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PubMed1993

Early and late effects of leukopenic reperfusion on the recovery of cardiac contractile function. Studies in the transplanted and isolated blood-perfused rat heart.

BACKGROUND: Since there is considerable evidence that leukocytes contribute to tissue injury during ischemia and reperfusion, the present study was designed to: (1) determine whether reperfusion in vivo with leukopenic blood affords protection in a model of reversible hypothermic ischemia, (2) determine the duration of any protection, (3) characterize the relation between protection and duration of leukopenic perfusion, and (4) assess the effect of leukopenic reperfusion on myocardial glutathione content. METHODS AND RESULTS: Rat hearts (n = 12 per group) were excised, immediately arrested with an infusion (2 minutes at 4 degrees C) of St Thomas' cardioplegic solution, and subjected to 4 hours of global ischemia (4 degrees C). The hearts were then transplanted (1 hour additional ischemic time) into the abdomen of saline-treated or leukopenic recipients. Leukopenia was induced by intraperitoneal administration of mustine hydrochloride (2 mg/kg) 3 days before study. Hearts were then reperfused in situ for 1, 4, or 24 hours, after which they were excised and either processed for histological examination (n = 4 per group) or perfused aerobically with bicarbonate buffer for 20 minutes, and contractile function was assessed (n = 8 per group); at the end of this period, some hearts (n = 5 per group) were taken for metabolite analysis. After 1 hour of reperfusion, contractile function in the saline-treated control group was significantly reduced compared with aerobic controls that had not been subjected to ischemia (left ventricular developed pressure [LVDP], 108 +/- 5 vs 126 +/- 3 mm Hg at an end-diastolic pressure of 12 mm Hg; P < .05). However, in the hearts with leukopenic reperfusion, LVDP (119 +/- 2 mm Hg) was similar to that of aerobic controls. This benefit, however, was lost after 4 and 24 hours of reperfusion. Cardiac compliance was not influenced by leukopenia. Coronary flow recovered significantly better in the leukopenic hearts during the first 4 hours of reperfusion (11.8 +/- 0.5 vs 9.3 +/- 0.4 mL/min at 1 hour and 10.0 +/- 0.5 vs 8.0 +/- 0.4 mL/min at 4 hours, P < .05), but again this benefit was lost after 24 hours of reperfusion. The myocardial contents of reduced and oxidized glutathione after 1, 4, and 24 hours of reperfusion were similar in saline-treated and leukocyte-depleted animals. In additional studies, the period of ischemia was extended to 8 hours, and similar results were obtained, with improved recovery of contractile function and coronary flow but not cardiac compliance in the leukopenic group after 1 hour of reperfusion. In further studies with the isolated blood-perfused rat heart, ischemia was induced for 8 hours; this was followed first by reperfusion for 0, 2, 10, 30, or 60 minutes with leukopenic blood and then by perfusion with blood from saline-treated animals for 60, 58, 50, 30, or 0 minutes, respectively. Reperfusion with leukopenic blood for 2 minutes did not improve the recovery of LVDP (106 +/- 7 vs 96 +/- 10 mm Hg in controls; NS) but when continued for 10, 30, or 60 minutes resulted in significant improvements (137 +/- 5, 138 +/- 3, and 150 +/- 10 mm Hg, respectively). Although coronary flow tended to be greater in all leukopenic groups, by the end of 60 minutes of reperfusion, only those hearts reperfused with leukopenic blood for the entire reperfusion period showed a significant improvement (3.4 +/- 0.3 vs 2.5 +/- 0.2 mL/min in controls; P < .05). Histological studies revealed no intravascular aggregation of leukocytes or features of myocyte necrosis. CONCLUSIONS: Reperfusion with leukopenic blood accelerated the rate of recovery of cardiac function after reversible myocardial injury but did not lead to a sustained increase in the eventual extent of recovery. Reperfusion with leukopenic blood for the first 10 minutes of reflow is sufficient to obtain this benefit.

Animals↗

PubMed1998

Staged reperfusion preserves the coronary flow reserve, especially in the regions not severely damaged by ischemic injury in the canine heart.

The objective of this study was to determine the effects of staged reperfusion on the progressive reduction in coronary blood flow (CBF) and coronary flow reserve during reperfusion and on the infarct size in the canine heart. Fifteen dogs underwent 90 min of left circumflex coronary artery occlusion and 3 hr of reperfusion. In the abrupt reperfusion group, the occluder was released completely at the initiation of reperfusion. In the staged reperfusion group, CBF was maintained at 20% of preocclusion values for 10 min after initiation of reperfusion, then gradually released, and completely released 20 min after initiation of reperfusion. There was no significant difference in CBF between the staged (n = seven) and abrupt (n = eight) groups after 3 hr of reperfusion. The repayment of flow debt in the staged reperfusion group was significantly greater than in the abrupt reperfusion group after 3 hr of reperfusion (260+/-120% vs 100+/-60%, staged vs abrupt at 3 hr, p < 0.03). The ratio of peak reactive hyperemic flow to resting flow in the staged reperfusion group was significantly greater than in the abrupt reperfusion group throughout the reperfusion phase (4.4+/-1.0 vs 2.6+/-0.6 at 3 hr, p < 0.001), and had returned to the preocclusion values after 3 hr of reperfusion. This preservation of the coronary flow reserve in the staged reperfusion group was observed in the epicardium (4.1+/-0.6 vs 2.8+/-0.7, staged vs abrupt at 3 hr, p < 0.01), but not in the endocardium or midmyocardium. Infarct size did not differ significantly between the two groups. Staged reperfusion in this study did not appear to attenuate the reduction of CBF, or to reduce infarct size, however preserved the coronary flow reserve, especially in the regions not severely damaged by ischemic injury.

