Visible Collateral Vessels Research Articles

Immediate recruitment of dormant coronary collaterals can provide more than half of normal resting perfusion during coronary occlusion in patients with coronary artery disease

BackgroundDormant coronary collaterals are highly prevalent and clinically beneficial in cases of coronary occlusion. However, the magnitude of myocardial perfusion provided by immediate coronary collateral recruitment during acute occlusion is unknown. We aimed to quantify collateral myocardial perfusion during balloon occlusion in patients with coronary artery disease (CAD).MethodsPatients without angiographically visible collaterals undergoing elective percutaneous transluminal coronary angioplasty (PTCA) to a single epicardial vessel underwent two scans with 99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT). All subjects underwent at least three minutes of angiographically verified complete balloon occlusion, at which time an intravenous injection of the radiotracer was administered, followed by SPECT imaging. A second radiotracer injection followed by SPECT imaging was performed 24 h after PTCA.ResultsThe study included 22 patients (median [interquartile range] age 68 [54-72] years. The perfusion defect extent was 19 [11-38] % of the LV, and the collateral perfusion at rest was 64 [58-67]% of normal.ConclusionThis is the first study to describe the magnitude of short-term changes in coronary microvascular collateral perfusion in patients with CAD. On average, despite coronary occlusion and an absence of angiographically visible collateral vessels, collaterals provided more than half of the normal perfusion.

Coronary collaterals provide more than half of normal perfusion in patients with coronary artery disease - quantification by myocardial perfusion SPECT during elective balloon occlusion

Abstract Funding Acknowledgements Type of funding sources: None. BACKGROUND The coronary collateral circulation is a preformed network of anastomotic connections acting as a "natural bypass" mechanism. Whilst the prevalence of collaterals varies between species, approximately 25% of patients have angiographically visible robust collaterals at the time of ST elevation myocardial infarction. While the presence of collaterals is associated with improved outcomes, the magnitude of myocardial perfusion which can be provided by the collateral circulation remains uncertain. PURPOSE The aim was to quantify collateral myocardial perfusion during experimental coronary balloon occlusion in patients with CAD. METHODS The study was approved by the local investigational review board, and all patients provided informed consent. Patients without prior infarction, bypass surgery, or angiographically visible collaterals undergoing elective percutaneous transluminal coronary angioplasty (PTCA) to a single epicardial vessel, underwent two scans with 99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT). All subjects underwent at least three minutes of angiographically verified complete balloon occlusion, at which time an intravenous injection of the radiotracer was administered, followed by SPECT imaging. A second radiotracer injection followed by SPECT imaging was performed 24 hours after PTCA. RESULTS The study included 21 patients (median [interquartile range] age 70 [56-74] years, 52% male). The degree of diameter stenosis of treated vessels ranged from 60-99%, with successful PTCA performed with a mean 5-minute balloon occlusion time, resulting in ≤20% residual stenosis in all cases. The vessels undergoing PTCA were 6 in the LAD, 5 in the LCx, and 10 in the RCA. For the cohort, the size of the perfusion defect was 16 [8-30]% of the LV and the collateral perfusion at rest within the perfusion defect was 64 [58-68]% of normal perfusion within that region. Collateral perfusion was negatively correlated with perfusion defect size (R2 = 0.85, p < 0.001), but did not differ by sex (p = 0.27) or age (p = 0.58). CONCLUSIONS: This is the first study to describe the magnitude of microvascular collateral perfusion in CAD. On average, despite coronary occlusion and an absence of angiographically visible collateral vessels, collaterals provide approximately 60% of the perfusion that reaches the jeopardized myocardium during coronary occlusion. This magnitude of collateral perfusion is much higher than previously speculated. A previous study using microspheres in dogs found that collateral perfusion in the setting of an occluded vessel was 6% of normal. By comparison, the current study found ten times greater collateral perfusion in patients with CAD. Abstract Figure. Collateral perfusion during occlusion.

Peripheral arterial disease: the role of extracellular volume measurements in lower limb muscles with MRI.

