Improved myocardial recovery after cardioplegic arrest with an oxygenated crystalloid solution

Possible enhancement of myocardial protection by oxygenation of a crystalloid cardioplegic solution was evaluated in a three-part study. In Part I, canine hearts underwent ischemia followed by heterogeneous cardioplegic arrest for 45 to 60 minutes. Oxygenation led to improved recovery in the left anterior descending region (47% versus 86% recovery, p less than 0.05) (15 minutes of ischemia) and in the circumflex region (9.5% versus 52% recovery, p less than 0.05) (30 minutes of ischemia). Part II was a blind prospective randomized study in 12 patients. It examined creatine kinase, myoglobin, and lactate as well as coronary sinus flow, oxygen consumption, and cardiac work 1 hour after aortic cross-clamping during atrial and during ventricular pacing. No significant difference was demonstrable between control and oxygenated solutions. In Part III, 57 coronary bypass patients were protected with a nonoxygenated solution while 94 patients received an identical oxygenated solution. Twelve-hour creatine kinase levels were similar in the nonoxygenated (9.5 +/- 16 IU, +/- standard deviation) and oxygenated (11 +/- 22 IU) groups if the cross-clamp interval was 28 minutes or less. In patients subjected to longer than 28 minutes of arrest, the 12 hour creatine kinase MB levels were more than twice as high in the nonoxygenated group (26.5 +/- 26 IU) compared to the oxygenated group (9.9 +/- 14 IU, p less than 0.05). In this canine model of heterogeneous cardioplegia and in the routine conduct of coronary bypass operations, oxygenated crystalloid cardioplegia is superior to an identical nonoxygenated solution.     

The effect of amino acids on the ischemic heart. Improvement of oxygenated crystalloid cardioplegic solution by an enriched branched chain amino acid formulation

This study was designed to test the effect of glucose and a formulation enriched with branched chain amino acids as additives to oxygenated crystalloid cardioplegic solution in the ischemic heart. Energy-depleted isolated working rat hearts were subjected to 68 minutes of normothermic global ischemia during which oxygenated cardioplegic solution was used to protect them. The hearts were then reperfused in the nonworking mode for 10 minutes and for a further 30 minutes in the working mode. The hearts were randomly divided into three groups, in which various oxygenated cardioplegic solutions were perfused. Group 1 (control) was subjected to modified St. Thomas' Hospital cardioplegic solution and groups 2 and 3 to the same solution with the addition of glucose (11.1 mmol/L) and glucose (11.1 mmol/L) and branched chain amino acids, respectively. Recovery of aortic flow, coronary flow, cardiac output, aortic pressure, adenosine triphosphate, creatine phosphate, and oxygen consumption was significantly better in group 2 than in group 1. In addition, recovery of aortic flow, coronary flow, cardiac output, aortic pressure, stroke volume, minute work, adenosine triphosphate, and creatine phosphate was found to be significantly enhanced in group 3. Release of adenine catabolites and lactic dehydrogenase from these hearts during postischemic reperfusion was significantly decreased. Thus, during global ischemia in the energy-depleted heart, the presence of glucose and branched chain amino acids in oxygenated crystalloid cardioplegic solution enhanced myocardial protection.     

Comparison of myocardial protective effects between GIK solution and St. Thomas solution by use of canine isolated heart-lung preparations

