The potential use of type-5 phosphodiesterase inhibitors in coronary artery bypass graft surgery

Exaggerated vasospasm, platelet activation, and early graft occlusion are significant barriers to successful coronary artery bypass grafting (CABG). Interestingly, vascular smooth muscle and platelets are predominant sources of type-5 phosphodiesterase (PDE5) in the body, and this enzyme is specifically inhibited by PDE5 inhibitors (eg, sildenafil citrate). Together with endogenous nitric oxide, sildenafil can induce pulmonary and coronary vasodilation, precondition the myocardium, reduce platelet activation, and potentially reduce early graft occlusion. Currently, there are no published clinical trials investigating sildenafil in coronary surgery. Recent studies on the potential use of sildenafil strongly support its beneficial effects in a wide range of patients with cardiovascular diseases. Therefore, we sought to review the literature, explore the current hypothesis that the use of sildenafil in coronary surgery patients can be beneficial, and attempt to define its potential place in the setting of CABG.

Risk factors for and economic implications of prolonged ventilation after cardiac surgery

OBJECTIVE

The study's objective was to identify predictors of prolonged ventilation and assess clinical and cost implications in patients undergoing cardiac surgery.

METHODS

Patients undergoing cardiac surgery were classified as (1) ventilated less than 96 hours or (2) ventilated 96 hours or more. Multivariate modeling was used to identify predictors of prolonged ventilation and to ascertain the impact of prolonged ventilation on in-hospital mortality and bed occupancy costs and 5-year survival.

RESULTS

A total of 7553 patients were studied; 197 (2.6%) had prolonged ventilation. Median ventilation times were 8 and 192 hours, and in-hospital mortality was 1.0% and 22.2% in the control and prolonged ventilation groups, respectively (P < .001). In-hospital mortality remained higher in the prolonged ventilation group after adjustment and when comparing propensity-matched patients (odds ratio 8.06; 95% confidence interval [CI] 4.27-15.2; P < .001 for propensity-matched groups). Independent predictors of prolonged ventilation were as follows: older age, New York Heart Association class, ejection fraction less than 50%, creatinine greater than 200 micromol/L, multiple valve replacements, aortic procedures, operative priority, reoperation for bleeding, inotropes, and preoperative intra-aortic balloon pump. Five-year survival was lower in the prolonged ventilation group (56.1% [95% CI 46.6%-64.6%] vs 88.8% [95% CI 87.9%-89.6%]) also after adjustment for imbalances and when comparing propensity-matched patients (hazard ratio 2.39; 95% CI 1.75-3.27; P < .001 for propensity-matched groups). Mean bed occupancy costs were 14,286 dollars (95% CI 12,731 dollars-15,690 dollars) and 2761 dollars (95% CI 2705 dollars-2814 dollars) in the prolonged ventilation and control groups, respectively (P < .001).

CONCLUSION

Prolonged ventilation is associated with high in-hospital mortality and costs, and poor 5-year survival. Identified predictors of prolonged ventilation might help to optimize the clinical management of these patients.

The Pathobiology of Endothelin-1 in Vein Graft Disease: Are ETA Receptor Antagonists the Solution to Prevent Vein Graft Failure?

Despite the exploration of a large number of disparate drugs in animal models and clinical trials, no pharmacological intervention, with the exception of aggressive lipid lowering therapy has reduced late vein graft failure in man. The importance of devising more effective strategies is exemplified by the considerable economic consequences of vein graft failure. Worldwide, there are currently more than 1,000,000 coronary artery bypass graft surgery (CABG) operations a year, the same number of patients undergoing infrainguinal bypass (IIBS) for vascular diseases of the lower limb. The pathophysiology of vein graft failure is complex, involving disparate factors that include adhesion of platelets and leukocytes, rheological forces, metalloproteinase expression, proliferation and migration of vascular smooth muscle cells, neointima formation, oxidative stress, hypoxia and neural re-organisation. Although this diverse aetiology may seem to preclude any single drug type as being effective in preventing vein graft failure, one factor that is involved in every facet of vein graft pathobiology is endothelin-1 (ET-1). Thus, in this review, we will consider the diverse aetiology of vein graft disease in relation to ET-1 and will then present an argument (with evidence) that ET-1(A) (ET(A)) receptor antagonists constitute a potentially effective means of preventing vein graft failure.

