Hypothermic Cardioplegic Arrest Research Articles

CARD18: Successful Transplantation of Porcine Hearts after 24 hr of Cold Ischemia Following Resuscitation using Ex Vivo Normothermic Perfusion

Background: Cold storage of hearts is limited to 6 hr prior to transplant. Extending preservation time may impact transplant coordination and potentially increase the organ pool, as marginal organs can be evaluated during ex vivo preservation. This study employs normothermic ex vivo heart perfusion (NEVHP) for the resuscitation and evaluation of hearts after 24 hr of cold static storage followed by transplantation. Methods: Porcine hearts (n=8) were recovered using standard techniques with antegrade hypothermic cardioplegic arrest. A catheter was placed in the LV to assess function. Inflow and outflow catheters were placed into the aorta and PA, respectively. Hearts were then placed in cold static storage in CoStorSol™ solution at 5 degrees Celsius for 24 hr. Following cold storage, hearts were supported by NEVHP for 8 hr with in-parallel hemofiltration. Coronary perfusion was maintained at 1 mL/min/g cardiac tissue. After NEVHP, 3 hearts were transplanted into 3 recipient pigs and 5 hearts were electively terminated. Results: Using NEVHP, all hearts were successfully resuscitated, as defined by resumption of sinus rhythm and preserved LV function. During NEVHP, mean values for LV systolic pressure = 51.2 ± 4.1 mmHg; coronary resistance = 0.49 ± 0.05 mmHg/mL/min; oxygen consumption = 1.1 ± 0.1 mL/min; and serum lactate = 3.08 ± 0.2 mmol/L (Fig 1A-D). No statistical differences were identified at endpoint compared to hour one. Average weight gain was 4.4 ± 1.0 g. Following transplantation, time to full bypass wean after aortic cross clamp removal was 120 ± 14 min. Animals were supported off bypass for 90 min prior to elective euthanasia. Conclusions: Hearts that underwent cold static storage for 24 hr can be routinely resuscitated to viable function using NEVHP. In addition, ex vivo perfusion allows for assessment of organ function prior to transplantation. Successful transplantation of these hearts corroborates adequate resuscitation and confirms viability after NEVHP.

Diazoxide preserves myocardial function in a swine model of hypothermic cardioplegic arrest and prolonged global ischemia

ObjectiveAdenosine triphosphate potassium sensitive channels provide endogenous myocardial protection via coupling of cell membrane potential to myocardial metabolism. Adenosine triphosphate potassium sensitive channel openers, such as diazoxide, mimic ischemic preconditioning, prevent cardiomyocyte swelling, preserve myocyte contractility after stress, and provide diastolic protection. We hypothesize that diazoxide combined with hyperkalemic cardioplegia provides superior myocardial protection compared with cardioplegia alone during prolonged global ischemia in a large animal model. MethodsTwelve pigs were randomized to global ischemia for 2 hours with a single dose of cold blood (4:1) hyperkalemic cardioplegia alone (n = 6) or with diazoxide (500 μmol/L) (n = 6) and reperfused for 1 hour. Cardiac output, myocardial oxygen consumption, left ventricular developed pressure, left ventricular ejection fraction, diastolic function, myocardial troponin, myoglobin, markers of apoptosis, and left ventricular infarct size were compared. ResultsFour pigs in the cardioplegia alone group could not be weaned from cardiopulmonary bypass. There were no differences in myoglobin, troponin, or apoptosis between groups. Diazoxide preserved cardiac output versus control (74.5 vs 18.4 mL/kg/min, P = .01). Linear mixed regression modeling demonstrated that the addition of diazoxide to cardioplegia preserved left ventricular developed pressure by 36% (95% confidence interval, 9.9-61.5; P < .01), dP/dt max by 41% (95% confidence interval, 14.5-67.5; P < .01), and dP/dt min by 33% (95% confidence interval, 8.9-57.5; P = .01). It was also associated with higher (but not significant) myocardial oxygen consumption (3.7 vs 1.4 mL O2/min, P = .12). ConclusionsDiazoxide preserves systolic and diastolic ventricular function in a large animal model of prolonged global myocardial ischemia. Diazoxide as an adjunct to hyperkalemic cardioplegia may allow safer prolonged ischemic times during increasingly complicated cardiac procedures.

