Myocardial distribution of antegrade cold crystalloid and tepid blood cardioplegia

BACKGROUND: Tepid blood (TB) cardioplegia combines the improved rheologic characteristics and the augmented oxygen and substrate delivery of blood cardioplegia with the advantages of moderate hypothermia. In addition, the intramyocardial distribution of continuous TB cardioplegia may also be better than intermittent cold crystalloid (CC) cardioplegia. We sought to compare the distribution of TB and CC cardioplegia at varying infusion pressures. METHODS: In situ, isolated canine hearts were randomized to antegrade, continuous TB (28 degrees C, n = 8) or intermittent CC (n = 8) cardioplegia infused at 50, 75, and 100 mm Hg. The regional distribution of cardioplegia at each pressure was measured by 15-microm colored microspheres. Cardioplegia distribution was measured from three areas each of the right ventricle (inflow, outflow, and apex) and the left ventricle (anterior, lateral, and posterior). Left ventricular samples were subdivided into subepicardial, midmyocardial, and subendocardial. RESULTS: Delivery of cardioplegia to all areas of the right and left ventricles showed a linear pressure-flow relationship over the range of pressures tested. Right ventricular distribution was two-thirds of that to the left ventricle, and left ventricular subepicardial distribution was approximately one half of subendocardial flow in both groups at all delivery pressures. However, the subendocardial to subepicardial ratio was significantly greater with TB cardioplegia than with CC cardioplegia. Transmural right ventricular cardioplegia flow was comparable in both groups. In contrast, left ventricular distribution of CC cardioplegia was greater than TB cardioplegia at all three pressures tested. CONCLUSIONS: The pressure-flow relationship in both CC and TB cardioplegia is linear in both the right and left ventricular myocardium over clinically applicable delivery pressures. The distribution of cardioplegia to the right ventricle is not altered by increased pressure.     

Myocardial protection during antegrade versus retrograde cardioplegia

BACKGROUND: It has been suggested that the right ventricular myocardium is suboptimally protected during retrograde blood cardioplegia. METHODS: Twenty patients undergoing an elective coronary bypass procedure were randomized to receive antegrade or retrograde mild hypothermic blood cardioplegia. Transventricular differences in oxygen extraction, lactate production, and pH were monitored during aortic cross-clamping, and myocardial biopsy specimens were taken from both ventricles before cannulation and 15 minutes after aortic declamping for analysis of adenine nucleotides and their breakdown products. The extent of myocardial injury was estimated by monitoring postoperative leakage of troponin T and the MB isoenzyme of creatine kinase. Hemodynamic recovery and postoperative complications were noted. RESULTS: The preoperative characteristics of the two groups were similar. Oxygen extraction and lactate production in the right ventricular myocardium were higher in the retrograde group. In this group, the right ventricle also extracted more oxygen and produced more lactate and acid than did the left ventricle. Tissue levels of adenine nucleotides tended to decrease in both ventricles during operation, with no differences between them. The level of adenosine catabolites did increase somewhat in the right ventricular myocardium of the retrograde cardioplegia group after aortic declamping. There was a tendency for more prominent efflux of troponin T and the MB isoenzyme of creatine kinase in the retrograde group. Nevertheless, the postoperative course was uneventful in both groups. CONCLUSIONS: Retrograde mild hypothermic blood cardioplegia leads to metabolic changes compatible with right ventricular ischemia. Nevertheless, tissue levels of high-energy phosphates are well preserved, and the postoperative course seems to be unproblematic. Care should be taken when retrograde normothermic blood cardioplegia is provided for patients with right ventricular hypertrophy, poor right ventricular function, or severe preoperative myocardial ischemia.     

