Junaid Y. Malek

Combined microsurgical and endovascular management of complex intracranial aneurysms

OBJECTIVEThe disciplines of microneurosurgery and cranial base surgery have reached maturity, and technical advances in the surgical management of aneurysms are limited. Although most aneurysms can be clipped microsurgically or coiled endovascularly, a subset of patients may require a combined approach. A consecutive series of patients with aneurysms in one surgeon’s cerebrovascular practice was reviewed retrospectively to analyze strategies for integrating microsurgical and endovascular techniques in the management of complex aneurysms. METHODSBetween 1997 and 2001, 596 aneurysms in 491 patients were treated microsurgically by the senior author (MTL) at the University of California, San Francisco, and 77 of these patients (96 aneurysms) were managed with a multimodality approach comprising a total of eight different combinations: selective revascularization and aneurysm occlusion (n = 23), endovascular and surgical trapping (n = 1), clipping of the aneurysm after attempted or incomplete coiling (n = 22), coiling after attempted or incomplete clipping (n = 5), clipping of recurrent aneurysm after coiling (n = 6), coiling of recurrent aneurysm after clipping (n = 1), clipping and coiling of multiple remote aneurysms (n = 13), and coiling after previous surgery (n = 6). RESULTSA total of 96 aneurysms were treated with combined therapy, of which 43% were large or giant in size and 34% had fusiform or dolichoectatic morphology. Complete angiographic obliteration was achieved in 91 aneurysms (95%). Overall, 66 patients (86%) had good outcomes (Glasgow Outcome Scale score of 4 or 5; mean follow-up, 9 mo). The treatment mortality rate was 9.1% (seven patients), and permanent treatment-associated neurological morbidity rate was 5.2% (four patients). CONCLUSIONEvolving endovascular technologies need to be integrated into the microsurgical management of aneurysms. Multimodality approaches are best used with complex aneurysms in which conventional therapy with a single modality has failed. Revascularization remains a unique surgical contribution to the overall management of aneurysms with which current endovascular techniques cannot be used. Multimodality management should be considered an elegant addition to the therapeutic armamentarium that, through simplification and increased safety, improves the treatment of complex aneurysms beyond what is achievable by performing clipping or coiling alone.

Vascular injury during anterior exposure of the spine

OBJECTIVES Fusion of the spine is often performed from an anterior approach requiring mobilization of aorta, iliac artery, and vein. This study describes the preferred techniques and incidence of vascular complications at a spine center. METHODS Information and operative notes on all consecutive patients undergoing anterior exposure were entered into a database that was retrospectively reviewed. Four hundred eighty-two procedures performed on 480 patients at one spine center between January of 1997 and December of 2002 were analyzed. Demographics, technique, levels of exposure, and history of prior spine surgery were recorded. Primary outcomes measured included intraoperative vascular complications, estimated operative blood loss, and operative mortality. Vascular injury was defined as any case in which a suture was required to control bleeding. Major vascular injuries were defined as those requiring transfusion, vascular reconstruction, or blood loss greater than 300 cc. RESULTS An intraoperative vascular injury occurred in 11% (54/480) of patients. The majority of these (45/54) were minor injuries treated with simple suture repair. Nine (1.9%) major vascular injuries did occur; the majority identified and treated during the exposure and not the spinal fusion. One patient required a return to the operating room 24 hours after the initial procedure for removal of packs placed to control severe bleeding from an avulsed branch of the internal iliac vein. Median estimated blood loss (EBL) was 150 cc and there were no mortalities. Eighty-three percent of overall injuries involved exposure of L4-5, and this was statistically significant odds ratio (OR) 2.73, P = .005. The lowest incidence of injury occurred when L5-S1 alone was exposed (5.1% of injuries) OR .34, P = .01. Prior spine procedures did not significantly increase the risk of injury, P = .67. Other factors that did not significantly increase risk included gender, multiple levels vs single levels and technique of exposure. CONCLUSION Exposure to the lumbar spine can be readily accomplished via a retroperitoneal approach. Minor vascular injuries during exposure, mostly venous, are not uncommon and are easily repaired. They are increased when L4-5 is part of the exposure and are lowest when L5-S1 alone is exposed. Major injuries occur in less than 2% of patients.