Effect of sildenafil citrate and a nitric oxide donating sildenafil derivative, NCX 911, on cavernosal relaxation and superoxide formation in hypercholesterolaemic rabbits

Hypercholesterolaemia promotes erectile dysfunction through increased superoxide formation and negation of nitric oxide (NO) bioactivity in cavernosal tissue. The source of superoxide has not been clearly defined, however. Sildenafil (Viagra), the standard therapy for erectile dysfunction, may also be rendered more effective by the presence of an NO donor. One drug that intrinsically fulfils this criterion is sildenafil nitrate (NCX 911), an NO donating derivative of sildenafil. The objective of this study, therefore, was to determine the source of superoxide and its effect on erectile function in corpus cavernosum from hypercholesterolaemic rabbits and to determine whether NCX 911 confers an improvement over sildenafil citrate in this model. Hypercholesterolaemia elicited an increase in superoxide formation by rabbit cavernosal tissue and a reduction of carbachol-stimulated relaxation both of which were reversed by diphenylene iodonium chloride and apocynin (NADPH oxidase inhibitors). In response to sodium nitroprusside, hypercholesterolaemia also caused an attenuation of cavernosal relaxation which was not reversed with NADPH oxidase inhibitors. Both sildenafil citrate and NCX 911 significantly reversed impaired carbachol-stimulated relaxation and inhibited superoxide formation by cavernosal tissue from hypercholesterolaemic rabbits, NCX 911 being more potent. NCX 911 also augmented cavernosal cGMP levels, an effect blocked by the guanylyl cyclase inhibitor, 1H-{1,2,4}oxadiazolo {4,3-a}quinoxalin-1-one (ODQ). These data demonstrate that hypercholesterolaemia promotes erectile dysfunction through an augmentation of superoxide derived from NADPH oxidase in cavernosal tissue. It also indicates that NO donating sildenafil may be therapeutically more beneficial than conventional sildenafil in treating erectile dysfunction with an oxidative stress-related aetiology.

Postoperative chest radiographic changes after on- and off-pump coronary surgery

AIM

A variety of chest radiograph abnormalities are recognized after coronary artery bypass grafting (CABG). This study analyzes the appearance of preoperative and postoperative chest radiographs in two groups of patients undergoing myocardial revascularization with or without the use of cardiopulmonary bypass (CPB).

METHODS

Chest radiographs (preoperative and at 1 day, 6 days and 6 to 8 weeks post operatively) were analyzed according to a detailed protocol in cases of conventional CABG on CPB (n=60) or off-pump coronary artery bypass (OPCAB) (n=60) surgery. On each film 17 different major potential postoperative abnormalities were analyzed.

RESULTS

Clinical findings were similar in the two groups. Patients undergoing OPCAB surgery had decreased blood loss, decreased red cell and platelet transfusion, significantly lower intubation time and required less postoperative inotropic support compared with patients undergoing CPB. The CPB group had a significantly higher incidence of left band atelectasis than the OPCAB group (37.6% vs 17.5%, p=0.01) at 6 days postoperatively. There was no other statistically significant difference in any of the 16 remaining major chest radiograph findings between the two groups.

CONCLUSION

Although OPCAB surgery is associated with improved clinical outcome compared with conventional CABG surgery, the analysis of postoperative chest radiographs demonstrated only a minor benefit as shown by a reduced degree of left band atelectasis in the OPCAB group.

