Recombinant lys-plasminogen given before, but not after, recombinant tissue-type plasminogen activator markedly improves coronary thrombolysis in dogs: relationship of thrombolytic efficacy with parameters of fibrinolysis

Recombinant tissue-type plasminogen activator (rt-PA) administration rapidly restores blood flow in thrombosed coronary arteries, but coronary arteries often reocclude after initial thrombolysis. This occurs because of the short half-life of rt-PA and rapid increase in plasminogen activator inhibitor (PAI-1) and alpha2-antiplasmin levels in plasma. We hypothesized that administration of lys-plasminogen, which binds to fibrin with 10 times greater affinity and results in a loose fibrin structure (as compared with native glu-plasminogen), before rt-PA would enhance the thrombolytic efficacy of rt-PA and modulate parameters of fibrinolysis. To examine this hypothesis, dogs with electrically induced stable thrombus in the left anterior descending coronary artery (LAD) were treated with saline (group A, n = 9) or lys-plasminogen (group B, 2 mg/kg, n = 5), followed 10 min later by rt-PA (1 mg/kg in 20 min). Four other dogs with occlusive LAD thrombus were first given rt-PA, followed by lys-plasminogen (2 mg/kg) 50 min later (group C). Lys-plasminogen given before rt-PA restored flow in all dogs in 14 +/- 4 min (vs. 22 +/- 9 min in group A, p < 0.05), continuing > 2 h (vs. 41 +/- 15 min in group A, p < 0.02). Lys-plasminogen given after rt-PA did not potentiate the effect of rt-PA. Plasma t-PA antigen concentrations were highest in group B dogs at 2 h after rt-PA infusion. PAI-1 and alpha2-antiplasmin plasma levels were suppressed in all dogs receiving lys-plasminogen whether it was given before or after rt-PA. Therefore, lys-plasminogen given before rt-PA markedly potentiates the effect of rt-PA and alters the parameters of fibrinolysis. In contrast, lys-plasminogen given after rt-PA does not influence the thrombolytic effect of rt-PA, whereas it suppresses PAI-1 and alpha2-antiplasmin levels in plasma. This study also suggests that binding of plasminogen to the clot is more important than the plasma levels of PAI-1 and alpha2-antiplasmin.     

Sixty-minute alteplase protocol: a new accelerated recombinant tissue-type plasminogen activator regimen for thrombolysis in acute myocardial infarction

OBJECTIVES: Our aim was to design and evaluate a new and easily administered recombinant tissue-type plasminogen activator (rt-PA) regimen for thrombolysis in acute myocardial infarction (AMI) based on established pharmacokinetic data that improve the reperfusion success rate. BACKGROUND: Rapid restoration of Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow is a primary predictor of mortality after thrombolysis in AMI. However, TIMI grade 3 patency rates 90 min into thrombolysis of only 50% to 60% indicate an obvious need for improved thrombolytic regimens. METHODS: Pharmacokinetic simulations were performed to design a new rt-PA regimen. We aimed for a plateau tissue-type plasminogen activator (t-PA) plasma level similar to that of the first plateau of the Neuhaus regimen. These aims were achieved with a 20-mg rt-PA intravenous (i.v.) bolus followed by an 80-mg i.v. infusion over 60 min (regimen A). This regimen was tested in a consecutive comparative trial in 80 patients versus 2.25 10(6) IU of streptokinase/60 min (B), and 70 mg (C) or 100 mg (D) of rt-PA over 90 min. Subsequently, a confirmation trial of regimen A in 254 consecutive patients was performed with angiographic assessment by independent investigators of patency at 90 min. RESULTS: The comparative phase of the trial yielded, respectively, TIMI grade 3 and total patency (TIMI grades 2 and 3) of 80% and 85% (regimen A), 35% and 50% (B), 50% and 55% (C) and 60% and 70% (D). In the confirmation phase of the trial, regimen A yielded 81.1% TIMI grade 3 and 87.0% total patency. At follow-up angiography 7 (4.1%) of 169 vessels had reoccluded. In-hospital mortality rate was 1.2%. Nadir levels of fibrinogen, plasminogen and alpha2-antiplasmin were 3.6 +/- 0.8 mg/ml, 60 +/- 21% and 42 +/- 16%, respectively (mean +/- SD). Fifty-seven patients (22.4%) suffered from bleeding; 3.5% needed blood transfusions. CONCLUSIONS: The 60-min alteplase thrombolysis in AMI protocol achieved a TIMI grade 3 patency rate of 81.1% at 90 min with no indication of an increased bleeding hazard; it was associated with a 1.2% overall mortality rate. These results are substantially better than those reported from all currently utilized regimens. Head to head comparison with established thrombolytic regimens in a large-scale randomized trial is warranted.     

