Intra-myocyte ion homeostasis during ischemia-reperfusion injury: effects of pharmacologic preconditioning and controlled reperfusion

BACKGROUND: This study determines whether controlled reperfusion or diazoxide improves intramyocyte Na(+) homeostasis using a porcine model of severe ischemia-reperfusion injury. METHODS: Three groups (n = 10 pigs per group) had 75 minutes of left anterior descending artery occlusion during bypass. Group 1 had no treatment (control group), group 2 had controlled reperfusion (500 mL warm cardioplegia) (controlled reperfusion group), and group 3 had diazoxide (50 micromol/L before left anterior descending artery occlusion) (diazoxide group). Biopsies were taken from the left anterior descending artery region before ischemia and at 3, 5, and 10 minutes postreperfusion. Intra-myocyte Na(+) and water contents were determined using atomic absorption spectroscopy, and Na(+) concentrations were calculated. RESULTS: Intra-myocyte Na(+) increased for the diazoxide group pigs at 3-minutes postreperfusion (21.9 +/- 2.9 vs 34.0 +/- 3.4 micromol/mL; p = 0.02), but decreased to 19.9 +/- 3.2 micromol/mL at 10 minutes postreperfusion (p = 1.0 vs baseline). At 10 minutes postreperfusion, intra-myocyte Na(+) in the controlled reperfusion group was lower than baseline (22.3 +/- 2.7 vs 17.2 +/- 3.1 micromol/mL; p < 0.001). Intra-myocyte Na(+) at 10 minutes postreperfusion for the diazoxide and controlled reperfusion groups was lower than for the control group (p < 0.05). CONCLUSIONS: Diazoxide and controlled reperfusion improved intra-myocyte Na(+) homeostasis after severe ischemia-reperfusion injury.     

Quinaprilat during cardioplegic arrest in the rabbit to prevent ischemia-reperfusion injury

OBJECTIVES: This study evaluated intracardiac angiotensin-converting enzyme inhibition as an adjuvant to cardioplegia and examined its effects on hemodynamic, metabolic, and ultrastructural postischemic outcomes. METHODS: The experiments were performed with an isolated, erythrocyte-perfused, rabbit working-heart model. The hearts excised from 29 adult New Zealand White rabbits (2950 +/- 200 g) were randomly assigned to four groups. Two groups received quinaprilat (1 microg/mL), initiated either with cardioplegia (n = 7) or during reperfusion (n = 7). The third group received l-arginine (2 mmol/L) initiated with cardioplegia (n = 7). Eight hearts served as a control group. Forty minutes of preischemic perfusion were followed by 60 minutes of hypothermic arrest and 40 minutes of reperfusion. RESULTS: All treatments substantially improved postischemic recovery of external heart work (62% +/- 6%, 69% +/- 3%, and 64% +/- 5% in quinaprilat during cardioplegia, quinaprilat during reperfusion, and l-arginine groups, respectively, vs 35% +/- 5% in control group, P <.001) with similarly increased external stroke work and cardiac output. When administered during ischemia, quinaprilat significantly improved recovery of coronary flow (70% +/- 8%, P =.028 vs quinaprilat during reperfusion [49% +/- 5%] and P =.023 vs control [48% +/- 6%]). l-Arginine (55% +/- 7%) showed no significant effect. Postischemic myocardial oxygen consumption remained low in treatment groups (4.6 +/- 1.2 mL. min(-1). 100 g(-1), 6.0 +/- 2.2 mL. min(-1). 100 g(-1), and 4.7 +/- 1.6 mL. min(-1). 100 g(-1) in quinaprilat during cardioplegia, quinaprilat during reperfusion, and l-arginine groups, respectively, vs 4.2 +/- 0.8 mL. min(-1). 100 g(-1) in control group), even though cardiac work was markedly increased. High-energy phosphates, which were consistently elevated in all treatment groups, showed a significant increase in adenosine triphosphate with quinaprilat during ischemia (2.24 +/- 0.14 micromol/g vs 1.81 +/- 0.12 micromol/g in control group, P =.040). Ultrastructural grading of mitochondrial damage revealed best preservation with quinaprilat during ischemia (100% [no damage], P =.001 vs control). CONCLUSION: These experimental findings have clinical relevance regarding prevention of postoperative myocardial stunning and low coronary reflow in patients undergoing heart surgery.     

Postischemic [Ca2+] repletion improves cardiac performance without altering oxygen demands

The positive inotropism expected with correction of postischemic hypocalcemia might be counterbalanced by potential aggravation of reperfusion injury, in particular by calcium overload. We evaluated the effect of normalizing blood calcium concentration ([Ca2+]) on postischemic left ventricular systolic and diastolic mechanics using oxygen consumption and indices derived from pressure-diameter relations. In 10 open-chest dogs on cardiopulmonary bypass, the hearts underwent 30 minutes of normothermic global ischemia followed by one hour of multidose hypothermic (4 degrees C), hypocalcemic (0.3 mmol/L) blood cardioplegia. After reperfusion, systemic [Ca2+] had decreased to 70% of control (p = 0.017). The left ventricular inotropic state was significantly depressed from baseline (control) values, but was restored to baseline levels by resumption of normocalcemia after one hour of reperfusion. Chamber stiffness increased by 308% (p = 0.006) after hypocalcemic reperfusion but decreased significantly after [Ca2+] correction. Recovery of left ventricular performance with [Ca2+] correction did not augment myocardial oxygen consumption from the postischemic uncorrected state (5.0 +/- 0.3 mL O2/min/100 g versus 5.3 +/- 0.3 mL O2/min/100 g). We conclude that normalizing [Ca2+] after blood cardioplegia improves postischemic left ventricular performance without adversely affecting compliance or oxygen consumption.     

