Regulation of Vascular Smooth Muscle Cell Growth by Survivin

The inhibitor of apoptosis protein survivin has long been of interest in the cancer literature for its role in both the regulation of cell proliferation and the inhibition of apoptosis. A growing body of literature has implicated survivin in the maladaptive pathways following vascular injury and, in particular, in the growth of vascular smooth muscle cells that comprise the hyperplastic neointimal lesions that characterize midterm vein bypass graft failure and restenosis following angioplasty and stenting. This review focuses on the emerging role of survivin in the regulation of smooth muscle cell growth and its implications for the prevention of restenosis following revascularization procedures. The expression, regulation, and function of survivin are addressed, as well as the current state of understanding regarding the effects of survivin inhibition in vitro and in vivo.

Distal digital embolization from a thrombosed aneurysmal hemodialysis arteriovenous fistula: the benefit of a hybrid approach

Aneurysmal degeneration of a hemodialysis arteriovenous fistula (AVF) is common; however, distal digital embolization from an AVF is extremely rare. Even though the ultimate fate of all arteriovenous hemodialysis access is thrombosis with minimal consequences, dislodgement of thrombus at the proximal anastomosis could lead to ischemia of the distal arterial circulation. We here present a case of a renal transplant patient with a thrombosed aneurysmal AVF who presented with acute digital ischemia successfully treated with combination catheter-directed thrombolysis and open repair. No similar report was found describing this entity treated with this approach.

Increased Risk of Deep Venous Thrombosis with Endovascular Cooling in Patients with Traumatic Head Injury

Endovascular therapeutic hypothermia has been shown to preserve neurological function and improve outcomes; however, its use and potential complications have not been fully described in patients with traumatic head injuries. We believe that the use of endovascular cooling leads to deep venous thrombosis (DVT) in this high-risk population. We performed a retrospective review of 11 patients with severe head injuries admitted to our Level I trauma center surgical intensive care unit who underwent intravascular cooling. Duplex sonograms were obtained after 4 days at catheter removal or with clinical symptoms that were suspicious for DVT. Patients had a mean age of 23.2 (range, 16–42) years and an Injury Severity Score of 31.9 (range, 25–43). The overall incidence of DVT was 50 per cent. The DVT rate was 33 per cent if catheters were removed in 4 days or less and 75 per cent if removed after 4 days (risk ratio = 2.25; odds ratio = 6; P = ns). An elevated international normalized ratio upon admission was protective against DVT (no DVT = 1.26 vs DVT = 1.09; P = 0.02). Inferior vena cava filters were placed in most patients with DVT. The use of endovascular cooling catheters is associated with increased risk of DVT in patients with traumatic head injuries. Therefore, we discourage the use of endovascular cooling devices in this patient population.

Increased risk of deep venous thrombosis with endovascular cooling in patients with traumatic head injury

Endovascular therapeutic hypothermia has been shown to preserve neurological function and improve outcomes; however, its use and potential complications have not been fully described in patients with traumatic head injuries. We believe that the use of endovascular cooling leads to deep venous thrombosis (DVT) in this high-risk population. We performed a retrospective review of 11 patients with severe head injuries admitted to our Level I trauma center surgical intensive care unit who underwent intravascular cooling. Duplex sonograms were obtained after 4 days at catheter removal or with clinical symptoms that were suspicious for DVT. Patients had a mean age of 23.2 (range, 16-42) years and an Injury Severity Score of 31.9 (range, 25-43). The overall incidence of DVT was 50 per cent. The DVT rate was 33 per cent if catheters were removed in 4 days or less and 75 per cent if removed after 4 days (risk ratio = 2.25; odds ratio = 6; P = ns). An elevated international normalized ratio upon admission was protective against DVT (no DVT = 1.26 vs DVT = 1.09; P = 0.02). Inferior vena cava filters were placed in most patients with DVT. The use of endovascular cooling catheters is associated with increased risk of DVT in patients with traumatic head injuries. Therefore, we discourage the use of endovascular cooling devices in this patient population.

Regulation of Vein Graft Hyperplasia by Survivin, an Inhibitor of Apoptosis Protein

OBJECTIVE

Survivin (SVV) is an inhibitor of apoptosis protein (IAP) that is upregulated in cancer and has recently been implicated in vascular injury. We sought to investigate the role of SVV in vein graft hyperplasia.