The myocardial protection afforded by GIK solution, widely used as cardioplegic solution in this country, was compared with that provided by St. Thomas solution or oxygenated St. Thomas solution. Eighteen isolated heart-lung preparations of dogs were made and their hearts were subjected to 3 hours cold (4 degrees C) cardioplegic arrest. GIK group hearts (n = 6) received 20 ml/kg of GIK solution at the time of aortic cross-clamp perfused through the aortic root and were subsequently given 10 ml/kg of GIK solution every 30 minutes. St. Thomas group hearts (n = 6) and oxygenated St. Thomas group hearts (n = 6) were treated identically except that cardioplegic solution were St. Thomas solution or fully oxygenated one. Four hearts of GIK group showed ventricular fibrillation immediately after reperfusion that required DC countershock. Temporary A-V block was recognized in two hearts. In the other two groups, however, neither ventricular fibrillation nor A-V block was found. Heart rate, coronary flow, aortic flow and LVSW were measured before arrest and after 60 minutes of reperfusion (mean aortic pressure 70 mmHg, left atrial pressure 4 mmHg). Post reperfusion % recovery rates (post-reperfusion/before arrest) of heart rate, coronary flow, aortic flow and LVSW (mean value +/- standard deviation) were 93.4 +/- 10.32%, 104.6 +/- 24.91%, 18.8 +/- 8.54%, 32.6 +/- 6.12% respectively for GIK group, 81.4 +/- 6.50%, 125.9 +/- 15.23%, 35.4 +/- 9.91%, 56.3 +/- 12.90% for St. Thomas group and 83.1 +/- 8.40%, 121.6 +/- 16.92%, 47.0 +/- 7.89%, 69.1 +/- 9.71% for oxygenated St. Thomas group. St. Thomas and oxygenated St. Thomas groups revealed significantly (p less than 0.05, p less than 0.01 respectively) more excellent functional preservation than GIK group. Intramyocardial pH was also measured by use of glass needle pH electrode punctured into the anterior interventricular septum. Preischemic intramyocardial pH (at 37 degrees C) was 7.49 +/- 0.106 in GIK group, 7.48 +/- 0.113 in St. Thomas group and 7.43 +/- 0.114 in oxygenated St. Thomas group. During 3 hours of cardioplegic arrest, intramyocardial pH (at 4 degrees C) decreased to 6.84 +/- 0.101 in GIK group, 7.03 +/- 0.088 in St. Thomas group and 7.23 +/- 0.239 in oxygenated St. Thomas group, which was significantly higher than GIK group (p less than 0.01). Therefore oxygenated St. Thomas solution was found to maintain more favorable energy supply to ischemic myocardium. These results clearly evidenced that St. Thomas and oxygenated St. Thomas solutions would provide more effective myocardial protection during ischemic arrest than GIK solution.     

Efficacy of crystalloid cardioplegic solutions in patients undergoing myocardial revascularization. Effect of infusion route and regional wall motion on preservation of adenine nucleotide stores

The effect of varying the mode of cardioplegic delivery and the presence of regional wall motion abnormalities on myocardial protection by crystalloid cardioplegic solutions was assessed in 68 patients undergoing coronary artery bypass grafting. Serial transmural biopsy specimens from the left ventricular apex were assayed for adenosine triphosphate. All patients had more than 75% stenosis of the left anterior descending coronary artery. They were prospectively randomized into Groups I and II to receive (I) all cardioplegic solution infused via the aortic root or (II) reinfusions of cardioplegic solution given both centrally and through the completed distal left anterior descending anastomosis. Patients were also stratified as to the presence of normal (N) or impaired (Ab) apicoanterior regional wall motion. Inadequate delivery of cardioplegia during ischemia in Group I was manifested by a 41% (p less than 0.01) depletion of adenosine triphosphate stores in abnormally contracting myocardium distal to the left anterior descending stenosis that was not repleted after restoration of coronary flow and a 27% (p less than 0.05) decline in ATP stores during reperfusion in myocardium with normal preoperative wall motion. In contrast, nucleotide stores were preserved at preischemic levels throughout ischemia and reperfusion in Group II regardless of preoperative wall motion. Preservation of ATP did not correlate with duration of ischemia, highest recorded septal temperature, or volume of cardioplegic solution infused. Two patients in each group had a new perioperative infarction. However, 38% of patients in Group IAb required transient inotropic support versus 5% in Group IIAb (p less than 0.05). These data emphasize that reinfusion of cardioplegic solutions distal to coronary obstructions is mandatory for optimal myocardial protection during coronary revascularization.     