Electroplegia: an alternative to blood cardioplegia for arresting the heart during conventional (on-pump) cardiac operation

BACKGROUND: Aortic cross-clamping is contraindicated in patients with severe atherosclerosis of the ascending aorta, and administration of chemical cardioplegia may be cumbersome in these patients. In this study, we demonstrate an alternative method of achieving cardioplegia by electrical stimulation of the vagus nerve. METHODS: In anesthetized canines, the left anterior descending coronary artery was reversibly ligated for 90 minutes, followed by cardiopulmonary bypass (CPB) and randomization to three groups (n = 8 each): (1) BCP group: 1 hour of intermittent hypothermic (4 degrees C) blood cardioplegia infusion; (2) CPB group: 1 hour of CPB alone; (3) EP group (group receiving electroplegia): 1 hour of intermittent vagal stimulation (total of 60 20-second electrical stimuli at 40 Hz, 6 to 10 V) with adjunctive pyridostigmine (0.5 mg/kg), verapamil (50 microg/kg), and propranolol (80 microg/kg) to potentiate hyperpolarization and suppress ectopic escape beats. RESULTS: The EP group achieved consistent intervals of arrest with 3.8 +/- 1.2 escape beats per 20-second stimulation period. After 2 hours of reperfusion off CPB, the left anterior descending coronary artery segmental shortening was reduced from baseline in all groups, but the segmental shortening recovered to a greater extent in the EP group than in either the CPB or BCP group (2.4% +/- 1.4% versus -1.3% +/- 1.3% versus -4.0% +/- 0.8%, p < 0.05). Infarct size (TTC stain, percentage of area at risk) was comparable among groups (EP: 20.9% +/- 4.7%; CPB: 29.6% +/- 3.2%; BCP: 25.1% +/- 5.7%). Postischemic left anterior descending coronary artery endothelial function (percent maximum relaxation to acetylcholine) was depressed in the EP group (68.6% +/- 7.6% versus 102.3% +/- 6.4%, p < 0.05), but was comparable versus nonischemic circumflex function in the BCP group (77.1% +/- 11.9% versus 100.4% +/- 10.0%, p = 0.15) and the CPB group (93.8% +/- 6.6% versus 93.3% +/- 6.6%). CONCLUSIONS: Electroplegia achieves elective intermittent cardiac arrest, avoids hypothermia, chemical cardioplegia, and aortic cross-clamping, with physiological outcomes comparable to blood cardioplegia.     

Protection of the hypertrophied pig myocardium. A comparison of crystalloid, blood, and Fluosol-DA cardioplegia during prolonged aortic clamping

The myocardial protective effects of crystalloid, blood, and Fluosol-DA-20% cardioplegia were compared by subjecting hypertrophied pig hearts to 3 hours of hypothermic (10 degrees to 15 degrees C), hyperkalemic (20 mEq/L) cardioplegic arrest and 1 hour of normothermic reperfusion. Left ventricular hypertrophy was created in piglets by banding of the ascending aorta, with increase of the left ventricular weight-body weight ratio from 3.01 +/- 0.2 gm/kg (control adult pigs) to 5.50 +/- 0.2 gm/kg (p less than 0.001). An in vivo isolated heart preparation was established in 39 grown banded pigs, which were divided into three groups to receive aerated crystalloid (oxygen tension 141 +/- 4 mm Hg), oxygenated blood (oxygen tension 584 +/- 41 mm Hg), or oxygenated Fluosol-DA-20% (oxygen tension 586 +/- 25 mm Hg) cardioplegic solutions. The use of crystalloid cardioplegia was associated with the following: a low cardioplegia-coronary sinus oxygen content difference (0.6 +/- 0.1 vol%), progressive depletion of myocardial creatine phosphate and adenosine triphosphate during cardioplegic arrest, minimal recovery of developed pressure (16% +/- 8%) and its first derivative (12% +/- 7%), and marked structural deterioration during reperfusion. Enhanced oxygen uptake during cardioplegic infusions was observed with blood cardioplegia (5.0 +/- 0.3 vol%), along with excellent preservation of high-energy phosphate stores and significantly improved postischemic left ventricular performance (developed pressure, 54% +/- 4%; first derivative of left ventricular pressure, 50% +/- 5%). The best results were obtained with Fluosol-DA-20% cardioplegia. This produced a high cardioplegia-coronary sinus oxygen content difference (5.8 +/- 0.1 vol%), effectively sustained myocardial creatine phosphate and adenosine triphosphate concentrations during the extended interval of arrest, and ensured the greatest hemodynamic recovery (developed pressure, 81% +/- 6%, first derivative of left ventricular pressure, 80% +/- 10%) and the least adverse morphologic alterations during reperfusion. It is concluded that oxygenated Fluosol-DA-20% cardioplegia is superior to oxygenated blood and especially aerated crystalloid cardioplegia in protecting the hypertrophied pig myocardium during prolonged aortic clamping.     