Crystalloid versus cold blood cardioplegia and cardiac troponin I release

BACKGROUND: Cardiac troponin I (CTnI) has been shown to be a marker of myocardial injury. The aim of this study was to compare antegrade crystalloid cardioplegia with antegrade cold blood cardioplegia with warm reperfusion using CTnI release as the criteria for evaluating the adequacy of myocardial protection. METHODS AND RESULTS: Seventy patients were randomly assigned to receive crystalloid or blood cardioplegia. CTnI concentrations were measured in serial venous blood samples drawn just before cardiopulmonary bypass and after aortic unclamping at 6, 9, 12, and 24 hours and daily thereafter for 5 days. ANOVA with repeated measures was performed to test the effect of the type of cardioplegia on CTnI release. The total amount of CTnI released was higher in the crystalloid cardioplegia group than in the blood cardioplegia group (11.2 +/- 8.9 versus 7.8 +/- 8.6 micrograms, P < .02). CTnI concentration was significantly higher in the crystalloid group than in the blood group in the samples drawn at hours 9 and 12. Three patients in each group had ECG evidence of perioperative myocardial infarction. Eight patients in the crystalloid group and five patients in the blood group had CTnI evidence of perioperative myocardial infarction. CTnI release was significantly lower in patients requiring no electrical defibrillation after aortic unclamping. CONCLUSIONS: Cold blood cardioplegia followed by warm reperfusion is beneficial in an unselected group of patients with a preserved left ventricular function undergoing an elective first coronary artery bypass grafting. CTnI allowed the diagnosis of small perioperative necrotic myocardial areas. The need for electrical defibrillation after aortic unclamping was related to a higher release of CTnI. A further study is necessary to determine whether this technique was beneficial because of cold blood cardioplegia, warm reperfusion, or both.     

A generalized consideration of myocardial preservation with cold crystalloid versus warm blood cardioplegia in heart valve replacement

The spontaneous as well as mitogen-induced in vitro production of interleukin-6 (IL-6) was studied in cultures of peripheral blood mononuclear cells (PBMC) from 14 children with marginal protein-energy malnutrition, 43 children with definite protein-energy malnutrition and 38 eutrophic controls of similar age, sex, race and socioeconomical condition. PBMC were cultured without added mitogen or stimulated with either lipopolysaccharide (LPS) or phytohemagglutinin (PHA). After 48 h incubation, cell-free culture supernatants were collected and stored at -70 degrees C. The amount of IL-6 in the supernatants was determined by a specific bioassay based on the proliferation of B9 hybridoma cells using human rIL-6 as standard. The mean level of IL-6 was significantly increased in supernatants from nonstimulated PBMC cultures from definitely malnourished children as compared with that observed in those of the controls. Stimulation with either LPS or PHA induced a rise in cytokine bioactivity in the supernatants of PBMC cultures from the different nutritional groups tested. Interestingly, IL-6 was significantly increased in the supernatants of PHA-stimulated cultures from malnourished children as compared with those of the controls.     

Ischemic preconditioning prior to myocardial protection with cold blood cardioplegia in coronary surgery

OBJECTIVE: Encouraging results on myocardial preconditioning in experimental models of infarction, stunning or prolonged ischemia raise the question whether preconditioning techniques may enhance conventional cardioplegic protection used for routine coronary surgery. METHODS: A prospective clinical trial was conducted to investigate the effect of additional ischemic normothermic preconditioning prior to cardioplegic arrest applying cold blood cardioplegia in patients scheduled for routine coronary surgery (3 vessel disease, left ventricular ejection fraction > 50%). Two cross clamp periods of 5 min with the hearts beating in sinus rhythm were applied followed by 10 min of reperfusion, each (n = 7, group I). Inducing moderate hypothermia cold blood cardioplegia was delivered antegradely. In control groups, cold intermittent blood cardioplegia (n = 7, group II) was used alone. Coronary sinus effluents were analyzed for release of creatine kinase (CK), CK-MB, lactate, and troponin T at 1, 3, 6, 9, and 12 h. In addition, postoperative catecholamine requirements were monitored. RESULTS: The procedure was tolerated well, and no perioperative myocardial infarction in any of the groups studied occurred. Concentrations of lactate tended to be higher in group I, but this difference was not significant. In addition, no significant differences for concentrations of CK, CK-MB, and troponin T were found. Following ischemic preconditioning an increased dosage of dopamine was required within the first 12 h postoperatively (group I: 2.63 +/- 1.44 microg/kg/min, group II: 0.89 +/- 1.06 microg/kg/min). CONCLUSIONS: Combining ischemic preconditioning and cardioplegic protection with cold blood cardioplegia does not appear to ameliorate myocardial protection when compared to cardioplegic protection applying cold blood cardioplegia alone. Inversely, contractile function seemed to be impaired when applying this protocol of ischemic preconditioning.     

