Atrionatriuretic peptide improves left ventricular function after myocardial global ischemia-reperfusion in hypoxic hearts

Atrionatriuretic peptide (ANP) is reported to be useful for attenuating myocardial ischemia–reperfusion injury and improving left ventricular function after reperfusion. However, ANP may be either ineffectual or harmful in cases where the myocardium has been chronically hypoxic since birth. This can be a result of the concomitant high levels of cyclic guanosine monophosphate (cGMP) produced within the myocardium. This study aimed to verify the validity of using ANP to improve left ventricular function after myocardial ischemia–reperfusion injury. For this purpose, a cyanotic congenital disease model that was developed using isolated rat hearts was used. Hearts were obtained from Sprague‐Dawley rats that were housed from birth until 6 weeks of age either in a hypoxic environment with 13–14% FiO₂ (hypoxic group) or in ambient air (normoxic group). These hearts were subjected to 30 min of normothermic global ischemia followed by 30 min of reperfusion using the Langendorff technique. Left ventricular functional recovery in hearts administered ANP (0.1 µM) into the reperfusion solution was compared with those hearts that were not administered ANP in both hypoxic (without ANP: n = 6, with ANP: n = 6, with ANP and HS‐142‐1[an antagonist of ANP]: n = 6) and normoxic hearts (without ANP: n = 6, with ANP: n = 6). In the hypoxic hearts, ANP administration improved the percent recovery of the left ventricular developed pressure (76.3 ± 9.2% without ANP vs. 86.9 ± 6.7% with ANP), maximum first derivative of the left ventricular pressure (82.4 ± 1.1% without ANP vs. 95.8 ± 6.5% with ANP), and heart rate (85.6 ± 4.7% without ANP vs. 96.1 ± 5.2% with ANP) after reperfusion. The improvement and recovery of these cardiac functions were closely related to significantly increased levels of postischemic cGMP release after ANP administration. The effect of ANP was blocked by HS‐142‐1. The improvements observed in the hypoxic group were similar to those found in the normoxic group. ANP administration during reperfusion improved left ventricular function after myocardial acute global ischemia–reperfusion equally in both the chronically hypoxic and age‐matched normoxic groups.     

Bilirubin rinse of the graft ameliorates ischemia reperfusion injury in heart transplantation

Ischemia and reperfusion contribute to substantial organ damage in transplantation. Clinically feasible measures for the prevention thereof are scarce. We tested whether rinsing rodent hearts with the antioxidant bilirubin ameliorates ischemia reperfusion injury (IRI). Left ventricular end‐diastolic pressure (LVEDP), left ventricular developed pressure (LVDevP), rate per pressure product (RPP), coronary flow, maximum (+dP/dt) and minimum (?dP/dt) rate of contraction were analyzed in Lewis rat hearts rinsed with bilirubin prior to reperfusion on a Langendorff apparatus after 12 h of cold ischemia. In vivo, isogenic C57Bl/6 mouse hearts rinsed with bilirubin were transplanted after 12 h of cold ischemia. Cardiac function and apoptosis were assessed 24 h after reperfusion. Heart lysates recovered 15 min after reperfusion were probed for the total and the phosphorylated forms of extracellular signal‐related protein kinases (ERK), JNK, p38‐MAPK, and Akt. In isolated perfused hearts, bilirubin rinse resulted in significantly lower LVEDP and improved LVDevP, RPP, coronary flow, +dP/dt and ?dP/dt. In vivo, after reperfusion, all mitogen‐activated protein kinases (MAPKs) were suppressed significantly by bilirubin pretreatment. Bilirubin rinse improved cardiac scores (3.4 ± 0.5 vs. 2.0 ± 1.0 in controls, P < 0.05) and significantly suppressed apoptosis. Ex vivo administration of bilirubin to heart grafts prior reperfusion ameliorates IRI and provides a simple and effective tool to ameliorate outcome in heart transplantation.     