METHODS AND RESULTS

Adenoviral constructs expressing a dominant-negative (AdT34A) and wild-type (AdWT) SVV were used. Proliferation and apoptosis were assayed on endothelial cells (ECs) and smooth muscle cells (SMCs) from human saphenous vein. A rabbit carotid interposition vein graft model (N=31) was used, with adventitial gene transfer of SVV constructs. In vitro, overexpression of SVV was associated with protection from cytokine-induced apoptosis in ECs and SMCs; conversely, AdT34A directly induced apoptosis in these cells. SMC proliferation was increased by AdWT infection, whereas AdT34A reduced proliferation; both effects were serum-dependent. Expression of platelet-derived growth factor (PDGF) in SMCs was regulated by functional SVV expression in analogous fashion. In vivo, proliferation and apoptosis (7 days), as well as wall thickness (30 days), were modified by adenoviral-mediated SVV expression. Adventitial angiogenesis was regulated by the SVV-expressing constructs in a fashion parallel to wall thickness changes.

CONCLUSIONS

SVV is a critical regulator of multiple processes, including proliferation, apoptosis, and angiogenesis, that determine the remodeling response of vein grafts following arterialization.

Survivin expression is up-regulated in vascular injury and identifies a distinct cellular phenotype

OBJECTIVES

The healing response to vascular injury is characterized by neointimal thickening. Proliferation and phenotypic transformation of vascular smooth muscle cells (SMCs) have been implicated in this process. We sought to investigate the role of survivin, a dual regulator of cell proliferation and apoptosis, in lesion formation after diverse forms of vascular injury.

METHODS

Rabbits underwent either carotid interposition vein grafting (n = 17) or bilateral femoral balloon injury (BI; n = 29); some in the BI group were placed on a high-cholesterol diet. A subset of BI arteries were treated with local adenoviral gene delivery of a survivin dominant negative-mutant (AdT34A) versus vector or saline controls. Survivin expression in vessels was analyzed by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and by immunohistochemistry (IHC), which also included markers of SMC differentiation. Specimens of human tissue including failed lower extremity bypass grafts and carotid plaque were also examined.

RESULTS

RT-PCR and IHC demonstrated increased survivin expression in all experimental models, colocalizing at early times with proliferating and alpha-actin-expressing cells but was largely absent in mature, contractile SMCs. Delivery of AdT34A after BI attenuated neointimal hyperplasia.

CONCLUSION

These studies provide strong evidence supporting a role for survivin in the cellular response to vascular injury.

CLINICAL RELEVANCE

The regulation of cell proliferation, death, and phenotype after vascular interventions remains incompletely understood. We investigated the role of the inhibitor of apoptosis protein survivin in diverse models of vascular injury. The results suggest that survivin is an important modulator of the generalized vascular injury response and may represent a relevant target for therapies targeting intimal hyperplasia.

Genetic therapy for vein bypass graft disease: current perspectives

Although continued progress in endovascular technology holds promise for less invasive approaches to arterial diseases, surgical bypass grafting remains the mainstay of therapy for patients with advanced coronary and peripheral ischemia. In the United States, nearly 400,000 coronary and 100,000 lower extremity bypass procedures are performed annually. The autogenous vein, particularly the greater saphenous vein, has proven to be a durable and versatile arterial substitute, with secondary patency rates at 5 years of 70 to 80% in the extremity. However, vein graft failure is a common occurrence that incurs significant morbidity and mortality, and, to date, pharmacologic approaches to prolong vein graft patency have produced limited results. Dramatic advances in genetics, coupled with a rapidly expanding knowledge of the molecular basis of vascular diseases, have set the stage for genetic interventions. The attraction of a genetic approach to vein graft failure is based on the notion that the tissue at risk is readily accessible to the clinician prior to the onset of the pathologic process and the premise that genetic reprogramming of cells in the wall of the vein can lead to an improved healing response. Although the pathophysiology of vein graft failure is incompletely understood, numerous relevant molecular targets have been elucidated. Interventions designed to influence cell proliferation, thrombosis, inflammation, and matrix remodeling at the genetic level have been described, and many have been tested in animal models. Both gene delivery and gene blockade strategies have been investigated, with the latter reaching the stage of advanced clinical trials.

