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Nitecapone as an additive to crystalloid cardioplegia in patients who had coronary artery bypass grafting
Nitecapone as an Additive to Crystalloid Cardioplegia in Patients Who Had Coronary Artery Bypass Grafting Antti E. Vento, MD, Juha Aittoma¨ki, MD, Kalervo A. Verkkala, MD, PhD, Lasse J. Heikkila¨, MD, PhD, Jarmo A. Salo, MD, PhD, Jorma Sipponen, MD, PhD, and O. Juhani Ra¨mo¨, MD, PhD Department of Thoracic and Cardiovascular Surgery, Helsinki University Central Hospital, Helsinki, Finland
Background. Nitecapone has been shown to have a protective effect against ischemia-reperfusion injury in experimental heart transplantation and in Langendorff preparations. This prospective, randomized study assessed the effects of nitecapone in patients who had coronary artery bypass grafting. Methods. Thirty patients with normal myocardial function were randomly divided into control patients (n ⴝ 15), who received crystalloid (Plegisol) cardioplegia, and nitecapone patients, who received nitecapone in a 50 M solution (n ⴝ 15) in Plegisol. Cardioplegia was administered as an initial dose of 15 mL/kg of body mass after cross-clamping and 2 mL/kg every 15 minutes. Simultaneous coronary sinus and aortic blood samples, and myocardial biopsies were taken at 1, 5, and 10 minutes after unclamping. Hemodynamics were measured invasively for 24 hours and with transesophageal echocardiography for 3 hours after cardiopulmonary bypass.
Results. There were no adverse effects. The incidence of ventricular arrhythmias was significantly lower in the treatment group during the recovery period (p ⴝ 0.02). Cardiac output and stroke volume did not differ significantly between the groups. The conjugated dienes gradient between the aorta and the coronary sinus increased significantly during the first minute of reperfusion in the control group (p ⴝ 0.02) compared with the nitecapone group. Myeloperoxidase activity in myocardial biopsies was higher in the control group (2.3 times higher at 5 minutes and 3.2 times higher at 10 minutes) than in the nitecapone group (p ⴝ 0.13). Conclusions. Nitecapone did not exert any significant hemodynamic effects in patients with normal ejection fraction.
I
Nitecapone’s toxicology has been studied by OrionFarmos Corporation (Certificate of Analysis 1995, Analytical Department, Orion-Farmos Corporation, Espoo, Finland). In addition, before the present human studies NC has also been tested in volunteers without any effect on hemodynamics itself [10]. Despite its potentially beneficial properties for abating ischemia-reperfusion injury, it has not yet been studied in a clinical setting. This study was designed to clarify the effects of NC on myocardial metabolism and functional recovery by adding NC to a cold crystalloid cardioplegia in patients with normal left ventricular function who had coronary artery bypass grafting.
schemia-reperfusion injury impairs myocardial recovery after cross-clamping during heart operations by causing arrhythmias and decreases myocardial function [1]. Myocardial protection is the key element to preventing this injury, and various methods and molecules have been examined to discover a drug capable of preserving the myocardium [2, 3]. In vitro, nitecapone (NC) (3-[3,4-dihydroxy-5-nitrophenyl]methylene-2,4-pentanedione) is a molecule with good antioxidative properties [4, 5]. It has also been tested in Langendorff preparations [6, 7], in a heterotopic transplantation model [8], and in pigs using a model resembling clinical heart ischemia in our own laboratory [9]. Nitecapone has been shown to recycle ascorbate and alfatocopherol [6, 7], to scavenge free radicals [4, 5], and to inhibit xanthine oxidase enzyme [5]. In addition, recent findings from our laboratory showed that one of the most important mechanisms is an inhibition of myeloperoxidase, indicating neutrophil inhibition.
Accepted for publication Feb 16, 1999. Address reprint requests to Dr Ra¨mo¨, Department of Thoracic and Cardiovascular Surgery, Helsinki University Central Hospital, Haartmaninkatu 4, 00290 Helsinki, Finland.
