Partnering to build surgical capacity in low-resource settings: a qualitative study of Canadian global surgeons.

OBJECTIVES: This qualitative study aimed to explore the perspectives of Canadian global surgeons with experience developing surgical education partnerships with low- and middle-income countries (LMICs) for the purpose of identifying factors for success. DESIGN: A purposive sample of leaders from global surgery programmes at Canadian Faculties of Medicine participated in virtual semi-structured interviews. A six-phase thematic analysis was performed using a constructivist lens on verbatim transcripts by three independent researchers. Key factors for success were thematically collated with constant comparison and inter-investigator triangulation in NVivo software until theoretical saturation was reached. PARTICIPANTS: Fifteen surgeons, representing 11 subspecialties at 6 Canadian academic institutions and a combined experience across 6 continents, were interviewed between January and June 2022. RESULTS: Four facilitators for success of global surgery training programmes were identified, with a strong undertone of relationship-building permeating all subthemes: (1) facilitative skill sets and infrastructure, (2) longitudinal engagement, (3) local ownership and (4) interpersonal humility. Participants defined facilitative skill sets to include demonstrated surgical competence and facilitative infrastructure to include pre-existing local networks, language congruency, sustainable funding and support from external organisations. They perceived longitudinal engagement as spanning multiple trips, enabled by strong personal motivation and arrangements at their home institutions. Ownership of projects by local champions, including in research output, was noted as key to preventing brain drain and catalysing a ripple effect of surgical trainees. Finally, interviewees emphasised interpersonal humility as being crucial to decolonising the institution of global surgery with cultural competence, reflexivity and sustainability. CONCLUSIONS: The interviewed surgeons perceived strong cross-cultural relationships as fundamental to all other dimensions of success when working in low-resource capacity-building. While this study presents a comprehensive Canadian perspective informed by high-profile leadership in global surgery, a parallel study highlighting LMIC-partners' perspectives will be critical to a more complete understanding of programme success.

Sphingosine-1-Phosphate Signaling Regulates Myogenic Responsiveness in Human Resistance Arteries.

We recently identified sphingosine-1-phosphate (S1P) signaling and the cystic fibrosis transmembrane conductance regulator (CFTR) as prominent regulators of myogenic responsiveness in rodent resistance arteries. However, since rodent models frequently exhibit limitations with respect to human applicability, translation is necessary to validate the relevance of this signaling network for clinical application. We therefore investigated the significance of these regulatory elements in human mesenteric and skeletal muscle resistance arteries. Mesenteric and skeletal muscle resistance arteries were isolated from patient tissue specimens collected during colonic or cardiac bypass surgery. Pressure myography assessments confirmed endothelial integrity, as well as stable phenylephrine and myogenic responses. Both human mesenteric and skeletal muscle resistance arteries (i) express critical S1P signaling elements, (ii) constrict in response to S1P and (iii) lose myogenic responsiveness following S1P receptor antagonism (JTE013). However, while human mesenteric arteries express CFTR, human skeletal muscle resistance arteries do not express detectable levels of CFTR protein. Consequently, modulating CFTR activity enhances myogenic responsiveness only in human mesenteric resistance arteries. We conclude that human mesenteric and skeletal muscle resistance arteries are a reliable and consistent model for translational studies. We demonstrate that the core elements of an S1P-dependent signaling network translate to human mesenteric resistance arteries. Clear species and vascular bed variations are evident, reinforcing the critical need for further translational study.

A modified portfolio diet complements medical management to reduce cardiovascular risk factors in diabetic patients with coronary artery disease.