Selective inhibition of factor Xa is more efficient than factor VIIa-tissue factor complex blockade at facilitating coronary thrombolysis in the canine model

OBJECTIVES: We determined the effect of adjunctive inhibition of the extrinsic coagulation pathway by factor VIIa-tissue factor complex inhibitors, DEGR VIIa and tissue factor pathway inhibitor (TFPI), and the selective factor Xa inhibitor, tick anticoagulant peptide (TAP), after thrombolytic therapy with tissue-type plasminogen activator (t-PA) in a canine model of electrically induced coronary thrombosis. BACKGROUND: Ongoing thrombin generation is considered an important component of the heightened thrombin activity associated with thrombolytic therapy and may be responsible for reperfusion failure and reocclusion. METHODS: Forty-two dogs with electrically induced coronary thrombus undergoing thrombolysis with t-PA (1 mg/kg over 20 min) were randomly assigned to one of the following adjunctive regimens: TAP (30 micrograms/kg body weight per min for 90 min, n = 10); TFPI (100 to 150 micrograms/kg per min for 90 min, n = 10); DEGR VIIa (1- to 2-mg/kg bolus, n = 10) and saline control (n = 12). The dogs were observed for 120 min after thrombolysis for reocclusion. RESULTS: All three active study agents accelerated the time to reperfusion by an average of 12 min (all p < 0.05). Duration of reflow was greatest with TAP (117 +/- 8 min, p < 0.05 compared with saline control), whereas DEGR VIIa and TFPI did not prolong the duration of reflow. Reocclusion rates were similar among control, DEGR VIIa and TFPI groups (70%, 78% and 67%, respectively). Tick anticoagulant peptide reduced the occurrence of reocclusion (0%, p < 0.05 compared with saline control). CONCLUSIONS: In this experimental model, during systematic blockade of various extrinsic coagulation pathway proteins, we demonstrated that whereas acceleration of thrombolysis occurs with factor VIIa-tissue factor complex inhibition, optimal enhancement of thrombolysis was achieved through specific factor Xa blockade.     

Beneficial effect of raxofelast, an hydrophilic vitamin E analogue, in the rat heart after ischemia and reperfusion injury

Several studies report that among the antioxidant agents used to reduce injury after myocardial ischemia/reperfusion, analogues of vitamin E (VE) seem to have a significant efficacy. Raxofelast is a potent antioxidant agent under investigation, structurally related to VE, having an excellent bioavailability and favourable physicochemical properties. We assessed raxofelast in a rat model of myocardial damage induced by 1 h of left coronary artery occlusion followed by 6 h of reperfusion. Myocardial ischemia/reperfusion produced: wide tissue necrosis (50.3+/-10.3%); membrane peroxidation, evaluated by assessing cardiac malondialdehyde (MAL) (87.8+/-15.8 nmol/g tissuev 9.53+/-2.4 nmol/g tissue) and plasma conjugated dienes (CD) (8.73+/-1.86 DeltaABS/mlv 1.61+/-0.45 DeltaABS/ml); endogenous antioxidant wasting [cardiac VE=23.5+/-10.2 nmol/g tissuev 61.4+/-13.4 nmol/g tissue, cardiac reduced glutatione (GSH)=2.15+/-1.23 micromol/g proteinv 7.34+/-0.92 micromol/g protein and cardiac superoxide dismutase (SOD)=8.9+/-4.1 U/mg proteinv 17. 5+/-4.2 U/mg protein]; depressed mean arterial blood pressure (MAP) (61.4+/-5.8 mmHgv 85.3+/-6.2 mmHg); heart rate (HR) (275+/-35 beats/minv 368+/-34 beats/min) and left-ventricular derivative developed force (LV dP/dtmax) (1050+/-187 mmHg/sv 2520+/-194 mmHg/s); and cardiac neutrophil accumulation, evaluated by assessing cardiac myeloperoxidase (MPO) (9.23+/-2.1 U/g tissuev 0.92+/-0.12 U/g tissue). Administration of raxofelast (25, 50 and 100 mg/kg i.p. 5 min after occlusion) limited myocardial necrosis (22.3+/-14.8%P<0. 005, following the highest dose), reduced lipid peroxidation (MAL=43. 5+/-14.7 nmol/g tissueP<0.001 and CD=4.01+/-2.21 DeltaABS/mlP<0.001, following the highest dose), restored the endogenous antioxidants VE (52.8+/-14.2 nmol/g tissueP<0.001, following the highest dose), SOD (14.2+/-2.7 U/mg proteinP<0.001, following the highest dose) and GSH (4.92+/-1.33 micromol/g proteinP<0.005, following the highest dose), improved hemodynamic parameters (MAP=68.1+/-5.3 mmHgP<0.05, HR=317+/-27 beats/minP<0.05, LV dP/dtmax=1427+/-143 mmHg/sP<0.05, following the highest dose) and reduced myocardial neutrophil infiltration (MPO=5.1+/-1.5 U/g tissueP<0.001, following the highest dose). These data suggest that raxofelast could be considered a useful drug to reduce myocardial infarction.     

