The mKATP Channels and protein-kinase C Are Involved in the Cardioprotective Effects of Genistein on Estrogen-Deficient Rat Hearts Exposed to Ischemia/Reperfusion: Energetic Study.

Estrogenic deficiency is considered a risk of coronary disease in women. The phytoestrogen genistein could be a safe preventive strategy. The first aim of this work was to validate a model of cardiac stunning in which natural estrogenic deficiency rats, ie, adult young male (YM) and aged female (AgF), are compared with young female rats (YF). The second aim was to study whether the in vivo administration of genistein prevents the stunning in estrogenic deficiency rats. The third aim was to evaluate whether in our estrogenic deficiency model exists a synergy between genistein and estradiol. The fourth aim was to characterize the underlying mechanisms of genistein. Stunning was induced by ischemia/reperfusion (I/R) in isolated hearts inside a calorimeter. The left ventricular pressure (P) and total heat rate (Ht) were simultaneously measured, while diastolic contracture and muscle economy (P/Ht) were calculated. During R, P/Ht and P recovered less in AgF and YM than in YF rat hearts. Genistein through i.p. (GST-ip) improved P and P/Ht in AgF and YM, but not in YF. In YM, the cardioprotections of GST-ip and estradiol were synergistic. After ischemia, GST-ip increased SR Ca leak causing diastolic contracture. The GST-ip cardioprotection neither was affected by blockade of PI3K-Akt, NO synthases, or phosphatases, but it was sensitive to blockade of protein-kinase C and mKATP channels. Results suggest that (1) estrogenic deficiency worsens cardiac stunning, (2) GST-ip was more cardioprotective in estrogenic deficiency and synergistic with estradiol, and (3) cardioprotection of GST-ip depends on the protein-kinase C and mKATP channel pathway activation.

Cardiomyocyte-specific overexpression of an active form of Rac predisposes the heart to increased myocardial stunning and ischemia-reperfusion injury.

The GTP-binding protein Rac regulates diverse cellular functions including activation of NADPH oxidase, a major source of superoxide production (O(2)(·-)). Rac1-mediated NADPH oxidase activation is increased after myocardial infarction (MI) and heart failure both in animals and humans; however, the impact of increased myocardial Rac on impending ischemia-reperfusion (I/R) is unknown. A novel transgenic mouse model with cardiac-specific overexpression of constitutively active mutant form of Zea maize Rac D (ZmRacD) gene has been reported with increased myocardial Rac-GTPase activity and O(2)(·-) generation. The goal of the present study was to determine signaling pathways related to increased myocardial ZmRacD and to what extent hearts with increased ZmRacD proteins are susceptible to I/R injury. The effect of myocardial I/R was examined in young adult wild-type (WT) and ZmRacD transgenic (TG) mice. In vitro reversible myocardial I/R for postischemic cardiac function and in vivo regional myocardial I/R for MI were performed. Following 20-min global ischemia and 45-min reperfusion, postischemic cardiac contractile function and heart rate were significantly reduced in TG hearts compared with WT hearts. Importantly, acute regional myocardial I/R (30-min ischemia and 24-h reperfusion) caused significantly larger MI in TG mice compared with WT mice. Western blot analysis of cardiac homogenates revealed that increased myocardial ZmRacD gene expression is associated with concomitant increased levels of NADPH oxidase subunit gp91(phox), O(2)(·-), and P(21)-activated kinase. Thus these findings provide direct evidence that increased levels of active myocardial Rac renders the heart susceptible to increased postischemic contractile dysfunction and MI following acute I/R.

Lack of the effect of superoxide dismutase and catalase on Na+,K+-ATPase activity in stunned rabbit hearts.