Sildenafil citrate and sildenafil nitrate (NCX 911) are potent inhibitors of superoxide formation and gp91phox expression in porcine pulmonary artery endothelial cells

Acute respiratory distress syndrome (ARDS) is associated with increased superoxide (O(2)(*-)) formation in the pulmonary vasculature and negation of the bioavailability of nitric oxide (NO). Since NO inhibits NADPH oxidase expression through a cyclic GMP-mediated mechanism, sildenafil, a type V phosphodiesterase inhibitor, may be therapeutically effective in ARDS through an augmentation of NO-mediated inhibition of NADPH oxidase. Therefore, the effect of sildenafil citrate and NO-donating sildenafil (NCX 911) on O(2)(*-) formation and gp91(phox) (active catalytic subunit of NADPH oxidase) expression was investigated in cultured porcine pulmonary artery endothelial cells (PAECs). PAECs were incubated with 10 nM TXA(2) analogue, 9,11-dideoxy-9alpha,11alpha-methanoepoxy-prostaglandin F(2alpha) (U46619) (+/-sildenafil or NCX 911), for 16 h and O(2)(*-) formation measured spectrophometrically and gp91(phox) using Western blotting. The role of the NO-cGMP axis was studied using morpholinosydnonimine hydrochloride (SIN-1), the diethylamine/NO complex (DETA-NONOate), the guanylyl cyclase inhibitor, 1H-{1,2,4}oxadiazolo{4,3-a}quinoxalin-1-one (ODQ), and the protein kinase G inhibitor, 8-bromoguanosine-3',5'-cyclic monophosphorothioate, Rp-isomer (Rp-8-Br-cGMPS). NO release was studied using a fluorescence assay and O(2)(*-)-NO interactions by measuring nitrites. After a 16-h incubation with 10 nM U46619, both NCX 911 and sildenafil elicited a concentration-dependent inhibition of O(2)(*-) formation and gp91(phox) expression, NCX 911 being more potent (IC(50); 0.26 nM) than sildenafil citrate (IC(50); 1.85 nM). These inhibitory effects were reversed by 1 microM ODQ and 10 microM Rp-8-Br-cGMPS. NCX 911 stimulated the formation of cGMP in PAECs and generated NO in a cell-free system to a greater degree than sildenafil citrate. The inhibitory effect of sildenafil was augmented by 1 muM SIN-1 and blocked partially by the eNOS inhibitor 10 microM N(5)-(1-iminoethyl)-ornithine (L-NIO). Acutely, sildenafil and NCX 911 also inhibited O(2)(*-) formation, again blocked by 1 microM ODQ. NCX 911 reacted with O(2)(*-) generated by xanthine oxidase, an effect that was inhibited by superoxide dismutase (500 U ml(-1)). Since O(2)(*-) formation plays contributory role in ARDS, both sildenafil citrate and NCX 911 may be indicated for treating ARDS through suppression of NADPH oxidase expression and therefore of O(2)(*-) formation and preservation of NO bioavailability.

Randomized Comparison Between Normothermic and Hypothermic Cardiopulmonary Bypass in Pediatric Open-Heart Surgery

BACKGROUND

The purpose of this study is to investigate the effect of cardiopulmonary bypass (CPB) temperature on myocardial reperfusion injury, oxidative stress, and inflammatory response in pediatric open heart surgery.

METHODS

Fifty-nine children (median age 78 months; interquartile range, 39-130) undergoing correction of simple congenital heart defects were randomized to receive either hypothermic (28 degrees C) or normothermic (35-37 degrees C) CPB. Troponin I and 8-isoprostane, complement activation C3a, interleukin (IL) -6, -8, and -10, were measured preoperatively, on removal of the aortic cross clamp, 30 minutes, 6, and 24 hours postoperatively.

RESULTS

Troponin I and 8-isoprostane were significantly raised, compared to baseline, in both groups, and remained high at 24 hours. Overall, troponin I and 8-isoprostane levels were 37% and 84% higher in the hypothermic than in the normothermic group, respectively (ratio 1.37, 95% CI 1.00 to 1.88, p = 0.053 and 1.84, 95% CI 1.22 to 2.78, p = 0.0045, respectively), and there was no evidence to suggest the treatment effect changed significantly over the time points measured (p = 0.63). Adjusting for aortic cross-clamp time reduced the effect of hypothermia on troponin (p = 0.18) but not on 8-isoprostane levels (p = 0.0028). The C3a, IL-6, and IL-8 release was similar in the two groups. The IL-10 release between the groups changed over time (p = 0.059) and examining differences at individual time points highlighted a statistically significant difference at the end of the cross-clamp time (p = 0.0079).