BACKGROUND & AIMS: Secondary prevention can improve outcomes in high risk patients. This study investigated the magnitude of cardiovascular risk reduction associated with consumption of a modified portfolio diet in parallel with medical management. DESIGN: 30 patients with type II diabetes, 6 weeks post bypass surgery received dietary counseling on a Modified Portfolio Diet (MPD) (low fat, 8 g/1000 kcal viscous fibres, 17 g/1000 kcal soy protein and 22 g/1000 kcal almonds). Lipid profiles, endothelial function and markers of glycemic control, oxidative stress and inflammation were measured at baseline and following two and four weeks of intervention. Seven patients with no diet therapy served as time controls. RESULTS: Consumption of the MPD resulted in a 19% relative reduction in LDL (1.9 ± 0.8 vs 1.6 ± 0.6 mmol/L, p < 0.001) with no change in HDL cholesterol. Homocysteine levels dropped significantly (10.1 ± 2.7 vs 7.9 ± 4 µmol/L, p = 0.006) over the study period. Flow mediated dilatation increased significantly in treated patients (3.8 ± 3.8% to 6.5 ± 3.6%, p = 0.004) while remaining constant in controls (p = 0.6). Endothelial progenitor cells numbers (CD34+, CD 133+ and UEA-1+) increased significantly following MPD consumption (p < 0.02) with no difference in migratory capacity. In contrast, time controls showed no significant changes. CONCLUSION: Dietary intervention in medically managed, high risk patients resulted in important reductions in risk factors. Clinical Trials registry number NCT00462436.

Preoperative carbohydrate loading in patients undergoing coronary artery bypass or spinal surgery.

BACKGROUND: Surgical stress creates a state of insulin resistance which may contribute to the development of hyperglycemia and, subsequently, postoperative complications. Consumption of an oral carbohydrate supplement before surgery may improve insulin sensitivity and reduce hyperglycemia. In this trial, we investigated the effects of carbohydrate supplementation on insulin resistance in coronary artery bypass graft and spinal decompression and fusion surgical patients. METHODS: Twenty-six patients undergoing coronary artery bypass graft and 12 undergoing spine surgery were randomized to receive 800 mL of an oral carbohydrate supplement the evening before and 400 mL 2 hours before surgery (CHO) or to fasting per standard hospital protocol (FAST). Baseline and postoperative measurements of insulin sensitivity were assessed using the short insulin tolerance test and homeostasis model assessment (HOMA). Interleukin-6, C-reactive protein, and free fatty acid levels were determined at baseline, postoperatively, and 24, 48, and 72 hours after surgery. Adiponectin was measured at baseline. Subjective feelings of well-being were measured immediately before surgery, and intra- and postoperative outcomes were documented. RESULTS: Postoperative insulin sensitivity did not differ significantly between the FAST and CHO groups whether measured by the short insulin tolerance test (rate of disappearance of blood glucose: 0.29%/min vs 0.38%/min; 99% confidence interval [CI] for difference, -0.17 to 0.32, P = 0.41) or HOMA (insulin resistance at values >1: 2.3 vs 3.3; 99% CI for difference, -0.8 to 2.8, P = 0.14). Circulating blood glucose levels after surgery in the CHO group, 6.2 mmol/L, tended to be lower than the FAST group, 6.9 mmol/L (99% CI for difference, -1.7 to 0.25, P = 0.05) and postoperative ß-cell function, measured by HOMA-ß (impaired ß-cell function at values <100%), tended to be higher in the CHO group, 87%, vs 47.5% in the FAST group (99% CI for difference, -9.4 to 88.4), but these differences were not significant. Adiponectin levels were not different between groups at baseline, and levels of free fatty acid, interleukin-6 and C-reactive protein were not affected by treatment. CONCLUSIONS: Preoperative carbohydrate loading did not improve postoperative insulin sensitivity. However, the observed postoperative blood glucose levels and ß-cell function as well as secondary outcomes warrant further study to reevaluate traditional fasting practices in surgical patients.

Sternal plate fixation for sternal wound reconstruction: initial experience (retrospective study).