The Harmful Effects of Ventricular Distention during Postischemic Reperfusion

To assess the effects of left ventricular distention during the early reperfusion period following ischemic arrest, 16 canine heart preparations were subjected to 45 minutes of hypothermic (27°C) cardioplegic arrest and normothermic reperfusion. Isovolumic left ventricular developed pressure and rate of rise of left ventricular pressure (dP/dt) were measured with an intraventricular balloon; endocardial/epicardial flow ratios were determined with microspheres; and myocardial gas tensions were monitored with mass spectrometry.During early reperfusion, Group 1 hearts (n = 8) were not distended (end-diastolic pressure = 0). Group 2 hearts (n = 8) were subjected to an end-diastolic pressure of 20 mm Hg for the initial 15 minutes of reperfusion. Group 2 hearts demonstrated impaired subendocardial blood flow after 5 minutes of reflow (0.75 ± 0.06 vs 0.96 ± 0.04, endocardial/epicardial flow rates, Group 2 vs Group 1) and persistent elevation of intramyocardial carbon dioxide (CO₂) tension (68 ± 4 vs 51 ± 4 mm Hg, Group 2 vs Group 1). In addition, postischemic ventricular function was significantly worse in Group 2 hearts (60 ± 7 vs 79 ± 3% of control dP/dt, Group 2 vs Group 1, and 53 ± 6 vs 81 ± 5% of control left ventricular developed pressure, Group 2 vs Group 1).These data demonstrate that even mild distention during early reperfusion can result in reduced subendocardial perfusion and delayed washout of tissue CO₂. Although myocardial blood flow and CO₂ tension subsequently returned to normal in the distended hearts, left ventricular performance remained significantly depressed. This injury can occur clinically in nonvented hearts prior to the resumption of effective ventricular contraction.     

The effect of controlled reperfusion in porcine hearts submitted to three hours of cold global ischemia

At present, many investigations of myocardial function following ischemic insults concentrate on the modalities of reperfusion rather than on the mode of preservation. In this study, we tried to define the effect of reperfusion using warm blood cardioplegia (WBC) after medium-term (3 h) cold global ischemia, as required in cardiac transplantation. Twenty-one porcine hearts were harvested after preservation with cold cardioplegia (St. Thomas Hospital solution) and topical cooling. Normothermic reperfusion with blood was initiated after 3 h of ischemia utilizing a special extracorporeal pump circuit. Twelve hearts served as controls (group A), while substrate-enriched WBC was applied during the initial 20 min of reperfusion in nine hearts (group B). Hearts in both groups were then studied for myocardial function and metabolism under both working and nonworking conditions for a maximum of 180 min. In the nonworking mode, left ventricular dp/dt was significantly higher in group B than in group A at 15 min (2201±785 mm Hg/sec vs 1515±732 mm Hg/sec) and at 180 min (1730±471 mm Hg/sec vs 836±147 mm Hg/sec;P<0.05). After 3 h, lactate production was significantly higher in group A (371±45 mg/dl) than in group B (108±44 mg/dl;P<0.05). Creatine kinase release into the coronary sinus was also significantly elevated in group A at 15 min (2807±1478 IU/l vs 1148±1272 IU/l;P<0.05). Similarly, the hemodynamic data obtained under working conditions in group B were superior to those in group A. We conclude that following 3 h of cold global ischemia, reperfusion with WBC improves myocardial function and metabolism. Cautious application in clinical heart transplantation is recommended.     

Sevoflurane reduces dysrhythmias during reperfusion in the working rat heart

Purpose. The effects of sevoflurane on myocardial reperfusion injury have not been well studied. The purpose of this study was to determine the effects of sevoflurane on myocardial function, arrhythmia, and metabolism during reperfusion in an isolated working rat heart model. Methods. Thirty-two hearts were divided into four groups according to the timing of 2.5% sevoflurane administration: group I, control, no sevoflurane; group II, sevoflurane administered only before ischemia; group III, sevoflurane only during reperfusion; group IV, sevoflurane during the whole study period. Myocardial contractility, myocardial ATP, lactate, and glycogen levels were assessed in the reperfusion period following global heart ischemia of 15 min duration. The incidence and duration of ventricular fibrillation were also observed in the reperfusion period. Results. There was no difference in cardiac output and left ventricular dP/dt max among the four groups at 10, 15, and 20 min after reperfusion. There was no difference in myocardial ATP, lactate and glycogen contents between the groups. The incidences of ventricular fibrillation during reperfusion were 100%, 63%, 100%, and 25% (P < 0.05 vs control), and the durations of ventricular fibrillation during reperfusion were 375 ± 269, 104 ± 98 (P < 0.05 vs control), 303 ± 189, and 93 ± 245 (P < 0.05 vs control) in groups I, II, III, and IV, respectively (mean ± SD). Conclusion. The administration of sevoflurane prior to reperfusion appears to provide myocardial protection, as assessed by reduced dysrhythmias during reperfusion. Received: December 14, 1999 / Accepted: July 25, 2000     

