- 0.32 mm with no procedural complications or in-hospital adverse events. Angiographic follow-up (n = 61) revealed restenosis in nine patients (14.7%) with rate by artery size of > 3 mm (n = 21) 0%; 2.5--3.0 mm (n = 28) 14.2%; and < 2.5 mm (n = 12) 41.6%. CONCLUSION: Intravascular red light therapy is safe, feasible, and reduces expected restenosis rate after coronary stenting.

Aged↗
PubMed2001

Low-power helium: neon laser irradiation enhances production of vascular endothelial growth factor and promotes growth of endothelial cells in vitro.

BACKGROUND AND OBJECTIVE: Numerous reports suggest that low-power laser irradiation (LPLI) is capable of affecting cellular processes in the absence of significant thermal effect. The objective of the present study was to determine the effect of LPLI on secretion of vascular endothelial growth factor (VEGF) and proliferation of human endothelial cells (EC) in vitro. STUDY DESIGN/MATERIALS AND METHODS: Cell cultures were irradiated with single different doses of LPLI (Laser irradiance from 0.10 to 6.3 J/cm(2)) by using a He:Ne continuous wave laser (632 nm). VEGF secretion by smooth muscle cells (SMC) and fibroblasts was quantified by sandwich enzyme immunoassay technique. The endothelial cell proliferation was measured by Alamar Blue assay. VEGF and transforming growth factor beta (TGF-beta) expression by cardiomyocytes was studied by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: We observed that (1) LPLI of vascular and cardiac cells results in a statistically significant increase of VEGF secretion in culture (1.6-fold for SMC and fibroblasts and 7-fold for cardiomyocytes) and is dose dependent (maximal effect was observed with LPLI irradiance of 0.5 J/cm(2) for SMC, 2.1 J/cm(2) for fibroblasts and 1.05 J/cm(2) for cardiomyocytes). (2) Significant stimulation of endothelial cell growth was obtained with LPLI-treated conditioned medium of SMC (maximal increase was observed with LPLI conditioned medium with irradiance of 1.05 J/cm(2) for SMC and 2.1 J/cm(2) for fibroblasts. CONCLUSIONS: Our studies demonstrate that low-power laser irradiation increases production of VEGF by SMC, fibroblasts, and cardiac myocytes and stimulates EC growth in culture. These data may have significant importance leading to the establishment of new methods for endoluminal postangioplasty vascular repair and myocardial photoangiogenesis.

Cells, Cultured↗
PubMed2000

Long-term follow-up after coronary stenting and intravascular red laser therapy.

A high restenosis rate remains a limiting factor for coronary angioplasty and stenting. Recently, use of intravascular red light therapy (IRLT) has been shown to be effective in different animal models and in humans in reducing the restenosis rate. Sixty-eight patients were treated with IRLT in conjunction with coronary stenting procedures. Mean age was 64 +/- 9 years. Treated lesions were type A (11), type B (42), and type C (18) with a mean lesion length of 16.5 +/- 2.4 mm. Reference vessel diameter and minimal lumen diameter (MLD) before therapy were 2.90 +/- 0.15 and 1.12 +/- 0.36 mm, respectively. After stenting and laser irradiation, MLD was 2.76 +/- 0.39 mm. No procedural complications or in-hospital adverse events occurred. All patients were followed up as depicted in the protocol. Sixty-one patients underwent angiographic restudy, which revealed restenosis in 9 patients (14.7%). Observed restenosis rate by artery size was > 3 mm (n = 21, 0%), 2.5 to 3.0 mm (n = 28, 14.2%), and <2.5 mm (n = 12, 41.6%). We conclude that IRLT is safe and feasible and reduces the expected restenosis rate in patients after coronary stenting in arteries of >2.5 mm.

Aged↗
PubMed2000

Endoluminal reconstruction of the arterial wall with endothelial cell/glue matrix reduces restenosis in an atherosclerotic rabbit.

OBJECTIVES: The objectives of this study were 1) to improve the attachment of reimplanted endothelial cells (EC) using a fibrin glue, and 2) to assess the impact of endothelial reseeding on restenosis eight weeks after balloon angioplasty. BACKGROUND: A possible mechanism contributing to restenosis after balloon angioplasty is the loss of the EC lining. Previous attempts to reseed EC had little effect due to rapid loss of the seeded cells. METHODS: Twelve atherosclerotic rabbits were subjected to angioplasty of iliac arteries and reseeding procedure. One iliac artery was subjected to EC/glue reconstruction and a contralateral site to EC seeding without glue. The animals were sacrificed after 4 h. In another series 12 rabbits were treated in the same fashion and were restudied at eight weeks. Additionally, in 10 animals one iliac was subjected to glue treatment, and another served as control. RESULTS: Histological examination demonstrated the ability of this method to reattach the EC/glue matrix circumferentially to 68.0 +/- 6.7% of the arterial wall in comparison with 13.5 +/- 3.9% reattachment after EC seeding. Morphometry at eight weeks showed that the lumen area was significantly greater in the EC/glue group (1.23 +/- 0.35 mm2) than in the EC seeding alone (0.65 +/- 0.02 mm2) and 0.72 +/- 0.41 mm2 in the glue group. This was principally accounted for by the statistically significant differences in the intimal area (0.76 +/- 0.18 mm vs. 1.25 +/-0.26 mm2 and 1.01 +/- 0.53 mm2, respectively). CONCLUSIONS: The attachment of EC after angioplasty can be greatly improved with fibrin glue matrix. The near 70% endothelial coverage achieved by this method resulted in a significant reduction of restenosis in atherosclerotic rabbit.