Peripheral arterial disease (PAD) is characterised by arterial occlusion and fibrosis in the lower extremities. Extracellular volume matrix fraction (ECV) is a biomarker of skeletal muscle fibrosis, but has not been applied to the lower extremities with PAD. This study investigated the clinical feasibility of using ECV for calf muscle fibrosis quantification by comparing normal controls (NC) and PAD patients. From October 2016 to December 2017, we recruited patients with PAD, and patients with head and neck cancer receiving fibular flap as NC group. All participants underwent magnetic resonance imaging (MRI) to determine the ECV of the calves and the differences between the NC and PAD groups. ECV was calculated from T1 values at steady-state equilibrium, defined as the point in time after contrast agent injection when the variance of T1 relaxation time in blood and muscle becomes less than 5%. A total of 46 patients (18 in the NC group and 28 in the PAD group) were recruited. Steady-state equilibrium was reached at 11-12min after contrast agent injection. The NC group had significantly lower mean ECV than the PAD group (12.71% vs. 31.92%, respectively, p < 0.001). In the PAD group, the mean ECV was slightly lower in patients with collateral vessels than in those without (26.58% vs. 34.88%, respectively, p = 0.047). Evaluation of skeletal fibrosis in PAD using ECV is feasible. ECV can help identify PAD patients with collateral vessel formation and lay the foundation for future research in PAD management. • Steady-state equilibrium for ECV measurement of the lower limbs can be reached at around 11-12 min. • Quantification of lower limb muscle fibrosis by measuring ECV is clinically feasible and can be used to differentiate between patients with PAD and histologically proven normal controls. • ECV can differentiate PAD patients with or without visible collateral vessels, further expanding its role in identifying the presence of collateral supply in clinical decision-making.

Cerebrovascular Reactivity Measured with ASL Perfusion MRI, Ivy Sign, and Regional Tissue Vascularization in Moyamoya

Arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) may be used to determine brain regions at risk for ischemia in patients with moyamoya vasculopathy and to identify patients who may benefit from surgical revascularization. We aimed to investigate whether 1) the severity of moyamoya is related to the presence of leptomeningeal collaterals and cerebrovascular reactivity (CVR), 2) the presence of collaterals and ivy sign reflects disturbed CVR, and 3) arterial transit artefacts (ATAs) and ivy sign reflect the presence of collaterals. We determined severity of moyamoya on digital subtraction angiography (DSA) according to the modified Suzuki classification in 20 brain regions and scored regional tissue revascularization using a 4-point scale. Regional CVR and ATAs were assessed on ASL perfusion MRI, ivy sign on fluid attenuation inversion recovery MRI. In 11 patients (median age 36 years; 91% female), we studied 203 regions. ATAs were associated with the presence of collaterals on DSA (P < 0.01). Of all regions with clearly visible collateral vessels on DSA, however, only 24% had ATAs. Ivy sign was not related to the presence or absence of collaterals nor to CVR. In 10% of regions with good vascularization on DSA, CVR was poor or showed steal. ATAs were associated with the presence of collaterals on DSA. Although DSA vascularization scores correlated with CVR, 10% of regions with good vascularization on DSA had absent CVR or steal on ASL-MRI. DSA and ivy sign did not provide adequate information on the hemodynamic status of brain tissue in patients with moyamoya vasculopathy.

The impact of the coronary collateral circulation on outcomes in patients with acute coronary syndromes: results from the ACUITY trial

ObjectiveWe sought to assess the prognostic role of collaterals in a large population of patients presenting with an acute coronary syndrome (ACS).MethodsThe coronary collateral circulation was assessed by an independent...

The coronary collateral circulation revisited

The coronary collateral circulation revisited

Development of New Hepaticoenteric Collateral Pathways after Hepatic Arterial Skeletonization in Preparation for Yttrium-90 Radioembolization

Development of new hepaticoenteric anastomotic vessels may occur after endovascular skeletonization of the hepatic artery. Left untreated, they can serve as pathways for nontarget radioembolization. The authors reviewed the incidence, anatomy, management, and significance of collateral vessel formation in patients undergoing radioembolization. One hundred thirty-eight treatments performed on 122 patients were reviewed. Each patient underwent a preparatory digital subtraction angiogram (DSA) and embolization of all hepaticoenteric vessels in preparation for yttrium-90 ((90)Y) administration. Successful skeletonization was verified by C-arm computed tomography (CACT) and technetium-99m macroaggregated albumin ((99m)TcMAA) scintigraphy. During the subsequent treatment session, DSA and CACT were repeated before administration of (90)Y, and the detection of extrahepatic perfusion prompted additional embolization. Forty-two patients (34.4%) undergoing 43 treatments (31.2%) required adjunctive embolization of hepaticoenteric vessels immediately before (90)Y administration. Previous scintigraphy findings showed extrahepatic perfusion in only three cases (7.1%). Vessels were identified by DSA in 54.1%, by CACT in 4.9%, or required both in 41.0%. The time interval between angiograms did not correlate with risk of requiring reembolization (P = .297). A total of 19.7% of vessels were new collateral vessels not visible during the initial angiography. Despite reembolization, three patients (7.1%) had gastric or duodenal ulceration, compared with 1.3% who never had visible collateral vessels, all of whom underwent whole-liver treatment with resin microspheres (P = .038). Development of collateral hepaticoenteric anastomoses occurs after endovascular skeletonization of the hepatic artery. Identified vessels may be managed by adjunctive embolization, but patients appear to remain at increased risk for gastrointestinal complications.