Animals↗

PubMed1993

Does reperfusion injury exist in humans?

Timely coronary reperfusion as treatment for acute myocardial infarction reduces myocardial infarct size, improves left ventricular function and survival. There is still concern that at the time of reperfusion, a further injury occurs to the myocardium. Theoretically, if this "reperfusion injury" could be treated and eliminated, the outcome for patients with myocardial infarction might further improve. The concept of reperfusion injury is closely tied to the concept that oxygen radicals generated at the time of reperfusion cause tissue damage. There are four basic forms of reperfusion injury. Lethal reperfusion injury is described as myocyte cell death due to reperfusion itself rather than to the preceding ischemia. This concept continues to be controversial in both experimental animal and clinical studies. Vascular reperfusion injury refers to progressive damage to the vasculature over time during the phase of reperfusion. Manifestations of vascular reperfusion injury include an expanding zone of no reflow and a deterioration of coronary flow reserve. This form of reperfusion injury has been documented in animal models and probably occurs in humans. Stunned myocardium refers to postischemic ventricular dysfunction of viable myocytes and probably represents a form of "functional reperfusion injury." This phenomenon is well documented in both animal models and humans. Reperfusion arrhythmias represent the fourth form of reperfusion injury. They include ventricular tachycardia and fibrillation that occur within seconds to minutes of restoration of coronary flow after brief (5 to 15 min) episodes of myocardial ischemia. True reperfusion arrhythmias occur in only a small percentage of patients receiving thrombolytic therapy for acute myocardial infarction and are not a sensitive indicator for successful reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Reperfusion-induced injury: a possible role for oxidant stress and its manipulation.

While some investigators recognize "reperfusion-induced injury" as an important component of the overall injury that occurs during ischemia and reperfusion, others question its existence. Resolution of this controversy is of considerable importance, particularly in an era of thrombolysis, since reperfusion-induced injury might be amenable to treatment. Although reperfusion is an absolute prerequisite for the recovery of ischemic tissue, it undoubtedly has some unfavorable effects. The identification of four (possibly sequential) components of reperfusion-induced injury helps to clarify the situation: a) Reperfusion after brief periods of ischemia can trigger arrhythmias in tissue that is potentially salvable; there is abundant experimental and clinical evidence for this form of reperfusion injury. b) Reperfusion may also be associated with "myocardial stunning"; however, given sufficient time, this prolonged postischemic contractile and metabolic dysfunction will recover. There is good experimental evidence and some clinical evidence for the existence of this type of reperfusion-induced injury. c) Reperfusion is commonly thought to cause lethal injury in cells that, until the time of reperfusion, were potentially salvable. However, conclusive evidence that reperfusion can kill cells does not yet exist. d) Reperfusion may alter the nature of necrotic processes in tissue that has already sustained lethal injury, while not altering the number of cells that die this may change the manner in which they die; this form of reperfusion injury could lead to differences in scar formation and vulnerability to aneurysm. There is considerable evidence for the existence of this form of reperfusion-induced injury. Many candidate mechanisms have been proposed for each form of reperfusion injury. Ionic disturbances (particularly for calcium) are often cited and, most recently, free radical-induced induced injury (oxidant stress) has been suggested as important. Considerable evidence exists that oxidant stress is involved in stunning and in reperfusion-induced arrhythmias, and characterization of underlying mechanisms might lead to novel therapeutic principles, such as antioxidant therapy. However, much remains to be learned.

Free Radicals↗

PubMed1999

A single cell model of myocardial reperfusion injury: changes in intracellular Na+ and Ca2+ concentrations in guinea pig ventricular myocytes.

To investigate the contribution of the changes in intracellular Na+ and Ca2+ concentrations ([Na+]i and [Ca2+]i) to myocardial reperfusion injury, we made an ischemia/reperfusion model in intact guinea pig myocytes. Myocardial ischemia was simulated by the perfusion of metabolic inhibitors (3.3 mM amobarbital and 5 microM carbonyl cyanide m-chlorophenylhydrazone) with pH 6.6 and reperfusion was achieved by the washout of them with pH 7.4. [Na+]i increased from 7.9 +/- 2.0 to 14.0 +/- 3.4 mM (means +/- S.E., p < 0.01 ) during 7.5 min of simulated ischemia (SI) and increased further to 18.8 +/- 3.0 mM at 7.5 min after reperfusion. [Ca2+]i, expressed as the ratio of fluo 3 fluorescence intensity, increased to 133 +/- 8% (p < 0.01) during SI and gradually returned to the control level after reperfusion. Intracellular pH decreased from 7.53 +/- 0.04 to 6.31 +/- 0.04 (p < 0.01) and recovered quickly after reperfusion. Reperfusion with the acidic solution or the continuous perfusion of hexamethylene amiloride (2 microM) prevented the reperfusion-induced increase in [Na+]i. When the duration of SI was prolonged to 15 min, the cell response after reperfusion varied, 16 of 37 cells kept quiescent, 21 cells showed spontaneous Ca2+ waves, and 4 cells out of these 21 cells became hypercontracted. In quiescent cells, both [Na+]i and [Ca2+]i decreased immediately after reperfusion. In cells with Ca2+ waves, [Na+]i transiently increased further at the early phase of reperfusion, while [Ca2+]i declined. In hypercontracted cells, [Na+]i increased as much as in 'Ca2+ wave' cells, but [Ca2+]i increased extensively and both ion concentrations continued to increase. Reperfusion with the Ca2+-free solution prevented both the [Ca2+]i increase and morphological change. In the presence of ryanodine (10 microM), the increase in [Ca2+]i after reperfusion was augmented and some cells became hypercontracted. We concluded that (1) Na+/H+ exchange is active both during SI and reperfusion, resulting in the additional [Na+]i elevation on reperfusion, (2) the [Na+]i level after reperfusion and the following Ca2+ influx via Na+/Ca2+ exchange are crucial for reperfusion cell injury, and (3) the Ca2+ buffering capacity of sarcoplasmic reticulum would also contribute to the Ca2+ regulation and cell injury after reperfusion.