Ischemic postconditioning: brief ischemia during reperfusion converts persistent ventricular fibrillation into regular rhythm

Objectives: Brief episodes of myocardial ischemia-reperfusion employed during reperfusion after a prolonged ischemic insult may attenuate the total ischemia-reperfusion injury. This phenomenon has been termed ischemic postconditioning. In the present study, we studied the possible effect of postconditioning on persistent reperfusion-induced ventricular fibrillation (VF) in the isolated rat heart model. Methods: Isolated Langendorff-perfused rat hearts (n=46) were subjected to 30 min of regional ischemia and reperfusion. The hearts with persistent VF (n=11) present after 15 min of reperfusion were then randomly assigned into one of the two groups: (1) control hearts (n=6), in which perfusion was continued without intervention; (2) postconditioned hearts (n=5) subjected to 2 min of global ischemia followed by reperfusion. Left ventricular pressures, heart rate, coronary flow, and electrogram were monitored throughout the experiment. Results: Conversion of VF into regular rhythm was observed in all hearts subjected to postconditioning. Regular beating was maintained by all postconditioned hearts during the subsequent reperfusion. None of the hearts in the control group had normal rhythm at the end of the experiment. At the end of reperfusion, the left ventricular developed pressure was lower in beating postconditioned hearts compared to the hearts that did not develop persistent VF. Conclusions: Ischemic postconditioning possesses strong antiarrhythmic effect against persistent reperfusion-induced tachyarrhythmias. Postconditioning may be an interesting, novel adjunct strategy to protect the heart.     

Intracellular calcium increasing at the beginning of reperfusion assists the early recovery of myocardial contractility after diltiazem cardioplegia

Objectives: We investigated the ability of diltiazem to prevent myocardial injury by assessing heart function and intracellular calcium concentrations before and after ischemia-reperfusion. Method: Isolated rat hearts underwent cardioplegia using the Langendorff perfusion model and were subjected to normothermic global ischemia for 60 minutes. The recovery rates for the heart function (heart rate, coronary flow, left ventricular systolic pressure) after reperfusion were monitored, and the intracellular Ca concentration was measured during ischemia and during the following reperfusion. Experimental groups were divided into three groups according to the diltiazem concentration used in the cardioplegic solution (potassium 20 mmol/l in Ringer's solution): (1) Group A: diltiazem 2.5 mg/l; (2) Group B: diltiazem 5 mg/l; and (3) Group C: no diltiazem. Results: Intracellular calcium concentration increased in all 3 groups during ischemia, but was significantly lower in Group B compared to either Group A or Group C. The heart function was significantly higher for Group A than for Group B or Group C. The hearts in Group B displayed markedly poor recovery in contractility and in heart rate. Conclusions: Generally, a decrease in intracellular Ca concentration improves the heart function during ischemia and after reperfusion. However, this study showed that some increase in intracellular Ca at the beginning of reperfusion assisted the contractility of rat heart.     

Experimental study of pegylated liposomal hemoglobin on norepinephrine release and reperfusion arrhythmias in isolated guinea pig hearts.

PURPOSE: Under myocardial reperfusion conditions, hemoglobin (Hb)-based artificial blood showed effectiveness for post-ischemic dysfunction. However, there are no studies about the effects of this product on reperfusion arrhythmias (ventricular fibrillation, VF) associated with norepinephrine (NE) release. This study was to evaluate the effects of the timing of the administration of pegylated liposomal Hb (LHb, P(50)=40-45 mmHg, 1 mg/mL) on NE release and VF. MATERIALS AND METHODS: Isolated guinea pig hearts (n=6 in each group) were randomly divided into four groups in Krebs-Henseleit solution being supplemented or not with LHb as follows: pre-ischemia (PRE), reperfusion (REP), or PRE+REP groups. The hearts were perfused for 30 min (preischemic period) and then subjected to 30 min of global ischemia, followed by 30 min of reperfusion with a normothermic Langendorff apparatus at 30 mm Hg aortic pressure in a constant pressure model. RESULTS: No differences were documented among the four groups in heart rate, left ventricular-developed pressure, or coronary flow rate. However, the REP group significantly decreased the duration of VF and NE release, but it did not inhibit the incidence of VF. CONCLUSION: These results suggest that the administration of LHb, especially with the timing of reperfusion, might prevent reperfusion arrhythmias linked to the inhibition of NE release.     

