Doxycycline reduces cardiac matrix metalloproteinase-2 activity but does not ameliorate myocardial dysfunction during reperfusion in coronary artery bypass patients undergoing cardiopulmonary bypass.

OBJECTIVES: Matrix metalloproteinase-2 proteolyzes intracellular proteins in the heart and induces acute myocardial contractile dysfunction in ischemia-reperfusion injury. Doxycycline, a matrix metalloproteinase inhibitor, prevented matrix metalloproteinase-2-induced troponin I cleavage in rat hearts and improved contractile function following ischemia-reperfusion. In patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass, increased atrial matrix metalloproteinase-2 activity was inversely correlated with cardiac mechanical function at 3 hours reperfusion. We performed a study in patients with coronary artery disease undergoing primary elective coronary artery bypass graft surgery with cardiopulmonary bypass to determine whether doxycycline reduces cardiac mechanical dysfunction, matrix metalloproteinase activity, and troponin I degradation after reperfusion. DESIGN: Randomized, double-blinded, placebo-controlled study. SETTING: University of Alberta Hospital. PATIENTS: Forty-two patients with coronary artery disease undergoing coronary artery bypass graft surgery with cardiopulmonary bypass. INTERVENTIONS: Patients were randomized to receive either oral administration of 20 mg of doxycycline or matching placebo pill twice a day at least 2 days prior to surgery, on the day of surgery, and for the first 3 postoperative days. MEASUREMENTS AND MAIN RESULTS: Left ventricular stroke work index was examined prior to cardiopulmonary bypass and at 24 hours reperfusion. Right atrial biopsies were collected before cardiopulmonary bypass and 10 minutes after aortic cross-clamp release to determine matrix metalloproteinase-2 activity and troponin I level. Blood was collected to determine matrix metalloproteinase activity and interleukin-6, C-reactive protein, and troponin I levels. Cardiac 72-kDa matrix metalloproteinase-2 activity was lower upon reperfusion in biopsies from the doxycycline group (p = 0.01), and the increase of matrix metalloproteinase-2 activity in the placebo group due to reperfusion did not appear in the doxycycline group (p = 0.05). Doxycycline, however, did not ameliorate cardiac mechanical dysfunction following reperfusion or the cardiopulmonary bypass-coronary artery bypass graft-induced increased plasma matrix metalloproteinase-9, interleukin-6, and C-reactive protein levels. Cardiopulmonary bypass-coronary artery bypass graft or doxycycline did not change tissue or plasma troponin I levels at 10 minutes reperfusion. CONCLUSIONS: Although doxycycline did not improve myocardial stunning following coronary artery bypass graft surgery with cardiopulmonary bypass, it reduced cardiac matrix metalloproteinase-2 activity in these patients. A larger trial and/or higher dose of doxycycline may yet be warranted.

Selective antegrade cerebral perfusion during aortic arch surgery confers survival and neuroprotective advantages.

OBJECTIVE: To assess the impact of using antegrade cerebral perfusion during aortic arch surgery on postoperative survival and neurologic outcomes. METHODS: All operations were performed at the same hospital between January 2001 and January 2009. Patients undergoing aortic arch surgery using antegrade cerebral perfusion during deep hypothermia were compared with patients undergoing aortic arch surgery without antegrade cerebral perfusion during the same study period. Multivariable logistic regression and Cox proportional hazards model were used to identify predictors of postoperative cerebrovascular accidents and midterm survival, respectively. There were 46 patients in the antegrade cerebral perfusion group and 78 patients in the non-antegrade cerebral perfusion group. RESULTS: There were no statistically significant differences in age, proportion of emergency operations, or proportion of type A aortic dissection between the 2 groups. There was a statistically significant and clinically important difference in the rates of postoperative cerebrovascular complications (2% antegrade cerebral perfusion vs 13% non-antegrade cerebral perfusion, P = .03), postoperative duration of mechanical ventilation (1.15 ± 0.19 days antegrade cerebral perfusion vs 2.13 ± 0.38 days non-antegrade cerebral perfusion, P = .02), and 3-year survival (93% antegrade cerebral perfusion vs 78% non-antegrade cerebral perfusion, P = .03). Antegrade cerebral perfusion was shown to be a significant predictor of reduced postoperative stroke rates and better survival at 3 years. CONCLUSIONS: Antegrade cerebral perfusion was associated with improved survival and neurologic outcomes in patients undergoing aortic arch surgery, especially for cases requiring prolonged aortic arch repair periods.