Angioplasty, Balloon↗
PubMed2000

Photoactivation of vascular iNOS and elevation of cGMP in vivo: possible mechanism for photovasorelaxation and inhibition of restenosis in an atherosclerotic rabbit models.

Recently, intravascular low-power red laser light (LPRLL) therapy has been proposed for the prevention of postangioplasty restenosis due to the observed inhibition of experimental neointimal formation. The objective of this study was to determine the impact of endoluminal LPRLL on vascular levels of inducible nitric oxide synthase (iNOS) and cyclic guanosine monophosphate (cGMP) to help define the mechanism of this effect. Eight atherosclerotic male adult New Zealand White rabbits weighing 4-6 kg were used in these studies. The iliac arteries were treated in separate zones with: (1) balloon inflation only; (2) laser illumination only; and (3) balloon inflation + laser illumination. An uninjured zone of the iliac artery served as a control. Laser irradiation (630 nm) was delivered to the vessel wall via a Cold laser Illuminator (Cook, Inc., Bloomington, IN), with a 3 mm-diameter balloon. Experiments demonstrated that vascular cGMP levels obtained immediately following treatment in the balloon only group was the lowest (0.29 +/- 0.05 pmol/mg protein) and significantly lower compared with the uninjured controls (1.01 +/- 0.07 pmol/ mg protein) (P < 0.001). In the laser only treated group cGMP levels were significantly increased (2.87 +/- 0.12 pmol/mg protein) compared with the uninjured control (P < 0.001) and the balloon only group (P < 0.001). Vascular cGMP levels in the balloon + laser group (2.09 +/0.07 pmol/mg protein) was also increased compared to the balloon only (P < 0.001) and control (P < 0.001) groups. Qualitative analysis of Western blot demonstrated that laser illumination induces iNOS. In contrast balloon dilatation did not induce iNOS. Balloon + laser treatment, however, tended to restore the expression of iNOS. Our study demonstrated that intravascular low dose laser irradiation induces iNOS and elevates vascular cGMP in an in vivo atherosclerotic rabbit model.

Angioplasty, Balloon↗
PubMed2000

Angiogenesis in a patient with ischemic limb induced by intramuscular injection of vascular endothelial growth factor and fibrin platform.

Direct revascularization of critical ischemia of the limb is often unsuccessful due to the anatomic extent and distribution of arterial occlusive disease, and no pharmacologic treatment has proved effective in treating this condition. Patients with ischemic limb may eventually require amputation and may develop serious morbidity and mortality. The goal of limb salvage in these patients has stimulated research into alternative treatment methods, including angiogenesis. Attempts have been made to apply growth factors directly or to encode DNA for such factors, but it is unknown whether these factors remain at the target site long enough to be effective. We report our strategy of using vascular endothelial growth factor in a fibrin network, which enables the sustained release of biologic material at the target site.

Aged↗
PubMed1999

Angiogenesis for the treatment of vascular diseases.

Critical ischemia of the limbs or myocardium is frequently accompanied by diffuse distal vascular disease making it unapproachable by conventional revascularization techniques. Pharmacological treatment is available for coronary artery disease but there has been no effective medical therapy for advanced ischemia of the limbs. In the search for alternative treatments for patients with diffuse distal disease, recent developments in vascular biology have directed attention towards use of vascular growth factors. Therapeutic angiogenesis has shown promising results in early clinical studies as shown by improved clinical status and in some cases angiographic studies. We employed an angiogenic strategy that utilizes enhanced vascular endothelial growth factor (VEGF) in a fibrin network, in two patients with critical limb ischemia. Objectively, we were able to demonstrate angiographically the growth of new blood vessels after administration of VEGF and fibrin composite. Fibrin glue provides for the slow release of and prolongs the availability of VEGF, thereby sustaining angiogenesis resulting in improved oxygenation of ischemic tissue. Further investigations are warranted to validate if angiogenesis may increase blood flow in patients with advanced vascular disease.

Clinical Trials as Topic↗
PubMed1999

Influence of different stent materials on endothelialization in vitro.

The objective of our study was to investigate the influence of different stent materials on endothelialization in vitro. Using the non-destructive Alamar Blue assay and scanning electron microscopy, we compared long-term growth and morphology of vascular cells on disks of three prospective stent materials, i.e., 316 L stainless steel, 18 K, and 24 K gold. Our results demonstrate superior human EC proliferative capacity on gold surfaces compared to that on 316 L stainless steel. Thus, both the hyperplasia and thrombotic complications which often follow stenting might be minimized by employing gold stents, which have a greater capacity than steel in supporting a functional neo-endothelium.