Recovery after prolonged cross-clamping tepid blood cardioplegia: report of a case

Despite a prolonged repetitive aortic cross-clamp time of 411 min, a patient who suffered a left ventricular rupture after undergoing mitral valve replacement following mitral valvuloplasty and Maze procedure recovered without any permanent residual left ventricular dysfunction. During the aortic cross-clamping we used tepid blood cardioplegia for myocardial protection. This case report serves to demonstrate the potential of tepid blood cardioplegia as an effective method of myocardial protection.     

Ultrastructural assessment of the myocardium receiving intermittent antegrade warm blood cardioplegia

PURPOSE: We compared the in vitro susceptibility of gram-positive bacteria to ciprofloxacin and ofloxacin using human corneal susceptibility levels. METHODS: The concentrations of ciprofloxacin and ofloxacin that can be attained in 99% of human corneas (Cornea99) after topical administration were calculated statistically from reported data. The minimal inhibitory concentrations (MICs) were determined for 95 corneal isolates of gram-positive bacteria (51 Staphylococcus aureus, 16 Streptococcus pneumoniae, 16 Streptococcus viridans group, and 12 coagulase-negative staphylococci). Susceptibility was interpreted by comparing the MICs with the respective Cornea99 for each antibiotic. Time-kill studies of representative gram-positive bacteria were tested using the Cornea99 and the maximal corneal concentrations reported for ciprofloxacin and ofloxacin. RESULTS: The Cornea99 of ciprofloxacin and ofloxacin were calculated to be 3.57 microg/ml (n = 22) and 2.22 microg/ml (n = 20), respectively. The reported mean corneal concentrations of ciprofloxacin (6.90 +/- 6.20 microg/ml) and ofloxacin (5.71 +/- 6.15 microg/ml) were comparable (p = 0.54). All gram-positive bacteria were equally susceptible to ciprofloxacin and ofloxacin (p = 0.54) based on the Cornea99. The time-kill studies determined that 8-24 h were required for both ciprofloxacin and ofloxacin to reach bactericidal levels. CONCLUSION: Ciprofloxacin and ofloxacin demonstrated comparable penetration into the cornea and provided equivalent in vitro efficacy against representative gram-positive bacteria. Time-kill studies indicated that 8-24 h of continual corneal concentrations of ciprofloxacin and ofloxacin were necessary in this study to reduce susceptible gram-positive bacteria by 99.9%.     

Time dependence of endothelium-mediated vasodilation by intermittent antegrade warm blood cardioplegia