Reactive oxygen species (ROS) have been implicated in the mechanism of postischemic contractile dysfunction, known as myocardial stunning. In this study, we examined protective effects of antioxidant enzymes, superoxide dismutase (SOD) and catalase, against ischemia/reperfusion-induced cardiac dysfunction and inhibition of Na+,K+-ATPase activity. Isolated Langendorff-perfused rabbit hearts were subjected to 15 min of global normothermic ischemia followed by 10 min reperfusion. The hearts treated with SOD plus catalase did not show significant recovery of left ventricular (LV) end-diastolic pressure compared with untreated ischemic reperfused hearts. Treatment with antioxidants had no protective effects on developed LV pressure or its maximal positive and negative first derivatives (+/-LVdP/dt). Myocardial stunning was accompanied by significant loss in sarcolemmal Na+,K+-ATPase activity and thiol group content. Inhibition of enzyme activity and oxidation of SH groups were not prevented by antioxidant enzymes. These results suggest that administration of SOD and catalase in perfusate do not protect significantly against cardiac dysfunction in stunned rabbit myocardium.

[Stunned myocardium after acute ischemic stroke]. / Atontamiento miocárdico luego del accidente cerebrovascular isquémico.

The so-called stunned myocardium, defined as transitory myocardial contractile dysfunction, has been clearly demonstrated in diverse clinical situations. However, stunned myocardium related to ischemic stroke has been poorly identified. We describe two patients with diagnosis of acute ischemic stroke who developed eletrocardiographic changes, cardiac enzyme increasing levels and myocardial dysfunction secondary to abnormal cardiac wall motion. At the same time the patients developed acute lung injury with rapid resolution, perhaps as a consequence of neurocardiogenic components.

Role of cyclic guanosine monophosphate in late preconditioning in conscious rabbits.

BACKGROUND: Although NO has been shown to serve both as the trigger and the mediator of the late phase of ischemic preconditioning (PC), it is unknown whether NO acts via activation of soluble guanylate cyclase (sGC). The objective of this study was to investigate the role of sGC in late PC in conscious rabbits using the selective sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). METHODS AND RESULTS: A total of 172 conscious rabbits were used. When nonpreconditioned rabbits were subjected to a sequence of 4-minute coronary occlusion/4-minute reperfusion cycles, myocardial cyclic guanosine monophosphate (cGMP) levels increased significantly at the end of the third and sixth occlusions. In rabbits preconditioned 24 hours earlier (on day 1) with six occlusion/reperfusion cycles, myocardial cGMP levels on day 2 were significantly higher than in nonpreconditioned rabbits even before ischemia but did not increase further during a second sequence of 4-minute occlusion/reperfusion cycles. Administration of ODQ before the six occlusion/reperfusion cycles on day 1 did not prevent the development of late PC against either stunning or infarction on day 2. In contrast, administration of ODQ on day 2 completely ablated the late PC effect against both stunning and infarction. CONCLUSIONS: These results indicate that enhanced synthesis of cGMP by sGC is not necessary for ischemia to trigger a late PC effect but is required for the protection to become manifest 24 hours later. This implies that NO participates in late PC via two distinct mechanisms; ie, it triggers late PC on day 1 via a cGMP-independent mechanism and it mediates late PC on day 2 via a cGMP-dependent mechanism.

Repetitive myocardial stunning in pigs is associated with the increased expression of inducible and constitutive nitric oxide synthases.

OBJECTIVES: Nitric oxide (NO) has complex effects on myocardial function particularly following ischaemia-reperfusion. The goal of this study was to examine the result of repetitive myocardial stunning on myocardial NO release and expression of inducible (iNOS) and constitutive (eNOS) NO synthases. METHODS AND RESULTS: Propofol anaesthetised pigs underwent ten, 2-min episodes of circumflex artery occlusion (n = 6) or acted as sham operated controls (n = 4). Measurements of segment shortening demonstrated a fall in function in the ischaemic territory to 52.5 +/- 7.3% (mean +/- S.E.M.) of baseline shortening 30 min after the stunning stimulus, recovering to 92 +/- 8.7% 5.5 h later. Function remained stable in sham controls. The change in venous-arterial [NO] between baseline and 6 h reperfusion was found to be significantly different between the two groups (0.2 +/- 0.7 in stunned vs. -4.3 +/- 1.6 microM in shams; P < 0.02). Western blotting and band optical density used to compare tissue from stunned territory (S), non-stunned territory (IC) and sham control animals (SC) demonstrated this was associated with an increase in the expression of both iNOS (S: 93 +/- 13.4, IC: 37 +/- 2.4 and SC: 25 +/- 4 [arbitrary units], P < 0.01 and P = 0.031) and eNOS (S: 104 +/- 7.4, IC; 62.5 +/- 7.4 and SC; 75.7 +/- 0.6, P < 0.03 and P < 0.01) in stunned myocardium. Immunocytochemistry localised iNOS reactivity to vascular smooth muscle cells and cardiomyocytes in stunned tissue and eNOS reactivity to endothelial cells. CONCLUSION: Recovery from repetitive myocardial stunning is associated with the increased expression of both iNOS and eNOS and would be compatible with a protective role for both these enzymes. This finding has possible relevance for both the late window of ischaemic preconditioning and myocardial hibernation.