Adenosine cardioplegia. Adenosine versus potassium cardioplegia: effects on cardiac arrest and postischemic recovery in the isolated rat heart

Adenosine is a potential cardioplegic agent by virtue of its specific inhibitory properties on nodal tissue. We tested the hypothesis that adenosine could be more effective than potassium in inducing rapid cardiac arrest and enhancing postischemic hemodynamic recovery. Isolated rat hearts were perfused with Krebs-Henseleit buffer or cardioplegic solutions to determine the time to cardiac arrest and the high-energy phosphate levels at the end of cardioplegia. Cardioplegic solutions contained adenosine 10 mmol/L, potassium 20 mmol/L, or adenosine 10 mmol/L + potassium 20 mmol/L and were infused at a rate of 2 ml/min for 3 minutes at 10 degrees C. Both time taken and total number of beats to cardiac arrest during 3 minutes of cardioplegia were reduced by adenosine 10 mmol/L and adenosine 10 mmol/L + potassium 20 mmol/L when compared with potassium 20 mmol/L alone (p less than 0.001). Tissue phosphocreatine was conserved by adenosine 10 mmol/L when compared with potassium 20 mmol/L, being 7.1 +/- 0.2 (mumol/gm wet weight (n = 7) and 6.0 +/- 0.3 mumol/gm wet weight (n = 5), respectively (p less than 0.05). Postischemic hemodynamic recovery was tested in isolated working rat hearts. After initial cardiac arrest, the cardioplegic solution was removed with Krebs-Henseleit buffer at a rate of 2 ml/min for 3 minutes at 10 degrees C, and thereafter total ischemia was maintained for 30 or 90 minutes at 10 degrees C before reperfusion. Adenosine 10 mmol/L enhanced recovery of aortic output when compared with potassium 20 mmol/L or adenosine 10 mmol/L + potassium 20 mmol/L, the percentage recovery after 30 minutes of ischemia being 103.0% +/- 4.4% (n = 6), 89.0% +/- 5.8% (n = 6), and 86.6% +/- 4.3% (n = 6), respectively (p less than 0.05 for comparison between adenosine 10 mmol/L and potassium 20 mmol/L). Thus adenosine cardioplegia caused rapid cardiac arrest and improved postischemic recovery when compared with potassium cardioplegia and with a combination of these two agents.     

Controlled postcardioplegia reperfusion: mechanism for attenuation of reperfusion injury

OBJECTIVE: Controlled reperfusion and secondary cardioplegia are used to minimize reperfusion injury. The mechanisms for their benefit are incompletely defined and may include attenuation of myocyte sodium uptake. METHODS: Pigs had 1 hour of cardioplegic arrest followed by reperfusion with blood (control) or warm cardioplegic solution followed by blood (test). Reperfusion injury in the control and test groups was quantified by measuring changes of intramyocyte ion content with atomic absorption spectrometry and by analyzing electrophysiologic recovery from recordings of reperfusion arrhythmias. RESULTS: Control animals had an increase in intramyocyte sodium content at 5 minutes after initiating reperfusion (+20.2 micromol/g dry weight, P <.04), whereas the test group had an insignificant decrease (-14.0 micromol/g dry weight, P =.33). The first rhythm after initiating reperfusion was more often ventricular fibrillation in the control group (100% vs 50%, P <.02), and the control group required more defibrillations to establish a nonfibrillating rhythm (4.5 +/- 1.2 vs 1.1 +/- 0.3, P <.03). CONCLUSIONS: Controlled reperfusion eliminated the increase in intramyocyte sodium that was observed in the control group at 5 minutes after cardioplegic arrest. This improvement in myocyte ion homeostasis during postcardioplegia reperfusion was associated with fewer reperfusion arrhythmias. These data support the hypothesis that attenuation of myocyte sodium gain during postischemic reperfusion is a mechanism by which controlled reperfusion and secondary cardioplegia are beneficial.     

Safety of prolonged aortic clamping with blood cardioplegia. III. Aspartate enrichment of glutamate-blood cardioplegia in energy-depleted hearts after ischemic and reperfusion injury

This study tests the hypothesis that aspartate enrichment of glutamate-blood cardioplegia improves metabolic and functional recovery after ischemic and reperfusion damage. Ischemic and reperfusion damage were produced in 15 dogs by 45 minutes of aortic clamping at 37 degrees C and 5 minutes of blood reperfusion, before 2 more hours of aortic clamping (simulated operation). Six received multidose blood cardioplegia at 4 degrees C. In nine others, the cardioplegic solution was infused at 37 degrees C for the first 5 minutes, followed by multidose infusions at 4 degrees C. Four received 26 mmol glutamate-enriched cardioplegic solution. In five, the glutamate (13 mmol) cardioplegic solution was enriched with aspartate (13 mmol). Oxygen uptake and ventricular function (stroke work index, left atrial pressure) were measured. These data suggest aspartate enrichment produced the highest oxygen uptake (32 +/- 4 versus 17 +/- 2 ml/100 gm for glutamate and 7 +/- 1 ml/100 gm for 4 degrees C blood cardioplegia). Complete functional recovery occurred in aspartate/glutamate-treated hearts (stroke work index 90% +/- 4%, left atrial pressure 12 +/- 2 mm Hg), whereas recovery was incomplete with both glutamate alone (stroke work index 66% +/- 14%, left atrial pressure 20 +/- 3 mm Hg) and 4 degrees C blood cardioplegia at low cardiac outputs. Eight of 10 hearts not receiving aspartate failed at high cardiac outputs. Aspartate enrichment of glutamate-blood cardioplegia improves recovery after severe ischemic/reperfusion damage by improving oxidative metabolism during cardioplegic infusion and during postischemic work.     

Successful orthotopic pig heart transplantation from non-heart-beating donors.