CONCLUSIONS

Normothermic CPB is associated with reduced oxidative stress compared with hypothermic CPB, and similar myocardial reperfusion injury and whole body inflammatory response, in children undergoing open heart surgery. A larger study with clinical outcomes as primary end points is now warranted.

Prednisolone augments superoxide formation in porcine pulmonary artery endothelial cells through differential effects on the expression of nitric oxide synthase and NADPH oxidase

1. Prednisolone, a potent anti-inflammatory drug, has proved ineffective in treating acute respiratory distress syndrome (ARDS). ARDS is associated with superoxide (O(2)(*-)) generation, which negates nitric oxide (NO). NO also downregulates NADPH oxidase and inhibits O(2)(*-) formation. A possible reason for the lack of effect of prednisolone may due to an inhibition of eNOS expression. In order to test this proposal, the effect of prednisolone on O(2)(*-) formation and the expression of gp91(phox) (catalytic subunit of NADPH oxidase) and eNOS in pig pulmonary artery (PA) segments and PA endothelial cells (PAECs) and PA vascular smooth muscle cells (PAVSMCs) was investigated. 2. PA segments and cells were incubated with prednisolone and tumour necrosis factor-alpha (TNF-alpha) for 16 h. O(2)(*-) formation was measured spectrophometrically and gp91(phox) and eNOS expression by Western blotting. The role of the NO-cGMP axis was studied using morpholinosydnonimine hydrochloride, the diethylamine/NO complex (DETA-NONOate), the guanylyl cyclase inhibitor, 1H-{1,2,4}oxadiazolo{4,3-a}quinoxalin-1-one (ODQ) and the stable cGMP analogues, 8-bromo cGMP and 8-(4-chlorophenylthio)-cGMP (8-pCPT-cGMP). NO release was studied using a fluorescence assay and O(2)(*-)-NO interactions with a nitrite/nitrate assay. 3. Prednisolone elicited significant increase in O(2)(*-) formation in intact PA segments and PAECs, but not PAVSMCs, in a concentration-dependent manner. In endothelium-denuded segments, prednisolone slightly enhanced O(2)(*-) release. TNF-alpha further increased prednisolone-enhanced O(2)(*-) formation in intact PA segments and PAECs. NADPH oxidase inhibitor, apocynin, inhibited O(2)(*-) formation. Increased O(2)(*-) release and gp91(phox) expression in PAECs elicited by prednisolone was blocked by SIN-1 (3-morpholinosydnonimine hydrochloride), DETA-NONOate, 8-pCPT-cGMP and 8-bromo cGMP. The effects of SIN-1 on gp91(phox) expression were reversed by ODQ. Finally, eNOS protein expression was significantly reduced by prednisolone. 4. Prednisolone increases O(2)(*-) in porcine PAECs through a downregulation of endogenous eNOS expression. Since the NO-cGMP axis inhibits gp91(phox) expression, the resultant decrease in endogenous NO formation then augments NADPH oxidase activity, which in turn results in increased O(2)(*-) formation. Since O(2)(*-) promotes inflammation, this mechanism may explain why prednisolone is ineffective in treating ARDS. Therapeutically, the coadministration of an NO donor may render prednisolone more effective in treating ARDS.

Safety, efficacy, and cost of intraoperative cell salvage and autotransfusion after off-pump coronary artery bypass surgery: A randomized trial

OBJECTIVE

We evaluated, in a randomized controlled trial, the safety and effectiveness of intraoperative cell salvage and autotransfusion of washed salvaged red blood cells after first-time coronary artery bypass grafting performed on the beating heart.

METHODS

Sixty-one patients undergoing off-pump coronary artery bypass grafting surgery were prospectively randomized to autotransfusion (n = 30; receiving autotransfused washed blood from intraoperative cell salvage) or control (n = 31; receiving homologous blood only as blood-replacement therapy). Homologous blood was given according to unit protocols.