Acute Effects of Biventricular Versus Right Ventricular Pacing on Left Ventricular Function and Twist Assessed by Magnetic Resonance Imaging in a Canine Post Myocardial Infarction Model of Cardiomyopathy

The acute effects of cardiac resynchronization therapy on left ventricular (LV) function have not been fully elucidated. In order to experimentally assess the acute effects of resynchronization, we developed a canine model of chronic myocardial infarction (MI) with right ventricular pacing (RVP) to simulate left bundle branch block. We first ligated the left anterior descending coronary artery and all visible collateral vessels and implanted a biventricular pacing (BVP) system under open-chest conditions in six mongrel dogs.

Autologous transplantation of bone marrow mononuclear cells for limb ischemia in a caucasian population with atherosclerosis obliterans

Autologous transplantation of bone marrow mononuclear cells (ATBMMNC) has been used successfully in critical limb ischemia. All reported patients were of Asian descent, however, and several studies included only young patients with thromboangiitis obliterans. Whether the beneficial results can be extrapolated to older Caucasian patients with atherosclerosis obliterans and a heavy burden of cardiovascular risk factors remains unclear. We enrolled 16 patients (age 78 +/- 2 year) with critical limb ischemia and a high prevalence of hypertension, smoking, diabetes, hypercholesterolemia and uremia. Mononuclear cells were isolated from the bone marrow and injected in the gastrocnemius muscle of the affected limb. Four patients died because of progressive gangrene (two) or unrelated causes (two). Three patients required an amputation and one patient a femorocrural bypass within 12 weeks. The remaining eight patients had a modest improvement of resting pain and/or trophic lesions. Transcutaneous oxygen pressure (ratio lesion/reference) improved from 0.51 +/- 0.11 before to 0.86 +/- 0.03 (P < 0.001) after 12 weeks, whereas ankle-brachial index did not change significantly (0.42 +/- 0.15 vs. 0.59 +/- 0.1; P = 0.23). The number of visible collateral vessels on digital subtraction angiography changed with 0.89 +/- 0.86 on a scale of 1-4 (P = 0.33). Capillary surface area in a biopsy of gastrocnemius, evaluated by immunostaining for endothelial nitric oxide synthase, increased from 0.61 +/- 0.07% to 2.38 +/- 0.73% (P < 0.05). Although ATBMMNC was associated with objective signs of neovascularization, symptomatic improvement was only modest and restricted to the least affected patients. The discrepancy with previous findings may be related to the high prevalence of cardiovascular risk factors which causes endothelial progenitor cell dysfunction.

Therapeutic angiogenesis in critical limb and myocardial ischemia.

Research in animal models of ischemia has shown that administration of angiogenic growth factors, either as a recombinant protein or by gene transfer, can augment nutrient perfusion through neovascularization to promote the development of supplemental collateral blood vessels that will constitute endogenous bypass conduits around occluded native arteries; a strategy termed "therapeutic angiogenesis." In animal models and clinical trials, the best studied cytokines with angiogenic activity are vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). Clinical trials of therapeutic angiogenesis in patients with critical limb ischemia demonstrated resolution of rest pain and/or improved limb integrity, increased pain-free walking time and ankle-brachial index, newly visible collateral vessels by digital subtraction angiography, and qualitative evidence of improved distal flow by magnetic resonance imaging. Initial clinical trials in patients with end-stage coronary artery disease using direct myocardial injection via thoracotomy resulted in large increases in exercise time and marked reductions in anginal symptoms, as well as objective evidence of improved perfusion and left ventricular function. Larger scale placebo-controlled trials have been limited to intracoronary and intravenous administration of recombinant protein, and have not shown significant improvement in exercise time or angina compared to placebo. Larger scale placebo-controlled studies of gene transfer using catheter-based endocardial delivery are in progress. Future clinical studies are required to determine the optimal dose, formulation, route of administration, and combinations of growth factors, as well as the requirement for endothelial progenitor cell or stem cell supplementation, to provide effective and safe therapeutic angiogenesis for patients with critical limb ischemia and chronic myocardial ischemia who are not candidates for conventional revascularization procedures.