Amiloride↗

PubMed1992

Postischaemic metabolic and functional recovery of rat heart after transient reperfusion with various low Ca2+ concentrations.

OBJECTIVE: The effects of transient low Ca2+ reperfusion after ischaemia on metabolic and functional recovery were studied in isolated rat hearts. METHODS: 31P nuclear magnetic resonance (NMR) was used to monitor creatine phosphate, ATP, intracellular inorganic phosphate (Pi), and intracellular pH during control perfusion (15 min), total ischaemia (30 min), and reperfusion (30 min). During early reperfusion (0-10 min) perfusate [Ca2+] amounted to 1.3 (control group), 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7 mmol.litre-1. During late reperfusion (10-30 min) perfusate [Ca2+] was 1.3 mmol.litre-1. Isolated rat hearts were used and perfused according to Langendorff. RESULTS: Recovery of creatine phosphate during early reperfusion was partly abolished during late reperfusion in the 0.1-0.4 mmol.litre-1 groups (p < 0.01). In the 0.1 mmol.litre-1 group creatine phosphate content after 30 min reperfusion was lower (p < 0.05) than in the control group. Recovery of ATP during early reperfusion in the 0.3 mmol.litre-1 group was better than in the control group (p < 0.01). After 30 min reperfusion ATP recovery was better in the 0.3 mmol.litre-1 group (p < 0.01) and worse in the 0.1 mmol.litre-1 group (p = 0.05) than in the control group. Decline of Pi during early reperfusion was more pronounced in the 0.2 and 0.3 mmol.litre-1 groups (p < 0.01) and in the 0.5 and 0.6 mmol.litre-1 groups (p < 0.05) than in the control group. In the 0.3 and 0.4 mmol.litre-1 groups, Pi after 30 min reperfusion was higher (p < 0.05) than after 10 min reperfusion. After 30 min reperfusion left ventricular developed pressure, measured with an intraventricular balloon, was lower in the 0.1 mmol.litre-1 group (p < 0.01) than in the control group. CONCLUSIONS: The data show that under the experimental conditions used successive postischaemic reperfusion with 0.1 and 1.3 mmol.litre-1 Ca2+ resulted in poorer metabolic and functional recovery of the hearts than continuous reperfusion with 1.3 mmol.litre-1 Ca2+. Postischaemic reperfusion with 0.1 mmol.litre-1 Ca2+ may predispose the heart to a mild calcium paradox. Successive reperfusion with 0.3 and 1.3 mmol.litre-1 Ca2+ was optimal in terms of ATP recovery but did not result in an increased recovery of left ventricular developed pressure.

Adenosine Triphosphate↗

PubMed1998

Suppression of reperfusion arrhythmias by preconditioning is inhibited by an ATP-sensitive potassium channel blocker, 5-hydroxydecanoate, but not by protein kinase C blockers in the rat.

It has been suggested that preconditioning (PC) against infarction in the rat heart is mediated by opening of ATP-sensitive potassium (KATP) channels, which may be induced by receptor-triggered activation of protein kinase C (PKC). However, the mechanism of suppression of reperfusion arrhythmias by PC remains unclear. This study first examined whether suppression of reperfusion arrhythmias by PC requires the activation of KATP channels, PKC, and opioid receptors. In anesthetized rats, reperfusion arrhythmias were induced by occluding the left main coronary artery for 5 min and subsequent reperfusion. In untreated control rats, the incidence of reperfusion ventricular tachycardia (VT) was 100%, and 80% of the VT deteriorated to ventricular fibrillation (VF). PC with 2-min ischemia/5-min reperfusion reduced the incidences of VT and VF to 30% and 0, respectively. Although a KATP channel blocker, 5-hydroxydecanoate (5-HD), alone caused no significant effect on the incidence of reperfusion VT, this agent blocked the suppression of reperfusion VT by PC (VT incidence, 91%). The incidence of reperfusion VF in the 5-HD-treated rats tended to be lower than that in the untreated controls and was not different between preconditioned and nonpreconditioned groups (30 vs. 27%). PKC inhibitors staurosporine and calphostin C modified neither reperfusion arrhythmias nor the antiarrhythmic effect of PC on reperfusion VT and VF. Naloxone (6 mg/kg, i.v.) did not alter the incidence or duration of VT in the nonpreconditioned heart. However, suppression of reperfusion VT by PC was prevented by naloxone (VT incidence, 70%). The incidence of reperfusion VF was similarly low in the naloxone-treated rats in both nonpreconditioned and preconditioned groups (20% vs. 0). In the second series of experiments, the effect of 5-HD on repetitive PC was assessed. Repetitive PC was performed with three cycles of 2-min ischemia/5-min reperfusion, which totally abolished reperfusion VT and VF. This antiarrhythmic effect of repetitive PC was not inhibited by 5-HD. These results suggest that KATP channels and opioid receptors may be partly involved in suppression of reperfusion arrhythmias, although their roles may be compensated for by other antiarrhythmic mechanisms in repetitive PC. In contrast with PC against infarction, PKC is unlikely to play a major role in PC against reperfusion arrhythmias in the rat.