The challenge and importance of defining critical limb ischemia

Thrombolytic therapy (TT) modifies the natural history of acute myocardial infarction (AMI) diminishing morbi-mortality rate. In recent studies, modification of infusion velocity, decreased the mortality 10 percentage points. OBJECTIVE: Test if rt PA administration over an hour is safe and practical. MATERIAL AND METHODS: A prospective, cooperative trial during 3 years, included patients with AMI with less than 6 hours of the onset of symptoms that received rt-PA therapy. Initially 10 mg bolus and then 90 mg over 60 minutes period. Together with the administration of rt-PA, 5000 units of heparin was given, followed by 1000 units per hour adjusted to keep PTT at 1.5 to 2 times normal. All patients received aspirin and according of the evolution adjuvant therapy. We defined bleeding complications and/or cerebrovascular accident related to thrombolytic therapy. RESULTS: We included 225 patients who received rt-PA. Average age was 57.1 +/- 22.2 years, 78.7% males and 21.3% females. Arrival time at hospital was 2.93 +/- 1.7 hours. 82.2% were in class I-II by NYHA. 59.2% had anterior wall location and 32.4% posterior-inferior wall 80% had reperfusion criteria. Only 7.1% required transfusion and 0.4% presented CNS bleeding. The survival rate was 95.2%. The mortality had no relation with bleeding. CONCLUSION: Fast infusion is an effective and safe method. Transfusion requirements are no greater, and CNS bleeding was noted in 0.4% of the cases.     

Production of less chronic nephrotoxicity by cyclosporine G than cyclosporine A in a low-salt rat model

Chronic tubulointerstitial nephropathy during long-term cyclosporine A (CsA) use has led to a search for equally effective but safer analogues. In this study we evaluated one of these analogues, cyclosporine G (CsG), in a rat model of chronic cyclosporine nephrotoxicity. CsG has immunosuppressive effects equivalent to CsA when dosed on a weight basis. Pair-fed Sprague-Dawley rats kept on a low-salt rice diet were given CsA 15 mg/kg, CsG 15 mg/kg, CsG 25 mg/kg, or vehicle subcutaneously. After 21 days, CsA animals had a lower glomerular filtration rate, measured by inulin clearance (0.16 +/- 0.04 ml/min/100 g) and higher serum creatinine (0.94 +/- 0.06 mg/dl) than CsG 15 mg/kg (GFR: 0.41 +/- 0.10 ml/min/100 g and serum creatinine: 0.68 +/- 0.09 mg/dl), CsG 25 mg/kg (GFR: 0.39 +/- 0.16 ml/min/100 g) or control rats (GFR: 0.62 +/- 0.06 ml/min/100 g; serum creatinine: 0.56 +/- 0.03 mg/dl), respectively (P < 0.05). The CsA group had considerable cortical and medullary injury (interstitial fibrosis and tubular atrophy), whereas both groups of CsG animals had more limited changes. Despite the same or larger doses of CsG on a weight basis, cyclosporine blood levels were significantly lower in CsG than CsA rats. We conclude that CsG, an analogue of cyclosporine with immunosuppressive activity equivalent to that of CsA, produced less nephrotoxicity in a model of chronic renal injury in rats, using both functional and structural parameters.     

Antithrombotic effects of MK-0852, a platelet fibrinogen receptor antagonist, in canine models of thrombosis

The antiaggregatory and antithrombotic actions of MK-0852, a cyclic heptapeptide antagonist of the platelet GP IIb/IIIa, were evaluated in a variety of canine models. In vitro, MK-0852 inhibited the aggregation of canine platelet-rich plasma induced by 10 microM ADP in the presence of 1 microM epinephrine with an IC50 value of 0.10 microM. The i.v. infusion of 1.0 and 3.0 micrograms/kg/min MK-0852 to anesthetized dogs significantly inhibited ex vivo platelet aggregation responses to ADP and collagen, with the 3.0 micrograms/kg/min infusion completely inhibiting ex vivo aggregation responses to both agonists. The i.v. administrations of 100 and 300 micrograms/kg MK-0852 suppressed platelet-dependent cyclic flow reductions in stenosed canine left circumflex (LCX) coronary artery for periods of 24 +/- 3 and 64 +/- 4 min, respectively. In a canine model of copper coil-induced femoral arterial thrombosis, i.v. MK-0852 (100 micrograms/kg + 1 microgram/kg/min), initiated 15 min before coil placement, reduced the incidence of occlusive thrombosis during the 45-min post-coil time period of continued therapy (1/5 MK-0852 vs. 7/7 saline; P < .01). MK-0852 was administered as an adjunctive therapy with tPA to evaluate its effects on thrombolysis after copper coil-induced femoral arterial thrombus formation. MK-0852 (i.v.; 100 micrograms/kg + 1 microgram/kg/min), initiated 15 min before tPA, reduced the incidence of post-thrombolysis reocclusion. During the 60-min period of continued drug infusion after the termination of tPA, 0 of 5 animals receiving MK-0852 reoccluded vs. 7/8 saline (P < .01). In a canine model of electrically induced LCX coronary artery thrombosis, i.v. MK-0852 (100 micrograms/kg + 3 micrograms/kg/min), initiated 15 min before the initiation of electrical injury, prevented occlusive thrombosis in 4 of 6 preparations despite the continued electrical stimulation of the vessel for 180 min. Thrombotic occlusion was delayed in the remaining two preparations (99 and 100 min), compared with occlusion in 4 of 4 saline-treated preparations (69.3 +/- 6.3 min). When administered as an adjunct to thrombolytic agents for lysis of electrically induced LCX coronary artery thrombi, i.v. MK-0852 (300 micrograms/kg + 3 micrograms/kg/min), initiated 15 min before tPA or streptokinase, both increased the incidence of reperfusion (tPA: 8/8 MK-0852 vs. 3/8 saline; streptokinase: 5/8 MK-0852 vs. 2/8 saline) and accelerated reperfusion. The incidence of reocclusion during continued adjunctive therapy was reduced.(ABSTRACT TRUNCATED AT 400 WORDS)     