The effects of Na+ -H+ exchange inhibitor, KB-R9032, administered at the time of reperfusion in perfused rat heart

BACKGROUND: We have reported that pretreatment with KB-R9032, a newly developed Na+ -H+ exchange inhibitor is protective against reperfusion-induced ventricular arrhythmia in the isolated perfused rat heart. This study was conducted to elucidate whether the drug is equally effective when it is given at the time of reperfusion. METHODS: Male Wistar rat hearts (n=32, 16 for each group) were perfused by means of Langendorff technique. Each heart was subjected to regional ischemia (occlusion of the left anterior descending coronary artery for 11 minutes) and to three minutes of reperfusion (release of the occlusion). KB-R9032 4 mg (one shot group) or a vehicle without drug (control) were given 30 seconds before the reperfusion to 30 seconds after the reperfusion. RESULTS: In the control group reperfusion-induced ventricular fibrillation (VF) occurred in 91.7% and the duration was 165 +/- 14.4 seconds, but, in one shot group, the incidence of VF decreased to 6.3% and the duration of VF was reduced to 0.4 +/- 0.4 seconds, respectively (P<0.05 vs control group). CONCLUSIONS: It has been shown in this study that the Na+/H+ exchange inhibitor KB-R9032 given at the time of reperfusion suppresses reperfusion arrhythmias in the ischemia-reperfusion model of isolated rat heart.     

Does adenosine administration during the early reperfusion period affect ischemic preconditioning?

We hypothesized that the adenosine administration during the early reperfusion period might affect ischemic preconditioning (IPC) and might reduce infarct size and enhance post-ischemic functional recovery. Twenty-four anesthetized rabbits underwent 30 min. normothermic global ischemia with 120 min. reperfusion in a buffer-perfused isolated, paced heart model and divided into four groups. Global ischemic hearts (GI, n = 6) were subjected to 30 min. global ischemia without intervention. Control hearts (n=6) were subjected to perfusion without ischemia. Ischemic preconditioned hearts (IPC, n=6) were subjected to one cycle of 5 min. global ischemia and 5 min. reperfusion prior to global ischemia. IPC + Ado hearts (n=6) received IPC and adenosine administration (100 m mol/L) during 3 min. early reperfusion period. Post-ischemic functional recovery was better in IPC + Ado hearts as compared to GI and IPC hearts, but the effect of post-ischemic functional recovery in IPC + Ado hearts became weaker during 120 min. reperfusion after prolong ischemic insult. Infarct size wre 1.0 ± 0.3% in Control hearts, 32.9 ± 5.1% in GI hearts, 13.8 ± 1.3% in IPC hearts and 8.1 ± 0.9% in IPC + Ado hearts. Infarct size in IPC hearts was significantly decreased (p<0.01) as compared to GI hearts. The reduction rate against myocardial necrosis in IPC + Ado hearts versus GI hearts was higher as compared to IPC hearts versus GI hearts (p<0.001, IPC+Ado hearts vs GI hearts; p<0.01, IPC hearts vs GI hearts; p = ns, IPC + Ado hearts vs Control hearts). These data suggest that adenosine administration during the early reperfusion period reinforce IPC effect and reduce myocardial reperfusion injury. Cardiomyoprotective effects of IPC and exogenous adenosine are exerted during early reperfusion after coronary occlusion in the isolated perfused rabbit hearts.     