Genetic interventions for vein bypass graft disease: a review

The failure of vein bypass grafting in the coronary or lower extremity circulation is a common clinical occurrence that incurs significant morbidity, mortality, and cost. Vein grafts are uniquely amenable to intraoperative genetic modification because of the ability to manipulate the tissue ex vivo with controlled conditions. Although the pathophysiology of vein graft failure is incompletely understood, numerous relevant molecular targets have been elucidated. Interventions designed to influence cell proliferation, thrombosis, inflammation, and matrix remodeling at the genetic level have been described, and many have been tested in animal models. Both gene delivery and gene blockade strategies have been investigated, with the latter now reaching the stage of advanced clinical trials. This review describes the basic and translational science of genetic interventions for vein graft disease and the current state of application in the clinic.

Mitral balloon valvotomy for patients with mitral stenosis in atrial fibrillation: immediate and long-term results

OBJECTIVES

The purpose of this study was to examine the effect of atrial fibrillation (AF) on the immediate and long-term outcome of patients undergoing percutaneous mitral balloon valvuloplasty (PMV).

BACKGROUND

There is controversy as to whether the presence of AF has a direct negative effect on the outcome after PMV.

METHODS

The immediate procedural and the long-term clinical outcome after PMV of 355 patients with AF were prospectively collected and compared with those of 379 patients in normal sinus rhythm (NSR).

RESULTS

Patients with AF were older (62 +/- 12 vs. 48 +/- 14 years; p < 0.0001) and presented more frequently with New York Heart Association (NYHA) class IV (18.3% vs. 7.9%; p < 0.0001), echocardiographic score >8 (40.1% vs. 25.1%; p < 0.0001), calcified valves under fluoroscopy (32.4% vs. 18.8%, p < 0.0001) and with history of previous surgical commissurotomy (21.7% vs. 16.4%; p = 0.0002). In patients with AF, PMV resulted in inferior immediate and long-term outcomes, as reflected in a smaller post-PMV mitral valve area (1.7 +/- 0.7 vs. 2 +/- 0.7 cm2; p < 0.0001) and a lower event free survival (freedom of death, redo-PMV and mitral valve surgery) at a mean follow-up time of 60 months (32% vs. 61%; p < 0.0001). In the group of patients in AF, severe post-PMV mitral regurgitation (> or =3+) (p = 0.0001), echocardiographic score >8 (p = 0.004) and pre-PMV NYHA class IV (p = 0.046) were identified as independent predictors of combined events at follow-up.

CONCLUSIONS

Patients with AF have a worse immediate and long-term outcomes after PMV. However, the presence of AF by itself does not unfavorably influence the outcome, but is a marker for clinical and morphologic features associated with inferior results after PMV.

Comparison of immediate and long-term results of mitral balloon valvotomy with the double-balloon versus Inoue techniques

There is controversy as to whether the double-balloon or Inoue technique of percutaneous mitral balloon valvotomy (PMBV) provides superior immediate and long-term results. This study compares the immediate procedural and long-term outcomes of patients undergoing PMBV using the double-balloon versus the Inoue techniques. Seven hundred thirty-four consecutive patients who underwent PMBV using the double-balloon (n = 621) or Inoue technique (n = 113) were studied. There were no statistically significant differences in baseline clinical and morphologic characteristics between the double-balloon and Inoue patients. The double-balloon technique resulted in superior immediate outcome, as reflected in a larger post-PMBV mitral valve area (1.9 +/- 0.7 vs 1.7 +/- 0.6 cm2; p = 0.005) and a lower incidence of 3+ mitral regurgitation after PMBV (5.4% vs 10.6%; p = 0.05). This superior immediate outcome of the double-balloon technique was observed only in the group of patients with echocardiographic score < or = 8 (post-PMBV mitral valve areas 2.1 +/- 0.7 vs 1.8 +/- 0.6; p = 0.004). Despite the difference in immediate outcome, there were no significant differences in event-free survival at long-term follow-up between the 2 techniques. Our study demonstrates that compared with the Inoue technique, the double-balloon technique results in a larger mitral valve area and less degree of severe mitral regurgitation after PMBV. Despite the difference in immediate outcome between both techniques, there were no significant differences in event-free survival at long-term follow-up.