RESULTS

The groups were well matched with respect to demographic and comorbid characteristics. Patients in the autotransfusion group had a significantly higher 24-hour postoperative hemoglobin concentration (11.9 g/dL; SD, 1.41 g/dL) than those in the control group (10.5 g/dL; SD, 1.37 g/dL) (mean difference, 1.02 g/dL; 95% confidence interval, 1.60-0.44 g/dL; P = .0007), as well as a 20% reduction in the frequency of homologous blood product use (11/31 vs 5/30; P = .095). Autotransfusion of washed red blood cells was not associated with any derangement of thromboelastograph values or laboratory measures of clotting pathway function (prothrombin time, activated partial thromboplastin time, and fibrinogen levels), increased postoperative bleeding, fluid requirements, or adverse clinical events. There was no statistical difference between groups in the total operation, hospitalization, and management costs per patient (median difference, USD 1015.90; 95% confidence interval, -USD 2260 to USD 206; P = .11). Conclusions Intraoperative cell salvage and autotransfusion was associated with higher postoperative hemoglobin concentrations, a modest reduction in transfusion requirements, no adverse clinical or coagulopathic effects, and no significant increase in cost compared with controls. This study supports its routine use in off-pump coronary artery bypass grafting surgery.

Transforming growth factor-beta is activated by plasmin and inhibits smooth muscle cell death in human saphenous vein

BACKGROUND

The effect of activation of endogenous transforming growth factor-beta (TGF-beta) on smooth muscle cell apoptosis was assessed in human saphenous vein.

METHODS

Segments of human saphenous vein, obtained at the time of bypass graft surgery, were cultured for 14 days. During this time, smooth muscle cells accumulated in the intima as a result of proliferation and migration, partly counterbalanced by apoptotic cell death.

RESULTS

Addition of exogenous TGF-beta(1) had no effect on smooth muscle cell proliferation or apoptosis. However, antibody neutralization of endogenous TGF-beta(1) caused significant increases in smooth muscle cell death in the media and intima without any change in proliferation. A plasmin inhibitor (alpha-N-acetyl-L-lysine methyl ester), a specific urokinase-type plasminogen activator (uPA) inhibitor (amiloride) and an anti-catalytic anti-uPA antibody all caused decreases in the tissue content of active TGF-beta and increases in smooth muscle cell death in the media and intima.

CONCLUSIONS

These data suggest that the amount of TGF-beta in human saphenous vein is sufficient, when in the active form, to protect smooth muscle cells against apoptosis. Adding exogenous TGF-beta(1) has no beneficial effect, but decreasing the amount of active TGF-beta causes smooth muscle cells to undergo apoptosis. Plasmin, generated by uPA, appears to be an important activator of endogenous latent TGF-beta.

Coronary artery bypass grafting on the beating heart: surgical revascularization for the next decade?

This review considers whether coronary artery bypass grafting (CABG) performed on the beating heart (off-pump or OPCAB) will supersede conventional CABG utilizing cardiopulmonary bypass (CPB) and cardioplegic arrest as the accepted gold standard. Randomized controlled trials, case-matched reports and observational studies have demonstrated lower morbidity in off-pump compared to conventional on-pump CABG with equivalent mid-term outcome at a significantly lower cost. Patients referred for surgical revascularization are increasingly elderly with more co-morbid medical conditions and elimination of CPB-related morbidity in these groups is associated with the most pronounced improvements in outcome, at least in observational studies. Long-term outcome, and in particular, long-term graft patency following OPCAB has not yet been reported. A barrier to the more widespread acceptance of OPCAB is the poor provision for training in off-pump techniques although structured cardiothoracic training that includes OPCAB surgery has been shown to be both possible and safe for patients. The evidence available to date therefore strongly supports the assertion that OPCAB may become the new gold standard in surgical revascularization. Whether it will ultimately replace conventional CABG, however, is dependent on the results of long-term patency studies and the wider development of adequate training programmes.