The effect of graft perfusion with warm blood cardioplegia for cadaver heart transplantation

This study was designed to verify the effect of reperfusion of donor hearts in a perfusion apparatus after 60 min of global ischemia prior to heart transplantation. Thirteen dogs were exsanguinated from the femoral artery and cardiac arrest was achieved. The hearts were left in situ at room temperature (25°C)for 60 min. In group A (n=7), the hearts were excised and reperfused 60 min after cardiac arrest in the perfusion apparatus with substrate-enriched warm blood cardioplegia (WBCP) containing a hydroxyl radical scavenger, EPC, followed by 45 min of blood perfusion, Next, the hearts were preserved in cold (4°C) University of Wisconsin (UW) solution. In group B (n=6), the hearts were perfused with cold (4°C) St. Thomas' solution 60 min after cardiac arrest and preserved in cold UW solution. Thereafter, all hearts in both groups were transplanted orthotopically to recipient dogs. In group A, 6 of 7 dogs were weaned from cardiopulmonary bypass (CPB). In group B, only 2 of 6 dogs were weaned from CPB. Moreover, 3 of the 6 hearts in group B did not start beating after transplantation (stone heart). This study suggested reperfusion of the donor heart in the perfusion apparatus with WBCP to be a beneficial preconditioning method when utilizing 60-min arrested hearts for transplantation. This study was supported in part by Senju Pharmaceutical Co. Ltd., Osaka, Japan     

Ghrelin May Inhibit Inflammatory Response and Apoptosis During Ischemia-Reperfusion Injury

BackgroundGhrelin, a novel growth hormone–releasing peptide, has both anti-inflammatory and anti-apoptotic effects on human endothelial cells. We evaluated the protective effects of ghrelin against ischemia-reperfusion injury (IRI) in a murine heterotopic cervical heart transplantation model.MethodsDonor hearts from C57BL/6J wild-type mice, which were kept in cold saline for 60 minutes, were heterotopically transplanted into C57BL/6J wild-type recipients. A day prior to heterotopic cervical heart transplantation, donor animals received either ghrelin (300 nmol/kg) or saline (0.3 mL) intraperitoneally. Upon reperfusion and postoperative day 1, ghrelin or saline was administered to the recipients. Donor hearts were procured on day 2.ResultsGhrelin injection did not result in any adverse effects in donors or recipients. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling–positive cells were significantly decreased in the ghrelin group (0.38% ± 0.21% vs 5.74% ± 3.68%; P < .001). Both cleaved caspase-3 activity and Bcl-2/Bax ratio from the ghrelin group were significantly reduced compared to those in the control. Furthermore, the phosphorylated Akt/Akt ratio was higher in the ghrelin group (0.44 ± 0.21 vs 0.14 ± 0.03; P = .043). Nuclear factor-kappa B p65 nuclear translocation was reduced in the ghrelin hearts compared to the controls (3.17% ± 1.84% vs 19.28% ± 13.14%; P = .009). Vascular cell adhesion molecule-1, intracellular adhesion molecule-1, nuclear factor-kappa B, and tumor necrosis factor alpha levels were also significantly reduced in the ghrelin-treated group. No significant difference was observed in 8-isoprostane production between groups.ConclusionGhrelin inhibits the inflammatory response and apoptosis during transplant-related IRI. This study demonstrates the protective effects of ghrelin against IRI.     

Atrial natriuretic peptide in the prevention of acute renal dysfunction after heart transplantation—a randomized placebo-controlled double-blind trial

Background

Acute kidney injury (AKI) and renal dysfunction after heart transplantation are common and serious complications. Atrial natriuretic peptide (ANP) has been shown to increase glomerular filtration rate (GFR) and exert renoprotective effects when used for the prevention/treatment of AKI in cardiac surgery. We tested the hypothesis that intraoperative and postoperative administration of ANP could prevent a postoperative decrease in renal function early after heart transplantation.

Methods

Seventy patients were randomized to receive either ANP (50 ng/kg/min) (n = 33) or placebo (n = 37) starting after induction of anesthesia and continued for 4 days after heart transplantation or until treatment with dialysis was started. The primary end-point of the present study was measured GFR (mGFR) at day 4, assessed by plasma clearance of a renal filtration marker. Also, the incidence of postoperative AKI and dialysis were assessed.

Results

Median (IQR) mGFR at day 4 postoperatively was 60.0 (57.0) and 50.1 (36.3) ml/min/1.72 m² for the placebo and ANP groups, respectively (p = .705). During ongoing ANP infusion, the need for dialysis was 21.6% and 9.1% for the placebo and ANP groups, respectively (p = .197). The incidences of AKI for the placebo and the ANP groups were 76.5% and 63.6%, respectively (p = .616). The incidences of AKI stage 1 were 32.4% and 21.2% for the placebo and ANP groups, respectively (p = .420) and for AKI stage 2 or 3, 37.8% and 42.4%, respectively (p = .808).