BACKGROUND: The technique of intermittent antegrade warm blood cardioplegia (IAWBC) exposes the heart to brief periods of normothermic ischemia. This may impair endothelial function in coronary arteries. METHODS: Three cardioplegic technique were tested in porcine hearts arrested for 32 to 36 minutes and reperfused for 30 minutes: IAWBC, antegrade cold blood cardioplegia (ACBC), and antegrade cold crystalloid cardioplegia (ACCC). In the hearts arrested with IAWBC, three different intervals of ischemia were used: three 10-minute intervals (IAWBC1), two 15-minute intervals (IAWBC2), and one 30-minute interval (IAWBC3). Rings from the coronary arteries were used to evaluate in vitro the contractile responses to U46619 and the relaxant responses to bradykinin, A23187, and sodium nitroprusside. RESULTS: All six groups (treatment groups and control group) displayed similar responses to U46619 (30 nmol/L) and nitroprusside. In the IAWBC1, IAWBC2, AND ACBC groups, endothelium-dependent relaxations to bradykinin and A23187 were preserved compared with controls, whereas those of the ACCC and IAWBC3 groups were significantly impaired (bradykinin: control, 8.72 +/- 0.07; IAWBC1, 8.73 +/- 0.03; IAWBC2, 8.65 +/- 0.05; IAWBC3, 8.30 +/- 0.07 [p < 0.05]; ACBC, 8.50 +/- 0.03; ACCC, 8.25 +/- 0.09 [p < 0.05]; A23187: control, 7.07 +/- 0.08; IAWBC1, 7.07 +/- 0.06; IAWBC2, 7.04 +/- 0.03; IAWBC3, 6.64 +/- 0.01 [p < 0.05]; ACBC, 6.80 +/- 0.05; ACCC, 6.60 +/- 0.08 [p < 0.05]; nitroprusside: control, 6.19 +/- 0.1; IAWBC1, 6.19 +/- 0.07; IAWBC2, 6.03 +/- 0.03; IAWBC3, 6.08 +/- 0.05; ACBC, 6.04 +/- 0.2; ACCC, 6.05 +/- 0.03; all values are expressed as the negative logarithm of the concentration producing 50% of the maximal response). CONCLUSIONS: Myocardial preservation with IAWBC with ischemic intervals of 15 minutes or shorter does not alter the endothelium-dependent relaxation to bradykinin or A23187 in porcine coronary arteries, but these responses are significantly impaired by ACCC and IAWBC with an ischemic interval of 30 minutes.     

Effects of cold and warm blood cardioplegia assessed by myocardial pH and release of metabolic markers

The optimal temperature of blood cardioplegia remains controversial. Interstitial myocardial pH was monitored online with a probe that was inserted in the anterior wall of the left ventricle. Venous pH, lactate production, and creatine kinase and troponin T release were measured in coronary sinus blood obtained in 14 dogs after ischemic arrest periods of 5, 10, 20, and 40 minutes with warm (n = 7; mean myocardial temperature, 35 degrees +/- 2 degrees C) and cold (n = 7; mean myocardial temperature, 12 degrees +/- 1 degree C) blood cardioplegic protection. Blood cardioplegic solution was delivered at a rate of 100 mL/min during the 10 minutes between each ischemic arrest. The interstitial myocardial pH decreased significantly (p < 0.05) from 7.1 +/- 0.3 to 6.53 +/- 0.3 after ischemia in animals perfused with warm blood cardioplegia and from 7.04 +/- 0.3 to 6.64 +/- 0.1 in those receiving cold blood cardioplegic protection; however, the difference between the groups was not significant (p > 0.05). Lactate production and creatine kinase and troponin T release increased significantly after ischemia, but there was no difference in the changes between the warm and cold blood cardioplegia groups. In conclusion, ischemia caused significant changes in all variables measured, and these changes were directly proportional to the duration of ischemia. However, there was no significant difference (p > 0.05) in the myocardial metabolic changes between the warm and cold blood cardioplegia groups in terms of the duration of ischemic arrest studied.(ABSTRACT TRUNCATED AT 250 WORDS)     

Recovery of postischemic contractile function is depressed by antegrade warm continuous blood cardioplegia

Drug-abusing (n = 25) and nonusing (n = 55) pregnant women from a publicly supported prenatal clinic were tested for level of social support and of pregnancy anxiety during the last half of pregnancy. Differences found between the groups were fewer than expected. Drug abusers did not differ from nonusers in overall level of social support or in Appraisal, Belonging, or Tangible subscales. Abusers were found to report lower levels of self esteem; lower self esteem was predicted by drug abuse, having more children and lower socioeconomic status. Drug abusers did not differ from nonusers in their overall feelings of pregnancy anxiety, but they did indicate higher fears for themselves and for the baby, and there was a tendency for higher depression and withdrawal.     