Phosphorylcholine-coated circuits improve preservation of platelet count and reduce expression of proinflammatory cytokines in CABG: a prospective randomized trial.

BACKGROUND: The interaction of blood with foreign artificial surfaces during cardiopulmonary bypass (CPB) has been recognized as a major stimulus in evoking a systemic inflammatory and metabolic response. Phosphorylcholine (PC) is a new-generation coating material designed to ameliorate biocompatibility and thereby to reduce the detrimental interactions of CPB. We studied the effects of PC-coated perfusion circuits on platelet function and the humoral and cellular response to CPB. METHODS: Thirty patients undergoing coronary artery bypass grafting were randomized to PC-coated (PC group, n = 15) and noncoated (control group, n = 15) circuit groups. Clinical data, total blood loss, and pre- and postoperative platelet counts were recorded and IL-6 and TNF-alpha, CD41a, CD42b, and CD62p were measured at induction of anesthesia, after the initiation of CPB and at termination of CPB. RESULTS: There was a significantly improved preservation of platelet count following CPB in the PC group (p = 0.028), which was sustained over a period of 72 hours. The use of PC-coated circuits further resulted in a significant attenuation of TNF-alpha and IL-6 expression (p < 0.05 and p < 0.01); however, we were unable to detect any differences in clinical outcomes. CONCLUSIONS: Despite similar clinical outcome, the obvious reduction of cytokine expression and improved preservation of platelet count suggest superior biocompatibility of PC-coated circuits.

Glutaraldehyde-fixed bioprosthetic heart valve conduits calcify and fail from xenograft rejection.

BACKGROUND: Glutaraldehyde fixation (G-F) decreases but likely does not eliminate the antigenicity of bioprosthetic heart valves. Rejection (with secondary dystrophic calcification) may be why G-F xenograft valves fail, especially in young patients, who are more immunocompetent than the elderly. Therefore, we sought to determine whether rejection of G-F xenograft occurs and to correlate this with graft calcification. METHODS AND RESULTS: Ascending aortas/valves (from rats [syngeneic] or guinea pigs [xenogeneic]) were transplanted (fresh or after 48 hour of G-F) into the infrarenal aortas of young rat recipients for 20 days. A xenogeneic group was also treated with steroids until graft harvest. The valves and media/adventitia were scored blindly for inflammation (0 to 4). Percent graft infiltration by T cells/macrophages was determined (immunohistochemistry), and rat IgG ELISAs were performed. There was >3 times more valve inflammation, >10 times more valve T-cell/macrophage infiltrate, and >3 times antibody rise in the G-F xenogeneic groups compared with the fresh syngeneic or the G-F syngeneic groups (P<0.05). There was >2 times more adventitial inflammation and T-cell/macrophage infiltrate in the xenogeneic groups (P<0.05). Steroid treatment decreased inflammation and antibody rise in the xenogeneic groups (P<0.05). Correlation analysis revealed media/adventitia inflammation (P=0.02) and percent macrophage (P=0.01) infiltration to be predictors of calcification. CONCLUSIONS: G-F xenografts have cellular/humoral rejection and calcify secondarily.

Pretransplant diabetes, not donor age, predicts long-term outcomes in cardiac transplantation.