Conclusion

The study failed to detect that ANP infusion attenuates renal dysfunction or decreases the incidence of AKI after heart transplantation.     

Efficacy of a hydroxyl radical scavenger (VF 233) in preventing reperfusion injury in the isolated rabbit heart.

We tested the hypothesis that 3,4,5,-trihydroxybenzamidoxime (VF 233), a demonstrated hydroxyl radical scavenger and an effective Fe3+ chelator, attenuates reperfusion injury and improves isovolumic left ventricular function. Eighteen isolated, perfused rabbit hearts with intracavitary balloons were subjected to normothermic, global ischemia until the initiation of ischemic contracture. Effects on the adenine nucleotide pool metabolites were determined by high-pressure liquid chromatography from right ventricular biopsy specimens before ischemia and at 15-minute intervals throughout reperfusion. In the experimental group (n = 9), a 5-mL bolus of 1 mol/L VF 233 was given immediately before reperfusion and followed by a continuous infusion (0.125 mumol/min). The control group (n = 9) received the vehicle solution at identical times. Rabbits treated with VF 233 had significant improvement in left ventricular function (expressed as percent return of left ventricular peak developed pressure) within 15 minutes of reperfusion (55.0 +/- 3.0 versus 66.2 +/- 4.1; p less than 0.05 by analysis of variance) after global ischemia and remained significantly improved throughout the reperfusion period. Myocardial adenine nucleotide pool intermediates were not significantly different between groups. These results demonstrate that administration of VF 233 significantly improves ventricular function but does not affect adenine nucleotide metabolism after ischemia and reperfusion.     

Continuous infusion of magnesium–lidocaine mixture for prevention of ventricular arrhythmias during on-pump coronary artery bypass grafting surgery

BackgroundDuring on-pump coronary artery bypass grafting (CABG) surgery, the incidence of reperfusion ventricular fibrillation (VF) is high and post-bypass ventricular arrhythmias are common. Both reperfusion VF and ventricular arrhythmias can cause additional myocardial injury to the already ischemic myocardium. This trial aimed to test the assumption that continuous combined magnesium and lidocaine infusion would be efficient and long lasting for the prevention of post-myocardial vascularization ventricular arrhythmias including VF.MethodsEighty ASA III patients, who were candidates for CABG surgery, were randomly assigned into two groups: Group I (control group, n = 40) and Group II (Group ML, n = 40). After endotracheal intubation, patients of control group were infused with plain normal saline in a volume equivalent to study drugs’ mixture volume. Patients of Group ML were infused with magnesium–lidocaine mixture to achieve a bolus of magnesium sulfate 2 g and lidocaine 100 mg followed by continuous infusion of Mg sulfate 500 mg/h and lidocaine 1 mg/min. The initial cardiac rhythm after aortic cross clamp (ACC) release and the occurrence of post-CPB significant ventricular arrhythmias were recorded.ResultsThe incidences of reperfusion VF and post-CPB ventricular arrhythmias in Group ML were significantly lower than that in control group (22.5% vs. 72.5%) (P < 0.001) and (7.5% vs. 25%) (P < 0.05), respectively. However, in Group ML, this beneficial effect was associated with higher incidence of sinus bradycardia (72.5% vs. 17.5%) and hence pacing needs (22.5% vs. 0.0%) when compared with control group.ConclusionOur study concluded that, during on-pump CABG surgery, the combined administration of magnesium and lidocaine as a bolus dose starting after intubation followed by continuous infusion reduced the incidence of reperfusion VF by 62% and post-CPB ventricular arrhythmias by 70% on expense of increased the incidence of sinus bradycardia and pacing.     