Adenosine Triphosphate↗

PubMed1998

Beneficial effects of early coronary reperfusion on left ventricular remodeling and systolic function in patients with acute myocardial infarction.

OBJECTIVE: To evaluate the beneficial effects of early coronary reperfusion on left ventricular remodeling (LVRM) and systolic function in patients with acute myocardial infarction (AMI). METHODS: Eighty-one patients with first AMI in the convalescent stage and having undergone left ventriculography (LVG) and coronary arteriography (CAG) were divided into four groups: the anterolateral wall (ALW) myocardial infarction (MI) non-reperfusion (n = 20) and reperfusion (n = 21), and inferoposterial wall (IPW) MI non-reperfusion (n = 20) and reperfusion (n = 20), according to infarct location and early treatment with or without successful coronary reperfusion therapy within 6 hours after onset of symptoms. By LVG, the parameters of LVRM and systolic function in the four MI groups were analyzed and compared with those in normal group (n = 25) and between the two reperfusion and non-reperfusion MI groups. RESULTS: In both ALW and IPW MI non-reperfusion groups, the left ventricular (LV) end-diastolic volume (EDV), circumference (EDC), short-axis dimension (EDD), short to long axis ratio (ED-D/L), sphericity index (ED-SI) and end-systolic volume (ESV) were all significantly increased (P < 0.01-0.001), while LV ejection fractions (LVEF) were significantly decreased (both P < 0.001) when compared with those of normal group; and the increase in ESV and decrease in LVEF were both significantly greater in ALW than in IPW MI groups (both P < 0.01). In both ALW and IPW MI reperfusion groups, however, the EDV, EDD, ESV, as well as the extent and severity of regional wall motion abnormality (RW-MA) were significantly smaller (P < 0.05-0.001), while LVEF were significantly higher (P < 0.01-0.001) when compared with those in the two non-reperfusion MI groups respectively. There were no longer significant differences in LVEF and ESV between ALW and IPW MI groups (both P > 0.05). The EDC in IPW MI reperfusion group and the ED-D/L and ED-SI in ALW MI reperfusion group were also significantly reduced compared with those in the two non-reperfusion MI groups respectively (P < 0.05-0.001). All the above parameters in the two reperfusion MI group were decreased to the normal in comparison with normal group except ESV and LVEF, and ED-D/L and ED-SI in IPW MI group. CONCLUSION: It was indicated that in both ALW and IPW MI non-reperfusion groups, LVRM had occurred in convalescent stage of AMI with an increase in EDV and EDC, spherical change in LV shape, and accompanying reduction in LV systolic function; and early coronary reperfusion in AMI could reduce the extent and severity of RWMA, prevent from LV enlargement and remodeling, and preserve or improve LV systolic function with more prominence in ALW MI.

Convalescence↗

PubMed1991

[Influence of reperfusion therapy on left ventricular remodeling after acute myocardial infarction].

To determine the relation between reperfusion therapy and left ventricular function and remodeling after acute myocardial infarction (AMI), 75 consecutive patients with anterior AMI were studied. The patients were divided into four groups according to the reperfusion outcome and time to reperfusion from onset of MI: 12 patients with spontaneous reperfusion, 18 patients with early (less than 4th) successful reperfusion, 16 patients with late (greater than or equal to 4th) successful reperfusion and 29 patients with unsuccessful reperfusion. The right oblique left ventriculograms (LVG), which was performed early (n = 19) and late after infarction (n = 75) were analyzed to assess left ventricular (LV) volume and global and regional LV function. At the late examination, spontaneous early and late reperfused patients showed smaller LV volume (endo diastolic and endo-systolic volume index) than unsuccessfully reperfused patients LV volume was similar in both early and late reperfused patients. Spontaneous and early reperfused patients showed higher LV ejection fraction (EF) and better regional wall motion (RWM) than unsuccessfully reperfused patients. Both EF and RWM was similar in late and unsuccessfully reperfused patients at the late examination. Endo-diastolic and endo-systolic volume index increased significantly with time in patients with unsuccessful reperfusion (n = 10), as compared with the index found in the early examination. In patients with late reperfusion (n = 5), end-diastolic volume index increased with time, but end-systolic volume index was unchanged. RMW improved in patients with early reperfusion (n = 4), but was unchanged in patients with late and unsuccessful reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1987

Biochemical basis for reperfusion arrhythmias.