BACKGROUND: With the aim to expand the severely limited donor pool by use of non-heart-beating donors we developed a technique for successful transplantation of hearts after 30 minutes of normothermic ischemia without donor pretreatment. METHODS: In control groups hearts were transplanted in a conventional fashion using crystalloid cardioplegia (Group I, n = 6) or BCP (Group II, n = 8) for induction of cardiac arrest. In the ischemic groups hearts were harvested after 30 minutes of normothermic ischemia, perfused with blood cardioplegia (BCP) (Group III, n = 9) or BCP containing the Na(+)-H(+)-exchange inhibitor HOE 642 (Group IV, n = 8) and transplanted orthotopically. RESULTS: All animals could be weaned from cardiopulmonary bypass. Low dose inotropic support was necessary in the ischemic groups only. Recovery of the maximal left ventricular stroke work index (LVSWImax) in Groups I vs II was 62.6+/-19.6% vs 73.3+/-23.3% (NS), maximal right ventricular stroke work index (RVSWImax) averaged 61.1+/-18.8 vs 87.8+/-31.7% (NS) as compared to the preoperative level. In the ischemic groups (III vs IV) LVSWImax was 27.3+/-11.7 vs 59.5+/-32.4% (p = 0.038), RVSWImax was 27.4+/-20.9 vs 64.2+/-46.6% (NS). CONCLUSIONS: The results indicate that (a) successful pig heart transplantation after 30 minutes of normothermic ischemia is possible without donor pretreatment, and (b) that HOE 642 improves posttransplant LVSWImax significantly.     

Polarized arrest with warm or cold adenosine/lidocaine blood cardioplegia is equivalent to hypothermic potassium blood cardioplegia

BACKGROUND: Hypothermic depolarizing hyperkalemic (K + 20 mEq/L) blood cardioplegia is the "gold standard" in cardiac surgery. K + has been associated with deleterious consequences, eg, intracellular calcium overload. This study tested the hypothesis that elective arrest in a polarized state with adenosine (400 micromol/L via adenosine triphosphate-sensitive potassium channel opening) and the Na + channel blocker lidocaine (750 micromol/L) as the arresting agents in blood cardioplegia provides cardioprotection comparable to standard hypothermic K + -blood cardioplegia. METHODS: Anesthetized dogs were placed on cardiopulmonary bypass and assigned to 1 of 3 groups receiving antegrade cardioplegia delivered every 20 minutes for 1 hour of arrest: cold (10 degrees C) K + -blood cardioplegia (n = 6), cold (10 degrees C) adenosine/lidocaine blood cardioplegia (n = 6), or warm (37 degrees C) adenosine/lidocaine blood cardioplegia (n = 6). After an hour of arrest, cardiopulmonary bypass was discontinued, and reperfusion was continued for 120 minutes. RESULTS: Time to arrest was longer with cold and warm adenosine/lidocaine blood cardioplegia (175 +/- 19 seconds and 143 +/- 19 seconds, respectively) compared with K + -blood cardioplegia (27 +/- 2 seconds; P < .001). Postcardioplegia left ventricular systolic function (slope of the end-systolic pressure/dimension relationship) was comparable among the 3 groups (K + -blood cardioplegia, 15.2 +/- 2.1 mm Hg/mm; cold adenosine/lidocaine blood cardioplegia, 15.9 +/- 3.4 mm Hg/mm; warm adenosine/lidocaine blood cardioplegia, 14.1 +/- 2.8 mm Hg/mm; P = .90). Plasma creatine kinase activity in cold and warm adenosine/lidocaine blood cardioplegia was similar to that in K + -blood cardioplegia at 120 minutes of reperfusion (cold adenosine/lidocaine blood cardioplegia, 11.5 +/- 2.1 IU/g protein; warm adenosine/lidocaine blood cardioplegia, 10.1 +/- 0.9 IU/g protein; K + -blood cardioplegia, 7.6 +/- 0.8 IU/g protein; P = .17). Postcardioplegia coronary artery endothelial function was preserved in all groups. CONCLUSIONS: Intermittent polarized arrest with warm or cold adenosine/lidocaine blood cardioplegia provided the same degree of myocardial protection as intermittent hypothermic K + -blood cardioplegia in normal hearts.     

Effects of Hot shot on recovery after hypothermic ischemia in neonatal lamb heart

BACKGROUND: Terminal warm blood cardioplegia, "Hot shot", is the method for providing an energy replenishment and/or early recovery of aerobic metabolism without electromechanical activity at initial reperfusion. The mechanism of beneficial effects of this Hot Shot is multifactorial. This study was designed to assess the effects of terminal warm blood cardioplegia by comparing with oxygenated terminal warm crystalloid cardioplegia. METHODS: In Group HS-B, n=8 (oxygenated blood; 37 degrees C, Ht: 20%, K+ 20 mEq/l, pH 7.237, PO2 219 mmHg) and in Group HS-C, n=8 (bloodless oxygenated (5% CO2+95%O2) crystalloid, 37 degrees C, K+ 20 mEq/l, pH 7.435, PO2 624 mmHg), terminal warm cardioplegia (20 ml/kg for 5 minutes) was studied in the isolated blood perfused neonatal lamb heart following 2 hr of cardioplegic ischemia. Another eight hearts served as control without any kind of terminal cardioplegia. After 60 min of reperfusion, LV function was measured. Coronary blood flow (CBF), oxygen content, and oxygen consumption (MVO2) were measured and the oxygen extraction ratio was calculated in Group HS-B and HS-C during terminal cardioplegia and/or reperfusion. Results are given as % recovery of preischemic values. RESULTS: HS-B as well as HS-C groups showed better functional recovery in maximum developed pressure (DP: 78.0+/-8.3 in HS-B vs 65.2+/-9.2%; p=0.018), maximum dp/dt (67.3+/-6.2 in HS-B, 65.3+/-7.4 in HS-C vs 55.8+/-5.0%; p=0.003, p=0.02), DP V10 (87.1+/-8.5 in HS-B vs 67.2+/-9.9%; p=0.0001), and peak dp/dt V10 (76.4+/-7.6 in HS-B, 69.8+/-8.1 in HS-C vs 58.6+/-6.9 %; p=0.0001) than the control group. Between the HS-B and HS-C groups, HS-B showed better functional recovery in terms of DP V10 (p=0.01). Oxygen delivery of terminal cardioplegia was almost four times higher in HS-B group (90.4+/-17.7 vs 18.7+/-1.1 mcl/ml), contrarily, HS-C group showed four times higher oxygen extraction ratio compared to HS-B group (0.78+/-0.06 vs 0.18+/-0.11), thus oxygen consumption during hot shot was maintained at the same level in both groups. CBF in the control group was lower than that in the other groups at 60 min of reperfusion. CONCLUSIONS: Reperfusion with both terminal warm cardioplegia including blood and oxygenated crystalloid cardioplegia resulted in better recovery of function and higher levels of CBF with slightly better function in terminal warm blood cardioplegia.     