Redo Resection of Residual Right Ventricular Outflow Tract Obstruction in a Postoperative Case of Tetralogy of Fallot under Moderately Hypothermic Extracorporeal Circulation and Cardioplegic Arrest: A

Following the introduction of intracardiac repair of tetralogy of Fallot, early mortality in 1950s was as high as 25%. However, by the mid-1980s, this has reduced to 2% and currently ~ 0% even in neonates and young infants despite the risk of reoperations, a large number of studies have documented satisfactory long-term survival rates in repaired tetralogy of Fallot, with a 30-year survival rate ranging from 86% to 91.7%

Does the Rewarmed Heart Restore the Myocardial Proteome to That of the Pre-Cooled State?--A Proteomic Analysis of Surgical Samples.

Hypothermia is utilized in cardiac and aortic surgery to protect organs from ischemic reperfusion injury. Although the cooled body is invariably rewarmed after the procedure, it is still unknown whether the rewarmed body regains its former biological state. This study determined the modulatory effects of hypothermia on the human myocardial proteome and whether subsequent rewarming restores the proteome to the state prior to cooling. A quantitative proteomic analysis was performed using isobaric tags for relative and absolute quantification labeling tandem mass spectrometry. Right atrial samples were taken 3 times (pre, during and post cooling) during deep hypothermic cardiopulmonary bypass (CPB) from 8 patients with aortic arch aneurysms and 3 corresponding time points during normothermic CPB from 8 patients with ascending aortic or valsalva aneurysms. In total, 697 proteins were identified, with 222 proteins having high protein confidence. Bioinformatic analyses revealed significant downregulation of 19 proteins associated with energy production at hypothermic cardioplegic arrest. On rewarmed beating, 10 proteins remained downregulated, including those regulating cardiac contraction and adaptor proteins, although levels of the aforementioned 19 downregulated proteins returned to their initial values. Additional echocardiographic evaluation demonstrated that hypothermia preserved the variables of diastolic function to a greater extent than normothermic surgery. Rewarming restores the human myocardial proteome to the pre-cooled state, except for proteins regulating cardiac contraction and adaptor proteins.

Beneficial Effects On Cardiac Performance and Cardioprotective Properties of Milrinone after Cold Ischemia

Background: Cold Ischemia-Reperfusion Injury (CIRI) is regarded as the major cause of early graft dysfunction after cardiac transplantations and is associated with rejection episodes. Consequently, it is one of the main therapeutic targets in order to improve survival after heart transplantation. The aim of this study was to evaluate hemodynamic effects of milrinone and its influence on the markers of myocardial damage when used in a piglet working heart model with a cold ischemia-reperfusion setting. Methods: Hearts of 18 piglets were examined in a homologous blood-perfused, working heart model to get baseline measurements. After hypothermic cardioplegic arrest and storage on ice for 60 minutes, the hearts received either milrinone or served as controls. All hearts were examined for 45 minutes in the working heart model. Hemodynamic parameter changes, h-FABP levels and myocardial oxygen consumption were assessed. Results: Significant difference between the groups was observed in cardiac output (MIL +14% vs. CON -33%; p<0.05), coronary sinus blood flow (MIL +84% vs. CON +17%; p<0.05) and relaxation (MIL +5% vs. CON -22%; p<0.01). In addition, significantly higher h-FABP (heart fatty acid binding proteine) levels after cold ischemia were measured in CON group (CON: 18.75 ng/ml; MIL 6.29 ng/ml; p<0.01). Conclusions: Milrinone has a positive effect on cardiac function after cardioplegic cardiac arrest with following cold-ischemia period in an isolated piglet heart model. Its use in a heart transplantation setting induces an improved hemodynamic performance and a better preservation from reperfusion injury.

Con: Cardiac Surgery Should Be Performed Under Warm Conditions

HYPOTHERMIA during cardiac surgery is a long-accepted technique for end-organ protection during the nonphysiologic period of cardiopulmonary bypass and, in particular, during periods of ischemia. Hypothermia decreases whole-body oxygen consumption and increases the ischemic tolerance of organ systems.1 In addition to systemic hypothermia, hypothermic cardioplegic myocardial arrest is a well-established approach to protect the heart during ischemic cross-clamp periods. Despite the benefits of cooling, hypothermia can produce deleterious effects on myocardial performance and systemic organ function during the perioperative period.