This study was designed to clarify the biochemical mechanism of reperfusion arrhythmias. Forty-three anesthetized dogs were divided into three groups; the occlusion group (n = 7), the reperfusion group (n = 24), and a group treated with the alpha 1-adrenergic blocker, bunazosin (n = 12). In the occlusion group, the left anterior descending coronary artery (LAD) was occluded for 15 min. In the reperfusion group and the bunazosin group, LAD was occluded for 15 min and then reperfused for 5 min with physiological saline or bunazosin (0.5 mg/kg) infused 5 min prior to the LAD occlusion. Seven dogs (29%) of the reperfusion group developed reperfusion arrhythmias, but 17 did not. In the bunazosin group, none developed arrhythmias. Immediately after the end of occlusion or reperfusion, myocardial plasma membrane and mitochondria were prepared from the normal and ischemic areas or the normal and reperfused areas. Phospholipase activity, phospholipid content, and free fatty acid (FFA) levels were determined. The mitochondrial calcium content was also measured. In the reperfusion-with-arrhythmias group, the content of calcium in the mitochondria obtained from the reperfused area and phospholipase activity in the reperfused myocardium was elevated significantly compared with those in the reperfusion-without-arrhythmias group. Phospholipid content in the plasma membrane prepared from the reperfused area also decreased significantly in the reperfusion-with-arrhythmias group. The FFA levels in the plasma membrane prepared from the reperfused area were increased. In the reperfusion-without-arrhythmias group and the bunazosin group, these changes were not observed. Fifteen minutes occlusion alone did not induce these changes observed in the reperfusion-with-arrhythmias group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗

PubMed1992

Sustained protection by acadesine against ischemia- and reperfusion-induced injury. Studies in the transplanted rat heart.

BACKGROUND: We have shown that acadesine (AICAr: 5-amino-4-imidazole carboxamide riboside) improves the early recovery of function of the ischemic and reperfused rat heart. In the present studies we used the transplanted rat heart, with reperfusion for up to 24 hours, to assess whether the beneficial effect of acadesine is a transient or a sustained phenomenon (i.e., to determine whether the drug improves the extent of recovery or only the rate). METHODS AND RESULTS: Hearts (n = 8 per group) were excised and immediately arrested with an infusion (2 minutes at 20 degrees C) of the St. Thomas' Hospital cardioplegic solution with or without the addition of acadesine (20 mumol/l). They were then subjected to 4 hours of global ischemia (20 degrees C), and the cardioplegic solution (with or without acadesine) was infused for 2 minutes every 30 minutes. The hearts then were transplanted (1 hour additional ischemic time) into the abdomens of recipient rats, which had been given acadesine (100 mg/kg i.v.) or saline. They were reperfused in situ for 30 minutes or 24 hours and then excised and perfused aerobically for 20 minutes. Contractile function was assessed, and the hearts were taken for metabolite analysis. Two sets of four groups (n = 8 per group) were studied (one set with 30 minutes and the other with 24 hours of reperfusion): group A, acadesine-free control; group B, acadesine during cardioplegia alone; group C, acadesine during reperfusion alone; and group D, acadesine during both cardioplegia and reperfusion. With 30 minutes of reperfusion, a significant improvement in functional recovery was seen in the two groups (groups B and D) in which acadesine had been added to the cardioplegic solution. Left ventricular developed pressure (LVDP) at 12 mm Hg of left ventricular end-diastolic pressure (LVEDP) was 104 +/- 3 mm Hg in both groups versus 88 +/- 3 mm Hg in the acadesine-free controls (p less than 0.05). No protection was observed after 30 minutes of reperfusion when acadesine had been added during reperfusion alone (89 +/- 4 mm Hg). In contrast, after 24 hours of reperfusion there was a significant improvement in postischemic LVDP in all acadesine-treated groups (group B, 104 +/- 6 mm Hg; group C, 106 +/- 7 mm Hg; and group D, 117 +/- 3 mm Hg versus only 73 +/- 6 mm Hg in the acadesine-free controls; p less than 0.05 in each case). Metabolite analysis indicated that at the end of ischemia ATP was less depleted and levels of tissue adenosine were higher in the acadesine group. During early (30 minutes) reperfusion, acadesine produced higher mean ATP contents, although this achieved a level of statistical significance only when the drug was administered during both cardioplegia and reperfusion. After 24 hours of reperfusion, the adenine nucleotide pools were similar in all groups. CONCLUSIONS: Acadesine can afford sustained functional protection against injury during extended periods of ischemia and reperfusion. We present evidence that the beneficial effect of acadesine may be mediated by two different components, with one operative during ischemia and early reperfusion and the other acting later in the reperfusion period.

Abdomen↗

PubMed1996

[Controlled reperfusion of the extremities for preventing local and systemic damage after prolonged ischemia. An experimental study with the swine model].