Insulin(GIK) improves myocardial metabolism in patients during blood cardioplegia

The aim of this study was to test the hypothesis that abnormalities of myocardial substrate metabolism during blood cardioplegic aortic cross-clamping and early reperfusion are attenuated further by insulin(GIK) than by alpha-ketoglutarate enrichment of blood cardioplegia alone. Twenty-eight males (47 to 78 years) undergoing coronary artery bypass grafting (CABG) participated in a prospective, controlled, randomized study. All patients had alpha-ketoglutarate-enriched blood cardioplegia. Insulin(GIK) was infused in 13 patients during aortic cross-clamping. Insulin(GIK) prevented lactate release during cardioplegia (1.5+/-15 vs -44+/-14 micromol/min, p = 0.04), and a significant extraction of lactate was induced shortly after declamping the aorta (15+/-3 vs 2+/-1%, p = 0.001). Free fatty acid uptake was reduced after cardioplegic cross-clamping (5.7+/-1.6 vs 16.0+/-3.8 micromol/min, p = 0.02). More positive/less negative levels of alanine, aspartate, glutamine, glycine, ornithine, taurine and tyrosine were found in all the insulin-treated patients. We conclude that insulin(GIK) attenuates abnormalities of myocardial substrate metabolism during blood cardioplegic aortic cross-clamping and early reperfusion further than is obtained with alpha-ketoglutarate enrichment of blood cardioplegia alone.     

The effects of Na movement on surgical myocardial protection: the role of the Na+-H+ exchange system and Na-channel in the development of ischemia and reperfusion injury.

OBJECTIVES: We investigated whether the Na+-H+ exchange inhibitor, HOE642 (Hoe), and/or the Na channel blocker, mexiletine (Mex), enhance a cardioprotective effect on St. Thomas' Hospital cardioplegic solution (STS) to clarify the mechanism by which intracellular Na+ is accumulated after cardioplegic arrest. MATERIALS AND METHODS: Isolated working rat hearts were perfused with Krebs-Henseleit bicarbonate buffer (KHBB). The hearts were then arrested with STS and subjected to normothermic global ischemia (30 min). This was followed by Langendorff reperfusion (15 min) and then a working reperfusion (20 min). In study A, we added Hoe (5, 10, and 20 microM), Mex (70 microM), or a combination of Hoe (20 microM) and Mex (70 microM), to STS. In study B, we added Hoe (20 microM), Mex (70 microM), or a combination of Hoe (20 microM) and Mex (70 microM) to KHBB during the first 3 min of Langendorff reperfusion. RESULTS: In study A, the addition of Hoe (10 and 20 microM) to STS showed a significantly greater postischemic recovery of cardiac output compared to the control group [63.1+/-5.7% (10 microM), 62.7+/-4.7% (20 microM), and 55.5+/-4.6% (control), respectively]. The postischemic recovery of cardiac output was significantly greater in the group of the combined addition (Hoe and Mex) to STS than that in the control, 20 microM Hoe, 70 microM Mex groups [70.3+/-3.7 (Hoe and Mex), 55.5+/-4.6% (control), 62.7+/-4.7% (Hoe 20 microM), and 60.2+/-4.7% (Mex 70 microM), respectively]. The myocardial water content in the postischemic period was 565.1+/-29.1, 525.8+/-2.9, 509.4+/-19.6, and 532.2+/-20.1; it was 497.3+/-9.1 mL/100 g dry weight in the control; and 10 microM Hoe, 20 microM Hoe, and 70 microM Mex in the combined use groups. In study B, there was no significant difference in the postischemic recovery of cardiac output in all experimental groups. CONCLUSION: The combined use of the Na+-H+ exchange inhibitor and Na+ channel blocker during cardioplegia may achieve a superior cardioprotective effect on myocardial damage because of ischemia and reperfusion.     