Acute hypoxia simultaneously induces the expression of gp91phox and endothelial nitric oxide synthase in the porcine pulmonary artery

BACKGROUND

The effect of hypoxia on the formation of superoxide (O2-), the expression of gp91phox and endothelial NO synthase (eNOS) were studied in pig intact pulmonary artery (PA) segments and PA vascular smooth muscle cells (PAVSMCs) and PA endothelial cells (PAECs).

METHODS

Segments and cells were incubated under hypoxic conditions for 2 hours (with or without enzyme inhibitors) and the formation of O2- measured spectrophotometrically. Protein expression was assessed using Western blotting and immunocytochemistry.

RESULTS

Hypoxia promoted the formation of O2- in PA segments, PAVSMCs and PAECs, an effect inhibited by diphenylene iodonium and apocynin (NAD[P]H oxidase inhibitors). Hypoxia induced O2- formation was enhanced by inhibition of eNOS and augmented by endotoxin and cytokines and re-oxygenation. Hypoxia also promoted the expression of gp91phox and eNOS. In intact PA segments hypoxia induced the expression of nitrotyrosine and eNOS in the endothelium.

CONCLUSIONS

The simultaneous upregulation of NAD[P]H oxidase and eNOS in response to hypoxia in the PA results in the simultaneous formation of O2-, NO, and ONOO-. This may represent either a protective mechanism designed to counter the pro-oxidant effect of hypoxia or a novel pathological mechanism underlying the progression of acute respiratory distress syndrome (ARDS).

In-Hospital Patients Exposed to Clopidogrel Before Coronary Artery Bypass Graft Surgery: A Word of Caution

BACKGROUND

The aim of our study was to investigate the independent effect of preoperative exposure to aspirin, heparin, and clopidogrel on early clinical outcomes of in-hospital referral patients undergoing first time coronary artery bypass graft (CABG) surgery.

METHODS

Outcomes for in-hospital referrals for CABG between January 2001 and January 2002 were prospectively recorded. Exposure to aspirin, heparin, and clopidogrel during the 5 days before surgery was recorded, and their effect on outcome was explored using multiple regression methods. The effect of clopidogrel given within 48 hours before surgery versus stopped at least 48 hours before the operation was also investigated.

RESULTS

In-hospital referral patients represented 40% (473 of 1,185) of the total surgical population; 304 (64.7%) were prescribed aspirin, 116 (24.7%) heparin, 91 (19.4%) clopidogrel, and 133 (28.3%) had all anticoagulants stopped 5 days before surgery. In-hospital mortality was 2.3% (95% confidence interval [CI]: 1.1 to 4.1) and was highest among those exposed to clopidogrel (odds ratio 16.9, 95% CI: 2.10 to 136, p = 0.008). Seven of the 11 deaths occurred in patients given clopidogrel. Postoperative intraaortic balloon pump, arrhythmia, reintubation, and stroke were all significantly more common when clopidogrel was prescribed (relative risk estimates all greater than 1.5, p values all < or = 0.021). Blood loss was 37% higher in the patients given clopidogrel (95% CI: +3% to +82%, p = 0.033). Clopidogrel patients were more likely to need a reoperation for bleeding (p < 0.001) and require transfusions (p < or = 0.015). Intubation time and hospital stay were also longer (p = 0.021 and p = 0.019, respectively). Heparin was also associated with longer hospital stay (p < 0.001) and aspirin use with reduced stay (p = 0.041), but for all other outcomes, no association with aspirin or heparin use was found. Comparison of subgroups of clopidogrel patients suggested mortality was highest when clopidogrel was given in the 48 hours before surgery.

CONCLUSIONS

Our study suggests that among in-hospital referral patients, preoperative exposure to clopidogrel within 5 days before CABG may increase early mortality and morbidity, and that the mortality risk is greatest when the drug is given within 48 hours of surgery.