© 1999 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
(Ann Thorac Surg 1999;68:413–20) © 1999 by The Society of Thoracic Surgeons
Patients and Methods Thirty men who had coronary artery bypass grafting were prospectively entered into this study, which was approved by the ethics committee of our hospital and the Ministry of Health of Finland. All patients gave their informed consent. The patients were randomly assigned to receive nitecapone (n ⫽ 15) or to serve as controls (n ⫽ 15). The surgical procedures consisted of coronary artery bypass grafting alone with venous or arterial grafts or both. 0003-4975/99/$20.00 PII S0003-4975(99)00514-7
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Anesthesia Patients were premedicated with lorazepam. Patients with a normal morning dosage of long-acting nitrates, beta- or calcium-channel blockers received their medication. Anesthesia was induced with 30 g/kg fentanylcitrate and 0.1 mg/kg midazolam and maintained with 0.3 g/kg per minute fentanylcitrate and 0.8 g/kg per minute midazolam infusions.
Operative Technique Patients were ventilated with a Siemens Servo Volume Ventilator (Siemens-Elema AB, Solna, Sweden). The aorta and right atrium were cannulated for cardiopulmonary bypass (CPB). Left ventricular pressure was measured with a 4F pediatric Swan-Ganz catheter (Arrow AI-07122; Arrow International Inc, Reading, PA) and a single-use transducer (Deltran II; Utah Medical Co, Midvale, UT). The catheter was introduced into the left ventricle through the right superior pulmonary vein and the mitral valve. A catheter was inserted into the coronary sinus through the right atrium with a 14F coronary sinus cannula (Research Medical Inc, Salt Lake City, UT). Cardiopulmonary bypass equipment consisted of a roller pump, a membrane oxygenator, and a cardiotomy reservoir. The extracorporeal circuit was primed with 2,000 mL of a crystalloid solution containing 5,000 IU of heparin. Before cannulation, patients received heparin at a dose of 3 mg/kg of body weight. Bypass was conducted at a flow rate of 2.0 to 2.4 L/m2 and mean arterial pressure was maintained at 40 to 80 mm Hg with nonpulsatile perfusion in mild hypothermia (30° to 32°C as a nasopharyngeal temperature). The rectal temperature was rewarmed to a minimum of 34°C and the nasopharyngeal temperature to 36° to 37°C before weaning from the CPB. The fraction of inspired oxygen was 100% during the perfusion and mixed venous saturation (SVO2) was maintained at over 75%. Lung ventilation was discontinued after the beginning of the perfusion and was subsequently resumed after declamping. After the discontinuation of CPB heparin was neutralized by using protamine sulfate. The duration of the reperfusion period before weaning from CPB was 30% of the aortic crossclamping time. An initial dose of 15 mL/kg of body weight of 4°C Plegisol solution was delivered into the aortic root in the control group or with 50 M of nitecapone in the treatment group through the aortic root cannula after application of the aortic clamp. Two milliliters of cardioplegic solution per kilogram of body weight was reinfused every 15 minutes and if ventricular fibrillation was present. Nitecapone was a gift from Orion-Pharma (Espoo, Finland) and was provided in the form of a sterile powder which was dissolved in sodium bicarbonate (NaHCO3) and then added to Plegisol solution.