Our previous studies in isolated rat hindlimbs using crystalloid perfusion solutions have shown that control of the initial reperfusion reduces postischemic complications. However, no experimental study has been undertaken to evaluate the concept of controlled limb reperfusion experimentally in an in-vivo blood-perfused model and to assess the local as well as systemic effects of normal blood reperfusion and controlled limb reperfusion. Of twenty pigs undergoing preparation of the infrarenal aorta and iliac arteries, six were observed for 7.5 hours and served as controls. Fourteen other pigs underwent 6 hours of complete infrarenal occlusion. Thereafter, embolectomy was stimulated in 8 pigs by removing the aortic clamp and establishing normal blood reperfusion at systemic pressure. In 6 other pigs, control of the composition of the reperfusate and control of the conditions of reperfusion was done during the first 30 min, followed by normal blood reperfusion. Six hours of infrarenal aortic occlusion lead to a severe decrease in high energy phosphates and muscle temperature and a slight increase in creating kinase (CK) and potassium in the systemic circulation. Normal blood reperfusion resulted in severe reperfusion injury: massive edema developed (80.6% vs. 76.6%, p < 0.0009), the tissue showed a marked decrease in oxygen consumption (7.3 +/- 1.1 vs. 14.3 +/- 2.5 mL )2/100 g/min, p < 0.02), glucose consumption (0.19 +/- 0.06 vs. 0.51 +/- 0.03 mg/100 g/min, p < 0.06), tissue ATP (18.3 +/- 1.9 vs. 36.1 +/- 0.9 mumol/g protein, p < 0.000001), total adenine nucleotides (26.3 +/- 2.6 vs. 45.8 +/- 1.5 mumol/g protein, p < 0.00001), muscle pH (5.9 +/- 0.1 vs. 7.3 +/- 0.1, p < 0.000006) and total calcium in the femoral vein (2. +/- 0.1 vs. 2.7 +/- 0.1 mmol/L, p < 0.002). Furthermore, a massive increase was seen in CK concentration (12,743 +/- 2,562 vs. 513 +/- 80 U/L, p < 0.0003), potassium (7.9 +/- 0.3 vs. 4.4 +/- 0.2 mmol/L, p < 0.000001) and muscle rigidity (60 +/- 11 vs. 122 +/- 1 degree, p < 0.00008). In sharp contrast, initial treatment of the ischemic skeletal muscle by controlled limb reperfusion resulted in normal water content (77.6 +/- 0.4 vs. 76.8 +/- 0.3%), oxygen consumption (13.2 +/- 1.6 vs. 14.9 +/- 3.2 mL O2/100 g/min), glucose consumption (0.58 +/- 0.18 vs. 0.46 +/- 0.11 mg/100 g/min), flow (5.4 +/- 1.1 vs. 4.6 +/- 4.6 +/- 0.5 mL/100 g/min) and muscle rigidity (106 +/- 4 vs. 122 +/- 1 degree). Furthermore, controlled limb reperfusion resulted in higher total adenine nucleotides content (78% vs. 57% of control), less tissue acidosis (6.6 +/- 0.2 vs. 5.9 +/- 0.1, p < 0.002), severely reduced CK release (2,618 +/- 702 vs. 12,743 +/- 2.562, p < 0.02) and potassium release (5.1 +/- 0.3 vs. 7.9 +/- 0.3 mmol/L, p < 0.0002) as compared to normal blood reperfusion. In conclusion this study shows that 6 hours of acute infrarenal aortic occlusion will result in a severe reperfusion injury (postischemic syndrome) if normal blood at systemic pressure is given in the initial reperfusion phase. In contrast, initial treatment of the ischemic skeletal muscle by controlled limb reperfusion reduces the metabolic, functional and biochemical alterations.

Animals↗

PubMed2003

Effect of prodromal angina pectoris on altering the relation between time to reperfusion and outcomes after a first anterior wall acute myocardial infarction.

To test the hypothesis that prodromal angina may favorably alter the relation between time to reperfusion and outcomes after acute myocardial infarction (AMI), we studied 658 patients with a first anterior AMI: 200 patients with early reperfusion (time to reperfusion <or=2 hours), 205 patients with intermediate reperfusion (2 to 4 hours), 197 patients with late reperfusion (4 to 12 hours), and 56 patients without reperfusion (no reperfusion). Serial measurements of left ventricular ejection fraction (LVEF) were obtained before reperfusion therapy and before hospital discharge in 450 patients. Thirty-day mortality (3%, 4%, 8%, and 27% in early, intermediate, late, and no reperfusion, respectively, p <0.001) and the change in LVEF (8 +/- 14%, 6 +/- 13%, 6 +/- 12%, and -1 +/- 9%, respectively, p <0.001) were dependent on time to reperfusion and were worse if reperfusion was not obtained. In early reperfusion, 30-day mortality (3% vs 2%, p = 0.88) and improvement of LVEF (9 +/- 14% vs 8 +/- 14%, p = 0.59) were not significantly different between patients with prodromal angina and patients without prodromal angina. In intermediate or late reperfusion, prodromal angina was associated with lower 30-day mortality (3% vs 8%, p = 0.049) and a greater improvement in LVEF (8 +/- 13% vs 5 +/- 13%, p = 0.037). In no reperfusion, 30-day mortality (25% vs 27%, p = 0.87) and the change in LVEF (-1 +/- 11% vs -1 +/- 9, p = 0.87) were poor, regardless of prodromal angina. These findings suggest that prodromal angina might favorably alter the relation between time to reperfusion and outcomes after AMI. However, prodromal angina did not afford any benefits if reperfusion was not achieved.

Adult↗

PubMed1997

Assessment of preservation induced reperfusion injury via intraoperative renal transplant blood flow and endothelin concentration studies.

PURPOSE: We investigated a possible relationship between levels of the vasoconstrictive peptide endothelin and renal transplant reperfusion injury, and modified a technique for measuring renal blood flow with an ultrasonic perivascular transit time flow probe. MATERIALS AND METHODS: Renal grafts in a swine transplant model were cold flushed with either Collins-2 or University of Wisconsin solution. Renal blood flow and renal vein endothelin levels after reperfusion of transplanted grafts, as well as histological parameters within the transplanted kidney were measured. The 5-minute post-reperfusion renal blood flow was used as the baseline allograft flow. The definition of reperfusion injury was a decrease in flow from baseline with no recovery within 1 hour of reperfusion. In 9 human recipients reperfusion injury was further verified by monitoring subsequent serum creatinine, urine output, graft survival and rejection episodes. RESULTS: In the swine model and human transplant recipients no evidence of post-reperfusion ischemia was noted by histological examination, supporting that moderate to mild reperfusion injury or ischemic injury cannot be clinically determined with this method. In the swine model the decrease flow from baseline in allograft post-reperfusion renal blood flow was significantly greater in kidneys preserved in Collins'-2 than in University of Wisconsin solution (41.75 +/- 5.69 versus 11.18 +/- 13.99 ml. per minute, p = 0.005), supporting that this technique can assess mild to moderate reperfusion injury. The increase in serum endothelin in the allografts from the swine model and in humans was not significantly different from baseline. Clinically, post-reperfusion renal blood flow changes correlated well with subsequent function. The 4 patients with renal transplant reperfusion injury had significantly higher serum creatinine values and lower urine output 1 week postoperatively than 5 patients with no evidence of injury (serum creatinine: 6.75 +/- 3.03 versus 2.08 +/- 1.28 mg./dl., p = 0.015). Reperfusion injury patients had more rejections (2 versus 1) and less graft survival (75% versus 100%) at 1-year followup compared to the nonreperfusion injury patients. CONCLUSIONS: Vasoactive factors other than endothelin most likely contribute to reperfusion injury. Furthermore, the ultrasonic transit time flow probe accurately measures post-reperfusion renal blood flow and offers a practical method for assessing acute reperfusion injury, which may help to optimize immunosuppressive strategies to decrease allograft loss associated with delayed graft function.