Gene Expression of Pro-Inflammatory Cytokines and Neuropeptides in Diabetic Wound Healing

The interaction between neuropeptides and cytokines and its role in cutaneous wound healing is becoming evident. The goal of the present study is to investigate the impact of diabetes on peripheral cytokine and neuropeptide expression and its role in diabetic wound healing. To achieve this goal, the effect of diabetes on wound healing, along with the role of inflammatory cytokines such as interleukin-6 (IL-6) and interleukin-8 (IL-8) secreted in the wound microenvironment, and neuropeptides such as substance P (SP) and neuropeptide Y (NPY), secreted from peripheral nerves is monitored in non-diabetic and diabetic rabbits. Rabbits in the diabetic group received alloxan monohydrate (100mg/kg i.v.). Ten days after diabetic induction, four full thickness circular wounds were created in both ears using a 6mm punch biopsy. Wound healing was monitored over 10 d and gene expression of cytokines and neuropeptides was assessed in the wounds. Compared with the non-diabetic rabbits, wounds of diabetic rabbits heal significantly slower. Diabetic rabbits show significantly increased baseline gene expression of IL-6 and IL-8, their receptors, CXCR1, CXCR2, GP-130, and a decrease of prepro tachykinin-A (PP-TA), the precursor of SP, whereas the expression of prepro-NPY (PP-NPY), the precursor of NPY is not different. Similarly, baseline protein expression of CXCR1 is higher in diabetic rabbit skin. Post-injury, the increase over baseline gene expression of IL-6, IL-8, CXCR1, CXCR2, and GP-130 is significantly less in diabetic wounds compared with non-diabetic wounds. Although there is no difference in PP-TA gene expression between non-diabetic and diabetic rabbits post-injury, the gene expression of PP-NPY is reduced in diabetic rabbits. In conclusion, diabetes causes dysregulation in the neuropeptide expression in the skin along with a suppressed focused inflammatory response to injury. This suggests that the chronic inflammation in the skin of diabetic rabbits inhibits the acute inflammation much needed for wound healing.

MARCKS silencing differentially affects human vascular smooth muscle and endothelial cell phenotypes to inhibit neointimal hyperplasia in saphenous vein

Intimal hyperplasia (IH) limits the patency of all cardiovascular vein bypass grafts. We previously found the myristoylated alanine‐rich C kinase substrate (MARCKS), a key protein kinase C (PKC) substrate, to be up‐regulated in canine models of IH. Here, we further characterize the role of MARCKS in IH and examine the phenotypic consequences of MARCKS silencing by small interfering RNA (siRNA) transfection in human vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) in vitro and use a rapid 10‐min nonviral siRNA transfection technique to determine the effects of MARCKS silencing in human saphenous vein cultured ex vivo. We demonstrate MARCKS silencing attenuates VSMC migration and arrests VSMC proliferation in part through the up‐regulation of the cyclin‐dependent kinase inhibitor p27kip1. Conversely, MARCKS silencing had little or no effect on EC migration or proliferation. These phenotypic changes culminated in reduced neointimal formation in cultured human saphenous vein. These data identify MARCKS as a pathogenic contributor to IH and indicate therapeutic MARCKS silencing could selectively suppress the “atherogenic,” proliferative phenotype of VSMCs without collateral harm to the endothelium. This approach could be readily translated to the clinic to silence MARCKS in vein bypass grafts prior to implantation.— Monahan, T. S., Andersen, N. D., Martin, M. C, Malek, J. Y., Shrikhande, G. V., Pradhan, L., Ferran, C, LoGerfo, F. W. MARCKS silencing differentially affects human vascular smooth muscle and endothelial cell phenotypes to inhibit neointimal hyperplasia in saphenous vein. FASEB J. 23, 557–564 (2009)

Temporal Network Based Analysis of Cell Specific Vein Graft Transcriptome Defines Key Pathways and Hub Genes in Implantation Injury