Open stent-grafting for adult patent ductus arteriosus with a distal aortic arch aneurysm

Closure of adult patent ductus arteriosus (PDA) is difficult for its variation. We report a case of open stent-grafting for a 67-year-old woman who had PDA and a concomitant distal aortic arch aneurysm. The pulmonary/systemic flow ratio was 1.88, and the pulmonary arterial pressure was 34/21(25). The operation was done through a median sternotomy under hypothermic cardioplegic arrest. We opened the anterior wall of the arch just distal to the left subclavian artery and placed a stent-graft into the descending aorta. At 5 months after discharge, three-dimensional computed tomography showed disappearance of PDA and no endoleak of the stent-graft.

Temperature preconditioning is optimal at 26°C and confers additional protection to hypothermic cardioplegic ischemic arrest

We have recently shown that brief episodes of hypothermic perfusion interspersed with periods of normothermic perfusion, referred to as temperature preconditioning (TP), are cardioprotective and can be mimicked by consecutive isoproterenol/adenosine treatment. Here we investigate the optimal temperature for TP and whether TP further enhances protection provided by hypothermic ischemia with or without polarized cardioplegic arrest. Three experimental groups of Langendorff-perfused rat hearts were used. In the first group, hearts were subjected to three episodes of hypothermic perfusion at 7, 17, 26 and 32°C during the TP protocol, followed by 30 min normothermic index ischemia and 60 min reperfusion (37°C). Protein kinase A (PKA) activity and cyclic AMP (cAMP) concentrations were measured prior to index ischemia. In the second group, TP (26°C) hearts were subjected to two hours hypothermic index ischemia at 26°C and two hours normothermic reperfusion. In the third group, TP (26°C) hearts or hearts treated with isoproterenol/adenosine (pharmacological simulation of TP) were subjected to four hours hypothermic index ischemia with procaine-induced polarized cardioplegia at 26°C followed by two hours normothermic reperfusion. Hemodynamic function recovery, lactate dehydrogenase release and infarct size were used to assess cardioprotection. TP at 26°C resulted in highest cardioprotection, increased cAMP concentration and PKA activity, while TP at 7°C exacerbated ischemia/reperfusion damage, and had no effect on cAMP concentration or PKA activity. TP at 26°C also protected hearts during hypothermic ischemia with or without polarized cardioplegia. Isoproterenol/adenosine treatment conferred additional protection similar to TP. In conclusion, the study shows that TP-induced cardioprotection is temperature dependent and is optimal at 26°C; TP confers additional protection to hypothermia and polarized cardioplegia; and that the pharmacological treatment based on the mechanism of TP (consecutive isoproterenol/adenosine treatment) is a potential cardioprotective strategy that can be used during heart surgery and transplantation.

Pre-conditioning with the soluble guanylate cyclase activator Cinaciguat reduces ischaemia–reperfusion injury after cardiopulmonary bypass