Comparison of alternative cardioplegic techniques

Cold potassium cardioplegia provides adequate protection for coronary bypass operations, but severe coronary stenoses limit cardioplegic delivery to ischemic regions. The traditional technique delivers cardioplegic solution into the aortic root during the performance of distal anastomoses. The proposed alternative technique constructs proximal as well as distal anastomoses during a prolonged cross-clamp period, but permits more uniform cooling. The two techniques were compared in a prospective concurrent trial of 45 patients undergoing elective coronary bypass grafting. The traditional technique was employed in 26 patients (Group A) and the alternative technique in 19 patients (Group B). In both groups, 700 to 1,000 ml of a crystalloid cardioplegic solution was infused into the aortic root after application of the aortic cross-clamp. In Group A (traditional technique), 500 ml was infused into the aortic root after each distal anastomosis. In Group B (alternative technique), cardioplegic solution was administered through the vein graft after each distal anastomosis, and a proximal anastomosis was constructed after distal anastomoses to the most ischemic regions to permit continued cardioplegic delivery to these regions. The cross-clamp period was shorter in Group A than in Group B (44 +/- 15 versus 60 +/- 18 minutes, p less than 0.01), but the mean temperature in the most ischemic region was warmer (Group A, 19 degrees +/- 3 degrees C; Group B, 15 degrees +/- 3 degrees C, p less than 0.05). The postoperative CK-MB was higher in Group A (Group A, 47 +/- 36; Group B, 21 +/- 9 IU/L, p less than 0.01). Cardiac lactate production persisted longer in Group A (Group A, 4 +/- 1; Group B, 1 +/- 1 hours postoperatively, p less than 0.05). Volume loading 4 hours postoperatively produced a similar increase in left atrial pressure and cardiac index in both groups. In response to volume loading, Group A patients produced lactate, but Group B patients extracted lactate (change in cardiac lactate extraction: Group A, -1.7 +/- 2.3; Group B, +2.5 +/- 5.1 mg/dl, p less than 0.05). The construction of proximal as well as distal anastomoses during a prolonged cross-clamp period permits more uniform cooling and immediate reperfusion. This alternative technique resulted in less injury (CK-MB release) and more rapid recovery of myocardial metabolism.     

High-volume crystalloid cardioplegia. An improved method of myocardial preservation

Controlled metabolic studies were used to gauge the relative efficacy of three cardioplegic techniques in 41 patients undergoing multiple coronary artery bypass grafts. Normal-volume (1,946 +/- 155 ml) crystalloid cardioplegia (NVCC) (14 patients) was compared to high-volume (4,961 +/- 282 ml) crystalloid cardioplegia (HVCC) (14 patients) and to blood cardioplegia (BC) (1,672 +/- 127 ml) (13 patients). Measurements of coronary blood flow, coronary vascular resistance, coronary arteriovenous oxygen difference, myocardial oxygen consumption and extraction, and myocardial lactate and potassium extraction and release were all measured in the isolated, vented, paced, beating heart, before and for 20 minutes after a 1 hour arrest interval during which revascularization was completed. Additionally, during administration of the cardioplegic solution, infusion flow rate, myocardial oxygen consumption and extraction, and lactate and potassium release and uptake were noted. The results indicate that during cardioplegic administration, myocardial oxygen consumption is 1 ml O2/min with crystalloid infusion and 2.6 ml O2/min during BC infusion. The volume of crystalloid solution administered contributed to increased oxygen utilization during HVCC compared to NVCC, whereas BC promoted the highest oxygen utilization of the three groups. Potassium absorption was nearly three times greater during BC than during crystalloid administration. During myocardial reperfusion, oxygen extraction was maintained at prearrest levels only in the HVCC group. Following both NVCC and BC, oxygen extraction was depressed during the first 5 minutes of reperfusion, and the difference between the latter two groups and HVCC was significant (p less than 0.01). The rapid recovery in normal metabolic function seen with HVCC allows early discontinuation of cardiopulmonary bypass without myocardial metabolic depression.     

Leukocyte-depleted blood cardioplegia reduces cardiac troponin T release in patients undergoing coronary artery bypass grafting.

OBJECTIVE: Activated neutrophils have been implicated in reperfusion injury of the myocardium. Leukocyte depletion at reperfusion may contribute to better myocardial protection during cardiac surgery. We tested the efficacy of leukocyte-depleted blood cardioplegia in reducing myocardial injury during coronary artery bypass grafting. METHODS: Subjects were 27 patients undergoing elective coronary artery bypass grafting divided into controls (perfused with nonfiltered blood cardioplegia, n = 12) and those undergoing leukocyte-depleted blood cardioplegia (n = 15). Oxygenated blood mixed with a potassium crystalloid cardioplegic solution was delivered through the aortic root at every 30 minutes during cardiac arrest and terminal warm blood was administered before aortic declamping in both groups. In leukocyte depletion, blood was filtered prior to the mixture with crystalloid solution in the cardioplegic reservoir. RESULTS: Patient profiles did not differ significantly between groups, nor did systemic leukocyte count during or after surgery despite more than 81% removal of leukocytes in cardioplegic delivery. No consistent differences between groups in creatine kinase or creatine kinase-MB were seen up to 18 hours after surgery. Peak troponin T levels were significantly lower in the leukocyte-depleted blood cardioplegia group (0.52 +/- 0.13 ng/ml), however, than in controls (3.85 +/- 0.85 ng/ml). CONCLUSION: We concluded that leukocyte-depleted blood cardioplegia reduces the release of cardiac troponin T in patients undergoing elective coronary artery bypass grafting and may produce better myocardial protection in patients with impaired cardiac function or a damaged myocardium.     