Allopurinol improves myocardial reperfusion injury in a xanthine oxidase-free model.

The ability of allopurinol to protect against reperfusion injury in the heart has usually been attributed to its xanthine oxidase (XO)-inhibiting properties. Human myocardium however, has exhibited low levels of XO activity. To investigate the effects of allopurinol in an XO-free model and determine whether pretreatment is necessary, 12 domestic pigs (15 kg to 20 kg) underwent occlusion of the left circumflex for 8 minutes followed by reperfusion for 4 hours. One group received allopurinol infusion (5 mg/kg IV) at occlusion over 45 minutes and a control group (n = 6) received a saline infusion (same volume). Left ventricular and aortic pressure, electrocardiograms, and regional wall motion (sonomicrometry) were monitored throughout the process. Regional blood flow (microspheres) were obtained before, during, and 5, 10, and 30 minutes after ischemia. Occlusion decreased transmural flow at the midpapillary level by 75% (0.28 versus 1.10 mL/minute/g). The allopurinol-treated group exhibited a mild, generalized hyperemia at 5 minutes (ischemic zone: 1.44 versus 1.10 mL/min/g, which returned to control levels at 10 and 30 minutes. In contrast, the control group was associated with only 80% restoration of resting blood flow at 5 minutes (0.84 versus 1.10 mL/min/g), which stabilized at 63% of control levels at 10 and 30 minutes. When evaluated for the propensity of arrhythmias using an arbitrary arrhythmia score, the allopurinol group demonstrated no myocardial ectopy when compared with the focal ectopy routinely encountered in the control group at all time intervals.(ABSTRACT TRUNCATED AT 250 WORDS)

[Exogenous adenosine and postischemic dysfunction in the isolated rabbit heart]. / Adenosina exógena y disfuncion postisquémica en el corazon aislado de conejo.

It is recognized that adenosine lessens the systolic alterations of the postischemic ventricular dysfunction ("stunned myocardium"), but little is known about the drug's effects on the diastolic phase of the cardiac cycle. The aim of this work was to determine the effect of adenosine when it was administered: a) before ischemia and during reperfusion, and b) from the early reperfusion period to the end of the experiment on the systolic and diastolic function of the "stunned myocardium". An additional objective was to determine whether adenosine modifies the release of creatine phosphokinase (CPK) and lactate dehydrogenase (LDH), in the "stunned myocardium". Rabbit isolated isovolumic hearts were perfused according to Langendorff's technique, and subjected to 15 minutes global ischemia and 30 minutes reperfusion. A small latex balloon was inserted into the left ventricle via the left atrium which allowed to measure the ventricular end-diastolic pressure (diastolic stiffness) and calculate the developed pressure, the maximal rate of pressure generation and maximal rate of pressure decay (+dP/dtmax and -dP/dtmax), the ratio between these two variables (+P/-P), and the time constant of isovolumic relaxation (tau, Tau). The adenosine administered both before the ischemia period, and at the beginning of reperfusion, attenuated the systolic and diastolic stiffness alterations without modifying the isovolumic relaxation. The administration of adenosine did not diminish the CPK and LDH release significantly when it was given before the ischemia period or the beginning of reperfusion.

Milrinone and levosimendan administered after reperfusion improve myocardial stunning in swine.