BACKGROUND AND AIM: Accepting donors of advanced age may increase the number of hearts available for transplantation. Objectives were to review the outcomes of using cardiac donors 50 years of age and older and to identify predictors of outcome at a single institution. METHODS: A retrospective analysis of all adult cardiac transplants (n = 338) performed at our institution between 1988 and 2002 was conducted. RESULTS: Of these, 284 patients received hearts from donors <50 years old and 54 received hearts from donors > or =50 years old. Recipients of hearts from older donors had a greater frequency of pretransplant diabetes (19% vs 33%), renal failure (16% vs 30%), and dialysis (3% vs 9%). There were no differences in ICU or postoperative length of stay, days ventilated, or early rejection episodes. Recipients of older donor hearts, however, had increased perioperative mortality (7% vs 17%; p = 0.03). Multivariate analysis identified older donors (OR 2.599; p = 0.03) and donor ischemia time (OR 1.006; p = 0.002) as significant predictors of perioperative mortality. Actuarial survival at 1 (87% vs 74%), 5 (76% vs 69%), and 10 (59% vs 58%) years was similar (p = 0.08) for the two groups. Separate multivariate analyses identified pretransplant diabetes as the sole predictor of long-term survival (HR 1.659; p = 0.02) and transplant coronary disease (HR 2.486; p = 0.003). CONCLUSIONS: Despite increased perioperative mortality, donors > or =50 years old may be used with long-term outcomes similar to those of younger donor hearts. This has potential to expand the donor pool. Pretransplant diabetes has a significant impact on long-term outcomes in cardiac transplantation and requires further investigation.

Is mitral valve surgery safe in octogenarians?

OBJECTIVE: To evaluate the outcomes of mitral valve surgery in octogenarians. METHODS: Data were collected prospectively from January 1996 to March 2004 at two surgical centers. Of 1386 consecutive patients with mitral valve surgery, 58 (4.2%) were aged > or = 80 years. Survival data were analyzed using Cox proportional hazards modeling and Kaplan-Meier actuarial log rank statistics. RESULTS: Octogenarians were similar to younger patients for the presence of pre-operative hypertension, hyperlipidemia, diabetes mellitus, and smoking history. Octogenarians had a higher incidence of cerebrovascular disease (19.0 versus 7.8%, P = 0.003), urgent in-hospital surgery (55.2 versus 28.6%, P < 0.001), and presence of ischemic disease requiring combined mitral valve plus revascularization surgery (72.4 versus 41.0%, P < 0.001). Mitral valve repair was performed in a similar proportion of octogenarians and younger patients (44.8 versus 45.6%). Thirty-day mortality for octogenarians was significantly higher than younger patients (15.5 versus 5.6%, P = 0.002), and actuarial survival of octogenarians was significantly decreased (P = 0.009). However, 52.3% of the octogenarians were alive at 7-years following surgery. Independent predictors of mortality from multivariate risk adjusted modeling of the entire cohort were: emergency surgery (hazards ratio [HR] = 2.94, P < 0.001), combined mitral valve plus revascularization surgery (HR = 2.27, P < 0.001), mitral valve replacement (HR = 1.85, P < 0.01), and age > or = 80 years (HR = 1.80, P = 0.02). CONCLUSIONS: Octogenarians undergoing mitral valve surgery have significantly greater incidence of urgent surgery, ischemic disease requiring combined revascularization surgery, and have decreased rates of survival. While caution is required when operating on these higher risk elderly patients, overall 52.3% of the octogenarians are alive at 7-years following surgery, which is greater than the survival of octogenarians in the community. The greatest survival benefit within octogenarians occurred when mitral valve repair was possible over replacement. Further study will more clearly define subgroups of octogenarians with potentially greater benefit from mitral valve surgery.

Saphenous vein harvest with SaphLITE system versus conventional technique: a prospective, randomized study.

BACKGROUND: Minimally invasive saphenous vein harvest (MIVH) techniques have been evaluated and reported with heterogeneous results. The aim of this study was to evaluate the efficacy of MIVH on the outcomes of postoperative leg wound healing and pain using the SaphLITE retractor system. METHODS: Two hundred twenty-five patients undergoing elective coronary artery bypass grafting surgery were randomized to receive either SaphLITE vein harvest (SVH) or conventional open vein harvest (OVH). RESULTS: There were no significant differences between the two groups in demographics, postoperative mortalities and major complications. For SVH group and OVH group, total leg wound length was 18.33 +/- 7.93 cm vs 46.10 +/- 15.63 cm (p < 0.001), and vein harvest time was 50.70 +/- 16.55 minutes vs 40.35 +/- 16.43 minutes (p < 0.001). In-hospital leg wound healing disturbance (LWHD) rate was 4.7% for SVH group and 1.7% for OVH group (p = 0.190). Delayed LWHD rate was 16.0% for SVH group and 39.5% for OVH group (p < 0.001). Combined, LWHD rate was 20.8% for SVH group and 41.2% for OVH group (p = 0.001). There was no significant difference in the worst postoperative leg wound pain or length of hospital stay between the 2 groups. Double-blinded histologic examinations revealed normal vascular structure in the harvested veins from both groups. CONCLUSIONS: Our study demonstrated that harvesting saphenous vein with SaphLITE retractor system is a good technique which is associated with reduced rate of delayed LWHD, preserved venous structural integrity, and acceptable harvest speed.