Effect of multidose cardioplegia and cardioplegic solution buffering on myocardial tissue acidosis

Multidose administration of cardioplegic solution during cardiac operation is intended to maintain both electromechanical arrest of the heart and myocardial hypothermia as well as to remove accumulated metabolites of anaerobic glycolysis. This study was conducted to assess the effect of multidose infusion of three different types of cardioplegic solution on tissue acidosis during global myocardial ischemia. Three groups of five dogs each were placed on cardiopulmonary bypass and the aorta was cross-clamped for 3 hours. The hearts were maintained at a constant temperature (20 degrees C) and cardioplegic solution was infused at an initial dose of 500 ml and five supplementary doses of 250 ml administered every 30 minutes. Group 1 received a crystalloid solution weakly buffered with sodium bicarbonate, Group 2 received a blood-based solution, and Group 3 received a crystalloid solution strongly buffered with histidine (Bretschneider's solution). The buffering capacities of the solutions used in Groups 2 and 3 were 40 and 60 times, respectively, that of the solution used in Group 1. The average myocardial tissue pH at the end of 3 hours of ischemia was 6.54 +/- 0.07 in Group 1, 7.23 +/- 0.05 in Group 2, and 7.19 +/- 0.06 in Group 3 (Group 1 significantly lower than Groups 2 and 3). Multidose infusion of a cardioplegic solution with low buffering capacity was unable to prevent the progressive development of tissue acidosis during 3 hours of ischemia. However, the multidose infusion of either blood-based or crystalloid solutions with high buffering capacity completely prevented any further reduction of tissue pH after the first 30 minutes of ischemia.     

Comparison of myocardial temperatures with multidose cardioplegia versus single-dose cardioplegia and myocardial surface cooling during coronary artery bypass grafting

Myocardial hypothermia with multidose cardioplegia has not been compared with single-dose cardioplegia and myocardial surface cooling with a cooling jacket in patients having coronary artery bypass grafting. In this study, 20 patients with three-vessel disease undergoing coronary bypass at 28 degrees C with bicaval cannulation, caval tapes, and pulmonary artery venting (4.9 +/- 0.7 grafts per patient) were prospectively randomized equally into group I (multidose cardioplegia) and group II (single-dose cardioplegia with a cooling jacket). The initial dose of cardioplegic solution was 1000 ml. Group I then received 500 ml of cardioplegic solution every 20 minutes, delivered into the aortic root and available grafts. In group II, after the cardioplegic solution had been administered, a cooling jacket covering the right and left ventricles was applied. In both groups temperatures were recorded every 30 seconds at five ventricular sites: (1) right ventricular epicardium; (2) right ventricular myocardium or cavity, 7 mm; (3) left ventricular epicardium; (4) left ventricular myocardium or cavity, 15 mm; and (5) septum, 20 mm. Group mean temperatures at each site at various times were compared within each group and between the two groups by analysis of variance. Aortic crossclamp time was 60.3 +/- 12.1 minutes in group I and 52.8 +/- 7.3 minutes in group II (p = 0.12); cardiopulmonary bypass time was 103.7 +/- 11.1 minutes in group I versus 87.7 +/- 12.7 minutes in group II (p less than 0.01). One minute after the cardioplegic solution was initially given, temperatures between groups at each site were not statistically different, but left ventricular epicardial temperatures within both groups were significantly higher than in the other four sites. Nineteen minutes after administration of the cardioplegic solution, temperatures in group I at all sites were higher than in group II. Similarly, throughout the entire period of aortic crossclamping, mean temperatures (except left ventricular myocardial site), maximum temperatures, and percentage of time all temperatures were 15 degrees C or higher were greater in group I than in group II. The following conclusions can be reached: 1. Initial myocardial cooling with 1000 ml of cardioplegic solution is not significantly limited by coronary artery disease but is suboptimal (16 degrees or 17 degrees C) in the inferior left ventricular epicardium because of continual warming from the aorta and subdiaphragmatic viscera. 2. Without myocardial surface cooling, excessive external myocardial rewarming to 18 degrees to 22 degrees C occurs within 20 minutes at all sites after delivery of the cardioplegic solution.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of antegrade cardioplegic infusion with simultaneously controlled coronary sinus occlusion on preservation of regionally ischemic myocardium after acute coronary artery occlusion and reperfusion