Modulation of kinin B1 but not B2 receptors-mediated rat paw edema by IL-1beta and TNFalpha

The modulatory effects of IL-1beta and TNF alpha on the rat paw edema induced by B1 agonists have been analyzed. In naive rats, i.d. injection of B1 agonists, des-Arg9-bradykinin and des-Arg10-kallidin (up to 300 nmol), causes a minimal increase in paw volume, while the B2 agonist tyrosine8-bradykinin (0.3-10 nmol) induces graded paw edema. The injection of des-Arg9-bradykinin (10-100) nmol or des-Arg10-kallidin (1-100 nmol), in paws pre-treated with IL-1beta or TNF alpha (both 5 ng/paw; 60 and 30 min prior, respectively), caused a graded edema formation. The edemas induced by des-Arg9-bradykinin (100 nmol) were evident at 15 min, reaching the maximum 60 and 30 min after treatment with IL-1beta (0.64 +/- 0.06 ml) or TNF alpha (0.47 +/- 0.05 ml), respectively, being reduced at 360 min. The B1 antagonist des-Arg9-NPC 17731 (1-30 nmol), but not the B2 antagonist Hoe 140 (10 nmol), produced marked inhibition of des-Arg9-bradykinin-induced paw edema. Dexamethasone (0.5 mg/kg, s.c., 4 h) or cycloheximide (1.5 mg/kg, s.c., 6 h) significantly prevented the edema caused by des-Arg9-bradykinin (100 nmol) in rats treated with IL-1beta (81 +/- 5% and 59 +/- 3%) or TNF alpha (78 +/- 4% and 43 +/- 2%). Indomethacin (2 mg/kg, i.p.) or meloxicam (3 mg/kg, i.p.), 1 h prior, significantly reduced the edema induced by des-Arg9-bradykinin (100 nmol) in IL-1beta (40 +/- 6% and 69 +/- 8%) or TNF alpha (43 +/- 3% and 53 +/- 9%) treated rats. It is suggested that i.d. injection of the IL-1beta or TNF alpha, produced up-regulation of B1 receptor-mediated paw edema, being this effect sensitive to dexamethasone and cycloheximide and to cyclo-oxygenase pathway.     

Estrogen-mediated neuroprotection after experimental stroke in male rats

BACKGROUND AND PURPOSE: We have previously shown that 17beta-estradiol reduces infarction volume in female rats. The present study determined whether single injection or chronic implantation of estrogen confers neuroprotection in male animals with middle cerebral artery occlusion (MCAO) and whether there is an interaction with endogenous testosterone. METHODS: Male Wistar rats were treated with 2 hours of reversible MCAO. In protocol 1, acute versus chronic estrogen administration was examined in groups receiving the following: Premarin (USP) 1 mg/kg IV, immediately before MCAO (Acute, n=13, plasma estradiol=171+/-51 pg/mL); 7 days of 25 microg (E25, n=10, 10+/-3 pg/mL) or 100 microg 17beta-estradiol (E100, n=12, 69+/-20 pg/mL) by subcutaneous implant; or saline (SAL, n=21, 3+/-1 pg/mL). Laser-Doppler flowmetry was used to monitor the ipsilateral parietal cortex throughout the ischemic period and early reperfusion. At 22 hours of reperfusion, infarction volume was determined by 0 2,3,5-triphenyltetrazolium chloride staining and image analysis. In protocol 2, rats were castrated to deplete endogenous testosterone and then treated with estradiol implants: castration only (CAST, n= 13, estradiol=5+/-2 pg/mL), sham-operated (SHAM, n= 10, 4+/-2 pg/mL), estradiol implant 25 microg (CAST+E25, n=16, 7+/-2 pg/mL) or 100 microg (CAST+E100, n=14, 77+/-14 pg/mL). RESULTS: Cortical infarct volumes were reduced in all estrogen-treated groups: Acute (21+/-4% of ipsilateral cortex), E25 (12+/-5%), and E100 (12+/-3%) relative to SAL (38+/-5%). Caudate infarction was similarly decreased: Acute (39+/-7% of ipsilateral striatum), E25 (25+/-7%), and E100 (34+/-6%) relative to SAL (63+/-4%). Castration did not alter ischemic outcome; cortical and caudate infarction (percentage of respective ipsilateral regions) were 37+/-5% and 59+/-5% in CAST and 39+/-7% and 57+/-5% in SHAM, respectively. Estrogen replacement reduced infarction volume in castrated animals in cortex (19+/-4% in CAST+E25 and 12+/-4% in CAST+E100) and in caudate (42+/-6% in CAST+25 and 20+/-7% in CAST + 100). Laser-Doppler flowmetry results during ischemia and reperfusion was not different among groups. CONCLUSIONS: Both acute and chronic 17beta-estradiol treatments protect male brain in experimental stroke. Testosterone availability does not alter estradiol-mediated tissue salvage after MCAO.     