Eight years survival after partial left ventriculectomy

Remodelling the left ventricle by partial left ventriculectomy (PLV) has been proposed as an alternative surgical treatment for end-stage heart failure. We present the case of a patient with dilated idiopathic cardiomyopathy who underwent PLV and remains in NYHA functional Class I eight years after the surgery.

Basal metabolic state of hearts of patients with congenital heart disease: the effects of cyanosis, age, and pathology

BACKGROUND

Experimental models have established numerous myocardial metabolic changes with chronic hypoxia and maturation. We conducted this study to specifically look at the effects of cyanosis, age, and pathology upon the basal metabolic state of the immature human heart.

METHODS

One hundred and eighty-one pediatric patients (37 cyanotic, 144 acyanotic) undergoing open heart surgery were recruited. A myocardial biopsy was collected before ischemia and analyzed for adenine nucleotides, purines, and lactate. The effect of cyanosis was estimated by an analysis of age-matched pairs of children with either ventricular septal defects or tetralogy of Fallot, and by multiple regression modeling. The effects of age and pathology were estimated in acyanotic children also by multiple regression modeling (adjustments were made for baseline differences).

RESULTS

The only effect of cyanosis was for lactate where the paired t test, and unadjusted and adjusted regression analyses were all consistent (ranging from 1.33 to 1.48 times higher in cyanotic than acyanotic children). The concentrations of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) declined with age, whereas the ATP/ADP ratio increased; these associations remained significant even in the adjusted regression analysis. None of the effects of acyanotic pathology were highly significant (p < 0.01), implying that few important metabolic differences were attributable to pathology.

CONCLUSIONS

Cyanosis and age are important factors that determine the basal metabolic state of the pediatric heart. Cyanotic patients have higher myocardial lactate concentrations, whereas young age is associated with lower ATP/ADP ratios and higher adenine nucleotide levels.

Calcium and the replication of human vascular smooth muscle cells: studies on the activation and translocation of extracellular signal regulated kinase (ERK) and cyclin D1 expression

Since the precise role of sarcoplasmic reticular Ca2+ in mediating vascular smooth muscle cells (VSMC) proliferation is unknown, the effect of pre-incubation with thapsigargin on extracellular signal regulated kinase (ERK) activation, the translocation of activated of ERK 1/2 to the nucleus, cyclin D1 expression, the onset of S phase and cytosolic Ca2+ levels were studied. Human saphenous vein VSMCs (hVSMC) were incubated with 10 nM thapsigargin for 24 h followed by stimulation with fetal calf serum and the activation of ERK1/2 and cyclin D1 assessed by western blotting, the intracellular distribution of ERK1/2 using indirect immunofluorescence, the onset of S-phase with the incorporation of bromodeoxyuridine and sarcoplasmic reticular Ca2+ status using FURA-2. Thapsigargin had a marginal effect on ERK1/2 activation only at 5 min and 10 min after stimulation with fetal calf serum. In contrast, the rapid translocation of ERK1/2 to the nucleus was completely blocked by thapsigargin. S phase was delayed by 8 h by thapsigargin which co-incided with the recovery of cytosolic Ca2+ levels and cyclin D1 expression. It is concluded that the inhibitory effect of thapsigargin (depletion of Ca2+ pools) on hVSMC replication is mediated through the inhibition of translocation of activated ERK1/2 to the nucleus and not to the phosphorylation of ERK, per se, which in turn prevents cyclin D1 expression and thus progression of the cell cycle.

Left ventricular volume reduction

The 'left volume ventricular reduction' operation was originally proposed by Dr Batista to reduce the diameter of the dilated left ventricle by excising a sizable amount of the ventricular free wall. Batista explains that the mechanism of cardiac improvement totally depends on La Place's law, therefore left ventricular wall tension is decreased by reducing the diameter leading to an increase in ejection fraction. Questions, however, still remain on diastolic function, preoperative judgement of left ventricular wall characteristics and late re-dilatation of the left ventricle. The operation was originally performed using normothermic cardiopulmonary bypass on the beating heart. Additional techniques with cardioplegic arrest, concomitant mitral valve repair, and closure of the left ventricle for improvement of hemostasis are shown.