Implantation of bone marrow mononuclear cells into ischemic myocardium enhances collateral perfusion and regional function via side supply of angioblasts, angiogenic ligands, and cytokines.

Bone marrow implantation (BMI) was shown to enhance angiogenesis in a rat ischemic heart model. This preclinical study using a swine model was designed to test the safety and therapeutic effectiveness of BMI. BM-derived mononuclear cells (BM-MNCs) were injected into a zone made ischemic by coronary artery ligation. Three weeks after BMI, regional blood flow and capillary densities were significantly higher (4.6- and 2.8-fold, respectively), and cardiac function was improved. Angiography revealed that there was a marked increase (5.7-fold) in number of visible collateral vessels. Implantation of porcine coronary microvascular endothelial cells (CMECs) did not cause any significant increase in capillary densities. Labeled BM-MNCs were incorporated into approximately 31% of neocapillaries and corresponded to approximately 8.7% of macrophages but did not actively survive as myoblasts or fibroblasts. There was no bone formation by osteoblasts or malignant ventricular arrhythmia. Time-dependent changes in plasma levels for cardiac enzymes (troponin I and creatine kinase-MB) did not differ between the BMI, CMEC, and medium-alone implantation groups. BM-MNCs contained 16% of endothelial-lineage cells and expressed basic fibroblast growth factor>>vascular endothelial growth factor>angiopoietin 1 mRNAs, and their cardiac levels were significantly upregulated by BMI. Cardiac interleukin-1beta and tumor necrosis factor-alpha mRNA expression were also induced by BMI but not by CMEC implantation. BM-MNCs were actively differentiated to endothelial cells in vitro and formed network structure with human umbilical vein endothelial cells. BMI may constitute a novel safety strategy for achieving optimal therapeutic angiogenesis by the natural ability of the BM cells to secrete potent angiogenic ligands and cytokines as well as to be incorporated into foci of neovascularization.

Revascularization in the rabbit hindlimb: dissociation between capillary sprouting and arteriogenesis.

Animal models of hindlimb ischemia are critical to our understanding of peripheral vascular disease and allow us to evaluate therapeutic strategies aimed to improve peripheral collateral circulation. To further elucidate the processes involved in revascularization following ischemia, we evaluated the temporal association between tissue ischemia, vascular endothelial cell growth factor (VEGF) release, angiogenesis (capillary sprouting), arteriogenesis (growth of the larger muscular arteries), and reserve blood flow (functional collateral flow). New Zealand White rabbits (male 3-4 kg) were evaluated at specific days (0, 5, 10, 20 or 40) following femoral artery removal for measurement of hindlimb blood flow, skeletal muscle lactate production and VEGF content, capillary density (a marker of angiogenesis), and angiographic score (a marker of arteriogenesis). Maximal capillary sprouting occurred within 5 days of femoral artery removal and was temporally associated with reduced resting hindlimb blood flow, increased lactate release and detectable levels of skeletal muscle VEGF. The growth of larger angiographically visible collateral vessels occurred after 10 days and was not temporally associated with ischemia or skeletal muscle VEGF content, but did coincide with a large functional improvement in the reserve blood flow capacity of the limb. Following femoral artery removal in the rabbit, the time course of angiogenesis and arteriogenesis were clearly distinct. Tissue ischemia and/or VEGF may stimulate capillary sprouting, but this response does not translate to a significant improvement in collateral flow. The growth and development of the larger collateral vessels was correlated with a large functional improvement in collateral flow, and occurred at a time when VEGF levels were undetectable.

Time course of arteriogenesis following femoral artery occlusion in the rabbit.