Combined administration of nitric oxide gas and iloprost during cardiopulmonary bypass reduces platelet dysfunction: a pilot clinical study.

BACKGROUND: Thrombocytopenia and platelet dysfunction are major mechanisms of cardiopulmonary bypass-induced postoperative hemorrhage. This study evaluated the effects of low amounts of nitric oxide, iloprost (prostacyclin analog), and their combination administered directly into the oxygenator on platelet function, platelet-leukocyte interactions, and postoperative blood loss in patients undergoing coronary artery bypass grafting. METHODS: Blood samples from 41 patients randomized to the control, nitric oxide (20 ppm), iloprost (2 ng x kg -1 x min -1 ), or nitric oxide plus iloprost groups were collected during cardiopulmonary bypass. Platelets and leukocytes were enumerated. Platelet membrane glycoprotein Ib and glycoprotein IIb/IIIa, P-selectin, platelet-derived microparticles, leukocyte CD11b/CD18 (Mac-1), and platelet-leukocyte aggregate were quantified by means of flow cytometry. Collagen and thrombin receptor-activating peptide-induced platelet aggregation in whole blood was analyzed by means of aggregometry. RESULTS: Both nitric oxide or iloprost attenuated cardiopulmonary bypass-induced thrombocytopenia, reduction of glycoprotein Ib and glycoprotein IIb levels, translocation of P-selectin, microparticle formation, Mac-1 upregulation, and suppression of collagen-induced aggregation. Nitric oxide plus iloprost was significantly more effective in preventing thrombocytopenia, microparticle formation, and P-selectin translocation. Moreover, this treatment preserved thrombin receptor-activating peptide-induced aggregation, which was not rescued by single treatments. Both nitric oxide and nitric oxide plus iloprost attenuated postoperative blood loss. CONCLUSIONS: Nitric oxide plus iloprost reduced the deleterious effects of cardiopulmonary bypass, such as thrombocytopenia, platelet activation, platelet-leukocyte aggregate formation, and suppression of platelet aggregative responses. The reduced postoperative bleeding observed with this treatment suggests that this is a new and clinically feasible therapeutic option for patients subjected to cardiopulmonary bypass.

Declining need for permanent pacemaker insertion with the bicaval technique of orthotopic heart transplantation.

BACKGROUND: The bicaval technique of orthotopic heart transplantation, in contrast to the standard biatrial technique, may better preserve right atrial anatomy and, thus, may be associated with less sinus node dysfunction and less atrioventricular valve dysfunction. OBJECTIVES: To compare the requirement for permanent pacemaker insertion and the incidence of atrioventricular valve dysfunction following heart transplantation with either the standard or the bicaval technique. PATIENTS AND METHODS: A retrospective analysis was conducted of a consecutive cohort of 105 patients, older than 18 years of age, undergoing heart transplantation with either the standard (n=48) or the bicaval (n=57) technique from December 1998 to December 2001. RESULTS: Cross-clamp (100 min versus 112 min; P=0.012) and donor ischemic (222 min versus 276 min; P=0.005) times were significantly prolonged in the bicaval group. Perioperative morbidity and mortality were statistically similar between the groups. Bicaval transplantation resulted in a significant decrease in the requirement for permanent pacemaker insertion at 30 days (13% versus 0%; P=0.008) and 90 days (17% versus 1.8%; P=0.01) after transplantation. There was a nonsignificant trend toward a decreased degree of tricuspid valve regurgitation (mean 1.81 versus 1.36; P=0.141) and mitral valve regurgitation (mean 1.04 versus 0.79; P=0.348) with the bicaval technique. CONCLUSIONS: Although associated with longer cross-clamp and donor ischemic times, the data demonstrated a significant reduction in the need for permanent pacemaker insertion at 30 and 90 days post-transplantation with the bicaval technique. There was no statistically significant difference in the degree of mitral and tricuspid valve regurgitation between the two groups.