Effects of albumin supplementation during cardioplegia administration: an in vitro analysis

Increasing, the colloid osmotic pressure (COP) of blood cardioplegia (BCP) may reduce myocardial edema and preserve cardiac function following cardiopulmonary bypass (CPB). The purpose of this study was to quantify the effects of albumin (ALB) supplementation on cardioplegia COP through an in vitro analysis. A self-contained cardioplegia delivery system administered supplemental ALB to four BCP ratios (1:1, 4:1, 8:1, and 20:1). In Group A, 25% ALB was combined with BCP at four delivery rates (0, 13, 25, and 50 mL ALB/L BCP), with a delivery rate of 0 mL ALB/L BCP serving as the control for all groups. Twenty-five percent ALB was added to crystalloid to create carrier solutions containing 12.5, 25, or 50 g ALB/L in Group B, while Group C combined an ALB delivery rate of 50 mL ALB/L BCP with each of the three carrier solutions. End-points included initial and post-supplementation hematocrit, total serum protein (TSP), and COP. Without supplemental ALB, TSP was less affected with increasing blood to crystalloid ratios (1:1-81.7 +/- 6.2%, 4:1-40.6 +/- 5.1%, 8:1-20.6 +/- 4.1%, 20:1-6.0 +/- 5.7%). The TSP of 1:1 and 4:1 BCP increased (p < .0003 and p < .02) across all methods of supplementation, while 8:1 BCP was similarly increased (p < .008), except with 12.5 and 25 g ALB/L carrier solutions. The greatest change from baseline COP was seen with the lower blood to crystalloid ratios (1:1-64.3 +/- 5.0% and 4:1-39.5 +/- 10.5%). In higher ratios, the effects of dilution were less profound (14.6 +/- 4.2 +/- 4.2% and 20:1-6.0 +/- 1.9%). COP of 1:1 BCP increased (p < .008) whenever ALB was added. In conclusion, TSP and COP of blood cardioplegic solutions is increased by supplemental albumin administration with quantitative enhancement dependent upon the dilutional effects of the blood to crystalloid ratio.     

Bradykinin preconditions postischemic arterial endothelial function in humans

BACKGROUND: Arterial endothelial dysfunction is an important mechanism of tissue injury caused by ischemia-reperfusion (I/R). Earlier studies of I/R have shown that intracoronary preinfusion with 2.5-5 microg/mL bradykinin (BK) could alleviate the postischemic myocardial damage. Using an experimental human model of I/R, we investigated whether preceding infusion with BK could prevent the I/R-induced arterial endothelial dysfunction. METHODS: The left radial artery (LRA) from 16 healthy male adults, 18 to 30 years old, was submitted to I/R by completely occluding the left brachial artery with a pressure tourniquet for 20 minutes (ischemia), followed by its release (reperfusion). Prior to I/R, half of the subjects were randomly assigned to receive either BK (5 microg/mL) or saline, both being infused into the left brachial artery (0.5 mL/min, 10 min). The infusion was followed by a 10-minute drug-free period. The endothelial function of the LRA was studied by measuring the flow-mediated dilation (FMD) at baseline (prior to drug infusion), and at 15 minutes of reperfusion. In addition, baseline radial artery diameter, plasma nitrate, and von Willebrand factor were measured at these time points, and immediately before I/R (pre-I/R). RESULTS: BK had no effect on the pre-I/R plasma nitrate (p > 0.5 vs. saline) and diameter of LRA (p > 0.5 vs. baseline). At 15 minutes of reperfusion, FMD was significantly decreased in the saline group as compared to baseline (absolute dilation: 0.08 +/- 0.03 vs. 3.02 +/- 0.8 mm, respectively, p < 0.01; percentage dilation: 3 +/- 0.6 vs. 8 +/- 0.6%, respectively, p < 0.001), but it remained unaffected in the BK group (absolute dilation: 3.06 +/- 0.9 vs. 3.27 +/- 0.8 mm, respectively, p > 0.5; percentage dilation: 7 +/- 0.7 vs. 8 +/- 0.8%, respectively, p > 0.5). A similar trend was observed with regard to plasma nitrate, which remained unchanged in the BK group (37.01 +/- 4.14 vs. 39.14 +/- 4.49 micromol/L, p > 0.5) but decreased in the saline group (35.91 +/- 3.03 vs. 28.91 +/- 2.81 micromol/L, p < 0.1). CONCLUSION: Infusion of BK could protect the arterial endothelial function against I/R injury in humans, possibly in part by preserving the endothelial NO availability. The findings support the use of BK in the prevention of tissue injury due to I/R and might reveal an additional mechanism whereby ACE inhibitors exert their preconditioning effects on myocardium.     

An asanguineous reperfusion solution. An effective adjunct to cardioplegic protection in high-risk valve operations

The protection afforded by cardioplegia during elective ischemic arrest can be partly compromised by a reperfusion injury, which may impede the recovery of cardiac function. We previously showed experimentally that this postischemic damage could be largely avoided by an appropriate crystalloid reperfusate. The present study was thus undertaken to assess the effects of this "reperfusion solution" clinically. One hundred twelve patients undergoing valve replacement with the aid of hypothermic cardioplegia (K+ 12 mEq, Mg2+ 26 mEq) were prospectively divided in two groups: Group I (n = 49) received an unmodified blood reperfusate. In Group II (n = 63), 1 L of the reperfusion solution was delivered just prior to removal of the aortic clamp. The formulation of the reperfusion solution adhered to the following principles: (1) maintenance of cardioplegia (K+ = 15 mEq), (2) replenishment of Ca2+ stores (Ca2+ = 2.5 mEq), (3) substrate provision (glutamate = 2,942 gm), (4) buffering (pH = 7.70 at 28 degrees C), and (5) hyperosmolarity (370 mOsm). The two groups were matched for preoperative data except for a higher incidence of isolated aortic valve replacement (p = 0.01) in Group II. Also, the cross-clamp time (mean +/- standard error of the mean) was longer in Group II (94 +/- 4 minutes versus 63 +/- 4 minutes, p less than 10(-6]. The reperfusion solution was found to increase both the rate and extent of postischemic functional recovery, as evidenced by (1) a lower proportion of catecholamine-supported patients 48 hours after operation (9/63 [14.28%] versus 16/49 [32.6%] in the control group [p less than 0.03]) and (2) a lower amount (gamma/kg/min) of dobutamine required to achieve stable hemodynamics (11 +/- 1 versus 26 +/- 6 in the control group [p less than 0.03]). A similar recovery pattern was noted in the high-risk subgroup of patients with mitral valve disease. Further, serial postoperative hemodynamic measurements were performed in 31 randomly selected patients (10 control and 21 reperfused). Although the reperfused patients were found to be at higher risk because of lower preoperative cardiac indices and longer cross-clamp times, they consistently achieved better postoperative hemodynamics with a lower incidence of catecholamine support. This hemodynamic improvement was particularly reflected by a higher left ventricular stroke work index throughout the postoperative course, the difference being significant 6 hours and 12 hours postoperatively.(ABSTRACT TRUNCATED AT 400 WORDS)     