Activation of the nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate (NO-sGC-cGMP) pathway can induce potent cardioprotection-like effects against ischaemia-reperfusion injury and nitro-oxidative stress. We investigated the effects of pharmacological pre-conditioning with Cinaciguat (BAY 58-2667), a novel sGC activator on peroxynitrite-induced endothelial dysfunction in vitro, as well as on myocardial and coronary vascular function during reperfusion in a canine model of cardioplegic arrest and extracorporeal circulation. Isolated coronary arterial rings exposed to peroxynitrite were investigated for vasomotor function. Vehicle- and Cinaciguat-pre-treated (8.33 μg h(-1) or 25 μg h(-1) intravenous (IV) for 30 min) anaesthetised dogs (n = 6-7 per group) underwent hypothermic cardiopulmonary bypass with 60 min of hypothermic cardioplegic arrest. Left- and right-ventricular end-systolic pressure-volume relationship (ESPVR) was measured by a pressure-volume conductance catheter at baseline and after 60 min of reperfusion. Coronary blood flow, vasodilatation to acetylcholine and myocardial level of adenosine triphosphate were determined. Pre-incubation of coronary rings with Cinaciguat improved peroxynitrite-induced endothelial dysfunction. Compared with control, pharmacological pre-conditioning with Cinaciguat (25 μg h(-1)) led to higher myocardial adenosine triphosphate content, to a better recovery of left- and right-ventricular contractility (Δ slope of left ventricular ESPVR given as percent of baseline: 102.4 ± 19.1% vs 56.0 ± 7.1%) and to a higher coronary blood flow (49.6 ± 3.5 ml min(-1) vs 28.0 ± 3.9 ml min(-1)). Endothelium-dependent vasodilatation to acetylcholine was improved in the treatment groups. Pre-conditioning with Cinaciguat improves myocardial and endothelial function after cardiopulmonary bypass with hypothermic cardiac arrest. The observed protective effects imply that pharmacological sGC activation could be a novel therapeutic option in the protection against ischaemia-reperfusion injury in cardiac surgery.

Surgical ventricular reconstruction with different myocardial protection strategies. A propensity matched analysis☆

The aim of this study is to compare outcomes of patients undergoing surgical ventricular reconstruction (SVR) with normothermic cardiopulmonary bypass (CPB) and beating heart or hypothermic CPB and cardioplegic arrest. Between 2001 and 2008, 588 patients underwent SVR. A propensity score matching was performed and 91 matched pairs were created: group 1 (G1) operated with normothermic CPB and beating-heart technique, and group 2 (G2) operated with hypothermic CPB and cardioplegic arrest. Mean age was 62+/-9 years in G1 and 63+/-10 years in G2 [not significant (NS)]. Average follow-up was 42.7+/-26 months (range 1-72). Major cardiac and cerebro-vascular events (MACCE) were assessed. Thirty-day mortality was 4% in G1 and 5% in G2 (NS). Kaplan-Meier survival at six years was 79+/-4% and 72+/-9% (NS) and freedom from MACCE was 82+/-4% and 83+/-7% in G1 and G2, respectively (NS). Left ventricular volume reduction, ejection fraction and New York Heart Association (NYHA) class improvement were significant in the overall population; no significant differences were found between groups. The following independent risk factors for cardiac death were identified: mitral valve regurgitation, surgery <3 months from myocardial infarction, NYHA class III-IV. This study showed that outcomes following SVR are not affected by myocardial protection strategies neither in cardiac function and clinical status nor in survival.

The novel synthetic serine protease inhibitor CU-2010 dose-dependently reduces postoperative blood loss and improves postischemic recovery after cardiac surgery in a canine model

Serine protease inhibitors such as aprotinin reduce perioperative blood loss and may improve postpump cardiac performance owing to their anti-inflammatory properties. After the "aprotinin era," we investigated the efficacy of the novel synthetic serine protease inhibitors CU-2010 with improved coagulatory and anti-inflammatory profile on blood loss and reperfusion injury in a canine model. Thirty-six dogs were divided into 6 groups: control, aprotinin (n = 8; Hammersmith scheme), and CU-2010 (0.5, 0.83, 1.25, and 1.66 mg/kg). All animals underwent 90 minutes of cardiopulmonary bypass with 60 minutes of hypothermic cardioplegic arrest. End points were blood loss during the first 2 hours after application of protamine, as well as recovery of myocardial contractility (slope of the end-systolic pressure-volume relationship, coronary blood flow, and vascular reactivity. CU-2010 dose-dependently reduced blood loss to a degree comparable with that of aprotinin at lower doses and even further improved at higher doses (control/aprotinin/CU-2010 in increasing doses: 142 +/- 13, 66 +/- 17, 95 +/- 16, 57 +/- 17, 46 +/- 3, and 13 +/- 4 mL; P < .05). Whereas aprotinin did not influence myocardial function, CU-2010 improved the recovery of end-systolic pressure-volume relationship (control 60 +/- 6 mg kg vs aprotinin 73 +/- 7 mg/kg vs CU-2010 1.66 mg/kg; 102% +/- 8%; P < .05). Coronary blood flow (52 +/- 4 vs 88 +/- 7 vs 96 +/- 7; P < .05) and response to acetylcholine (44% +/- 6% vs 77% +/- 7% vs 81% +/- 6%; P < .05) were improved by both aprotinin and CU-2010. The novel serine protease inhibitor CU-2010 significantly reduced blood loss after cardiac surgery comparable with aprotinin. Furthermore, an additionally improved anti-inflammatory profile led to a significantly improved postischemic recovery of myocardial and endothelial function.