A comparative analysis of outcome after heart transplantation in patients aged 60 years and older: the University of Alberta experience.

BACKGROUND: The Registry of the International Society for Heart and Lung Transplantation (ISHLT) 2001 Annual Report indicated that the vast majority of heart transplant recipients are between 50 and 64 years of age. However, patient age beyond 60 years may have higher long-term mortality compared to younger patients. The purpose of this study was to compare short- and intermediate-term results including rates of acute rejection, transplant coronary artery disease, infections, malignancy, and mortality in cardiac transplant recipients 60 years or older with those below the age of 60 years. METHODS: We retrospectively analyzed the results of 50 patients aged 60 years and older who underwent heart transplantation at the University of Alberta from January 1990 to December 2000 and compared them with the results of 225 younger patients undergoing heart transplantation in the same time period. RESULTS: The older and younger groups had similar rates for treated acute rejection episodes (20.0% vs. 12.6%), transplant coronary artery disease (4.0% vs. 1.1%), and mortality (10.5% vs. 14.3%), respectively. No differences were noted with regards to quality and quantity of infection or malignancy rates. Five-year actuarial survival between the older and younger patients was also comparable at 89.5% vs.86.9% (p > 0.05). CONCLUSIONS: Heart transplantation in patients 60 years of age and older can be performed as successfully as in younger patients (< 60 years) with comparable morbidity and mortality, suggesting that patient age per se should not be an exclusion criterion for heart transplantation.

Long-term outcome of isolated coronary artery bypass surgery in patients with severe left ventricular dysfunction.

BACKGROUND: Coronary artery bypass grafting (CABG) is indicated in patients with coronary artery disease and impaired ventricular function. However, earlier studies have suggested that prognosis of patients with severe left ventricular dysfunction is extremely poor. We used the APPROACH registry to derive contemporary estimates of prognosis associated with CABG for this high-risk patient population. METHODS AND RESULTS: The study group consisted of 7841 patients who had isolated CABG in the province of Alberta, Canada between 1996 and 2001. Patients with markedly reduced left ventricular function (ejection fraction [EF] <30%, Lo EF, n =430) were compared with those with moderate reduction in ventricular function (EF 30% to 50%, Med EF, n =2581) and those with normal left ventricular function (EF >50%, normal [Nl] EF, n=4830). The operative mortality was higher in the patient group with Lo EF (4.6%) compared with Med EF and Nl EF groups (3.4% and 1.9%, respectively, P<0.001). At 5 years, survival was 77.7% for Lo EF patients compared with 85.5% and 91.2% for Med EF and Nl EF patients, respectively (P<0.001). After controlling for other independent variables, the adjusted hazard ratio for death was 1.98 (95% CI, 1.49 to 2.62) for Lo EF relative to Nl EF. The mortality rate at 1 year was significantly lower for Lo EF patients who underwent CABG than it was for nonrevascularized Lo EF patients (risk-adjusted odds ratio, 0.36; 95% CI, 0.24 to 0.55). CONCLUSIONS: In the modern era of cardiac surgery, CABG can be performed in Lo EF cases with an acceptable perioperative mortality risk. Our estimate of 5-year survival in this high-risk group is better than previously reported in the literature from earlier periods.

Characteristics and outcomes of patients bridged to cardiac transplantation on centrifugal ventricular assist devices: a case series of the early experience of one Canadian transplant centre.

