Michael A. Curi

Prevention of restenosis by a herpes simplex virus mutant capable of controlled long-term expression in vascular tissue in vivo.

Neointimal hyperplasia resulting from vascular smooth muscle cell (SMC) proliferation and luminal migration is the major cause of autologous vein graft failure following vascular coronary or peripheral bypass surgery. Strategies to attenuate SMC proliferation by the delivery of oligonucleotides or genes controlling cell division rely on the use of high concentrations of vectors, and require pre-emptive disruption of the endothelial cell layer. We report a genetically engineered herpes simplex virus (HSV-1) mutant that, in an in vivo rabbit model system, infects all vascular layers without prior injury to the endothelium; expresses a reporter gene driven by a viral promoter with high efficiency for at least 4 weeks; exhibits no systemic toxicity; can be eliminated at will by administration of the antiviral drug acyclovir; and significantly reduces SMC proliferation and restenosis in vein grafts in immunocompetent hosts.

Routine early postoperative duplex scanning is unnecessary following uncomplicated carotid endarterectomy.

Although early postoperative duplex scanning has become routine after carotid endarterectomy (CEA), it is unclear whether the results of these scans alter clinical management. The purpose of this study was to critically examine the usefulness of early postoperative duplex scans in evaluating the ipsilateral carotid artery (for technical perfection) as well as the contralateral carotid artery (for potential velocity changes after improvements in ipsilateral flow). Consecutive patients undergoing CEA between January 1995 and June 1999 in a tertiary hospital setting were studied. Patients underwent early postoperative duplex scanning according to the discretion of the operating surgeon and the availability of the patient. In 212 patients 236 CEAs were performed with selective use of patch closure (49%), intraluminal shunting (19%), and intraoperative completion imaging studies (1 4%). Neurologic complications included 3 transient ischemic attacks (TIAs) (1.3%), 3 nondisabling strokes (1.3%), and 3 disabling strokes (1.3%). There was 1 30-day death from myocardial infarction. Patients were followed up for a median of 18 months (range 0-72 months). Sixty-five percent of patients undergoing uncomplicated CEA (147/227) underwent early duplex surveillance within 6 months of operation. Unsuspected sonographic abnormalities were discovered in 8 patients (5%), including 7 cases of mild internal carotid artery (ICA) stenosis (> 50% by velocity criteria) and 1 case of common carotid artery (CCA) stenosis (intimal flap). None of the patients with ICA stenosis developed symptoms or required operation at any time. The CCA intimal flap was electively repaired without complication. Postoperative changes in velocity in the contralateral ICA were found in 8/48 (17%) cases. There were 3 cases of increased velocity, upgrading 1 from 0-49% to 50-79% stenosis and upgrading 2 from 50-79% to 80-99% stenosis. The latter patients both underwent uneventful contralateral CEA. There were 6 cases of decreased velocity, resulting in downgrading of stenoses from 50-79% to 0-49% (n = 5) or from 80-99% to 50-79% (n = 1). Only the latter patient underwent contralateral CEA; the remainder have been followed up without intervention. Early scanning appeared to offer no clinical benefit; survival and neurologic outcome were the same in the 135 patients scanned within the first 6 months as in the 68 patients whose first postoperative scan occurred later (4-year neurologic event rate 0% in both groups; patient survival with early duplex 98 ± 1.5%, without early duplex 96 ±2.6%; p = NS). Early ipsilateral duplex abnormalities following CEA are infrequent in asymptomatic patients and, even if found, rarely alter management. Patients with bilateral stenosis being considered for contralateral CEA should undergo repeat duplex scanning after the first operation, because of the significant rate (19%) of contralateral velocity changes induced by ipsilateral CEA.

Sustained inhibition of experimental neointimal hyperplasia with a genetically modified herpes simplex virus

OBJECTIVE Reported herein is a potential strategy for sustained smooth muscle cell (SMC) inhibition with a virulence-attenuated herpes simplex virus (HSV). Experiments were conducted in vitro to demonstrate selective SMC cytotoxicity and in vivo to demonstrate reduced neointimal hyperplasia (NIH) in a clinically relevant animal model. METHODS In vitro: Cultured human umbilical artery smooth muscle cells (UASMC) and venous endothelial cells (HUVEC) were exposed to varying multiplicities of infection (MOI) of a gamma(1)34.5-deleted HSV-1 virus (R849). Cell survival was assessed at 48 and 72 hours with a colorimetric MTT viability assay. In vivo: New Zealand White rabbit external jugular veins (n = 21) were exposed to R849 (2.5 x 10(6) pfu/mL) or culture medium at 110 to 120 mm Hg for 10 minutes, then fashioned as vein patches on carotid arteries. Carotid arteries were ligated distally to decrease blood flow and stimulate a hyperplastic response (ultra-low shear stress model). After 2, 4, 12, and 24 weeks, patched segments were perfusion-fixed with glutaraldehyde and morphometrically examined for NIH formation. RESULTS In vitro: At 48 hours, R849 exhibited preferential cytotoxicity to UASMC compared with HUVEC, with 11% +/- 10% of UASMCs and 49% +/- 8% of HUVECs surviving after infection with MOI = 25 (P <.05). Higher MOI resulted in poor survival of both cell lines. In vivo: Blood flow was similarly reduced in all animals both at surgery (0.9 +/- 0.1 mL/min vs 1.6 +/- 0.3 mL/min) and at harvest (2.7 +/- 0.4 mL/min vs 2.5 +/- 0.5 mL/min). R849-infected patches exhibited markedly less NIH than control patches did at 2 weeks (162 +/- 14 microm vs 49 +/- 6 microm; P <.05), 4 weeks (190 +/- 27 microm vs 67 +/- 8 microm; P <.05), and 12 weeks (233 +/- 18 microm vs 113 +/- 2 microm; P <.05). CONCLUSION The virulence-attenuated HSV strain R849 demonstrates selective cytotoxicity for SMC and is capable of sustained inhibition of NIH in an experimental model of vein graft failure.