Sildenafil Citrate Augments Myocardial Protection in Heart Transplantation

Sildenafil citrate has been shown to induce myocardial protective effects in a variety of experimental settings. Whether these effects could be used to enhance myocardial protection afforded by crystalloid cardioplegia, volatile anesthesia and hypothermia during cardiac transplantation remains to be established. We investigated the use of sildenafil-mediated cardioprotection in a rat model of heterotopic cardiac transplantation. Sildenafil citrate (0.7 mg/kg) was administered intravenously to the donor 30 min before onset of ischemia or 5 min before reperfusion in the recipient. In situ cardioplegic arrest was followed by an ischemic time of 3 or 6 hr, transplantation, and blood reperfusion. Myocardial functional recovery was studied in vivo by using a left ventricular balloon and cellular injury quantified by assay of troponin I release and apoptosis. Sildenafil preconditioning but not postconditioning significantly improved initial myocardial systolic and diastolic function after 3 hr of hypothermic cardioplegic arrest (114+/-4 mm Hg vs. 83+/-4 mm Hg generated pressure, [P<0.01]). The protective effect of sildenafil declined over a 3-hr period of reperfusion along with overall myocardial function, no longer reaching statistical significance at 3 hr. The protective effects of sildenafil were abolished by the putative blocker of the mitochondrial ATP sensitive potassium channel, 5-hydroxydecanoate, before sildenafil administration. Protein kinase C delta showed significant translocation after sildenafil administration in the donor. We conclude that sildenafil citrate pretreatment augments myocardial functional recovery after an ischemic time relevant to clinical cardiac transplantation. This effect is associated with protein kinase C activation/translocation and inhibited by 5-hydroxydecanoate.

The novel synthetic serine-protease inhibitor CU2010 dose-dependently reduces postoperative blood loss and improves postischemic recovery myocardial and endothelial function

Objective: Serine-protease inhibitors such as aprotinin reduce perioperative blood loss and may improve post pump cardiac performance due to their anti-inflammatory properties. After the „aprotinin era“, we investigated the efficacy of the novel synthetic serine-protease inhibitor CU2010 on blood loss and reperfusion injuryin a canine model. Methods: 36 dogs were divided into six groups: control, aprotinin (Hammersmith scheme), and CU2010 (0.5, 0.83, 1.25 and 1.66mg/kg). All animals underwent 90-minute cardiopulmonary bypass with 60 minutes of hypothermic cardioplegic arrest. Endpoints were blood loss during the first two hours after protamin, recovery of myocardial contractility (slope of the end-systolic pressure volume relationship, Ees), coronary blood flow and vascular reactivity. Results: CU2010 dose-dependently reduced blood loss comparble to aprotinin (Figure 1, *p<0.05). While aprotinin did not influence myocardial function CU2010 improved the recovery of Ees (control: 60±6 vs. aprotinin: 73±7 vs. CU2010: 102±8%, p<0.05). Coronary blood flow (52±4 vs. 88±7 vs. 96±7%, p<0.05) and response to acethylcholine (44±6 vs. 77±7 vs. 81±6%, p<0.05) was improved by both aprotinin and CU2010. Conclusions: The novel serine-protease inhibitor CU2010 significantly reduce blood loss comparable to aprotinin. Furthermore, it led to a significantly improved postischemic recovery of myocardial and endothelial function.

Leukocyte-Aprotinin Atrial Fibrillation Study (LAFFS): Impact of Aprotinin and Leukofiltration on Atrial Fibrillation, Renal Insufficiency and Encephalopathy Post-Cardiopulmonary Bypass.