This study was conducted to assess the protective effects of antegrade infusion of cardioplegic solution with simultaneously controlled coronary sinus occlusion on regionally ischemic myocardium after acute coronary occlusion and reperfusion. Twelve sheep were subjected to 1 hour of occlusion of the distal left anterior descending coronary artery. Sheep in group I (n = 6) were subjected only to infusion of potassium crystalloid cardioplegic solution into the aortic root, whereas in group II (n = 6) a stitch was snared around the proximal coronary sinus for its subsequent occlusion during antegrade infusions of cardioplegic solution. All animals were placed on cardiopulmonary bypass. Five hundred milliliters of cardioplegic solution at 4 degrees to 8 degrees C was administered in three divided doses during the total cross-clamp period of 30 minutes. The occlusion of the left anterior descending artery was then released, and the animals were weaned from bypass and studied for an additional 4 hours. Coronary sinus pressure, myocardial temperature, regional function assessed by pairs of ultrasonic crystals, global function assessed by rate of rise of left ventricular pressure and cardiac output, and the area at risk and area of necrosis were determined. The heart was excised at the end of the experiment and stained. Animals treated by the technique of antegrade infusion combined with coronary sinus occlusion had more homogeneous myocardial cooling during cardioplegic infusions and better recovery of the first derivative of left ventricular pressure and regional segment shortening at 90 and 270 minutes of reperfusion than those treated with antegrade infusion alone (p less than 0.01 and p less than 0.05, respectively). The group treated by antegrade infusion of cardioplegic solution combined with coronary sinus occlusion had an area of necrosis/area at risk ratio of 40.5% +/- 1.2%; the antegrade infusion group, 58.3% +/- 4.1% (p less than 0.01). These data suggest that antegrade infusion combined with coronary sinus occlusion may be an improved method of global and regional myocardial protection in the presence of an occluded coronary artery.     

Retrograde coronary sinus perfusion of cardioplegic solution in Jatene operation in neonates and infants

The clinical benefits of retrograde coronary sinus perfusion of a cardioplegic solution were investigated in 7 neonates and 23 infants undergoing Jatene operation. After an initial infusion of albumin-containing crystalloid cardioplegic solution via the aortic root, 21 patients received additional solution delivered by retrograde coronary sinus perfusion (retrograde group) and 9 patients received by selective antegrade coronary perfusion (antegrade group) every 20 to 30 minutes. There were no differences in age, weight, and left ventricular preoperative pressure and morphology between the two groups. Aortic cross-clamping time was 130 +/- 18 minutes in retrograde group and 147 +/- 20 minutes in antegrade group. Postoperative assays of CPK-MB, GOT and LDH, and hemodynamic measurements immediately after cessation of cardiopulmonary bypass (CPB) were carried out in all patients. Although there was no significant difference between the two groups in terms of enzyme indexes, retrograde group showed a greater variation of sigma CPK-MB from patient to patient than antegrade group. However, hemodynamic parameters of CVP, left atrial pressure and rate-pressure product at 20-30 minutes after CPB were similar in the two groups. Six neonates in retrograde group also demonstrated the similar enzyme indexes and hemodynamic state immediately after CPB to other older patients. We concluded, therefore, that retroperfusion of cardioplegic solution in neonates and infants provides satisfactory myocardial protection as well as antegrade perfusion, and it was a useful means of cardioplegic delivery in Jatene operation, because of its simplicity.     

Ischemic myocardial protection. Comparison of nonoxygenated crystalloid, oxygenated crystalloid, and oxygenated fluorocarbon cardioplegic solutions

This study was designed to compare myocardial protection with a nonoxygenated crystalloid solution, an oxygenated crystalloid solution, and an oxygenated fluorocarbon cardioplegic solution. Postischemic ventricular performance was studied in three equal (N = 7) groups of dogs subjected to 120 minutes of global ischemia induced at an average myocardial temperature of 18.5 degrees +/- 1.4 degrees C (range 17.0 degrees to 21.0 degrees C). Left ventricular global and regional function was evaluated by sonomicrometry and micromanometers before ischemia and at 45 and 60 minutes after ischemia. Stroke volume index, left ventricular pressure-minor external diameter loop area, percent shortening, first derivative of left ventricular pressure, mean velocity of circumferential fiber shortening, and the slope of the end-systolic pressure were used to evaluate myocardial contractility. In vitro oxygen content of the three cardioplegic solutions was measured at a mean injection temperature of 8.3 degrees +/- 0.6 degrees C: 0.8 +/- 0.1 vol% (nonoxygenated crystalloid cardioplegia), 3.2 +/- 0.2 vol% (oxygenated crystalloid cardioplegia), and 6.2 +/- 0.2 vol% (oxygenated fluorocarbon cardioplegia). Recovery of global and regional function was significantly (p less than 0.05) better with both oxygenated solutions than with the nonoxygenated solution. Differences between the oxygenated crystalloid and fluorocarbon groups were not significant. We conclude: (1) Compared to nonoxygenated crystalloid cardioplegia, oxygenated crystalloid and oxygenated fluorocarbon cardioplegic solutions gave superior myocardial protection during 2 hours of ischemic arrest; (2) no difference was found in protective effects between an oxygenated crystalloid and an oxygenated fluorocarbon solution.     