Cell Division↗
PubMed1998

Photoremodeling of arterial wall reduces restenosis after balloon angioplasty in an atherosclerotic rabbit model.

OBJECTIVES: This study evaluated the long-term impact of endoluminal low power red laser light (LPRLL) on restenosis in an atherosclerotic rabbit model. BACKGROUND: Despite widespread application of balloon angioplasty for treatment of coronary artery disease, restenosis limits its clinical benefits. Restenosis is a complex process and may be partly attributed to the inability of the vascular endothelium to regenerate and cover the denuded area at the site of arterial injury. We previously demonstrated that LPRLL stimulates endothelial cell proliferation in vitro and contributes to rapid endothelial regeneration after balloon injury in nonatherosclerotic rabbits. METHODS: Rabbit abdominal aortas (n = 12) were treated in separate zones with balloon dilation and balloon dilation plus laser illumination. Endoluminal laser therapy was performed using a laser-balloon catheter delivering a single dose of 10 mW for 3 min from a helium-neon laser (632 nm). Angiography was performed before and after treatment and was repeated 8 weeks before harvesting the aortas. RESULTS: Quantitative angiographic analysis demonstrated no differences in the minimal lumen diameter (MLD) between the two zones before treatment; an increase in the MLD in both zones after balloon angioplasty and a significant versus slight reduction of the MLD in the balloon treatment versus balloon plus laser zones at 8 weeks. Histologic examination showed a very high level of myointimal hyperplasia in the balloon treatment zones but a minimal level in the LPRLL-treated zones. Morphometric analysis revealed a statistically significant difference in the lumen area, intimal area and intima/media ratio between the balloon versus balloon plus laser treatment sites. CONCLUSIONS: Our experimental data indicate that endoluminal irradiation with LPRLL prevents restenosis after balloon angioplasty in an atherosclerotic rabbit model.

Angioplasty, Balloon, Coronary↗
PubMed1992

Milwaukee Prehospital Chest Pain Project--phase I: feasibility and accuracy of prehospital thrombolytic candidate selection.

This study prospectively determined the feasibility and accuracy of prehospital thrombolytic therapy candidate selection by base station emergency physicians. During a 6-month period, paramedics acquired and transmitted prehospital 12-lead electrocardiograms (ECGs) and then applied a thrombolytic therapy contraindication checklist. Emergency physicians interpreted prehospital ECGs and prospectively selected candidates for thrombolytic therapy. A safety committee of cardiologists reviewed prehospital ECGs, checklists and hospital records to determine accuracy independently. Six hundred-eighty stable adult prehospital patients with a chief complaint of nontraumatic chest pain were initially evaluated. Two hundred forty-one patients were excluded because of (1) unsuccessful electrocardiographic transmission (149), (2) transport to nonparticipating facilities (72), and (3) unavailable medical records (20). No prehospital thrombolytic therapy was administered in this study. Of 439 cases, 91 (21%) had the final diagnosis of acute myocardial infarction, 38 (8.7%) had diagnostic prehospital ECGs, and 12 (2.7%) were selected by emergency physicians as candidates for thrombolytic therapy. Seventy percent of patients with myocardial infarction had checklist exclusions for thrombolytic therapy. Prehospital evaluation increased mean scene time (paramedic arrival on scene to scene departure) by 4 minutes. The median time from chest pain onset to paramedic arrival in patients with myocardial infarction was 60 minutes. The estimated average time saved if prehospital thrombolytic therapy had been available was 101 +/- 81 minutes. The safety committee concluded that acceptable accuracy of emergency physician prehospital electrocardiographic interpretation, checklist and case selection was achieved. It is concluded that emergency physicians can accurately identify candidates for prehospital thrombolytic therapy.

Adult↗
PubMed1988

Spontaneous recovery of left ventricular function following acute anterior myocardial infarction.

Four patients with acute anterior wall myocardial infarction showing spontaneous and marked improvement in systolic left ventricular function are described. All 4 patients showed abnormal Q waves and severe wall motion abnormalities soon after acute infarction. In all 4 patients, at least some regeneration of R-wave forces occurred and the regional wall motion in the involved area of the left ventricle improved dramatically without coronary angioplasty or surgical revascularization during the intervening period. The improvement in left ventricular function was attributed to spontaneous increase in nutrient flow to the involved area. It is concluded that Q waves and severe wall motion abnormalities do not necessarily indicate irreversible scar formation.

Electrocardiography↗
PubMed1988

Hyperventilation and myocardial infarction.

Chest pain that is associated with hyperventilation is often considered to be benign and noncardiac in nature. While not commonly recognized, hyperventilation can provoke coronary vasospasm. We report a man who presented with hyperventilation and developed myocardial infarction. In the setting of hyperventilation, chest pain and ST segment elevation, coronary vasospasm must be considered.

Coronary Angiography↗