Purpose: Atrial fibrillation remains the leading postoperative complication following cardiopulmonary bypass. A randomized trial was undertaken to evaluate the effectiveness of leukocyte filtration and aprotinin, applied separately and in combination, on the incidence of post-operative atrial fibrillation. A secondary component of the study was the impact of these adjunct interventions on post-surgical renal and neurological dysfunction. Methods: A total of 1,220 patients undergoing primary isolated coronary artery bypass grafting were randomly assigned to one of four treatment groups. The control group (305 patients) received standard cardiopulmonary bypass with moderately hypothermic (34ºC) cardioplegic arrest. In the filtration group (310 patients) leukocyte reducing filters were incorporated into the bypass circuit and deployed strategically. The aprotinin group (285 patients) received full Hammersmith dose aprotinin. The combination therapy group (320 patients) received both aprotinin and leukocyte filtration. Results: The incidences of atrial fibrillation were 25% in the control group, 16% in the filtration group, 19% in the aprotinin group and 10% in the combination therapy group (P < 0.001). Renal dysfunction was detected in 3% of the control group, 2% of the filtration group, 8% of the aprotinin group, and 5% of the combination group (P < 0.005). Neurological dysfunction occurred in 2% of the control group, 2% of the filtration group, 1% of the aprotinin group, and 2% of the combination group (P = n.s.). Conclusions: Combination therapy with aprotinin and leukocyte filtration markedly reduced atrial fibrillation post-cardiopulmonary bypass, and was more effective than the individual treatments. Aprotinin treatment increased the incidence of renal dysfunction, and the addition of leukocyte filtration partially mitigated this detrimental effect of aprotinin. Thus, strategic leukocyte filtration augments aprotinin's anti-arrhythmic effects while suppressing its nephrotoxic sequelae.

Ischemic and inflammatory lung impairment by extracorporeal circulation: Effect of PARP-inhibition by INO1001

Objective Among the complications after cardiac surgery the development of postoperative pulmonary distress is a serious problem. Typically, the patients leave the operating theatre with good blood gas values and O 2-saturation, but develop their respiratory problems within the next hours/days. We investigated whether extracorporeal circulation may induce biochemical and histological changes in the lungs which may help to explain this development. Methods Piglets (6–10 kg) were anaesthetized using isoflurane and underwent extracorporeal circulation (ECC) with hypothermic (25–28 °C) cardioplegic arrest for 90 min followed by 3 h reperfusion. An additional group received a poly(ADP-ribose) polymerase (PARP)-Inhibitor, INO1001. Cardiopulmonary monitoring was performed during the whole procedure. Finally, lungs were explanted and investigated by histomorphometry and immunohistology for heat shock protein HSP70 (indicator for cellular damage) and TNFα in comparison to normal piglets without ECC. Results Histologically we found significant swelling of the type I alveocytes (thickness increased from 2.4 to 3.2 μm), interstitial oedema, intra-alveolar erythrocyte (4.8 versus 0.4 erythrocytes/alveole) and granulocyte accumulation and fibrinous exudates. There was a significant up-regulation of TNFα and of the cellular repair enzyme HSP70, while in control piglets only minimal levels were observed. INO1001 significantly reduced ECC-induced elevation in TNFα and in HSP70. Despite the dramatic changes after heart-lung-machine (HLM), blood gases and gas transport were almost not affected at that time. Conclusions ECC can lead to early significant histological and histochemical changes which have similarities with a beginning early stage shock lung, although – at 3 h reperfusion – gas transport is still sufficient. INO1001 can partially antagonize these changes.

A rat model of cardiopulmonary bypass with cardioplegic arrest and hemodynamic assessment by conductance catheter technique