BACKGROUND: Median sternotomy infection and bony nonunion are two commonly described complications which occur in 0.4-5.1% of cardiac procedures. Although relatively infrequent, these complications can lead to significant morbidity and mortality. The aim of this retrospective study is to evaluate the initial experience of a transverse plate fixation system following wound complications associated with sternal dehiscence with or without infection following cardiac surgery. METHODS: A retrospective chart review of 40 consecutive patients who required sternal wound reconstruction post sternotomy was performed. Soft tissue debridement with removal of all compromised tissue was performed. Sternal debridement was carried using ronguers to healthy bleeding bone. All patients underwent sternal fixation using three rib plates combined with a single manubrial plate (Titanium Sternal Fixation System®, Synthes). Incisions were closed in a layered fashion with the pectoral muscles being advanced to the midline. Data were expressed as mean±SD, Median (range) or number (%). Statistical analyses were made by using Excel 2003 for Windows (Microsoft, Redmond, WA, USA). RESULTS: There were 40 consecutive patients, 31 males and 9 females. Twenty two patients (55%) were diagnosed with sternal dehiscence alone and 18 patients (45%) with associated wound discharge. Thirty eight patients went on to heal their wounds. Two patients developed recurrent wound infection and required VAC therapy. Both were immunocompromised. Median post-op ICU stay was one day with the median hospital stay of 18 days after plating. CONCLUSION: Sternal plating appears to be an effective option for the treatment of sternal wound dehiscence associated with sternal instability. Long-term follow-up and further larger studies are needed to address the indications, benefits and complications of sternal plating.

Complete mapping of the tricuspid valve apparatus using three-dimensional sonomicrometry.

OBJECTIVE: Many surgeons consider the tricuspid valve to be a second-class structure. Our objective was to determine the normal anatomy and dynamic characteristics of the tricuspid valve apparatus in vivo and to discern whether this would aid the design of a tricuspid valve annuloplasty ring model. METHODS: Sixteen sonomicrometry crystals were placed around the tricuspid annulus, at the bases and tips of the papillary muscles, the free edges of the leaflets, and the right ventricular apex during cardiopulmonary bypass in 5 anesthetized York Hampshire pigs. Animals were studied after weaning of cardiopulmonary bypass on 10 cardiac cycles of normal hemodynamics. RESULTS: Sonomicrometry array localizations demonstrate the multiplanar shape of the tricuspid annulus. The tricuspid annulus reaches its maximum area (97.9 ± 25.4 mm(2)) at the end of diastole and its minimum area (77.3 ± 22.5 mm(2)) at the end of systole, and increases again in early diastole. Papillary muscles shorten by 0.8 to 1.5 mm (11.2%) in systole, and chordae tendineae straighten by 0.8 to 1.7 mm (11.4%) in systole. CONCLUSIONS: The shape of the tricuspid annulus is a multiplanar 3-dimensional one with its highest point at the anteroseptal commissure and its lowest point at the posteroseptal commissure, and the anteroposterior commissure is in a middle plane in between. The tricuspid annulus area reaches its maximum during diastole and its minimum during systole. The papillary muscles contract by the same amount of chordal straightening. The optimal tricuspid annuloplasty ring may be a multiplanar 3-dimensional one that mimics the normal tricuspid annulus.

Increased myocardial expression of angiopoietin-2 in patients undergoing urgent surgical revascularization for acute coronary syndromes.

BACKGROUND: Myocardial ischemia triggers the expression of multiple angiogenic factors including vascular endothelial growth factor and its receptors. However, vascular endothelial growth factor does not act in isolation. OBJECTIVE: To identify other genes important in the angiogenic response to clinically relevant myocardial ischemia. METHODS AND RESULTS: Paired intraoperative biopsies of ischemic and nonischemic myocardium were obtained from 12 patients with acute coronary syndromes (ACS) undergoing urgent coronary artery bypass graft surgery. Real-time polymerase chain reaction demonstrated significant upregulation of angiopoietin-2 (Ang-2) in ischemic myocardium, to a greater extent than other classical angiogenic factors. Microarray gene profiling identified Ang-2 to be among the top 10 differentially upregulated genes, in addition to genes involved in inflammation, cell signalling, remodelling and apoptosis. CONCLUSIONS: The present document is the first report of microarray analysis of patients with ACS, and supports an important role for Ang-2 in the angiogenic response to severe ischemia in the human heart. Common gene expression patterns in ACS may provide opportunities for targeted pharmacological and cellular intervention.