Stress and the immune system: preliminary observations in rheumatoid arthritis using an in vivo marker of immune activity

This study measured volumetric liver blood flow and galactose clearance concurrently during orthotopic liver transplant in human subjects. Ultrasound transit time flowmeters measured hepatic artery and portal vein flow 1-3 h after reperfusion. Galactose (100 mg/min) was infused over 45-60 min to steady state for calculation of clearance. Mean +/- S.D. total volumetric flow was 1966 +/- 831 ml/min with portal flow contributing 86%. Mean galactose clearance was 1988 +/- 641 ml/min. There was a significant correlation (p < 0.05, r = 0.61) between volumetric total liver blood flow and galactose clearance. The data show that: (i) the newly transplanted liver is capable of metabolizing galactose within 1-3 h of reperfusion; and (ii) liver blood flow is high in the newly implanted liver. The clinical importance of this observation is that there is increased clearance of high first pass substances by the transplanted liver which may be of importance in patient management.     

Neuroprotection afforded by a combination of eliprodil and a thrombolytic agent, rt-PA, in a rat thromboembolic stroke model

In the present study, we have assessed the efficacy of eliprodil, a neuroprotective agent which blocks both the modulatory polyamine site of the NMDA receptor and neuronal voltage-sensitive calcium channels, alone or in combination with the thrombolytic agent, rt-PA, in a rat embolic stroke model using a neurological score and the volume of the infarct as endpoints. Embolization was induced by intracarotid injection of an arterial blood clot. Eliprodil, administered at the dose of 1 mg/kg, iv. 10 min and 2 h 30 after embolization, reduced the neurological deficit by 54% (P < 0.01) and the total volume of the brain lesion by 49%. Thrombolysis with rt-PA (2.5 mg/kg, as a 30 min iv infusion beginning 1 h after embolization) decreased the neurological deficit by 48% (P < 0.05) and the size of the total infarct by 55% (P < 0.05). Combined therapy greatly improved the degree of neuroprotection as assessed by neurological and histological outcomes (70% (P < 0.001) and 89% (P < 0.01) neuroprotection, respectively). These results demonstrate that the administration of a neuroprotective drug (eliprodil) or a thrombolytic agent (rt-PA) similarly reduce the volume of brain damage and the neurological deficit in a rat embolic stroke model. Combined cytoprotective therapy and thrombolysis markedly improved the degree of neuroprotection and may, thus, represent a valuable approach for the treatment of stroke in humans.     

Telomere length, telomerase activity and telomerase RNA expression during mouse mammary tumor progression

The effects of intraportal administration of prostaglandin E1 (PGE1) on portal venous flow, hepatic arterial flow, peripheral tissue blood flow, and systemic arterial flow before and after 60 min total liver ischemia followed by 70% partial hepatectomy in rats were investigated. Total liver ischemia was induced by occluding the hepatoduodenal ligament for 60 min. PGE1 at a dose of 0.5 microg/kg/min was infused intraportally for 15 min before inducing hepatic ischemia (preischemic period) and for 60 min after ischemia (postischemic reperfusion period) in the treatment group. Normal saline was infused in the control group. Seventy percent partial hepatectomy was performed during ischemia. Serum biochemical analysis and liver tissue histology were carried out 1, 3, and 24 h, and 1 and 24 h after reperfusion respectively. One-week survival of the PGE1 group was improved to 70% compared to that of the control group of 30%. Postischemia reperfusion values of portal and peripheral tissue blood flows in the PGE1 group were 6.33 +/- 0.600 ml/min and 27.2 +/- 23.5 (arbitrary), and were significantly different from those of the control group of 4.34 +/- 0.400 ml/min and 23.5 +/- 5.54 (arbitrary), respectively. There was no significant difference in hepatic arterial flow between the two groups. Serum alkaline phosphatase decreased significantly in the prostaglandin group. Histological examination revealed a significant portal venous congestion in the control group 1 and 24 h after reperfusion. The extent of the sinusoidal congestion was also severe in the control group 24 h after reperfusion. It was concluded that PGE1 has a protective effect against liver damage when the liver was injured by warm ischemia and reperfusion followed by partial resection.     

Long-term prognosis of young patients after myocardial infarction in the thrombolytic era

BACKGROUND: Myocardial infarction (MI) in young adults is a rare event. In the Framingham study, the 10-year incidence rate of MI per 1,000 was 12.9 in men 30-34 years old. Overall, 4-8% of patients with acute MI are < or = 40 years old. HYPOTHESIS: It was the purpose of this study to assess the in-hospital and long-term morbidity and mortality in patients < or = 40 years old with acute myocardial infarction compared with older patients in the thrombolytic era. METHODS: A consecutive series of 75 patients aged < or = 40 years (mean 35.0 +/- 4.8) with acute myocardial infarction was compared with an equally sized group of patients aged > 40 years (mean 65.1 +/- 9.8). RESULTS: Thrombolysis or direct percutaneous transluminal coronary angioplasty was performed in 52 versus 24% (p = 0.0004) and 5.3 versus 2.7% (p = NS) in younger and older patients, respectively. Significantly fewer young patients had multivessel disease (28 vs. 64%, p < 0.004). No in-hospital mortality was observed in patients with reperfusion therapy irrespective of age. After a mean followup time of 47 +/- 35 months, cardiac mortality was 0 and 11% (p < 0.03), respectively, in young and older patients with, and 3 versus 24% (p < 0.02) without reperfusion therapy, respectively. In addition, significantly fewer patients in the younger age group developed recurrent angina pectoris (12 vs. 39%, p = 0.0004) or congestive heart failure (9 vs. 34%, p = 0.0005) irrespective of reperfusion therapy. CONCLUSION: Our observations demonstrate that long-term prognosis after myocardial infarction in young patients is excellent in the thrombolytic era.     