The use of combined antegrade-retrograde infusion of blood cardioplegic solution in pediatric patients undergoing heart operations.

The benefits of combined antegrade-retrograde infusion of blood cardioplegic solution are becoming well known in adult coronary and valvular heart operations. Many of these advantages relate directly to the pediatric patient. They include prompt arrest and even distribution, particularly with aortic insufficiency or open aortic root, avoiding or limiting ostial cannulation, allowing uninterrupted surgical procedures, and flushing air/debris from the coronary arteries. We therefore report on the first 123 pediatric patients at the University of California, Los Angeles, to receive myocardial protection with antegrade (aortic) infusion in conjunction with retrograde (coronary sinus) infusion of blood cardioplegic solution. We employed a retroplegia catheter with a self-inflating and deflating occlusion balloon on the tip of a pressure-monitored infusion cannula that remains in the coronary sinus during the operation. Induction blood cardioplegic solution, 30 ml/kg in equally divided doses, is administered in the coronary sinus first antegrade at an aortic pressure less than 80 mm Hg, followed by retrograde infusion at less than 40 mm Hg. Maintenance cardioplegic solution (15 ml/kg) is administered every 20 minutes through one or both of the infusion cannulas, depending on the surgical procedure. Patients' ages ranged from 1 week to 16 years with a mean of 4.6 years. The following procedures were included in descending order: Fontan 20, atrioventricular valve repair/replacement (and complete atrioventricular canal) 16, aortic root/Konno/Ross 16, Rastelli 13, aortic valve repair/replacement 13, ventricular septal defect (and double-outlet right ventricle) 13, tetralogy of Fallot 10, coronary artery reimplantation/fistula repair 6, truncus arteriosus 4, arterial switch 3, bidirectional Glenn 2, sinus venosus 2, and aortopulmonary window, Senning, Stansel, interrupted aortic arch, and Ebstein's, 1 each. Aortic crossclamp times ranged from 6 to 219 minutes with a mean of 87 minutes. Myocardial oxygen consumption data for a series of six patients indicated the supplemental benefit for retrograde infusion of cardioplegic solution along with antegrade infusion, particularly in hypertrophied myocardium. Three deaths occurred (2.4% 30-day mortality), in the following patients: the first with truncus arteriosus and interrupted aortic arch, the second with complete atrioventricular canal and pulmonary hypertension, and the third with truncal valve regurgitation and replacement. There were no complications related to the retroplegia catheter. From this initial positive experience, we conclude that (1) combined antegrade-retrograde infusion of blood cardioplegic solution can be safely used in an expanding number of pediatric heart operations in all age groups, and (2) combined antegrade-retrograde infusion of blood cardioplegic solution may provide additional myocardial protection, with excellent surgical outcome, in complex congenital heart repairs.     

The effect of temperature and hematocrit level of oxygenated cardioplegic solutions on myocardial preservation