Cardiopulmonary bypass (CPB) is known to induce systemic inflammation and cardiac dysfunction associated with a significant morbidity. Aim of the study was to develop an in vivo model of rat CPB with hypothermic cardiac arrest and the use of cardioplegia. The CPB circuit consisted of a venous reservoir, membrane oxygenator, heat exchanger, and roller pump. CPB was instituted in adult male Wistar rats (400-500 g) for 60 min at a flow rate of 120 ml x kg(-1) x min(-1), including 15 min cooling to 32 degrees C, 30 min cardiac arrest with the use of cold crystalloid cardioplegia after aortic cross clamping, and 15 min of reperfusion and rewarming to 37 degrees C. Arterial blood pressure (MAP) and heart rate (HR) were monitored, arterial blood samples were analyzed. Left ventricular (LV) function parameters were assessed by intraventricular conductance catheter. Important technical aspects are: ventilation is required during partial bypass; anticoagulation should be performed immediately prior to CPB to reduce blood loss; active suction on venous drainage allows higher pump flows; and the small priming volume of the extracorporeal circuit (8 ml) avoids the need for donor blood. MAP remained stable prior to and during CPB.MAP and HR were significantly decreased 60 min after weaning from bypass. Hct was significantly lowered after hemodilution, but remained stable during CPB and 60 min after weaning from bypass. BE and pH remained stable throughout the experiment.Without inotropic support diastolic and systolic LV function parameters were impaired after 30 min of cardioplegic arrest followed by 15 min of reperfusion. Myocardial TNF-alpha mRNA levels were slightly increased (1.28-fold, p = 0.71), and IL-6 mRNA was significantly increased in the cardioplegia group (90.3-fold, p = 0.001). Both IL-6 and TNF-alpha plasma levels were significantly elevated in the cardioplegia group (TNF-alpha: 4.6-fold increase,p < 0.05; IL-6: 426.8-fold increase, p < 0.001). We have developed a rat CPB with mild hypothermic cardioplegic arrest. This rodent model is suitable to study clinically relevant problems related to CPB,myocardial protection and systemic inflammation.

Effects of KR‐33028, a novel Na+/H+ exchanger‐1 inhibitor, on ischemia and reperfusion‐induced myocardial infarction in rats and dogs

The present study was performed to evaluate the cardioprotective effects of KR-33028, a novel Na+/H+ exchanger subtype 1 (NHE-1) inhibitor, in rat and dog models of coronary artery occlusion and reperfusion. In anesthetized rats subjected to a 45-min coronary occlusion and a 90-min reperfusion, KR-33028 at 5 min before occlusion (i.v. bolus) dose-dependently reduced myocardial infarct size from 58.0% to 46.6%, 40.3%, 39.7%, 33.1%, and 27.8% for 0.03, 0.1, 0.3, 1.0, and 3.0 mg/kg respectively (P < 0.05). In anesthetized beagle dogs that underwent a 1.0-h occlusion followed by a 3.0-h reperfusion, KR-33028 (3 mg/kg, i.v. bolus) markedly decreased infarct size from 45.6% in vehicle-treated group to 16.4% (P < 0.05), and reduced the reperfusion-induced release in creatine kinase myocardial band isoenzyme (MB), lactate dehydrogenase, troponin-I, glutamic oxaloacetic transaminase, and glutamic pyruvic transaminase. In separate experiments to assess the effects of timing of treatment, KR-33028 (1 mg/kg, i.v. bolus) given 10 min before or at reperfusion in rat models also significantly reduced the myocardial infarct size (46.3% and 44.1% respectively) compared with vehicle-treated group. In all studies, KR-33028 caused no significant changes in any hemodynamic profiles. In an isolated rat heart model of hypothermic cardioplegia, KR-33028 (30 mum), which was added to the heart preservation solution (histidin-tryptophan-ketoglutarate) during hypothermic cardioplegic arrest, significantly improved the recovery of left ventricular developed pressure, heart rate and dP/dt(max) after reperfusion. Taken together, these results indicate that KR-33028 significantly reduced the myocardial infarction induced by ischemia and reperfusion in rats and dogs, without affecting hemodynamic profiles.