Inhibitory effects of glibenclamide and pertussis toxin on the attenuation of ischemia-induced myocardial acidosis following ischemic preconditioning in dogs

Ischemic preconditioning is known to be mediated by several humoral factors, such as adenosine, norepinephrine, and bradykinin. We examined intracellular signal transduction of ischemic preconditioning following receptor stimulation. Alterations in the pH of the ischemic bed were monitored to assess the response of control and ischemic-preconditioned myocardium to glibenclamide and pertussis toxin. Pentobarbital-anesthetized open-chest dogs were subjected to 40 min of ligation of the left anterior descending coronary artery. Ischemic preconditioning was elicited by 25-min periods of coronary ligation followed by 5 min of reperfusion before a 40-min period of ligation. Glibenclamide (0.3 mg/kg)was given i.v. 20 min before the onset of ischemic preconditioning. Pertussis toxin (6-10 micrograms/kg) was given i.v. 3 days before the experiment. Tissue myocardial pH was measured by a glass micro-pH electrode. Ischemia for 5 min decreased myocardial pH and reperfusion returned it to the preischemic levels. Ischemia for 40 min decreased the myocardial pH from 7.43 +/- 0.06 to 6.43 +/- 0.08. Ischemic preconditioning significantly attenuated the decrease in myocardial pH (6.57 +/- 0.06) induced by 40 min of ischemia. Pretreatment with either glibenclamide or pertussis toxin completely abolished the effect of ischemic preconditioning on ischemic myocardial acidosis. Ischemic preconditioning can attenuate ischemia-induced myocardial acidosis in dogs, and this effect is mediated by activation of adenosine triphosphate-sensitive potassium channels and pertussis toxin-sensitive guanosine triphosphate-binding protein.     

Comparative effects of staphylokinase and alteplase in rabbit bleeding time models

BACKGROUND: The pathogenesis of bleeding associated with thrombolytic therapy remains largely unknown, although spontaneous bleeding appears to correlate with bleeding time prolongation. Here, the comparative effects on cuticle bleeding times (CBT) and ear puncture bleeding times (EBT) of recombinant staphylokinase (Sak) and alteplase (recombinant tissue-type plasminogen activator, rt-PA) at equivalent doses, alone and in combination with aspirin and heparin, were studied in rabbits. METHODS AND RESULTS: Groups of 4 to 9 rabbits were allocated to one of the 8 following intravenous infusions: saline; aspirin 15 mg/kg and heparin - 100 IU/kg bolus and 10 IU/kg infusion over one hour; 1.5 mg/kg rt-PA; 1.5 mg/kg rt-PA plus aspirin and heparin; 4.5 mg/kg rt-PA; 0.5 mg/kg Sak; 0.5 mg/kg Sak plus aspirin and heparin and 1.5 mg/kg Sak. Bleeding times were determined 30 and 15 min before and 5, 15, 30 and 60 min after the administration over one min of saline, rt-PA or Sak, by simultaneously severing a nail cuticle (CBT) and by puncturing the ear (EBT). Bleeding times were unaffected by saline and by both doses of Sak in monotherapy. Heparin-aspirin and low dose rt-PA significantly lengthened EBT but not CBT. Both CBT and EBT were significantly prolonged (to a mean of > 4 times pretreatment at 5 min) after high-dose rt-PA and after the combined administration of heparin and aspirin with either Sak or tr-PA. rt-PA provoked significantly longer bleeding than Sak in the CBT (p = 0.001; mean estimated difference = 23 min), but not in the EBT. rt-PA but not Sak degraded plasma fibrinogen dose-dependently. CBT correlated inversely with fibrinogen (r= -0.66, p=0.001) but EBT did not. CONCLUSION: At equivalent doses Sak displays a significantly higher fibrin specificity and prolongs bleeding time less than rt-PA, particularly in the nail cuticle bleeding time model in which larger vessels are injured that require fibrinogen for hemostasis.     

Reduction in QT interval dispersion by successful thrombolytic therapy in acute myocardial infarction. TEAM-2 Study Investigators