The ideal temperature and hematocrit level of blood cardioplegia has not been clearly established. This study was undertaken (a) to determine the optimal temperature of blood cardioplegia and (b) to study the effect of hematocrit levels in blood cardioplegia. A comparison of myocardial preservation was done among seven groups of animals on the basis of variations in hematocrit levels and temperature of oxygenated cardioplegic solution. The experimental protocol consisted of a 2-hour hypothermic cardioplegic arrest followed by 1 hour of normothermic reperfusion. Group 1 received oxygenated crystalloid cardioplegic solution at 10 degrees C. Groups 2 through 7 received oxygenated blood cardioplegic solution with the following hematocrit values and temperatures: (2) 10%, 10 degrees C; (3) 10%, 20 degrees C; (4) 10%, 30 degrees C; (5) 20%, 10 degrees C; (6) 20%, 20 degrees C; and (7) 20%, 30 degrees C. Parameters studied include coronary blood flow, myocardial oxygen extraction, myocardial oxygen consumption, and myocardial high-energy phosphate levels of adenosine triphosphate and creatine phosphate during control (prearrest), arrest, and reperfusion. Myocardial oxygen consumption at 30 degrees C during arrest was significantly higher than at 10 degrees C and 20 degrees C, which indicates continued aerobic metabolic activity at higher temperature. Myocardial oxygen consumption and the levels of adenosine triphosphate and creatine phosphate during reperfusion were similar in all seven groups. Myocardial oxygen extraction (a measure of metabolic function after ischemia) during initial reperfusion was significantly lower in the 30 degrees C blood group than in the 10 degrees C blood group at either hematocrit level and in the oxygenated crystalloid group, which suggests inferior preservation. The hematocrit level of blood cardioplegia did not affect adenosine triphosphate or myocardial oxygen consumption or extraction. It appears from this study that blood cardioplegia at 10 degrees C and oxygenated crystalloid cardioplegia at 10 degrees C are equally effective. Elevating blood cardioplegia temperature to 30 degrees C, however, reduces the ability of the solution to preserve metabolic function regardless of hematocrit level. Therefore, the level of hypothermia is important in blood cardioplegia, whereas hematocrit level has no detectable impact, and cold oxygenated crystalloid cardioplegia is as effective as hypothermic blood cardioplegia.     

Reduction of myocardial infarction after emergency coronary artery bypass grafting for failed coronary angioplasty with use of a normothermic reperfusion cardioplegia protocol

Emergency coronary artery bypass grafting is necessary in 2.7% to 13.5% of patients undergoing elective percutaneous transluminal coronary angioplasty. Myocardial infarction develops in 11% to 49% of these patients, with 18% to 46% of infarcts resulting in new Q waves. Since February 1987 a revised protocol for myocardial preservation has been used in 19 patients undergoing emergency bypass grafting for failed angioplasty. Cardioplegia is induced with a normothermic blood cardioplegic solution. Multiple maintenance doses of cold (4 degrees C) blood cardioplegic solution are then delivered through the aortic root and vein grafts. Before the aortic crossclamp is removed, normothermic reperfusion cardioplegic solution is delivered through the aortic root and vein grafts. This group was compared with all patients undergoing emergency bypass grafting for failed angioplasty before February 1987. These 45 patients received cold induction of cardioplegic solution, multiple maintenance doses of cold cardioplegic solution, and no reperfusion cardioplegic solution. The prevalence of myocardial infarction in the group receiving cold cardioplegic solution was 65% versus 26% in the group receiving normothermic cardioplegic solution (p less than 0.007). Multivariate analysis identified the use of the normothermic cardioplegia protocol (p less than 0.005), nontotal occlusion of the angioplasty vessel (p less than 0.03), and presence of collateral flow to the angioplasty vessel (p less than 0.04) as being independently associated with absence of myocardial infarction.     

Effects of oxygenated cardioplegic solutions on myocardial aerobic metabolism.

Oxygenated cardioplegic solutions can deliver sufficient oxygen to support aerobic metabolism of heart tissue during cardiac arrest, but little is known about oxygen use after cardioplegic solution infusion. Exhaustion of myocardial oxygen stores after infusion of oxygenated crystalloid cardioplegic solution or Krebs-Henseleit buffer was measured in rat hearts. Since nicotinamide adenine dinucleotide accumulates when mitochondria become anaerobic, the epicardium was monitored during perfusion and ischemia. As ischemia progressed, nicotinamide adenine dinucleotide fluorescence increased, indicating exhaustion of oxygen. After buffer perfusion, at 37 degrees C, 50% of peak fluorescence was seen at 13 +/- 1 seconds and 90% at 37 +/- 3 seconds. Oxygenated cardioplegic solution increased these intervals to 57 +/- 6 and 114 +/- 9 seconds, respectively. Oxygenated cardioplegic solution at 10 degrees C increased the time to 50% fluorescence to 238 +/- 12 seconds and to 90% to 320 +/- 14 seconds. Differences between buffer and cardioplegic solution were less at 10 degrees C. Aerobic metabolism was completely abolished 6 minutes after infusion of 10 degrees C oxygenated cardioplegic solution. Maintenance of continuous aerobic metabolism during surgical cardiac arrest would require frequent administration of oxygenated crystalloid cardioplegic solution.     