OBJECTIVES: We assessed the effect of milrinone application timing after reperfusion against myocardial stunning as compared with levosimendan in swine. Furthermore, we examined the role of p38 mitogen-activated protein kinase (p38 MAPK) in the milrinone-induced cardioprotection. DESIGN: All swine were subjected to 12-minutes ischemia followed by 90-minutes reperfusion to generate stunned myocardium. Milrinone or levosimendan was administered intravenously either for 20 minutes starting just after reperfusion or for 70 minutes starting 20 minutes after reperfusion. In another group, SB203580, a selective p38 MAPK inhibitor, was administered with and without milrinone. Regional myocardial contractility was assessed by percent segment shortening (%SS). RESULTS: Milrinone starting just after reperfusion, but not starting 20 minutes after reperfusion, improved %SS at 30, 60, and 90 minutes after reperfusion compared with that in the control group. SB203580 abolished the beneficial effect of milrinone. On the other hand, levosimendan starting 20 minutes after reperfusion, but not for 20 minutes starting just after reperfusion, improved %SS at 60 and 90 minutes after reperfusion. CONCLUSIONS: Milrinone should be administered just after reperfusion to protect myocardial stunning through p38 MAPK, whereas levosimendan improvement of contractile function could be mainly dependent on its positive inotropic effect.

Administration of the Rho-kinase inhibitor fasudil before ischemia or just after reperfusion, but not 30 min after reperfusion, protects the stunned myocardium in swine.

OBJECTIVES: We assessed the effect of administration time for fasudil treatment of the stunned myocardium in 40 anesthetized open chest swine. MATERIALS AND METHODS: All swine were subjected to 12 min ischemia followed by reperfusion to generate stunned myocardium. Group A (n = 11) received saline in place of fasudil both before ischemia and after reperfusion. Group B (n = 10) received 30 min intravenous fasudil at a rate of 13 mug/kg/min starting 45 min before ischemia and received saline after reperfusion. Groups C (n = 10) and D (n = 9) received saline before ischemia, and received fasudil at a rate of 13 microg kg(-1) min(-1) starting just before reperfusion in group C and 30 min after reperfusion in group D. In both groups, treatment lasted 30 min. Myocardial contractility was assessed by percent segment shortening (%SS). RESULTS AND DISCUSSION: Three swine in group A, 2 swine in each of groups B and C, and one swine in group D had ventricular fibrillation or tachycardia after reperfusion and were excluded from further analysis. The changes of %SS from baseline at 90 min after reperfusion in groups B and C were 68 +/- 8% and 75 +/- 8%, respectively, which were significantly higher than in group A or D (47 +/- 10% or 43 +/- 8%). CONCLUSION: We conclude that fasudil administered before ischemia or just after reperfusion, but not 30 min after reperfusion, protects the stunned myocardium.

Endothelial nitric oxide synthase overexpression provides a functionally relevant angiogenic switch in hibernating pig myocardium.

OBJECTIVES: We investigated whether retroinfusion of liposomal endothelial nitric oxide synthase (eNOS) S1177D complementary deoxyribonucleic acid (cDNA) would affect neovascularization and function of the ischemic myocardium. BACKGROUND: Recently, we demonstrated the feasibility of liposomal eNOS cDNA transfection via retroinfusion in a model of acute myocardial ischemia/reperfusion. In the present study, we used this approach to target a phosphomimetic eNOS construct (eNOS S1177D) into chronic ischemic myocardium in a pig model of hibernation. METHODS: Pigs (n = 6/group) were subjected to percutaneous implantation of a reduction stent graft into the left anterior descending artery (LAD), inducing total occlusion within 28 days. At day 28, retroinfusion of saline solution containing liposomal green fluorescent protein or eNOS S1177D cDNA (1.5 mg/animal, 2 x 10 min) was performed. Furthermore, L-nitroarginine-methylester (L-NAME) was applied orally from day 28, where indicated. At day 28 and day 49, fluorescent microspheres were injected into the left atrium for perfusion analysis. Regional functional reserve (at atrial pacing 140/min) was assessed at day 49 by subendocardial segment shortening (SES) (sonomicrometry, percent of ramus circumflexus region). RESULTS: The eNOS S1177D overexpression increased endothelial cell proliferation as well as capillary and collateral growth at day 49. Concomitantly, eNOS S1177D overexpression enhanced regional myocardial perfusion from 62 +/- 4% (control) to 77 +/- 3% of circumflex coronary artery-perfused myocardium, unless L-NAME was co-applied (69 +/- 5%). Similarly, eNOS S1177D cDNA improved functional reserve of the LAD (33 +/- 5% vs. 7 +/- 3% of circumflex coronary artery-perfused myocardium), except for L-NAME coapplication (13 +/- 6%). CONCLUSIONS: Retroinfusion of eNOS S1177D cDNA induces neovascularization via endothelial cell proliferation and collateral growth. The resulting gain of perfusion enables an improved functional reserve of the hibernating myocardium.