Hemodynamically “insignificant” stenoses stimulate neointimal thickening in experimental vein grafts

Vein graft stenoses <50% are believed to be clinically “insignificant” because they cause little decrement in blood flow. However, the possible deleterious effects of minor flow disturbances on long-term cellular proliferation are unknown. The purpose of this study was to evaluate the effect of artificially created 50% stenoses on neointimal thickening in experimental vein grafts. Fifteen male New Zealand White rabbits underwent carotid interposition bypass grafting using the external jugular vein. Mid-graft 50% stenoses were created in eight grafts by the application of a two-millimeter internal diameter stainless steel clip. After four weeks, the grafts were perfusion-fixed, excised, and histologic sections were examined for neointimal thickening. Application of the clip caused a 50% reduction in external diameter (3.9±0.4 mm to 2.0 mm), causing only slight perturbations in pressure gradient (ΔP=2.1±1.1 to 2.3±1.5 mmHg) and mean blood flow (flow 16±3.0 to 14±4.4 ml/min). After four weeks, four grafts had occluded (two from each group) and one clip had become dislodged, leaving ten grafts for analysis. Neointimal thickness was minimal in control grafts (88±12 µm), but was significantly increased in stenotic grafts both immediately proximal (200±39 µm; p=0.03) and immediately distal to the stenosis (230±50 µm; p=0.02). Hemodynamically “insignificant” stenoses stimulate vein graft neointimal thickening. These results support the continued use of graft surveillance and an aggressive approach to the treatment of “minimal” vein graft lesions.

Adjunctive Use of Thoracic Stent Cuffs to Treat Infrarenal Aortic Necks Too Large for Standard EVAR

Objectives: To evaluate early outcomes and short-term durability of thoracic stent cuffs in patients with abdominal aortic aneurysms (AAA) and infrarenal necks too large for standard endovascular aneurysm repair (EVAR) who were symptomatic, not suitable for open surgery, and could not wait for a custom fenestrated device to be created. Methods: From July 2010 to December 2012, 13 patients with juxtaor pararenal AAA underwent endovascular repair with thoracic aortic endografts as proximal aortic cuffs in conjunction with standard EVAR devices. The patients were symptomatic and were deemed unfit for open surgery due to severe cardiopulmonary and/or renal comorbidities. All patients had infrarenal neck diameters greater than the indications for use for standard aortic endografts. Primary end points were technical success (as defined by aneurysm exclusion without endoleak), follow-up aneurysm exclusion by computed tomographic angiogram, and 30-day and longterm mortality. Results: Thirteen patients (10 men, 3 women) with a mean age of 77.1 years underwent EVAR who presented with symptomatic juxtaor pararenal abdominal aortic aneurysms. The mean aneurysm size was 7.2 cm, and the mean infrarenal aortic neck diameter was 35.5 mm measured by centerline analysis. Technical success was achieved in 100% of cases. The 30-day mortality was 8% (one of 13 patients). At a mean follow-up of 524 days, there have been no endoleaks or other aneurysm related mortalities. There was one death due to stroke at 605 days postop. Conclusions: Complex endovascular repair of juxta and pararenal AAA using thoracic stents cuffs can be safely and successfully performed in symptomatic patients medically unfit for open repair. Using thoracic stent cuffs below the visceral vessels may reduce the complexity and possibly the risk of repair when compared with fenestrated endografts. These techniques can be used for urgent and emergent cases where the wait time for fenestrated technology is prohibitive. Although our results have demonstrated short-term success, long-term durability of this technique with further evaluation is required.

Gene Therapy for Cardiovascular Disease

During the past decade, gene therapy for the treatment of many inherited and acquired medical problems has become the subject of increasing focus in both the scientific litera ture and the lay press. This review examines the history and current status of gene therapy for advanced chronic periph eral and myocardial ischemia.