A clinical comparison of potassium and magnesium-potassium crystalloid cardioplegia: metabolic considerations

Controlled metabolic studies were used to gauge the relative efficacy of two cardioplegic solutions in 28 patients (14 in each group) undergoing multiple coronary artery bypass grafts. A solution containing magnesium-potassium (Plegisol) was compared to a standard potassium crystalloid cardioplegic solution. Measurements of coronary blood flow, coronary vascular resistance, coronary arteriovenous oxygen difference, myocardial oxygen consumption and extraction, and myocardial lactate and potassium extraction and release were all measured in the isolated, vented, paced, beating heart, before and for 15 minutes after a one hour arrest interval during which time revascularization was completed. During cardioplegic administration, the infusion flow rate, myocardial oxygen consumption and extraction, and lactate and potassium release and uptake were noted. The results indicate that during cardioplegic administration, the total oxygen consumed for both potassium and magnesium-potassium solutions did not significantly differ. The flow rate of the Mg-K solution was significantly higher than that of the potassium solution alone (510 vs. 398 ml/min). There was no lactate production during Mg-K administration, but 0.13 mEq/min of lactate was produced while potassium crystalloid cardioplegia was given. During myocardial reperfusion, oxygen extraction was maintained near prearrest levels in both groups. The only significant difference noted between the potassium and magnesium-potassium solutions were the higher coronary blood flow and oxygen consumption immediately upon reperfusion in the Mg-K group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endothelial cell damage following crystalloid cardioplegic solution infusion. Scanning electron microscope study of coronary bypass grafts

Scanning electron microscope studies of coronary bypass grafts were carried out in six routine bypass operations. Infusion of the initial crystalloid cardioplegic medium into the aortic root after aortic cross clamping was performed in every case. In two cases, pieces of aorta below and above the cross-clamped site, le, having and not having had contact with the crystalloid cardioplegic medium, were studied. The endothelial lining of the veins showed normal structure following distention with blood. Following infusion with a crystalloid cardioplegic solution, the endothelial cells had almost completely vanished and the flow surface was composed mainly of collagen fibers. The aortic samples taken from below the cross-clamp site showed similar destruction of the endothelium that was observed in vein grafts after crystalloid cardioplegic solution infusion, whereas the aortic samples taken from above the cross-clamp site disclosed normal endothelium.     

Effect of oxygenated crystalloid cardioplegia on the functional and metabolic recovery of the isolated perfused rat heart

The use of an oxygenated crystalloid cardioplegic solution to improve myocardial preservation during elective cardiac arrest was evaluated with the isolated perfused rat heart used as a model. Experiments were conducted at 4 degrees C and 20 degrees C. The oxygen tension of the nonoxygenated and oxygenated cardioplegic solutions averaged 117 and 440 mm Hg, respectively. At 4 degrees C, the adenosine triphosphate content of hearts subjected to 120 minutes of oxygenated cardioplegia was significantly higher than that of the nonoxygenated cardioplegia group. However, functional recovery during reperfusion was similar for both groups. At 20 degrees C, the myocardial adenosine triphosphate concentration decreased at a significantly faster rate during ischemia in the group receiving nonoxygenated cardioplegia compared with the oxygenated cardioplegia group. Hearts subjected to 180 minutes of ischemia with oxygenated cardioplegia had a normal ultrastructural appearance whereas hearts subjected to 120 minutes of nonoxygenated cardioplegia showed severe ischemic damage. Myocardial functional recovery in the group receiving oxygenated cardioplegia exceeded that of the group receiving nonoxygenated cardioplegia. The use of myocardial adenosine triphosphate concentration at the end of the ischemic period to predict subsequent cardiac output, peak systolic pressure, and total myocardial work showed significant positive correlations.     

Anoxic hypothermic cardioplegia compared to intermittent anoxic fibrillatory cardiac arrest. Clinical and metabolic experience with 1080 patients.

Appropriately applied, hypothermic cardioplegia allows an excellent surgical setting that can significantly reduce the myocardial ischemic injury resulting from anoxia. One thousand eighty adult and pediatric patients underwent a variety of corrective cardial surgical procedures utilizing cold potassium cardioplegic solution injected into the coronary arteries via the aortic root. Myocardial septal temperature was maintained at 18--20 degrees during arrested time. This group of patients was compared to a group of 220 patients that underwent intermittent normothermic ischemic arrest to perform cardiac surgical procedures. Significant reduction in morbidity, mortality, perioperative myocardial infarction was noted in favor of the cardioplegic group. Metabolic coronary sinus blood analysis in the group undergoing surgery with cardioplegia revealed favorable changes in myocardial lactate and oxygen extraction.