Blood cardioplegia supplementation with the sodium-hydrogen ion exchange inhibitor cariporide to attenuate infarct size and coronary artery endothelial dysfunction after severe regional ischemia in a canine model

BACKGROUND: Activation of the sodium-hydrogen ion exchange mechanism results in accumulation of intracellular calcium through the sodium-calcium ion antiport mechanism. Administration of a sodium-hydrogen ion exchange inhibitor before or during ischemia attenuates myocardial ischemia and reperfusion injury. However, the cardioprotection exerted by sodium-hydrogen ion exchange inhibitors as adjuncts to cardioplegia without perioperative administration has not been tested in a model of surgical reperfusion of acute coronary occlusion with cardiopulmonary bypass. This study tested the hypothesis that sodium-hydrogen ion exchange inhibitor-supplemented blood cardioplegia would reduce postcardioplegia injury after severe regional ischemia. METHODS: In anesthetized open-chest dogs, the left anterior descending coronary artery was occluded for 75 minutes, after which total cardiopulmonary bypass was initiated. After crossclamping, cold (4 degrees C) antegrade blood cardioplegia was delivered every 20 minutes for a total of 60 minutes of cardioplegic arrest. In 8 dogs, the blood cardioplegic solution was unsupplemented (vehicle group), whereas in 8 others the solution was supplemented with the sodium-hydrogen ion exchange inhibitor cariporide (10 micro mol/L, cariporide group). RESULTS: In the in vitro studies, the direct effects of cariporide on neutrophil function were determined. Isolated canine neutrophils were stimulated by platelet activating factor. Cariporide attenuated superoxide anion production in a concentration-dependent manner, with no appreciable effect at 10 micro mol/L (the concentration used in blood cardioplegia) and a peak effect at 100 micro mol/L. In the in vivo cardiopulmonary bypass model, infarct size was significantly (P <.05) smaller in the cariporide group than in the vehicle group (22.4% +/- 3.5% vs 40.1% +/- 5.1% of area at risk), although there were no group differences in postischemic regional wall motion after 2 hours of reperfusion (0.1% +/- 0.9% vs -0.2% +/- 0.3% systolic shortening). Transmural myocardial edema in the area at risk was significantly decreased in the cariporide group (80.6% +/- 0.5%) relative to the vehicle group (83.1% +/- 0.6%). Myeloperoxidase activity in the area at risk, an index of neutrophil accumulation, was significantly lower in the cariporide group than in the vehicle group (4.7 +/- 0.9 absorbence units/[min. g tissue] vs 10.3 +/- 2.3 absorbence units/[min. g tissue]). In isolated postischemic left anterior descending coronary artery rings, maximum relaxation in response to the endothelium-dependent vasodilator acetylcholine was significantly greater in the cariporide group than in the vehicle group (77.5% +/- 7.4% vs 51.4% +/- 8.0%), whereas smooth muscle relaxation in response to nitroprusside was comparable between groups. CONCLUSION: In this canine model, supplementation of blood cardioplegia with cariporide, a sodium-hydrogen ion exchange inhibitor, reduced infarct size, attenuated neutrophil accumulation in the area at risk, and reduced postischemic coronary artery endothelial dysfunction without directly inhibiting neutrophil activity. Cariporide as an adjunct to blood cardioplegia without perioperative administration attenuated surgical ischemia-reperfusion injury in jeopardized myocardium.     

The effects of propofol on cardiac function after 4 hours of cold cardioplegia and reperfusion

OBJECTIVE: To examine whether propofol protects against postischemic myocardial dysfunction and apoptosis during reperfusion after prolonged cold ischemia in isolated rat hearts. DESIGN: A prospective, randomized, controlled study. SETTING: A university laboratory. PARTICIPANTS: Animals. INTERVENTIONS: The isolated hearts of 40 Sprague-Dawley male rats were perfused with modified Krebs-Hennseleit solution for 15 minutes for a stabilization period and 15 minutes for a perfusion period and then underwent 4 hours of global cold ischemia followed by 60 minutes of reperfusion. Four groups were studied (n = 10 for each group). Ten hearts served as an untreated control group. Propofol (2 micromol/L) treatment was performed only before ischemia in the PRE group, only during reperfusion in the POST group, and both before and after ischemia in the ALL group. MEASUREMENTS AND MAIN RESULTS: Infusion of propofol during reperfusion improved recovery of left ventricular-developed pressure (LVDP) from 61.2% +/- 8.5% (control) to 86.3% +/- 12.1% (POST) and 74.9% +/- 13.2% (ALL, both p < 0.05), whereas preischemic infusion of propofol (64.3% +/- 9.7%, PRE) did not improve recovery of LVDP. Infusion of propofol during reperfusion significantly reduced the number of apoptotic cells and led to a smaller infarct size than control and PRE groups (p < 0.05, respectively). CONCLUSIONS: Propofol infusion during the reperfusion period produced a cardioprotective effect and inhibited apoptosis of cardiomyocytes in the ischemia-reperfusion model, with prolonged cold ischemia, in isolated rat hearts.     