Cardiac Troponin T to evaluate myocardial protection via intermittent cold blood or continuous warm blood cardioplegia in coronary artery bypass grafting

The effects of a speech-coding strategy of cochlear implant (CI) on cortical activity were evaluated using positron emission tomography. The CIs used in the present study were those of a 22-channel system using the Multipeak speech-coding strategy (MPEAK) and the spectral peak strategy (SPEAK). On comparing the 2 groups, it was found that the speech-tracking performance was significantly higher in the SPEAK group than in the MPEAK group. Regional cerebral blood flow (rCBF) was measured during the silent resting, noise stimulus and speech stimulus periods. The increase in rCBF was localized mainly in the primary auditory area during the noise stimulus period. The increase in rCBF in the auditory association area during the speech stimulus period was stronger in the SPEAK group than in the MPEAK group. This finding suggests that the SPEAK strategy activates more speech processing neuronal networks in the auditory association area than the MPEAK strategy.     

Determination of cardiac troponin I forms in the blood of patients with acute myocardial infarction and patients receiving crystalloid or cold blood cardioplegia

To determine the forms of cardiac troponin I (cTnI) circulating in the bloodstream of patients with acute myocardial infarction (AMI) and patients receiving a cardioplegia during heart surgery, we developed three immunoenzymatic sandwich assays. The first assay involves the combination of two monoclonal antibodies (mAbs) specific for human cTnI. The second assay involves the combination of a mAb specific for troponin C (TnC) and an anti-cTnI mAb. The third assay was a combination of a mAb specific for human cardiac troponin T (cTnT) and an anti-cTnI mAb. Fifteen serum samples from patients with AMI, 10 serum samples from patients receiving crystalloid cardioplegia during heart surgery, and 10 serum samples from patients receiving cold blood cardioplegia during heart surgery were assayed by the three two-site immunoassays. We confirmed that cTnI circulates not only in free form but also complexed with the other troponin components (TnC and cTnT). We showed that the predominant form in blood is the cTnI-TnC binary complex (IC). Free cTnI, the cTnI-cTnT binary complex, and the cTnT-cTnI-TnC ternary complex were seldom present, and when present, were in small quantities compared with the binary complex IC. Similar results were obtained in both patient populations studied. These observations are essential for the development of new immunoassays with improved clinical sensitivity and for the selection of an appropriate cTnI primary calibrator.     

The effects of using a leukocyte removal filter during cold blood cardioplegia

During myocardial ischemia, neutrophils and platelets exert negative effects on the myocardium. In this study, we used a leukocyte removal filter during cardioplegia, and investigated its effect on myocardial damage during reperfusion by measuring the plasma levels of granulocyte components, platelet components, and cardiac enzymes [creatinine phosphokinase (CK) and creatinine phosphokinase myocardial band (CK-MB)] in 24 patients who underwent cardiopulmonary bypass. The patients were divided into two groups of 12 according to whether or not a filter was placed in the cardioplegic route. Blood samples were drawn directly from the coronary sinus before aortic cross clamping, and at 1, 5, and 15 min after declamping. Group F, which had the filter, showed better cardiac enzyme and lipid peroxidation results than group N, which did not. The results of this study suggest that the application of a filter during cold blood cardioplegia may reduce myocardial damage.     

Myocardial protection in normal and hypoxically stressed neonatal hearts: the superiority of blood versus crystalloid cardioplegia

OBJECTIVES: Blood cardioplegia predominates in the adult because it provides superior myocardial protection, especially in the ischemically stressed heart. However, the superiority of blood over crystalloid cardioplegia in the pediatric population is unproved. Furthermore, because many pediatric hearts undergo a preoperative stress such as hypoxia, it is important to compare the different methods of protection in both normal and hypoxic hearts. METHODS: Twenty neonatal piglets were supported by cardiopulmonary bypass and subjected to 70 minutes of cardioplegic arrest. Of 10 nonhypoxic hearts, five (group 1) were protected with blood cardioplegia and five (group 2) with crystalloid cardioplegia (St. Thomas' Hospital solution). Ten other piglets underwent 60 minutes of ventilator hypoxia (inspired oxygen concentration 8% to 10%) before cardioplegic arrest. Five (group 3) were then protected with blood cardioplegia and the other five (group 4) with crystalloid cardioplegia. Myocardial function was assessed by means of pressure volume loops and expressed as a percentage of control. Coronary vascular resistance was measured with each infusion of cardioplegic solution. RESULTS: No difference was noted between blood (group 1) or crystalloid cardioplegia (group 2) in nonhypoxic hearts regarding systolic function (end-systolic elastance 104% vs 103%), diastolic stiffness (156% vs 159%), preload recruitable stroke work (102% vs 101%), or myocardial tissue edema (78.9% vs 78.9%). Conversely, in hearts subjected to a hypoxic stress, blood cardioplegia (group 3) provided better protection than crystalloid cardioplegia (group 4) by preserving systolic function (end-systolic elastance 106% vs 40%; p < 0.05) and preload recruitable stroke work (103% vs 40%; p < 0.05); reducing diastolic stiffness (153% vs 240%; p < 0.05) and myocardial tissue edema (79.6% vs 80.1%); and preserving vascular function, as evidenced by unaltered coronary vascular resistance (p < 0.05). CONCLUSION: This study demonstrates that (1) blood or crystalloid cardioplegia is cardioprotective in hearts not compromised by preoperative hypoxia and (2) blood cardioplegia is superior to crystalloid cardioplegia in hearts subjected to the preoperative stress of acute hypoxia.     