We examined the time course of arteriogenesis (collateral artery growth) after femoral artery ligation and the effect of monocyte chemoattractant protein-1 (MCP-1). New Zealand White rabbits received MCP-1 or phosphate buffered saline (PBS) for a 1-week period, either directly or 3 weeks after femoral artery ligation (non-ischemic model). A control group was studied with intact femoral arteries and another 1 min after acute femoral artery ligation. Collateral conductance index significantly increased when MCP-1 treatment started directly after femoral artery ligation (acute occlusion: 0.94+/-0.19; without occlusion: 168.56+/-15.99; PBS: 4.10+/-0.48; MCP-1: 33.96+/-1.76 ml/min/100 mmHg). However, delayed onset of treatment 3 weeks after ligation and final study of conductance at 4 weeks showed no significant difference against a 4-week control (PBS: 79.08+/-7.24; MCP-1: 90.03+/-8.73 ml/min/100 mmHg). In these groups increased conductance indices were accompanied by a decrease in the number of visible collateral vessels (from 18 to 36 identifiable vessels at day 7 to about four at 21 days). We conclude that the chemokine MCP-1 markedly accelerated collateral artery growth but did not alter its final extent above that reached spontaneously as a function of time. We show thus for the first time that a narrow time window exists for the responsiveness to the arteriogenic actions of MCP-1, a feature that MCP-1 may share with other growth factors. We show furthermore that the spontaneous adaptation by arteriogenesis stops when only about 50% of the vasodilatory reserve of the arterial bed before occlusion are reached. The superiority of few large arterial collaterals in their ability to conduct large amounts of blood flow per unit of pressure as compared to the angiogenic response where large numbers of small vessels are produced with minimal ability to allow mass transport of bulk flow is stressed.

Collateral recruitment and “warm-up” after first exercise in ischemic heart disease

Background Proposed mechanisms for “warm-up” after angina on first exercise include ischemic preconditioning and collateral recruitment. The aim of this study was to determine whether patients with ischemic heart disease and well-developed coronary collateral vessels have a greater warm-up response than those with no visible collateral vessels. Methods And Results Fifteen patients with a total coronary occlusion and collateral vessels and 18 patients with a single coronary artery stenosis and no angiographically visible collateral vessels were studied. Warm-up was measured as the difference in ST depression on the second compared with the first of 2 sequential treadmill exercise tests separated by 10 minutes of rest. There was a trend for the duration of second exercise to increase more in patients with occlusion than in those with stenosis (+1.3 vs +0.54 minutes, respectively, P =.087). In both groups, ST depression was less on second exercise than on first exercise. The size of this decrease was greater in the occlusion group than in the stenosis group. ST depression at equivalent submaximal exercise decreased by 0.52 vs 0.19 mm, respectively (P =.049). The rate of increase in ST depression during exercise decreased by 1.08 versus 0.55 mm/min, respectively (P =.034). These differences were less after adjustment for ST depression on first exercise (P =.11 and P =.063, respectively). Conclusions The trend for a greater decrease in ST depression on second compared with first exercise in the patients with total coronary occlusion suggests that an increase in collateral flow is a mechanism for warm-up after first exercise in ischemic heart disease. (Am Heart J 2000;140:121-5.)

Constitutive Expression of phVEGF 165 After Intramuscular Gene Transfer Promotes Collateral Vessel Development in Patients With Critical Limb Ischemia

To the Editor: Baumgartner et al1 reported a significant advance in angiogenic gene therapy. They induced collateral neovascularization in 10 critically ischemic limbs by injection of vascular endothelial growth factor (phVEGF165) into the muscles of the ischemic limbs. The effect of the therapy was demonstrated by a significant rise in ankle-brachial index, newly visible collateral blood vessels on the contrast angiogram, healing of the patients’ former ulcers, and improvement in pain-free walking time. The authors cautiously claim that such …

Quantification of collateral flow in humans: a comparison of angiographic, electrocardiographic and hemodynamic variables