Enhanced expression and localization of heme oxygenase-1 during recovery phase of porcine stunned myocardium.

Myocardial adaptation to ischemia involves up-regulated expression of a number of genes implicated in conferring cytoprotection. We have previously shown that myocardial ischemia followed by reperfusion leads to a co-ordinated expression of mRNAs encoding heme oxygenase-1 (HO-1) and ubiquitin in pigs. HO-1 participates in biological reaction leading to the formation of the antioxidant, bilirubin and the putative cellular messenger, carbon monoxide. In the present study, we examined the expression and cellular localization of HO-1 in the heart during myocardial stunning in anesthetized pigs. After thoracotomy, the LAD was occluded for 10 min and reperfused for 30 min (group I, n = 4), again occluded for 10 min and reperfused for 30 min (group II, n = 6), 90 min (group III, n = 4), 210 min (group IV, n = 5) and for 390 min (group V, n = 4). Myocardial tissue specimens were collected in 10% formalin as well as in liquid nitrogen and processed for immunohistochemistry and mRNA expression analysis, respectively. In the distribution territory of the LAD (experimental, E), systolic wall thickening was significantly decreased (39 +/- 6%) as compared to that of the area perfused by left circumflex coronary artery (LCx, control) in group I and remained depressed in all subsequent groups. Northern blot analysis revealed that the expression of a single mRNA species of 1.8 kb encoding HO-1 was significantly induced in E as compared to control in groups II and III with maximum mRNA levels in group II (1.9 +/- 0.4 fold vs. control). Immunoreactive HO-1 was localized in the cytoplasm of cardiomyocytes as well as in the perivascular regions in all groups. Semiquantitative analysis of HO-1 staining showed significantly enhanced levels of HO-1 in perivascular region in E as compared to respective controls derived from groups III and IV. These results suggest that myocardial adaptive response to ischemia involves up-regulation of HO-1 in cells of perivascular region indicating that this enzyme may participate in regulating vascular tone via CO and thereby, contributing in pathophysiologically important defense mechanism(s) in the heart.

A potential role for nitric oxide in myocardial stunning.

Nitric oxide (NO) production by the human heart has been demonstrated in patients undergoing cardiac surgery. Similar to what has been described in other species, a basal production of NO by the human heart is seen (126 +/- 42 pmol/min per gram). Following reperfusion, at the end of the procedure, the level of NO production increases significantly reaching concentrations of 1430 +/- 330 pmol/min per gram. Increased activity for the enzyme NO synthase (NOS) (8.0 +/- 1.2 pmol/mg prebypass vs 26.4 +/- 4.8 pmol/mg postbypass) coincides with changes in NO production and occurs at a time when myocardial stunning is clinically detectable. The significance of these findings is discussed and suggest a role for NO in the pathophysiology of myocardial stunning.

Reversible myocardial dysfunction in critically ill, noncardiac patients: a review.

OBJECTIVE: To review reversible myocardial dysfunction affecting critically ill patients without cardiac pathology. DATA SOURCES: The bibliography for the study was compiled through a search of different databases for the period 1966-2001. References cited in the selected articles also were reviewed. STUDY SELECTION: The selection criteria included all articles published on reversible myocardial dysfunction in critically ill patients. CONCLUSIONS: Reversible myocardial dysfunction may develop in a situation of critical pathology, but the etiology of reversible myocardial dysfunction is not fully understood. This dysfunction may be accompanied by increases in enzyme concentrations and electrocardiographic changes. Reversible myocardial dysfunction probably is underdiagnosed, although its presence is associated with a worsening of the prognosis and with more specific therapeutic options. Further studies are necessary to define its true incidence and clinical implications.