Hemodynamic Measurements Invasive hemodynamics were measured through an 8F Swan-Ganz catheter (Baxter Health Corp, Santa Ana,
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CA) using the AS\3 monitor (Datex, Helsinki, Finland), radial artery pressure, and through a left ventricular pressure catheter. Hemodynamic variables were recorded after the induction of anesthesia and after the insertion of the left ventricular catheter before venous and coronary sinus cannulation. The hemodynamic surveillance was continued after declamping, sternum closure, and at 2, 3, 6, and 24 hours after CPB. The left ventricular pressure catheter was pulled back into the left atrium after 3 hours of CPB and removed after the final measurements 24 hours after CPB. Left ventricular internal diameter was measured at the midpapillary level with a 5-MHz biplane transesophageal echocardiography probe (Aloka SSD-880; Aloka Co, Tokyo, Japan). Left ventricular function values were calculated in a blinded fashion offline on videotape. The measurements were made at six different time points. The first two measurements were, after the induction of anesthesia and immediately before cannulation of the great vessels, and the last four were after decannulation, and at 1, 2, and 3 hours after CPB. At the first measurement point, left ventricular pressure was estimated by systolic arterial pressure. Three pressure points were used to calculate left ventricular elastance and enddiastolic volume recruitable stroke work. Ejection fraction, fractional area change, and stroke work (SW) were calculated using the baseline values.
Blood Sampling Blood samples were obtained from the coronary sinus and aorta before the onset of CPB, and at 1, 5, and 10 minutes after declamping. Blood specimens were drawn with a 20-mL syringe and collected into heparinized tubes which were immediately capped and stored in ice-cold water. The samples were centrifuged in a temperature controlled centrifuge (Minifuge, RF, HeraeusChrist GmbH, Hanau, Germany) at 3,000 ⫻ g at a temperature of 4°C, for 15 minutes. The supernatant was placed in Eppendorff tubes and kept at ⫺70°C until assayed. Myocardial biopsies were taken with biopsy needle (Gallini, Mirandola, Italy) from the wall of the left ventricle for glutathione, superoxide dismutase, ubiquinone, and myeloperoxidase measurements at the same period of time. Biopsy samples were immediately frozen and stored at ⫺70°C until assayed.
Biochemistry Myeloperoxidase activity was determined using a modification of the method described by Suzuki and associates [11] in which the enzyme catalyzes the oxidation of 3,3⬘, 5,5⬘-tetramethylbenzidine by H2O2 to yield a blue chromogen with a maximum wavelength of 655 nm. Superoxide dismutase activity was determined using the method described by Laihia and colleagues [12] in which the xanthine or xanthine oxidase-dependent chemiluminescence was enhanced by both lucinogenin and linoleate. Glutathione content was estimated by the method described by Saville [13].
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Table 1. Patient and Operative Data Parameter Age (y) Preoperative ejection fraction Degree of coronary disease ⬎ 50% Left coronary main stem Left anterior descending artery Left circumflex artery Right coronary artery Previous myocardial infarction Number of bypasses Cross-clamp time (min) Perfusion time (min)
Control Group
Nitecapone Group
59.7 ⫾ 2.1 55.2 ⫾ 3.5
60.5 ⫾ 2.6 56.9 ⫾ 2.3
1 15 12 12 6 3.1 ⫾ 0.19 57.6 ⫾ 4.1 92.8 ⫾ 5.2
2 14 12 12 10 3.4 ⫾ 0.16 62.0 ⫾ 4.7 98.5 ⫾ 5.8
There were no statistically significant differences between the groups.
Ubiquinone concentration was analyzed using standard high pressure liquid chromatography (HPLC) procedures with ultraviolet detection [14]. Low-density lipoprotein (LDL) oxidation products and conjugated dienes (LDL-DC) were measured as previously described by Vasankari and coworkers [15]. Lowdensity lipoprotein oxidation was estimated by the baseline level of diene conjugation in the lipid fraction of LDL (LDL-BDC). Low-density lipoprotein–total peroxyl radical trapping antioxidant potential (LDL-TRAP) was estimated in vitro by the plasma potency in resisting 2,2’ azobis (2-amino propane) hydrochloride (ABAP)-induced peroxidation. A solution of 0.45 mL of 0.1 mmol sodium phosphate buffer, pH 7.4, containing 0.9% NaCl, 0.02 mL of 120 mmol linoleic acid, 0.05 mL of luminol (0.5 mg/mL), and 100-L low-density lipoprotein samples was mixed in the cuvette and the assay was initiated with 0.05 mL of ABAP (83 mg/mL). Chemiluminescence in duplicate cuvettes at 37°C was measured until a peak value for each sample was detected. Peroxyl radical trapping capacity was defined by the half-peak time point. ␣-tocopherol analogue served as a standard radical scavenger. To obtain an estimation of the relative antioxidant power of given LDL preparations, the results were expressed in relation to the cholesterol concentration of the preparations (LDLTRAP-CHOL) [16].