BACKGROUND: Centrifugal ventricular assist devices (VADs) have been used successfully to bridge patients in cardiogenic shock to cardiac transplantation, though complications are frequent and often life-threatening. PURPOSE: To describe characteristics and examine outcomes of patients bridged to cardiac transplantation on centrifugal VADs. METHODS: A retrospective health record review was conducted on all adults over a 12 year period (N=20) placed on centrifugal VADs with the intent to bridge to cardiac transplantation at a major Canadian transplant centre. RESULTS: Complications of VAD support necessitated removal of 12 patients from the transplant list; seven (35%) survived to cardiac transplantation. Of the seven recipients, five survived to discharge and four remain alive and well. CONCLUSIONS: Bridging patients on centrifugal VADs to cardiac transplantation requires improvement, including maintaining patient stability during the period of early VAD institution, aggressively managing complications of VAD support, and consideration of long-term pulsatile devices. However, if patients survive to transplantation, good long-term outcomes are expected.

Under-utilization of mechanical circulatory support in Canada: why and what can be done?

In October of 2002, a workshop was held as part of the Canadian Cardiovascular Congress in Edmonton, Canada, entitled "Under-Utilization of Mechanical Circulatory Support in Canada. Why and What Can Be Done?" The workshop examined various issues related to the use of mechanical circulatory support devices in the Canadian context. Representatives from all Canadian centers with active mechanical circulatory support programs were invited to participate and participants included surgeons and cardiologists, as well as other affiliated health professionals. Opinions were solicited from the workshop participants and a series of recommendations were formulated.

In vivo gene transfer of the O2-sensitive potassium channel Kv1.5 reduces pulmonary hypertension and restores hypoxic pulmonary vasoconstriction in chronically hypoxic rats.

BACKGROUND: Alveolar hypoxia acutely elicits pulmonary vasoconstriction (HPV). Chronic hypoxia (CH), despite attenuating HPV, causes pulmonary hypertension (CH-PHT). HPV results, in part, from inhibition of O2-sensitive, voltage-gated potassium channels (Kv) in pulmonary artery smooth muscle cells (PASMCs). CH decreases Kv channel current/expression and depolarizes and causes Ca2+ overload in PASMCs. We hypothesize that Kv gene transfer would normalize the pulmonary circulation (restore HPV and reduce CH-PHT), despite ongoing hypoxia. METHODS AND RESULTS: Adult male Sprague-Dawley rats were exposed to normoxia or CH for 3 to 4 weeks and then nebulized orotracheally with saline or adenovirus (Ad5) carrying genes for the reporter, green fluorescent protein reporter+/-human Kv1.5 (cloned from normal PA). HPV was assessed in isolated lungs. Hemodynamics, including Fick and thermodilution cardiac output, were measured in vivo 3 and 14 days after gene therapy by use of micromanometer-tipped catheters. Transgene expression, measured by quantitative RT-PCR, was confined to the lung, persisted for 2 to 3 weeks, and did not alter endogenous Kv1.5 levels. Ad5-Kv1.5 caused no mortality or morbidity, except for sporadic, mild elevation of liver transaminases. Ad5-Kv1.5 restored the O2-sensitive K+ current of PASMCs, normalized HPV, and reduced pulmonary vascular resistance. Pulmonary vascular resistance decreased at day 2 because of increased cardiac output, and remained reduced at day 14, at which time there was concomitant regression of right ventricular hypertrophy and PA medial hypertrophy. CONCLUSIONS: Kv1.5 is an important O2-sensitive channel and potential therapeutic target in PHT. Kv1.5 gene therapy restores HPV and improves PHT. This is, to the best of our knowledge, the first example of K+ channel gene therapy for a vascular disease.

Human ABO blood group is important in survival and function of porcine working hearts.

Pig organs express alphaGal antigen and thus are hyperacutely rejected if perfused by human blood. Human B/A antigens are similar to pig alphaGal antigen, suggesting that the corresponding antibodies may cross-react. Our purpose was to determine if there is a human ABO blood-group difference in porcine-human xenotransplantation. Plasma from six A, five B, seven AB, and six O individuals pooled by blood group were tested in an ex-vivo porcine working heart model. Blood-group A plasma-perfused hearts survived 20 +/- 14 min (n = 5), B 241 +/- 9 min (n = 3), AB 151 +/- 37 min (n = 5), and O 9 +/- 1 min (n = 8). A and O were different (p < 0.001) from B and AB. Function was significantly better in group B. Edema accumulation and creatine kinase change was highest in A and O. All groups had comparable levels of anti-alphaGal antibody, as well as comparable perfusion and operative conditions. Multivariate linear regression analysis showed the anti-B antibody levels to be predictive of survival (p < 0.001). At higher plasma concentrations, hearts perfused with B plasma survived longer (p = 0.01) than AB (218 +/- 45 min, n = 4 vs. 6 +/- 0 min, n = 3). These results suggest a human ABO blood-group difference in porcine-to-human xenotransplantation, which may be mediated by the anti-A and anti-B antibodies.