Phosphorylation by protein kinases A and C of myofibrillar proteins in rabbit stunned and non-stunned myocardium.

We tested the hypothesis that altered phosphorylation of myofibrillar proteins is involved in post-ischemic myocardial stunning. Myofibrillar proteins were isolated from Langendorff perfused control rabbit hearts, hearts submitted to 15 min normothermic ischemia and hearts submitted to 15 min ischemia followed by 10 min of reperfusion (stunned hearts). The in vivo level of phosphorylation of specific contractile proteins by protein kinases A and C was indirectly detected by the amount of 32P incorporated in vitro in the presence of these protein kinases and saturating concentration of [gamma-32P]-ATP (back-phosphorylation method). In control experiments the back-phosphorylation technique was able to detect PKA- or PKC-induced protein phosphorylation in hearts treated with isoproterenol and phorbol ester, respectively. In stunned hearts, contractile function was significantly suppressed compared to the period before ischemia. We found no difference in myofibrillar protein profile (on densitometry of the Coomassie-stained gels after SDS-PAGE) and in PKA mediated 32P incorporation when comparing control, ischemic and stunned myocardium. Three different PKCs were used for phosphorylation: commercial purified rat brain PKC, partially purified rat brain PKC or rabbit partially purified cardiac PKC. Cardiac PKC mainly phosphorylated troponin I, whereas brain PKC phosphorylated both troponin T and troponin I. No significant difference in 32P incorporation mediated by either brain or cardiac PKC was found between control, ischemic and ischemic/reperfused myofibrils. These data indicate that myocardial stunning does not cause changes in PKC- or PKA-mediated Pi incorporation into myofibrillar proteins detectable by the back-phosphorylation method.

Hemin, inducer of heme-oxygenase 1, improves functional recovery from myocardial stunning in conscious dogs.

OBJECTIVE: To examine the effects of pretreatment with hemin, an inducer of the potential antioxidative enzyme heme-oxygenase 1 (HO-1) or heat-shock protein 32, on myocardial stunning. DESIGN: Randomized animal study. SETTING: Animal laboratory of a university hospital. PARTICIPANTS: Chronically instrumented mongrel dogs (n = 44). INTERVENTIONS: Dogs underwent chronic instrumentation for measurement of hemodynamics and myocardial wall thickening fraction (WTF). Experiments with 12 dogs were performed on separate days in a crossover fashion: (1) 10 minutes of left anterior descending (LAD) coronary artery occlusion after application of hemin (9 mg/kg/d) for 1 week and (2) 10 minutes of LAD coronary artery occlusion without hemin pretreatment. In control experiments (n = 32), the reversible induction of HO-1, using gel electrophoresis and Western blotting, was determined. MEASUREMENTS AND MAIN RESULTS: WTF was measured as a baseline value before hemin administration and at predetermined time points until complete recovery from stunning. LAD artery occlusion caused a significant reduction in the WTF in the LAD-perfused area with and without hemin, without significant hemodynamic changes. At all time points, after 1 minute of reperfusion, the WTF as percentage of baseline values was significantly higher after hemin pretreatment (p < 0.05). Baseline WTF values were reached after 24 hours with and after >48 hours without hemin pretreatment (p < 0.05). CONCLUSION: Hemin pretreatment attenuates myocardial stunning in conscious dogs.

Effect of myocardial stunning on thiol status, myofibrillar ATPase and troponin I proteolysis.