Evaluation of taste sensitivity in patients undergoing coronary artery bypass graft surgery.

Patients report changes in their perception of food tastes following cardiac surgery. This study was designed to explore changes in taste sensitivity following coronary artery bypass graft (CABG) surgery. Detection and recognition thresholds for sweet (sucrose), salty (sodium chloride), sour (citric acid), and bitter (quinine hydrochloride) were determined using the multiple forced-choice ascending concentration series method at baseline (presurgical), discharge, 5 weeks, and 16 weeks post-CABG. Demographic and gastrointestinal data were also obtained. Mixed-model analyses for repeated measures were performed using the baseline scores as reference. Thirty-three patients (mean age=61.8+/-8 years), consented to participate in the study between January 2003 and January 2006, with 13 completing all visits. Detection and recognition thresholds for sweet were significantly lower at discharge compared with baseline (1.7+/-1.2 vs 2.43+/-1.4 and 5.1+/-1.8 vs 5.5+/-1.3, respectively; P<0.05). This difference remained significant 4 months after surgery. Detection and recognition thresholds for salt also declined with time, with significant differences at 4 months post-surgery (2.3+/-2.0 vs 1.8+/-1.5; P<0.001 and 5.3+/-1.3 vs 4.2+/-2.2; P<0.05, respectively). The same trends were noted for the detection of sour and the recognition of bitter. Patients undergoing CABG demonstrated stable or improved taste sensitivity during the recovery period. Further studies aimed at clarifying the relationships between the biological state, taste sensitivity, reported taste changes, and food intake will help to clarify the clinical impact of taste changes and subsequently to guide clinical nutrition care.

Can local application of Tranexamic acid reduce post-coronary bypass surgery blood loss? A randomized controlled trial.

BACKGROUND: Diffuse microvascular bleeding remains a common problem after cardiac procedures. Systemic use of antifibrinolytic reduces the postoperative blood loss. The purpose of this study was to examine the effectiveness of local application of tranexamic acid to reduce blood loss after coronary artery bypass grafting (CABG). METHODS: Thirty eight patients scheduled for primary isolated coronary artery bypass grafting were included in this double blind, prospective, randomized, placebo controlled study. Tranexamic acid (TA) group (19 patients) received 1 gram of TA diluted in 100 ml normal saline. Placebo group (19 patients) received 100 ml of normal saline only. The solution was purred in the pericardial and mediastinal cavities. RESULTS: Both groups were comparable in their baseline demographic and surgical characteristics. During the first 24 hours post-operatively, cumulative blood loss was significantly less in TA group (median of 626 ml) compared to Placebo group (median of 1040 ml) (P = 0.04). There was no significant difference in the post-op Packed RBCs transfusion between both groups (median of one unit in each) (P = 0.82). Significant less platelets transfusion required in TA group (median zero unit) than in placebo group (median 2 units) (P = 0.03). Apart from re-exploration for excessive surgical bleeding in one patient in TA group, no difference was found in morbidity or mortality between both groups. CONCLUSION: Topical application of tranexamic acid in patients undergoing primary coronary artery bypass grafting led to a significant reduction in postoperative blood loss without adding extra risk to the patient.

Sternal plating for primary and secondary sternal closure; can it improve sternal stability?