Leukocyte-depleted terminal blood cardioplegia provides superior myocardial protective effects in association with myocardium-derived nitric oxide and peroxynitrite production for patients undergoing prolonged aortic crossclamping for more than 120 minutes

OBJECTIVES: This study was designed to examine the myocardial protective effect of leukocyte-depleted terminal blood cardioplegia in association with nitric oxide and peroxynitrite production, especially for patients undergoing prolonged aortic crossclamping. METHODS: Fifty-four patients (34 men, 20 women, mean age 56.7 +/- 12.7 years) undergoing aortic valve replacement were randomly allocated to one of two groups; group LDTC (n = 27) received 10 minutes of leukocyte-depleted terminal blood cardioplegic solution, and group CONT (n = 27) served as controls. Each group was subdivided into 2 groups: aortic crossclamping for less than 120 minutes in groups LDTC-S (n = 13) and CONT-S (n = 14); aortic crossclamping for 120 minutes or more in groups LDTC-L (n = 14) and CONT-L (n = 13). RESULTS: After aortic unclamping, group LDTC-L showed higher incidence of spontaneous defibrillation (78.6% vs 30.8%, P =.0213), higher plasma nitrate + nitrite in the coronary sinus effluent (32.5 +/- 4.1 vs 28.7 +/- 3.0 micromol/L, P =.0013), lower differences between coronary sinus effluent and arterial blood in the percentage ratio of nitrotyrosine to tyrosine (myocardium-derived peroxynitrite; 2.987% +/- 0.576% vs 3.951% +/- 0.952%, P =.0036), and plasma polymorphonuclear-elastase (113.9 +/- 21.3 vs 155.5 +/- 41.6 microg/L, P =.0029) and malondialdehyde (2.75 +/- 0.67 vs 4.02 +/- 0.96 micromol/L, P =.0005) than group CONT did. Postoperatively, group LDTC-L showed lower human-heart fatty acid-binding protein (111.4 +/- 25.2 vs 156.4 +/- 38.6 IU/L, P =.0013), lower creatine kinase-muscle and brain (19.2 +/- 4.7 vs 24.8 +/- 6.5 IU/L, P =.0120), and smaller requirement of catecholamine (5.44 +/- 2.29 vs 8.45 +/- 3.42 microg x kg(-1) x min(-1), P =.0122). There were no significant differences in these parameters between groups LDTC-S and CONT-S. CONCLUSIONS: This study demonstrated that leukocyte-depleted terminal blood cardioplegia provided superior myocardial protective effects and regulated myocardial-derived nitric oxide and peroxynitrite production only for patients undergoing aortic crossclamping for more than 120 minutes. The results suggest that prolonged aortic crossclamping deteriorates the tolerance to leukocyte-mediated myocardial injury accompanied by endothelial dysfunction associated with nitric oxide and peroxynitrite production.     

Postischemic infusion of 17-beta-estradiol protects myocardial function and viability

BACKGROUND: Females demonstrate improved cardiac recovery after ischemia/reperfusion injury compared with males. Attenuation of myocardial dysfunction with preischemic estradiol suggests that estrogen may be an important mediator of this cardioprotection. However, it remains unclear whether post-injury estradiol may have clinical potential in the treatment of acute myocardial infarction. We hypothesize that postischemic administration of 17beta-estradiol will decrease myocardial ischemia/reperfusion injury and improve left ventricular cardiac function. MATERIALS AND METHODS: Adult male Sprague Dawley rat hearts (n = 20) (Harlan, Indianapolis, IN) were isolated, perfused with Krebs-Henseleit solution via Langendorff model, and subjected to 15 min of equilibration, 25 min of warm ischemia, and 40 min reperfusion. Experimental hearts received postischemic 17beta-estradiol infusion, 1 nm (n = 4), 10 nm (n = 4), 25 nm (n = 4), or 50 nm (n = 4), throughout reperfusion. Control hearts (n = 4) were infused with perfusate vehicle. RESULTS: Postischemic recovery of left ventricular developed pressure was significantly greater with 1 nm (51.6% +/- 7.4%) and 10 nm estradiol (47.7% +/- 8.6%) than with vehicle (37.8% +/- 9.7%) at end reperfusion. There was also greater recovery of the end diastolic pressure with 1 nm (47.8 +/- 4.0 mmHg) and 10 nm estradiol (54.0 +/- 4.0) compared with vehicle (75.3 +/- 7.5). Further, 1 nm and 10 nm estrogen preserved coronary flow after ischemia and decreased coronary effluent lactated dehydrogenase compared with controls. Estrogen at 25 nm and 50 nm did not provide additional benefit in terms of functional recovery. Estrogen at all concentrations increased extracellular signal-regulated protein kinase phosphorylation. CONCLUSIONS: Postischemic infusion of 17beta-estradiol protects myocardial function and viability. The attractive potential for the clinical application of postischemic estrogen therapy warrants further study to elucidate the mechanistic pathways and differences between males and females.