Mesenteric injury after cardiopulmonary bypass: Role of poly(adenosine 5′-diphosphate-ribose) polymerase*

To investigate the effects of the ultrapotent poly(adenosine 5'-diphosphate-ribose) polymerase (PARP) inhibitor INO-1001 on cardiac and mesenteric function during reperfusion in an experimental model of cardiopulmonary bypass with cardioplegic arrest. Prospective, randomized, and blinded experimental study. Research laboratory. : Twelve anesthetized dogs underwent cardiopulmonary bypass with hypothermic cardioplegic cardiac arrest. After 60 mins of hypothermic cardiac arrest, either PARP inhibitor INO-1001 (1 mg/kg, n = 6) or vehicle (control, n = 6) was administered during reperfusion. Left ventricular hemodynamic variables were measured by combined pressure-volume-conductance catheters. Coronary and mesenteric blood flow and vasodilatory responses to acetylcholine and sodium nitroprusside as well as mesenteric lactate and creatinine phosphokinase release were also determined. The administration of INO-1001 led to a significantly improved recovery of left ventricular systolic function (p < .05) after 60 mins of reperfusion. Coronary and mesenteric blood flow were also significantly higher in the INO-1001 group (p < .05). Although the vasodilatory response to sodium nitroprusside was similar in both groups before and after cardiopulmonary bypass and similar in response to acetylcholine before cardiopulmonary bypass, PARP-inhibited dogs had lower mesenteric vascular resistance after cardiopulmonary bypass (p < .05). Mesenteric lactate and creatinine phosphokinase release was significantly lower in the PARP inhibitor treated group (p < .05). PARP inhibition with INO-1001 improves the recovery of myocardial function and prevents mesenteric vascular dysfunction and tissue injury after cardiopulmonary bypass with hypothermic cardiac arrest.

Up-regulation of endothelin-converting-enzyme mRNA expression following cardioplegic arrest.

Endothelin-1 (ET-1) is believed to play an important role in cardiac ischaemia/reperfusion injury. ET-1 is synthesized from preproET-1 by the action of ET-converting enzyme (ECE). It is unclear to what extent the ET system is activated following prolonged ischaemia. In this study we used a model mimicking the conditions of the donor heart during transplantation. Isolated rat hearts perfused with Krebs-Henseleit buffer were subjected to 30 min of normothermic perfusion, then 4 h of cardioplegic arrest at 4 degrees C with St Thomas' Hospital solution, followed by reperfusion for 2 h. Hearts were freeze-clamped at different time points during the protocol. Using quantitative reverse transcription-PCR, relative levels of ET-1 and ECE mRNA expression were measured and compared with a housekeeping gene (ribosomal protein L32). During reperfusion there was a consistent decrease in coronary flow to approx. 85-90% of pre-ischaemic flow. There was no significant alteration in preproET-1 mRNA expression during 2 h of reperfusion. However, ECE mRNA expression was increased by 77.5% at 1 h and by 74.6% at 2 h following ischaemia compared with pre-ischaemic values (P<0.05). Thus we conclude that ECE mRNA expression is increased following prolonged hypothermic cardioplegic arrest. Elevations in the expression of this enzyme may help to explain the role of the ET system in the pathogenesis of ischaemia/reperfusion injury following cardiac surgery and transplantation.

Sialic acid or troponin T to detect perioperative myocardial damage in patients undergoing elective coronary artery bypass grafting.

Sialic acid (SA), a family of acetylated derivatives of neuraminic acid, is elevated in patients with coronary heart disease. Cardiac troponin T (cTnT), myoglobin (Mb), and creatine kinase-MB (CK-MB) are specific markers of myocardial injury and are, at present, widely used to detect perioperative myocardial damage during coronary artery bypass grafting (CABG) surgery. The present study investigated the net myocardial release of SA and the cardiac markers (cTnT, Mb, CK-MB) during reperfusion after hypothermic cardioplegic cardiac arrest in 25 patients undergoing elective CABG. Additional paired arterial, central venous, and coronary sinus blood samples were obtained after atrial cannulation before aortic cross-clamping (preischemic sample) and at 1 and 10 min after aortic declamping (reperfusion samples). There were no increase in the SA, cTnT, Mb and CK-MB concentrations before aortic cross-clamping, but there was considerable release of these markers within 10 min after aortic declamping: cTnT release was significantly higher compared with baseline values before aortic cross-clamping. In contrast to SA, Mb, and CK-MB, the difference between baseline and release values for cTnT at 1 min after aortic declamping was not significant. The rate of increase for SA was significantly higher than for Mb, CK-MB and cTnT. SA is a unique and novel marker that could be particularly useful in assessing myocardial cell damage in patients undergoing cardiac surgery.