Propranolol therapy in patients undergoing myocardial revascularization

The records of 185 consecutive patients having myocardial revascularization were reviewed with regard to preoperative administration of propranolol and intraoperative or postoperative complications. Tachycardia and hypertension before cardiopulmonary bypass were slightly more common in patients never taking propranolol or those who had discontinued it for more than 48 hours before operation. There was no statistically significant difference in the incidence of postbypass hypotension among patients who took propranolol within 24 hours of operation, those who discontinued it more than 24 hours before operation, and those who never took the drug. Operative mortality was not significantly different among patients who received propranolol within 48 hours of operation (3%), those who never took it and those who discontinued it more than 48 hours before operation (4%). Early in the series, five patients had an acute myocardial infarction within 48 hours after routine preoperative withdrawal of propranolol. Because complete withdrawal of propranolol in patients with unstable angina pectoris may lead to acute myocardial infarction, we recommend gradual withdrawal of the drug during 48 hours before operation. If this is not possible because anginal pain recurs or intensifies, then reduced doses may be given safely up to 10 hours before revascularization, provided that the patient is a satisfactory candidate for bypass and that adequate myocardial revascularization can be accomplished.     

Improvement in exercise performance after unsuccessful myocardial revascularization

Two types of mechanosensitive units were found in the parenchyma of the rat mammary gland (SA and RA). Most of SA units had a spontaneous activity 1-3/sec. and responded to an abrupt displacement with a decline in the activity for 5-10 sec. RA had no such a response. The relation between average firing rate and displacement velocity at a constant displacement amplitude was linear for both SA and RA. RA however had the velocity threshold higher than SA. The number and frequency of SA afferent impulses decreased at a repeated stimulation. Electron microscopy revealed that free nerve endings correspond to SA and RA.     

A study of the 30 minutes following reperfusion after crystalloid and cold blood cardioplegia by enzymatic and metabolic analysis of coronary blood flow

Post-ischemic reperfusion phenomena were studied in two methods of myocardial protection: crystalloid cardioplegia (St Thomas n(o) 2) and cold blood cardioplegia (Buckherg) during cardiopulmonary bypass for human myocardial revascularisation. Myocardial protection was assessed on the course of hemodynamic parameters, reperfusion arrhythmias and biochemical analysis of the coronary flow after cross-clamp removal: creatine phosphokinase (CPK-MB) and nucleotide adenine metabolites (adenosine, inosine, hypoxanthine, xanthine and uric acid). The study was performed in two groups of 14 patients. Hemodynamic conditions were similar in both groups during reperfusion in order to avoid different coronary flow. Under these conditions, myocardial protection by cold blood cardioplegia reduced reperfusion arrhythmias, and resulted in a loss of CPK-MB release. Furthermore, cold blood cardioplegia provided protection of myocardial energy metabolism by reducing the loss of metabolites, purine bases and oxypurine bases into the coronary sinus. Our results also show that hypoxanthine is probably the final product of ATP degradation in human myocardial tissue.