Vein graft failure occurs between 1 and 6 months after implantation due to obstructive intimal hyperplasia, related in part to implantation injury. The cell-specific and temporal response of the transcriptome to vein graft implantation injury was determined by transcriptional profiling of laser capture microdissected endothelial cells (EC) and medial smooth muscle cells (SMC) from canine vein grafts, 2 hours (H) to 30 days (D) following surgery. Our results demonstrate a robust genomic response beginning at 2 H, peaking at 12–24 H, declining by 7 D, and resolving by 30 D. Gene ontology and pathway analyses of differentially expressed genes indicated that implantation injury affects inflammatory and immune responses, apoptosis, mitosis, and extracellular matrix reorganization in both cell types. Through backpropagation an integrated network was built, starting with genes differentially expressed at 30 D, followed by adding upstream interactive genes from each prior time-point. This identified significant enrichment of IL-6, IL-8, NF-κB, dendritic cell maturation, glucocorticoid receptor, and Triggering Receptor Expressed on Myeloid Cells (TREM-1) signaling, as well as PPARα activation pathways in graft EC and SMC. Interactive network-based analyses identified IL-6, IL-8, IL-1α, and Insulin Receptor (INSR) as focus hub genes within these pathways. Real-time PCR was used for the validation of two of these genes: IL-6 and IL-8, in addition to Collagen 11A1 (COL11A1), a cornerstone of the backpropagation. In conclusion, these results establish causality relationships clarifying the pathogenesis of vein graft implantation injury, and identifying novel targets for its prevention.

Neuroprotection against Ischemia by Metabolic Inhibition Revisited: A Comparison of Hypothermia, a Pharmacologic Cocktail and Magnesium Plus Mexiletine

ABSTRACT: Previous studies have suggested that metabolic inhibition is neuroprotective, but little evidence has been provided to support this proposal. Using the in vitro rabbit retina preparation as an established model of the central nervous system (CNS), we measured the rate of glucose utilization and lactate production, and the light‐evoked compound action potentials (CAPs) as indices of neuronal energy metabolism and electrophysiologic function, respectively. We examined the effect of three (3) treatments options: hypothermia (i.e., 33°C and 30°C), a six‐member pharmacologic “cocktail” (tetrodotoxin (0.1 μM), 2‐amino‐4‐phosphonobutyric acid (20 μM), 2‐amino‐5‐phosphonovaleric acid (1 mM), amiloride (1 mM), magnesium (10 mM) and lithium (10 mM)) and the combination of magnesium (Mg2+ 1 mM) and mexiletine (Mex, 300 μM) on in vitro rabbit retinas, to see if there is a correlation between neuronal energy metabolism during ischemia (simulated by the reduction of oxygen from 95% to 15% and glucose from 6 mM to 1 mM), and the subsequent recovery of function. Hypothermia and the “cocktail” significantly inhibited both the rate of glucose utilization and lactate production, whereas Mg2+ and/or Mex showed only a nonsignificant tendency toward a reduction, compared to control retinas. Recovery of light‐evoked CAPs was significantly improved in hypothermia‐ and cocktail‐treated retinas, as well as with retinas exposed to the combination of Mg2+ plus Mex, but not with Mg2+ or Mex alone, relative to control retinas. A linear regression analysis of the % recovery of function versus the % reduction in the rate of glucose utilization during ischemia showed a significant correlation ( r2= 0.80 , correlation coefficient = 0.9 , p < 0.05 ) between these two parameters. This and other data discussed provide convincing evidence that there is a correlation between metabolic inhibition, achieved during ischemia, and neuroprotection.