To investigate the mechanism underlying postischemic contractile dysfunction (myocardial stunning) we examined myocardial sulflhydryl group content, myofibrillar Ca2+-dependent Mg2+-ATPase activity and protein profile after global ischemia and reperfusion. The Langerdorff-perfused rabbit hearts were subjected to 15 min normothermic ischemia followed by 10 min reperfusion and myofibrils were isolated from homogenates of left ventricular tissues. Depressed contractile function during reperfusion was accompanied by a decrease in total sulfhydryl group content. However, myofibrillar protein profile was unchanged and Western immunoblotting analysis showed no significant differences in troponin I immunoreactive bands between control and stunned hearts. Likewise, myofibrillar Mg2+-ATPase activity was unaltered after ischemia and reperfusion. We conclude that myocardial stunning is not caused by altered myofibrillar function and protein degradation but may be partly due to the oxidative modification of as yet undefined proteins.

Prominent negative T waves with QT prolongation indicate reperfusion injury and myocardial stunning.

To observe the clinical course after reperfusion and recovery from myocardial stunning of the left ventricular anterior wall, we prospectively reviewed and analyzed cardiac enzymes, ECG changes, echocardiograms, and cineangiograms in 8 patients with the acute ischemic syndrome who fulfilled the following criteria: 1) no history of previous myocardial infarction, 2) repeated and/or prolonged episodes of chest pain, 3) critical stenosis of the left anterior descending artery with wall motion abnormalities, 4) successful emergency percutaneous transluminal coronary angioplasty, and 5) normal wall motion on repeat cineangiography 4 to 8 weeks later. Creatine kinase (CK) and/or its cardiac isoenzyme (CK-MB) were minimally elevated in all cases. Wall motion was normalized with the reduction of end-systolic volume (end-diastolic volume: from 139 +/- 25 to 140 +/- 37 ml, ns, end-systolic volume: from 68 +/- 16 to 39 +/- 13 ml, p < 0.001, ejection fraction: from 51 +/- 6 to 71 +/- 6%, p < 0.001). Serial echocardiograms showed normalization of wall motion within 4 to 28 days. T wave inversion in the left precordial leads developed 30 min to 5 hours after the cessation of chest pain or successful reperfusion, and prominent negative T waves (1.6 +/- 0.6 mV) with QT prolongation (0.56 +/- 0.08 sec) in V3 or V4 reached their peak values within one to 5 days. ECG abnormalities resolved after 21 to 95 days. These ECG findings may indicate reperfusion injury and the presence of myocardial stunning in the anterior wall of the left ventricle.

Immunocytochemical evidence for inducible nitric oxide synthase and cyclooxygenase-2 expression with nitrotyrosine formation in human hibernating myocardium.

BACKGROUND: Myocardial hibernation may result from repetitive episodes of transient ischaemia leading to prolonged dysfunction. Inducible nitric oxide synthase (iNOS) expression has been demonstrated in animals following brief, non-lethal ischaemia-reperfusion injury. We therefore, hypothesised that in human hibernating myocardium: 1). iNOS would be present; 2). the reaction of nitric oxide and superoxide would form the strong oxidant peroxynitrite; 3) that this process would be accompanied by the expression of cyclooxygenase-2 (Cox-2) which interacts with NOS and whose products could further affect myocardial function. METHOD AND RESULTS: In sixteen patients with coronary artery disease (CAD), left ventricular biopsies were obtained from chronically dysfunctional segments subtended by a stenotic artery (> 75 %) and shown to be viable by (18)F-fluorodeoxyglucose positron emission tomography. Comparison was made with myocardial biopsies (n = 8) from normally contracting myocardium in patients undergoing coronary surgery, from unused transplant donors and at post-mortem. Regional wall motion score improved in all patients 6 months post-revascularisation (from 2.7 +/- 0.7 to 1.5 +/- 0.5; p < 0.001), confirming hibernation. Immunocytochemistry localized reactivity to iNOS, Cox-2 and nitrotyrosine (a marker of peroxynitrite formation) to cardiomyocytes from hibernating segments. No difference in reactivity to endothelial NOS was seen between hibernating and control cardiomyocytes. CONCLUSION: Cox-2 and iNOS are co-expressed in hibernating myocardium with nitrotyrosine suggesting nitric oxide production and peroxynitrite formation. We propose that this is secondary to ischaemia-reperfusion and that the products of these enzymes may have consequences for myocardial contractile function and survival.