CD44 expression in renal ischemia-reperfusion injury in rats

Renal ischemia-reperfusion injury (IRI) is an invariable consequence of transplantation. The tubuloepithelial expression of CD44 is markedly enhanced in autoimmune renal injuries. The aim of this experimental study was to evaluate the effect of IRI on the expression of CD44 in rat kidney. Thirty male Sprague-Dawley rats were used. The rats were divided into three groups. The rats in group 1 (n = 10) underwent laparotomy and left nephrectomy (Sham surgery). The rats in group 2 (n = 10) underwent laparotomy, 1 h renal ischemia, followed by 1 h of reperfusion and then left nephrectomy was performed. The rats in group 3 (n = 10) underwent laparotomy, 1 h renal ischemia, followed by 24 h of reperfusion and then left nephrectomy was performed. Histopathological findings and the immunohistochemical expression of CD44 in ischemic and reperfused rat kidneys were investigated. In histopathologic evaluation, non-specific changes were observed in group 2 and early phase of IRI were present in group 3. CD44 was expressed in both group 2 and 3 but not in group 1. The mean immunohistochemical staining percentages of rat kidneys in group 1, 2, and 3 were 0.00 ± 0.00, 39.90 ± 5.53, and 26.20 ± 8.38, respectively. The immunohistochemical staining pattern was more dense in group 2 than in group 3 (P < 0.001). In conclusion, the expression of CD44 in renal tubuloepithelial cells was significantly increased after IRI. The increase in CD44 expression was more prominent during the early phase of IRI and started to decline after 24 h of reperfusion.     

Effects of liraglutide and ischemic postconditioning on myocardial salvage after I/R injury in pigs*

Objectives. Acute STEMI is routinely treated by acute PCI. This treatment may itself damage the tissue (reperfusion injury). Conditioning with GLP-1 analogs has been shown to reduce reperfusion injury. Likewise, ischemic postconditioning provides cardioprotection following STEMI. We tested if combined conditioning with the GLP-1 analog liraglutide and ischemic postconditioning offered additive cardioprotective effect after reperfusion of 45?min coronary occlusion of left anterior descending artery (LAD). Design. Fifty-eight non-diabetic female Danish Landrace pigs (60?±?10kg) were randomly assigned to four groups. Myocardial infarction (MI) was induced by occluding the LAD for 45?min. Group 1 (n?=?14) was treated with i.v. liraglutide after 15?min of ischemia. Group 2 (n?=?17) received liraglutide treatment concomitant with ischemic postconditioning, after 45?min of ischemia. Group 3 (n?=?15) recieved ischemic postconditioning and group 4 (n?=?12) was kept as controls. Results. No intergroup differences in relative infarct size were detected (overall mean 57?±?3%; p?=?0.68). Overall mortality was 34% (CI 25–41%) including 26% post-intervention, with no intergroup differences (p?=?0.99). Occurrence of ventricular fibrillation (VF) was 59% (CI 25–80%) including 39% postintervention with no intergroup differences (p?=?0.65). Conclusions. In our closed-chest pig-model, we were unable to detect any cardioprotective effect of liraglutide or ischemic postconditioning either alone or combined.     

Optimal temperature of continuous lidocaine perfusion for the heart preservation

Objective: During cardiovascular surgery, lidocaine is administered to the cardioplegic system to stabilize cell membrenes and prevent arrhythmia. Lidocaine is also commonly used in hypothermia Both lidocaine and hypothermia are myocardially protective. Under normothermia, lidocaine displays its full pharmacological effects, which are apt, however, to be suppressed under hypothermia. We conducted experiments to determine the optimal temperature for myocardial protection in continuous lidocaine cardioplegia. Methods: In Langendorff mode, rat hearts were continuously perfused with 1 mMol/l of lidocaine solution at 36±0.5°C (Group A), 24±0.5°C (Group B), or 7±0.5°C (Group C) during preservation. Cardiac function and intracellular calcium concentration were measured during both preservation and reperfusion. Heat shock protein 70 (HSP70) was subsequently analyzed by Western blotting. Results: Rapid cardiac arrest was obtained in Groups A and C. Heart rate recovery was good and ultimately the best in Group B, but worst in Group A. During lidocaine perfusion, the volume of coronary perfusion flow decreased gradually in all groups. After reperfusion, Group A showed only a slight increase in coronary perfusion, While Groups B and C showed a marked increase. Left ventricular contractility showed good recovery in all groups. The calcium concentration increased slightly in Group A, but decreased in Groups B and C. No calcium overload was evident in Group A. The same HSP70 level was detected in all groups. Conclusion: Lidocaine used in normothermia does not decrease cardiac metabolism or oxygen consumption, and displays full, pharmacological effectiveness in preventing ischemic injury. We found 36°C to be the optimal temperature for heart preservation by coronary perfusion with lidocaine cardioplegia.     