Endoluminal intervention for limb salvage after failed lower extremity bypass graft

BACKGROUND Lower extremity bypass graft failure in patients with limb-threatening ischemia carries an amputation rate of greater than 50%. Redo bypass is often difficult due to the lack of conduit, adequate target, or increased surgical risk, and resultant limb salvage rates are reduced significantly compared with the index operation. We set forth to investigate whether endovascular treatment in this setting would result in an acceptable limb salvage rate. METHODS A single-institution, retrospective review from June 2004 to December 2007 of patients with failed grafts who underwent endovascular treatment with percutaneous balloon angioplasty (PTA) of their native circulation was performed. Stents were selectively used in cases of post-PTA residual stenosis or flow-limiting dissection. Technical success was defined as a residual stenosis less than 30%. Percutaneous attempts at bypass graft salvage were excluded. Demographics, comorbidities, procedural data, and follow-up information were recorded. Descriptive, logistic regression and life-table analyses were performed. RESULTS Twenty-four lower extremities were treated in 23 patients with failed bypass grafts. Average patency of the index graft before failure was 647 days (range 5-2758). Mean age was 68 years (range 51-85), 62% were male and 81% had diabetes mellitus (DM). 87.5% of limbs treated had TransAtlantic InterSociety Consensus (TASC) C and D lesions and 62% had multiple lesions. Technical success was achieved in 100%. Mean follow-up was 25.6 months. At follow-up, there were 17 PTA failures, which resulted in: amputation (4), redo-bypass (3), and redo-PTA (11). Freedom from surgical revision and PTA failure was 89% (+/- 0.07 SE) and 28% (+/- 0.09 SE) respectively. PTA secondary patency was 72% (+/- 0.09 SE) and limb-salvage was 81% (+/- 0.08 SE) at both 12 and 24 months. Overall survival was 83% (+/- 0.07 SE) and 77% (+/- 0.09 SE) at 12 and 24 months, respectively. CONCLUSIONS Endovascular treatment of patients with previously failed bypass grafts results in a high rate of limb salvage. This is a reasonable option in selected patients and the primary choice in those with poor targets, conduit, or excess surgical risk. Endovascular salvage should be considered before proceeding to primary amputation.

Endothelial Cells Are Susceptible to Rapid siRNA Transfection and Gene Silencing Ex Vivo

BACKGROUND Endothelial gene silencing via small interfering RNA (siRNA) transfection represents a promising strategy for the control of vascular disease. Here, we demonstrate endothelial gene silencing in human saphenous vein using three rapid siRNA transfection techniques amenable for use in the operating room. METHODS Control siRNA, Cy5 siRNA, or siRNA targeting glyceraldehyde-3-phosphate dehydrogenase (GAPDH) or endothelial specific nitric oxide synthase (eNOS) were applied to surplus human saphenous vein for 10 minutes by (i) soaking, (ii) applying 300 mm Hg hyperbaric pressure, or (iii) 120 mm Hg luminal distending pressure. Transfected vein segments were maintained in organ culture. siRNA delivery and gene silencing were assessed by tissue layer using confocal microscopy and immunohistochemistry. RESULTS Distending pressure transfection yielded the highest levels of endothelial siRNA delivery (22% pixels fluorescing) and gene silencing (60% GAPDH knockdown, 55% eNOS knockdown) as compared with hyperbaric (12% pixels fluorescing, 36% GAPDH knockdown, 30% eNOS knockdown) or non-pressurized transfections (10% pixels fluorescing, 30% GAPDH knockdown, 25% eNOS knockdown). Cumulative endothelial siRNA delivery (16% pixels fluorescing) and gene silencing (46% GAPDH knockdown) exceeded levels achieved in the media/adventitia (8% pixels fluorescing, 24% GAPDH knockdown) across all transfection methods. CONCLUSION Endothelial gene silencing is possible within the time frame and conditions of surgical application without the use of transfection reagents. The high sensitivity of endothelial cells to siRNA transfection marks the endothelium as a promising target of gene therapy in vascular disease.

Late gastric conduit ischemia from celiac artery stenosis salvaged by stent therapy

Gastric conduit necrosis after esophagectomy usually presents early in the postoperative phase. The etiology of this ischemia most often lies in the inability of the isolated right gastroepiploic artery to provide adequate blood supply to the entire conduit. Here we describe an unusual presentation of late gastric conduit ischemia, occurring many years after surgery as a result of atherosclerosis and stenosis of the celiac artery. Successful salvage of the gastric conduit was achieved with stenting of the celiac artery.