BACKGROUND: QT dispersion (QTd, equals maximal minus minimal QT interval) on a standard ECG has been shown to reflect regional variations in ventricular repolarization and is significantly greater in patients with than in those without arrhythmic events. METHODS AND RESULTS: To assess the effect of thrombolytic therapy on QTd, we studied 244 patients (196 men; mean age, 57 +/- 10 years) with acute myocardial infarction (AMI) who were treated with streptokinase (n = 115) or anistreplase (n = 129) at an average of 2.6 hours after symptom onset. Angiograms at 2.4 +/- 1 hours after thrombolytic therapy showed reperfusion (TIMI grade > or = 2) in 75% of patients. QT was measured in 10 +/- 2 leads at 9 +/- 5 days after AMI by using a computerized analysis program interfaced with a digitizer. QTd, QRSd, JT (QT minus QRS), and JT dispersion (JTd, equals maximal minus minimal JT interval) were calculated with a computer. There were significant differences in QTd (96 +/- 31, 88 +/- 25, 60 +/- 22, and 52 +/- 19 milliseconds; P < or = .0001) and in JTd (97 +/- 32, 88 +/- 31, 63 +/- 23, and 58 +/- 21 milliseconds; P = .0001) but not in QRSd (25 +/- 10, 22 +/- 7, 28 +/- 9, and 24 +/- 9 milliseconds; P = .24) among perfusion grades 0, 1, 2, and 3, respectively. Similar results were obtained comparing TIMI grades 0/1 with 2/3 and 0/1/2 with 3. Patients with left anterior descending (versus right and left circumflex) coronary artery occlusion showed significantly greater QTd (70 +/- 29 versus 59 +/- 27 milliseconds, P = .003) and JTd (74 +/- 30 versus 63 +/- 27 milliseconds, P = .004). Similarly, patients with anterior (versus inferior/lateral) AMI showed significantly greater QTd (69 +/- 30 versus 59 +/- 27 milliseconds, P = .006) and JTd (73 +/- 30 versus 63 +/- 27 milliseconds, P = .007). Results did not change when Bazett's QTc or JTc was substituted for QT or JT or when ANOVA included adjustments for age, sex, drug assignment, infarct site, infarct vessel, and number of measurable leads. On ANCOVA, the relation of QTd or JTd and perfusion grade was not influenced by heart rate. CONCLUSIONS: Successful thrombolysis is associated with less QTd and JTd in post-AMI patients. The results are equally significant when either QT or JT is used for analysis. These data support the hypothesis that QTd after AMI depends on reperfusion status as well as infarct site and size. Reduction in QTd and its corresponding risk of ventricular arrhythmia may be mechanisms of benefit of thrombolytic therapy.     

Quantification of the modifications in the dominant frequency of ventricular fibrillation under conditions of ischemia and reperfusion: an experimental study

The characteristics of ventricular fibrillatory signals vary as a function of the time elapsed from the onset of arrhythmia and the maneuvers used to maintain coronary perfusion. The dominant frequency (FrD) of the power spectrum of ventricular fibrillation (VF) is known to decrease after interrupting coronary perfusion, though the corresponding recovery process upon reestablishing coronary flow has not been quantified to date. With the aim of investigating the recovery of the FrD during reperfusion after a brief ischemic period, 11 isolated and perfused rabbit heart preparations were used to analyze the signals obtained with three unipolar epicardial electrodes (E1-E3) and a bipolar electrode immersed in the thermostatized organ bath (E4), following the electrical induction of VF. Recordings were made under conditions of maintained coronary perfusion (5 min), upon interrupting perfusion (15 min), and after reperfusion (5 min). FrD was determined using Welch's method. The variations in FrD were quantified during both ischemia and reperfusion, based on an exponential model deltaFrD = A exp (-t/C). During ischemia deltaFrD is the difference between FrD and the minimum value, while t is the time elapsed from the interruption of coronary perfusion. During reperfusion deltaFrD is the difference between the maximum value and FrD, while t is the time elapsed from the restoration of perfusion. A is one of the constants of the model, and C is the time constant. FrD exhibited respective initial values of 16.20 +/- 1.67, 16.03 +/- 1.38, and 16.03 +/- 1.80 Hz in the epicardial leads, and 15.09 +/- 1.07 Hz in the bipolar lead within the bath. No significant variations were observed during maintained coronary perfusion. The fit of the FrD variations to the model during ischemia and reperfusion proved significant in nine experiments. The mean time constants C obtained on fitting to the model during ischemia were as follows: E1 = 294.4 +/- 75.6, E2 = 225.7 +/- 48.5, E3 = 327.4 +/- 79.7, and E4 = 298.7 +/- 43.9 seconds. The mean values of C obtained during reperfusion, and the significance of the differences with respect to the ischemic period were: E1 = 57.5 +/- 8.4 (P < 0.01), E2 = 64.5 +/- 11.2 (P < 0.01), E3 = 80.7 +/- 13.3 (P < 0.01), and E4 = 74.9 +/- 13.6 (P < 0.0001). The time course variations of the FrD of the VF power spectrum fit an exponential model during ischemia and reperfusion. The time constants of the model during reperfusion after a brief ischemic period are significantly shorter than those obtained during ischemia.     

Protective effect of hyperin against myocardial ischemia and reperfusion injury

AIM: To study the protective and antiperoxidative effects of hyperin (hyperoside; quercetin-3-O-galactoside; Hyp) on myocardial ischemia/reperfusion. METHODS: The rabbit anterior descenging branch of left coronary artery was occluded for 60 min and then released to allow reperfusion for 20 min. Hemodynamics (LVP, LV +/- dp/dt) and electrocardiogram (ECG, lead II) were monitored continuously with polygraph. After reperfusion, the blood sample and myocardium were taken to assay plasma creatine phosphokinase (CPK), lactate dehydrogenase (LDH), and cations in myocardium. Using a Langendorff system, the isolated heart of rat was initiated by ischemia for 40 min followed by 30 min of reperfusion. Malondialdehyde (MDA) contents of cardiac effluent and myocardium were measured with fluorescence spectrophotometer. RESULTS: Hyp 10 mg.kg-1 i.v. depressed changes in LVP, LV +/- dp/dtmax, ECG, plasma CPK, LDH, and cations (Ca2+, Mg2+, Na+) in myocardium induced by ischemia/reperfusion in rabbits. Hyp 10 and 100 mumol.L-1 markedly reduced the increase in MDA production in isolated rat hearts after ischemia/reperfusion. CONCLUSION: Hyp possesses a protective effect against myocardial ischemia/reperfusion injury via attenuating lipid peroxidation.     