Pretreatment of Human Myocardium with Adenosine During Open Heart Surgery

Background: Depressed myocardial performance after cardiac surgery can be contributed to ischemic reperfusion injury (IRI) incurred during and following the cardiopulmonary bypass (CPB). Myocardial preconditioning (PC) achieved by brief ischemia and subsequent reperfusion appears to be a clinically useful method of improved cardiac protection during surgery involving CPB by retarding IRI. Based on animal studies, activation of cardiac adenosine (ADO) receptors prior to the prolonged ischemic period appears to mimic this PC phenomenon. Aims and Methods: We investigated whether the human myocardial PC can be mimicked with ADO in the setting of the coronary artery bypass graft (CABG). The specific proposed objective of this study was to determine whether ADO infusion just prior to starting the CPB can improve post-CPB myocardial hemodynamics. Patients undergoing elective CABG with poor ventricular function (ejection fraction ± 30%), and with at least three-vessel disease were selected for this study (n = 7 ADO, and n = 7 control). Results: Our results show that ADO infusion (250–350 μg/kg ± 10 min) just prior to CPB resulted in an immediately improved postbypass cardiac index (Cl) in the OR (Cl increase of 41.5%± 11.1% for ADO vs 9.7%± 6.0% for control, p < 0.05). Forty hours postoperatively in the intensive care unit, ADO patients had improved Cl (3.3 ± 0.2 L/min per m2 for ADO, vs 2.6 ± 0.1 L/min per m2 for control, p < 0.05), stroke volume index (35 ± 3 mL/m2 per beat for ADO, vs 26 ± 4 L/min per m2 for control, p < 0.05). ADO patients maintained lowered resting heart rate (90 ± 6 for ADO, vs 108 ± 4 for control, p < 0.05) 40 hours after the surgery. ADO patients also released significantly less CPK during the first 24 hours of the postoperative period. Conclusion: Based on these measurements, ADO pretreated patients had improved ventricular performance postoperatively. It also appears that ADO pretreatment results in lowered postoperative myocardial energy demand and less myocellular injury during CPB. To our knowledge, this is the first study to demonstrate that human myocardium can be hemodynamically improved with ADO pretreatment, and may be protected against IRI incurred during and following the CPB. We believe that a cardiac surgeon may now have the unique opportunity to confer myocardial protection during and after a cardiac surgical procedure.     

Anti-CD18 Attenuates Myocardial Stunning in the Isolated Neonatal Lamb Heart

Abstract Cardiac surgery for congenital heart disease often results in postoperative depression of myocardial function due to myocardial ischemia and stunning. The Boston Circulatory Arrest study indicated that myocardial stunning is also observed postoperatively in the immature heart. Neonates less than 3 months of age (N = 162) experienced cardiac outputs that averaged 20% of baseline values in spite of myocardium protection with Plegisol cardioplegia. In order to minimize the effects of myocardial stunning on the immature heart, we examined the effects of preischemic administration of monoclonal antibodies to leukocyte adhesion molecule CD18 (monoclonal R15.7 [Boehringer-lngelheim]) on the function of blood perfused neonatal lamb hearts. Hearts were arrested for 2 hours with a 15°C K⁺ cardioplegia solution. Antibody treated hearts (N = 9) had significantly better (p < 0.05) recovery of left ventricular (LV) developed pressure (83.9% ± 2.2% vs 73.6% ± 3.0% for controls), LV dP/dt (78.4% ± 3.3% vs 67.4% ± 3.4% for controls), coronary blood flow (159.5% ± 12.2% vs 84.4% ± 3.5% for controls), and myocardial oxygen consumption (129.8% ± 16.5% vs 71.2% ± 6.2% for controls) than controls. In addition, recovery of coronary vascular resistance in response to 10^?6 M acetylcholine was significantly better (p = 0.08) in antibody treated hearts (38.4% ± 4.3%) than in control hearts (13.4% ± 12.8%). These results support the notions that leukocyte adherence to the endothelium contributes to reperfusion injury after ischemia and that monoclonal antibodies to CD18 may reduce the effects of myocardial stunning after cardiac surgery.