Animals↗

PubMed1995

Reperfusion arrhythmias: role of early afterdepolarizations studied by monophasic action potential recordings in the intact canine heart during autonomically denervated and stimulated states.

INTRODUCTION: The precise mechanism of reperfusion arrhythmias is not established. The role of early afterdepolarizations (EADs) and triggered activity in the genesis of reperfusion ventricular arrhythmia was investigated. METHODS AND RESULTS: Monophasic action potentials (MAPs) were recorded in the canine heart using Ag-AgCl contact electrodes from the left and right ventricular endocardium and the left ventricular epicardial border zone during 10 minutes of occlusion of the proximal left anterior descending coronary artery followed by 2 minutes of reperfusion. Ventricular arrhythmias during ischemia and reperfusion were studied in three autonomically varied groups. Group 1 (n = 8) had intact autonomic neural innervation; group 2 (n = 8) had bilateral transection of ansae subclavii and vagi; and group 3 (n = 8) underwent bilateral transection of ansae subclavii and vagi with bilateral ansae subclavii stimulation during reperfusion. Ventricular fibrillation (VF) on reperfusion occurred in 2, 3, and 5 animals in the innervated, denervated, and sympathetically stimulated groups, respectively. Rapid ventricular tachycardia during ansae subclavii stimulation, antecedent to VF, occurred in 4 of 5 episodes in the sympathetically stimulated group. The frequency of premature ventricular complexes, couplets, and triplets on reperfusion was not significantly different among the three groups. Phase 2 or phase 3 EADs were noted during the acute ischemic phase in 6 of 8, 7 of 8, and 7 of 8 animals in the three groups, respectively (and persisted during reperfusion in the majority). Thus, these EADs were not a de novo phenomenon during reperfusion. Of the 72 MAP recording sites, only one demonstrated de novo phase 2 EADs during reperfusion. EADs disappeared during reperfusion in 6 animals (prior to the onset of VF in 4), and 5 dogs developed reperfusion VF without EADs being recorded. There was no direct correlation between the presence of EADs during reperfusion and the development of VF. The prevalence and onset of reperfusion VF was not significantly different in the presence of sympathetic stimulation. CONCLUSION: This study demonstrates that EADs can be recorded in the majority of dogs during both ischemia and reperfusion and do not appear to be a major mechanism responsible for reperfusion ventricular tachycardia and VF.

Action Potentials↗

PubMed1991

The 1990 Merck Frosst Award. Ischemic and reperfusion injury in the heart. Cellular mechanisms and pharmacological interventions.

Reperfusion in the heart represents an important form of tissue injury, particularly in view of the emerging importance of reperfusion protocols aimed at salvaging the ischemic myocardium. Both the manifestations and the causes of reperfusion injury are multifold. With respect to the former, reperfusion injury can be characterized by various abnormalities including development of arrhythmias, contractile dysfunction, ultrastructural damage as well as various defects in intracellular biochemical homeostasis. The mechanisms underlying myocardial reperfusion injury are equally complex, but most likely involve numerous processes acting in concert resulting in eventual cell death. In this review, a description of various such potential mechanisms, which represent primary interests of the author, are presented. An understanding of these mechanisms has led to novel pharmacological approaches towards the protection of the reperfused myocardium. For instance, several lines of evidence implicate enhanced eicosanoid, and in particular prostaglandin, synthesis in reperfusion injury, since (1) such injury is involved with enhanced prostaglandin biosynthesis, (2) inhibition of prostaglandin synthesis with various nonsteroidal anti-inflammatory drugs attenuates injury, and (3) exogenous prostaglandins increase injury. Another intracellular process that is emerging as an important contributor to reperfusion injury in the heart is the Na+/H+ exchanger, which is most likely activated upon reperfusion. Such activation would lead to numerous intracellular disturbances including the increased synthesis of prostaglandins and elevated intracellular Ca2+ concentrations. Indeed, inhibitors of Na+/H+ exchange such as amiloride have been shown to effectively inhibit reperfusion injury. Reperfusion is also associated with depressed mitochondrial function, particularly in subsarcolemmal mitochondria which are rapidly injured as a result of both ischemic and reperfusion conditions. Preservation of mitochondrial function with dissimilar approaches such as carnitine or phosphatidylcholine administration markedly reduces reperfusion injury-. A nonpharmacological novel approach towards the protection of the reperfused myocardium represents the induction of so-called stress or heart shock proteins in the heart prior to initiation of ischemia and reperfusion. The salutary effect of the heat shock response may be dependent not on the heat shock proteins themselves, but through the concomitant elevation of tissue catalase content resulting in enhanced detoxification of intracellular hydrogen peroxide. Thus reperfusion injury represents numerous complex events such that manipulations aimed at limiting such injury can be initiated to prevent specific defects with the ultimate goal of an overall reduction in cell damage.