BACKGROUND: Sternal instability with mediastinitis is a very serious complication after median sternotomy. Biomechanical studies have suggested superiority of rigid plate fixation over wire cerclage for sternal fixation. This study tests the hypothesis that sternal closure stability can be improved by adding plate fixation in a human cadaver model. METHODS: Midline sternotomy was performed in 18 human cadavers. Four sternal closure techniques were tested: (1) approximation with six interrupted steel wires; (2) approximation with six interrupted cables; (3) closure 1 (wires) or 2 (cables) reinforced with a transverse sternal plate at the sixth rib; (4) Closure using 4 sternal plates alone. Intrathoracic pressure was increased in all techniques while sternal separation was measured by three pairs of sonomicrometry crystals fixed at the upper, middle and lower parts of the sternum until 2.0 mm separation was detected. Differences in displacement pressures were analyzed using repeated measures ANOVA and Regression Coefficients. RESULTS: Intrathoracic pressure required to cause 2.0 mm separation increased significantly from 183.3 +/- 123.9 to 301.4 +/- 204.5 in wires/cables alone vs. wires/cables plus one plate respectively, and to 355.0 +/- 210.4 in the 4 plates group (p < 0.05). Regression Coefficients (95% CI) were 120 (47-194) and 142 (66-219) respectively for the plate groups. CONCLUSION: Transverse sternal plating with 1 or 4 plates significantly improves sternal stability closure in human cadaver model. Adding a single sternal plate to primary closure improves the strength of sternal closure with traditional wiring potentially reducing the risk of sternal dehiscence and could be considered in high risk patients.

Predictors of packed red cell transfusion after isolated primary coronary artery bypass grafting--the experience of a single cardiac center: a prospective observational study.

BACKGROUND: Preoperative patients' characteristics can predict the need for perioperative blood component transfusion in cardiac surgical operations. The aim of this prospective observational study is to identify perioperative patient characteristics predicting the need for allogeneic packed red blood cell (PRBC) transfusion in isolated primary coronary artery bypass grafting (CABG) operations. PATIENTS AND METHODS: 105 patients undergoing isolated, first-time CABG were reviewed for their preoperative variables and followed for intraoperative and postoperative data. Patients were 97 males and 8 females, with mean age 58.28 +/- 10.97 years. Regression logistic analysis was used for identifying the strongest perioperative predictors of PRBC transfusion. RESULTS: PRBC transfusion was used in 71 patients (67.6%); 35 patients (33.3%) needed > 2 units and 14 (13.3%) of these needed > 4 units. Univariate analysis identified female gender, age > 65 years, body weight < or = 70 Kg, BSA < or = 1.75 m(2), BMI < or = 25, preoperative hemoglobin < or = 13 gm/dL, preoperative hematocrit < or = 40%, serum creatinine > 100 micromol/L, Euro SCORE (standard/logistic) > 2, use of CPB, radial artery use, higher number of distal anastomoses, and postoperative chest tube drainage > 1000 mL as significant predictors. The strongest predictors using multivariate analysis were CPB use, hematocrit, body weight, and serum creatinine. CONCLUSION: The predictors of PRBC transfusion after primary isolated CABG are use of CPB, hematocrit < or = 40%, weight < or = 70 Kg, and serum creatinine > 100 micromol/L. This leads to better utilization of blood bank resources and cost-efficient targeted use of expensive blood conservation modalities.

Pre-operative modification of dietary glycemic index improves pre but not post-operative indices of insulin resistance in patients undergoing coronary artery bypass graft surgery.

BACKGROUND: Improving insulin sensitivity in coronary artery bypass grafting (CABG) patients may translate into improved glycemic control and postoperative outcomes. The implementation of a low glycemic index (LGI) diet in the pre-operative period may improve insulin sensitivity and subsequently impact on the development of post-operative insulin resistance. The aim of this study was to determine whether a short term LGI diet would reduce postoperative insulin resistance. METHODS: Eleven non-diabetic patients referred for elective CABG surgery were randomized to consume either a high glycemic index (HGI)(5) or LGI (6) diet for three weeks prior to their surgery. Outcomes, including insulin sensitivity (SITT, HOMA), were measured at baseline, preoperatively and postoperatively. RESULTS: Substitution of HGI or LGI foods resulted in an average 8.6 unit increase, or 11.0 unit decrease, respectively, in glycemic index. Insulin sensitivity (HOMA) improved significantly in the LGI group preoperatively compared to the HGI group (p = 0.018). Insulin sensitivity (SITT) was significantly reduced postoperatively in both groups, but no significant difference was found between groups. There was a trend in the LGI group towards improved glycemic control which warrants further investigation. CONCLUSION: A preoperative LGI diet presents a non-invasive cardio-protective opportunity warranting clinical trial.