OBJECTIVESEvaluation of collateral vascular circulation according to hemodynamic variables and its relation to myocardial ischemia.BACKGROUNDThere is limited information regarding the hemodynamic quantification of recruitable collateral vessels.METHODSAngiography of the donor coronary artery was performed before and during balloon coronary occlusion in 63 patients with one vessel disease. Patients were divided into groups of those with an absence of collateral vessels (group 1, n = 10), those with recruitable collateral vessels (group 2, n = 23) and those with spontaneously visible collateral vessels (group 3, n = 30). During balloon inflation the coronary wedge/aortic pressure ratio (Pw/Pao) was determined as were collateral blood flow velocity variables, using a 0.014″ Doppler guide wire. Myocardial ischemia was defined as ≥0.1 mV ST-shift on a 12 lead electrocardiogram at 1 min coronary occlusion.RESULTSMyocardial ischemia was present in all patients of group 1, in 14 patients of group 2 and in 3 patients of group 3. Recruitable collateral flow without ischemia showed similar hemodynamic values as in group 3 while these values were similar to group 1 in regard to the presence of recruitable collateral vessels showing ischemia. Logistic regression analysis revealed both Pw/Pao and Vicolas independent predictors for the function of collateral vessels.CONCLUSIONSHemodynamic variables of collateral vascular circulation are better markers of the functional significance of collateral vessels than is coronary angiography. The total collateral blood flow velocity integral and coronary wedge/aortic pressure ratio are good and independent predictors of the function of collateral vessels producing complementary information.

Therapeutic Angiogenesis in Ischemic Heart Disease

Introduction: Coronary heart disease is the leading cause of death in the Western world. Traditionally, patients with coronary heart disease requiring a revascularizing procedure have had to undergo either coronary artery bypass surgery, which usually involves open thoracotomy, or percutaneous transluminal balloon angioplasty, or a related procedure. Unfortunately, especially in patients with severe diffuse coronary heart disease, revascularization by these means can be difficult or even impossible. It has been shown that incomplete revascularization is a predictor of a worsened postoperative outcome (i.e., recurrent angina, myocardial infarction, or even death). We have known for a long time that many patients with ischemic disease develop angiographically visible collateral vessels. Initial research focused on the enlargement of preexisting collateral vessels, a process for which Wolfgang Schaper has proposed the term “neoarteriogenesis.”1 It is now clear that true “angiogenesis,” defined as the formation of new vessels by sprouting from preexisting vessels, also occurs. The latter also should be differentiated from the earliest embryological process of new vessel formation directly from mesodermal endothelial cell precursors, which is called “vasculogenesis.”2 In the last few years, clinical trials have been initiated with the goal of enhancing angiogenesis to treat peripheral vascular disease and ischemic heart disease. In this review, we will summarize the underlying concepts for this novel mode of therapy, plus the available information on its efficacy. The sprouting of capillaries from preexisting vessels (angiogenesis) is a normal and necessary process to supply the growing organism with nutrients and oxygen. Ischemic vascular disease, along with wound healing and the monthly endometrial proliferation, are conditions in which angiogenesis may be beneficial or necessary. Of course, angiogenesis is also part of the pathogenic mechanism of tumors, hemangiomas, proliferative retinopathies, and inflammatory diseases like rheumatoid arthritis and psoriasis.3 Even in ischemic vascular disease, it is possible that vascularization of atherosclerotic plaques by vessels arising from the vasa vasorum leads to hemorrhages with consequent plaque instability,4 and thus enhancing angiogenesis may promote vessel pathology. The vasculature of a 70 kg adult is lined by approximately 1,000 m2 of quiescent endothelial cells with a very low turnover rate that can exceed 1,000 days.3 Upon angiogenic activation (e.g., by growth factors released during ischemia), a local inflammatory reaction often can be observed with increased local vascular permeability, vasodilation, and accumulation of monocytes and macrophages. These latter cells release more cytokines and growth factors, which lead to the accumulation of additional inflammatory cells. They also release enzymes that promote the proteolytic degradation of the underlying extracellular matrix and basal membrane. Such degradation causes the endothelial cells to detach from their neighboring cells and the underlying matrix, followed by chemotactic migration and proliferation. Subsequently, formation of a lumen occurs and, eventually, maturation and growth of the newly formed vessel.2,5,6 In vessels larger than capillaries, vascular smooth muscle cells proliferate and migrate as well. In addition, it recently has been shown that circulating endothelial cell precursors released from the bone marrow participate in the formation of new vessels in the setting of tissue ischemia.7 Investigators currently are assessing the importance and contribution of the latter mechanism to neovascularization in the adult organism. If it proves substantial, the traditional means of differentiating between angiogenesis and vasculogenesis may need to be reconsidered.