Endothelium-derived hyperpolarizing factor in human internal mammary artery is 11,12-epoxyeicosatrienoic acid and causes relaxation by activating smooth muscle BK(Ca) channels.

BACKGROUND: Left internal mammary arteries (LIMAs) synthesize endothelium-derived hyperpolarizing factor (EDHF), a short-lived K(+) channel activator that persists after inhibition of nitric oxide (NO) and prostaglandin synthesis. EDHF hyperpolarizes and relaxes smooth muscle cells (SMCs). The identity of EDHF in humans is unknown. We hypothesized that EDHF (1) is 11,12-epoxyeicosatrienoic acid (11,12-EET); (2) is generated by cytochrome P450-2C, CYP450-2C; and (3) causes relaxation by opening SMC large-conductance Ca(2+)-activated K(+) channels (BK(Ca)). METHODS AND RESULTS: The identity of EDHF and its mechanism of action were assessed in 120 distal human LIMAs and 20 saphenous veins (SVs) obtained during CABG. The predominant EET synthesized by LIMAs is 11,12-EET. Relaxations to exogenous 11,12-EET and endogenous EDHF are of similar magnitudes. Inhibition of EET synthesis by chemically distinct CYP450 inhibitors (17-octadecynoic acid, N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide), or a selective EET antagonist (4,15-epoxyeicosa-5(Z)-enoic acid) impairs EDHF relaxation. 11,12-EET activates a BK(Ca) current and hyperpolarizes LIMA SMCs. Inhibitors of BK(Ca) but not inward-rectifier or small-conductance K(Ca) channels abolish relaxation to endogenous EDHF and exogenous 11,12-EET. BK(Ca) and CYP450-2C mRNA and proteins are more abundant in LIMAs than in SVs, perhaps explaining the lack of EDHF activity of the SV. Laser capture microdissection and quantitative RT-PCR demonstrate that BK(Ca) channels are primarily in vascular SMCs, whereas the CYP450-2C enzyme is present in both the endothelium and SMCs. CONCLUSIONS: In human LIMAs, EDHF is 11,12-EET produced by an EDHF synthase CYP450-2C and accounting for approximately 40% of net endothelial relaxation. 11,12-EET causes relaxation by activating SMC BK(Ca) channels.

Coronary artery bypass surgery with heparin-coated perfusion circuits and low-dose heparinization.

OBJECTIVE: To evaluate the safety and efficacy of heparin-coated perfusion circuits with low-dose heparinization and centrifugal pumping compared with the standard method during coronary artery bypass grafting. DESIGN: Prospective, randomized, single-blind clinical trial. SETTING: A primary care institution. PATIENTS: Ninety patients who underwent first-time elective coronary artery bypass grafting were eligible for the study. After giving informed consent, they were randomly assigned to 1 of 3 groups (30/group). INTERVENTIONS: Perfusion on regular uncoated bypass equipment with a roller pump and full-dose heparinization (300 IU/kg bolus, activated clotting time [ACT] > 400 s) (group 1), on a heparin-coated oxygenator with a centrifugal pump and full-dose heparinization (group 2) and on fully heparin-coated bypass equipment with a centrifugal pump and low-dose heparinization (100 IU/kg bolus, ACT of 180-400 s) (group 3). Standard coronary artery bypass grafting was performed. OUTCOME MEASURES: Postoperative bleeding, transfusion requirements and clinical outcomes. RESULTS: There were no complications related to the study protocol. Study groups were similar in terms of postoperative bleeding, transfusion requirements and clinical outcomes. CONCLUSIONS: Heparin-coated cardiopulmonary bypass with low-dose heparinization and centrifugal pumping is a safe practice but showed no advantages over the use of regular uncoated bypass circuits for coronary bypass surgery.