Triple nutrient supplementation improves survival, infarct size and cardiac function following myocardial infarction in rats.

BACKGROUND AND AIM: We evaluated the impact of triple nutrient supplementation (TNS: carnitine, taurine and coenzyme Q(10)) vs. carnitine alone (CARN) or placebo on survival, infarct size, cardiac function and metabolic gene expression using a model of myocardial infarction (MI) in rats. METHODS AND RESULTS: Male Wistar rats were randomized to three groups divided in two independent studies prior to ligation of the left anterior descending coronary artery (LAD): TNS vs. Placebo and TNS vs. CARN. Nutrient supplementation [L-carnitine (300 mg/day), coenzyme Q(10) (15 mg/kg body weight/day) and taurine (0.1M)] was administered daily for four weeks prior to and for 10 days after MI. At that time, cardiac function and infarct size were measured. Metabolic gene (mRNA) expression in the peri-infarct tissue of left ventricle from TNS, placebo or corresponding time-control rats (TNS or placebo without LAD ligation) was measured 10 days after MI. When compared to placebo, TNS significantly improved survival (60% vs. 34%, p<0.02), cardiac function, and reduced infarct size (30+/-7% vs. 42+/-9%, p<0.001). Although CARN improved survival like TNS (45% vs. 50%, not significant), it did not reduce infarct size (32+/-14% vs. 19+/-10%, p<0.05) or delay myocardial remodeling. In the placebo group, MI was associated with a significantly altered pattern of metabolic gene expression (glucose transporter 1, liver carnitine palmitoyl transferase 1, medium-chain acyl-CoA dehydrogenase; p<0.01 for all three) in the left ventricle peri-infarct tissue. In contrast, gene expression was normalized in the group receiving TNS. CONCLUSIONS: Our results support the potential cardioprotective impact of TNS during myocardial ischemia. In contrast to carnitine supplementation alone, TNS improved survival as well as cardiac function, gene expression and delayed remodeling.

Factors influencing patient knowledge of warfarin therapy after mechanical heart valve replacement.

BACKGROUND AND RESEARCH OBJECTIVE: Patients with mechanical heart valves must follow lifelong warfarin therapy. Warfarin, however, is a difficult drug to manage because it has a narrow therapeutic window and potentially serious side effects. Successful anticoagulation treatment is dependent upon the patient's knowledge of this drug; however, little is known regarding the determinants of such knowledge. Therefore, the purpose of this study was to determine the influence of both in-hospital teaching practices as well as socioeconomic status and demographic variables on patients' knowledge of warfarin therapy. SUBJECTS AND METHODS: A telephone survey was conducted among 100 patients 3 to 6 months after mechanical heart valve replacement. A previously validated 20-item questionnaire was used to measure the patient's knowledge of warfarin, its side effects, and vitamin K food sources. Demographic information, socioeconomic status data, and medical education information were also collected. Knowledge scores were compared using the Student t test or one-way analysis of variance. Variables with P < or = .2 on univariate analysis were entered in multiple stepwise regression analysis. RESULTS AND CONCLUSIONS: Sixty-one percent of participants had scores indicative of insufficient knowledge of warfarin therapy (score < or = 80%). Age was negatively related to warfarin knowledge scores (r = 0.27, P = .007). Patients with family incomes greater than $25,000, who had greater than a grade 8 education, and who were employed or self-employed had significantly higher warfarin knowledge scores (P = .007, P = .002, and P = .001, respectively). Gender, ethnicity, and warfarin therapy before surgery were not related to warfarin knowledge scores. Furthermore, none of the in-hospital teaching practices significantly influenced knowledge scores, whereas receiving postdischarge community counseling significantly improved knowledge scores (P = .001). Multivariate regression analysis revealed that understanding the concept of International Normalized Ratio, knowing the acronym, age, and receiving community counseling after discharge were the strongest predictors of warfarin knowledge. Accessing postdischarge counseling resulted in significantly improved warfarin knowledge scores. Because improved knowledge has been associated with improved compliance and control, our findings support the need to develop a comprehensive postdischarge education program or at least to ensure that patients have access to a community counselor to compliment the in-hospital education program.