Treatment of thromboangiitis obliterans (Buerger's disease) by intramuscular gene transfer of vascular endothelial growth factor: Preliminary clinical results

Purpose: Thromboangiitis obliterans (TAO), or Buerger's disease, a distinct form of vascular occlusive disease that afflicts the peripheral arteries of young smokers, is often characterized by an inexorable downhill course even in patients who discontinue smoking once a stage of critical limb ischemia associated with ulceration or gangrene is reached. As part of a phase I clinical trial to document the safety and efficacy of intramuscular gene transfer of naked plasmid DNA-encoding vascular endothelial growth factor (phVEGF 165) in the treatment of critical limb ischemia, we treated TAO in 6 patients. Methods: Seven limbs in 6 patients (3 men, 3 women; mean age, 33 years; range, 33 to 51 years) who satisfied the criteria for TAO and had signs or symptoms of critical limb ischemia were treated twice, 4 weeks apart, with 2 or 4 mg of phVEGF 165, which was administered by direct intramuscular injection at 4 arbitrarily selected sites in the ischemic limb. The gene expression was documented by enzyme-linked immunosorbent assay that was performed on peripheral blood samples. Results: The ulcers that were nonhealing for more than 1 month healed completely in 3 of 5 limbs after the intramuscular phVEGF 165 gene therapy. Nocturnal rest pain was relieved in the remaining 2 patients, although both continue to have claudication. The evidence of the improved perfusion to the distal ischemic limb included an increase of more than 0.1 in the ankle brachial index in 3 limbs, an improved flow shown with magnetic resonance imaging in 7 of the 7 limbs, and newly visible collateral vessels shown with serial contrast angiography in 7 of the 7 limbs. The adverse consequences of the phVEGF 165 gene tranfer were limited to transient ankle or calf edema in 3 of the 7 limbs. Two patients with advanced distal forefoot gangrene ultimately required below-knee amputation despite the evidence of improved perfusion. A histologic section disclosed the classic pathologic findings of TAO. Conclusion: Therapeutic angiogenesis with phVEGF 165 gene transfer, if instituted before the development of forefoot gangrene, may provide a novel therapy for patients with advanced Buerger's disease that is unresponsive to standard medical or surgical treatment methods. (J Vasc Surg 1998;28:964-75.)

Coronary flow reserve in the contralateral artery increases after successful coronary angioplasty in patients with spontaneously visible collateral vessels

ObjectiveTo test the hypothesis that coronary flow reserve could increase in the angiographically normal contralateral artery after successful coronary angioplasty of an ipsilateral coronary artery.DesignCoronary flow reserve was estimated using...

Constitutive expression of phVEGF165 after intramuscular gene transfer promotes collateral vessel development in patients with critical limb ischemia.

Preclinical studies have indicated that angiogenic growth factors can stimulate the development of collateral arteries, a concept called "therapeutic angiogenesis." The objectives of this phase 1 clinical trial were (1) to document the safety and feasibility of intramuscular gene transfer by use of naked plasmid DNA encoding an endothelial cell mitogen and (2) to analyze potential therapeutic benefits in patients with critical limb ischemia. Gene transfer was performed in 10 limbs of 9 patients with nonhealing ischemic ulcers (n=7/10) and/or rest pain (n=10/10) due to peripheral arterial disease. A total dose of 4000 microg of naked plasmid DNA encoding the 165-amino-acid isoform of human vascular endothelial growth factor (phVEGF165) was injected directly into the muscles of the ischemic limb. Gene expression was documented by a transient increase in serum levels of VEGF monitored by ELISA. The ankle-brachial index improved significantly (0.33+/-0.05 to 0.48+/-0.03, P=.02); newly visible collateral blood vessels were directly documented by contrast angiography in 7 limbs; and magnetic resonance angiography showed qualitative evidence of improved distal flow in 8 limbs. Ischemic ulcers healed or markedly improved in 4 of 7 limbs, including successful limb salvage in 3 patients recommended for below-knee amputation. Tissue specimens obtained from an amputee 10 weeks after gene therapy showed foci of proliferating endothelial cells by immunohistochemistry. PCR and Southern blot analyses indicated persistence of small amounts of plasmid DNA. Complications were limited to transient lower-extremity edema in 6 patients, consistent with VEGF enhancement of vascular permeability. These findings may be cautiously interpreted to indicate that intramuscular injection of naked plasmid DNA achieves constitutive overexpression of VEGF sufficient to induce therapeutic angiogenesis in selected patients with critical limb ischemia.