Evidence that mitochondrial respiration is a source of potentially toxic oxygen free radicals in intact rabbit hearts subjected to ischemia and reflow

Previous in vitro studies have shown that isolated mitochondria can generate oxygen radicals. However, whether a similar phenomenon can also occur in intact organs is unknown. In the present study, we tested the hypothesis that resumption of mitochondrial respiration upon reperfusion might be a mechanism of oxygen radical formation in postischemic hearts, and that treatment with inhibitors of mitochondrial respiration might prevent this phenomenon. Three groups of Langendorff-perfused rabbit hearts were subjected to 30 min of global ischemia at 37 degrees C, followed by reflow. Throughout ischemia and early reperfusion the hearts received, respectively: (a) 5 mM KCl (controls), (b) 5 mM sodium amobarbital (Amytal, which blocks mitochondrial respiration at Site I, at the level of NADH dehydrogenase), and (c) 5 mM potassium cyanide (to block mitochondrial respiration distally, at the level of cytochrome c oxidase). The hearts were then processed to directly evaluate oxygen radical generation by electron paramagnetic resonance spectroscopy, or to measure oxygen radical-induced membrane lipid peroxidation by malonyl dialdehyde (MDA) content of subcellular fractions. Severity of ischemia, as assessed by 31P-nuclear magnetic resonance measurements of cardiac ATP, phosphocreatine, and pH, was similar in all groups. Oxygen-centered free radical concentration averaged 3.84 +/- 0.54 microM in reperfused control hearts, and it was significantly reduced by Amytal treatment (1.98 +/- 0.26; p < 0.05), but not by KCN (2.58 +/- 0.96 microM; p = not significant (NS)), consistent with oxygen radicals being formed in the mitochondrial respiratory chain at Site I. Membrane lipid peroxidation of reperfused hearts was also reduced by treatment with Amytal, but not with KCN. MDA content of the mitochondrial fraction averaged 0.75 +/- 0.06 nM/mg protein in controls, 0.72 +/- 0.06 in KCN-treated hearts, and 0.54 +/- 0.05 in Amytal-treated hearts (p < 0.05 versus both groups). Similarly, MDA content of lysosomal membrane fraction was 0.64 +/- 0.09 nM/mg protein in controls, 0.79 +/- 0.15 in KCN-treated hearts, and 0.43 +/- 0.06 in Amytal-treated hearts (p < 0.05 versus both groups). Since the effects of Amytal are known to be reversible, in a second series of experiments we investigated whether transient mitochondrial inhibition during the initial 10 min of reperfusion was also associated with beneficial effects on subsequent recovery of cardiac function after wash-out of the drug. At the end of the experiment, recovery of left ventricular end-diastolic and of developed pressure was significantly greater in those hearts that had been treated with Amytal during ischemia and early reflow, as compared to untreated hearts.(ABSTRACT TRUNCATED AT 400 WORDS)     

XV454, a novel nonpeptide small-molecule platelet GIIb/IIIa antagonist with comparable platelet alpha(IIb)beta3-binding kinetics to c7E3

XV454 demonstrated high potency (IC50 = 14-25 nM) in inhibiting human platelet aggregation induced by adenosine diphosphate (ADP, 10 microM), thrombin receptor agonist peptide (TRAP) (10 microM), or collagen (20 microg/ml). XV454 exhibited a high degree of selectivity for platelet alpha(IIb)beta3 in comparison with c7E3, which is a nonspecific antagonist for both alpha(IIb)beta3 and alpha(v)beta3. Both XV454 and c7E3 bind with high affinity to either activated (A) or unactivated (U) human, baboon, or canine platelets. XV454 binds with a relatively higher affinity [Kd = 0.5 nM (A), 0.6 nM (U)] as compared with c7E3 [Kd = 9.1 nM (A), 9.2 (U) nM]. XV454 demonstrated a tight association with human, baboon, and, to a lesser extent, with canine platelets (t(1/2) of dissociation = 110 +/- 6, 80 +/- 10, and 23 +/- 2 min, respectively). Both c7E3 and XV454 associate tightly with a slower dissociation rate with unactivated human platelets: t(1/2) of 42 and 116 min, respectively. In non-human primates, oral (0.1 mg/kg, p.o.) and intravenous (0.05 mg/kg, i.v. bolus administration of XV454 methyl ester pro-drug resulted a long-lasting maximal antiplatelet efficacy for < or = 72 h with significant but reversible prolongation of bleeding time and without effects on platelet count, clinical chemistry, or hemodynamic profile. In conclusion, XV454 represents a potent antiplatelet agent in inhibiting platelet aggregation along with a high affinity and relatively slow dissociation rate from human platelet GPIIb/IIIa receptors that allow a long-lasting antiplatelet efficacy after single i.v. or oral administration.