Animals↗

PubMed1991

Immediate functional benefits after controlled reperfusion during surgical revascularization for acute coronary occlusion.

This study tests the hypothesis that contractile dysfunction that often develops after acute coronary occlusion despite emergency revascularization can be avoided by careful control of the composition of the initial reperfusate and the conditions of the reperfusion. Between January 1987 and May 1989, 31 consecutive patients with acute coronary occlusion (90% resulting from percutaneous transluminal coronary angioplasty failures) were reperfused during emergency myocardial revascularization according to one of two different protocols. In 23 patients the reperfusate was normal blood given at systemic pressure ("uncontrolled reperfusion"); in eight patients the ischemic segment was reperfused during the first 20 minutes with a regional blood cardioplegic solution (substrate-enriched, hyperosmotic, hypocalcemic, alkalotic, diltiazem-containing) at 37 degrees C at a pressure of 50 mm Hg. Thereafter total bypass was prolonged for an additional 30 minutes before extracorporeal circulation was discontinued ("controlled reperfusion"). Assessment of regional contractility (echocardiography, radionuclide ventriculography), electrocardiographic evidence of myocardial infarction, release of creatine kinase and isoenzyme of creatine kinase, and hospital mortality was performed. Regional contractility was quantified with a scoring system from 0 (normokinesis) to 4 (dyskinesis). Data are expressed as mean +/- standard error of the mean. Both groups were well matched for age, sex, and the distribution of the occluded artery. In the controlled-reperfusion group there was a greater prevalence of previous infarctions (63% versus 43%), additional significant stenosis (1.3 +/- 0.2 versus 0.8 +/- 0.2), and cardiogenic shock (38% versus 17%) compared with the uncontrolled-reperfusion group. Furthermore, the interval between coronary occlusion and reperfusion was significantly longer in the controlled-reperfusion group (4.0 +/- 0.5 versus 2.3 +/- 0.3 hr; p less than 0.05). Regional contractility returned to normal in all patients treated by controlled reperfusion (wall motion score = 0.8 +/- 0.3, normokinesis = 0, slight hypokinesis = 1). In contrast, regional contractility remained severely depressed after uncontrolled reperfusion with normal blood (score 2.5 +/- 0.2; p less than 0.05), with only four of 23 patients with a score less than 2 (2 = severe hypokinesis). Postoperatively enzymes and electrocardiographic changes were similar in both groups. One patient died of mitral insufficiency in the controlled-reperfusion group, despite complete recovery of wall motion in the angioplasty-related artery. Conversely, the four of 23 deaths after uncontrolled reperfusion occurred in patients who sustained infarct in the area of the coronary occlusion (mortality 13% versus 17%). In conclusion, these preliminary clinical results indicate that immediate recovery of segmental contractility can be achieved after acute coronary occlusion if the initial reperfusion is controlled.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗

PubMedDate not supplied

[Reperfusion arrhythmias].

Reperfusion arrhythmias originate as a consequence of the complex of cellular and humoral reactions accompanying the opening of coronary artery. As the primary cause of their generation are considered the chemically defined substances that are produced and accumulated in myocardium during reperfusion. The key role is ascribed to free oxygen radicals but of importance are also other substances such as calcium, thrombin, platelet activating factor, inositol triphosphate, angiotensin II and others. These chemical mediators of reperfusion arrhythmias operate as modulators of cellular electrophysiology causing the complex changes at the level of ion channels. It is supposed that in the genesis of reperfusion arrhythmias unlike ischemic arrhytmias operate nonreentrant mechanisms such as abnormal or enhanced automacy and triggered activity due to afterdepolarizations. As a typical reperfusion arrhythmia is considered an early (within 6 hours after start of thrombolysis), frequent (> 30 episodes/hour) and repetitive (occurring during > 3 consecutive hours) accelerated idioventricular rhythm (AIVR). AIVR with such characteristics has a high specificity and positive predictive accuracy but relative low sensitivity as a predictor of reperfusion. Thus, in occurrence of AIVR, recanalization of infarction-related coronary artery is very probable, but in absence of AIVR, reperfusion is still not excluded. The following arrhythmias are regarded also as markers of reperfusion: frequent premature ventricular complexes (> twofold increase in frequency within 90 minutes after the start of thrombolysis), a significant increase of episodes in nonsustained ventricular tachycardia, sinus bradycardia and probably also high-degree atrioventricular blocks. At present, there is no definite evidence, as to whether sustained ventricular tachycardia and especially ventricular fibrillation can be caused by reperfusion. Reperfusion arrhythmias are an important noninvasive marker of successful recanalization of infarction-related coronary artery. However, they are also a sign of reperfusion injury and a finding which may limit the favourable effect of reperfusion. In account of that, there is a very intensive search for pharmacologic interventions which could protect or attenuate the reperfusion injury and thereby also the genesis of reperfusion arrthythmias. Although promising results were obtained with many substances antagonizing the effects of mediators of reperfusion injury, there is no definite recommendation for their use under clinical conditions. However, the results from the latest clinical trials with ACE inhibitors are very promising. These trials render relative conclusive evidence, that ACE inhibitors could have a protective effect against reperfusion arrhythmias. (Ref. 89, Tab. 1.)

Arrhythmias, Cardiac↗