Myocardial metabolism and improved outcomes after high risk heart surgery.

The healthy heart relies primarily upon the oxidation of fatty acids for energy, with the remaining coming from the oxidation of glucose and lactate. Changes in energy requirements are met by altering the balance of fuels depending upon the hormonal milieu as well as upon the availability of oxygen and substrates. The use of carbohydrates for fuel is metabolically more efficient and may improve the coupling between glycolysis and pyruvate oxidation. Therefore, promoting a shift in metabolic fuel substrate use during times of reduced oxygen availability may represent a cardioprotective strategy. Subsequently, there has been interest in pharmacologic strategies such insulin or drugs like ranolazine and dichloroacetate that stimulate carbohydrate oxidation either by enhancing oxidation at the pyruvate dehydrogenase complex or by limiting fatty acid oxidation. There is evidence that nutrients may also be able to stimulate carbohydrate oxidation. Previous studies by our group suggest that a combination of nutrients (carnitine, coenzyme Q10, and taurine) may work together, resulting in pleiotropic cardioprotective effects. Our current studies are investigating the potential of nutrients as both a preventative and adjunctive treatment before and after an ischemic event. These investigations will determine the role of nutritional supplementation in the care of patients with ischemic injury.

Tetrahydrobiopterin deficiency exaggerates intimal hyperplasia after vascular injury.

Decreased levels of tetrahydrobiopterin (BH4), an absolute cofactor for nitric oxide synthase (NOS), lead to uncoupling of NOS into a superoxide v. nitric oxide producing enzyme, and it is this uncoupling that links it to the development of vascular disease. However, the effects of in vivo deficiency of BH4 on neointimal formation after vascular injury have not been previously investigated. Hph-1 mice, which display 90% deficiency in guanine triphosphate cyclohydrolase I, the rate limiting enzyme in BH4 synthesis, were used. Hph-1 and wild-type mice, treated with either vehicle or BH4 (n = 15 per group), were subjected to wire-induced femoral artery injury, and NOS expression and activity, inflammation, cell proliferation, superoxide production, and neointimal formation were assessed. The major form of NOS expressed over vessel wall after vascular injury was endothelial NOS. Hph-1 mice exhibited lower NOS activity (2.8 +/- 0.3 vs. 4.5 +/- 0.4 pmol/min/mg protein, P < 0.01), and higher aortic superoxide content (5.2 +/- 2.0 x 10(5) cpm vs. 1.6 +/- 0.7 x 10(5) cpm, P < 0.01) compared with wild-type controls, indicating uncoupling of NOS. Treatment of hph-1 mice with BH4 significantly increased NOS activity (from 2.8 +/- 0.3 to 4.1 +/- 0.4 pmol.min(-1).mg protein(-1), P < 0.05), and attenuated superoxide production (from 5.2 +/- 2.0 x 10(5) cpm to 0.8 +/- 0.7 x 10(5) cpm, P < 0.05). Hph-1 mice also had higher inflammatory reactions and more cell proliferation after vascular injury. Furthermore, hph-1 mice responded by a marked increase in neointimal formation at 4 wk after vascular injury, compared with wild-type controls (intima:media ratio: 4.5 +/- 0.5 vs. wild-type 0.7 +/- 0.1, P < 0.001). Treatment of hph-1 mice with BH4 prevented vascular injury-induced increase in neointimal formation (intima:media ratio: 1.4 +/- 0.1 vs. hph-1, P < 0.001). Treatment had no effect on wild-type controls. In summary, we describe, for the first time, that in vivo BH4 deficiency facilitates neointimal formation after vascular injury. Modulation of BH4 bioavailability is an important therapeutic target for restenosis.