Statistical Analysis Patients were randomizly assigned to treatment group. Data are expressed as the mean ⫾ the standard error of Table 2. Arrhythmias Type of Arrhythmia Ventricular arrhythmia Postoperative day 1 Postoperative day 2 After postoperative day 3 Total Atrial fibrillation
Control Group
Nitecapone Group
6 5 5 9 3
2 0 0 2 4
p 0.21
0.02 NS
Fig 1. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Heart rate (HR) was increased in both groups and was lower in the nitecapone (NC) group than in the control (C) group (p ⫽ 0.06). (ind ⫽ induction of anesthesia).
mean. The 2 test was used for clinical variables. Differences between the treatment groups in hemodynamics were statistically evaluated using repeated measures analysis of variance, which included the baseline value as a covariate. The biochemical parameters (gradients) were analyzed by the Wilcoxon rank sum test at each timepoint. Statistical calculations were carried out with SAS software (SAS Institute, Cary, NC). A p value less than 0.05 was considered statistically significant.
Results Patients from the two groups did not differ significantly with respect to age, preoperative ejection fraction, degree of coronary artery disease, or the operation as shown in Table 1. There were no technical complications related to myocardial biopsies.
Hemodynamics There were no significant differences in the use of inotropic agents between the groups. The incidence of atrial fibrillation (Table 2) was almost the same in both groups, but the incidence of ventricular arrhythmias (extrasystoles) was four times greater in the control group than in the NC group ( p ⫽ 0.02). Heart rate remained at a lower level in the NC group throughout the follow-up time (Fig 1). Mean arterial pressure values were stable during the follow-up period and showed no significant differences between the two groups (Fig 2). Cardiac output (CO) increased up to 60% in the NC group but only 43% in the control group after 24 hours of CPB (Fig 3) (p ⫽ 0.75). Cardiac index (CI) values naturally showed a similar trend during the follow-up period (Fig 4) (p ⫽ 0.67). Stroke volume values decreased in both groups during the first 3 hours, but after 6 hours the values increased
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Fig 2. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Mean arterial pressure (MAP) was over 60 mm Hg in both groups (p ⫽ 0.66). Abbreviations as in Figure 1.
Fig 4. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Cardiac Index (CI) reflected better myocardial recovery at 6 and 24 hours after CPB (p ⫽ 0.67). Abbreviations as in Figure 1.
more in the NC group than in the control group (Fig 5) ( p ⫽ 0.37). The filling pressures, central venous pressure, pulmonary artery diastolic pressure, and pulmonary capillary wedge pressure, were lower in the NC-group than in the control group. (Figs 6 – 8). Systemic vascular resistance and pulmonary vascular resistance values were not significantly different between the groups. Data not shown here.
after the termination of CPB. After that stroke work increased close to the preoperative level. Ejection fraction and fractional area change values showed a curve almost parallel to the X-axis without any significant changes at any time points. Elastance values in the NC group were higher up to 1 hour after CPB (Table 3).
Biochemistry
The myocardial function was examined during the operation with esophageal echocardiography. Stroke work decreased in both groups after induction up to 1 hour
Creatine kinase-MB values showed no significant differences between the groups on the first and the second postoperative days. Plasma creatinine values did not differ between the groups. Coronary sinus ubiquinone values were decreased in both groups at both 5 and 10 minutes after declamping.
Fig 3. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Cardiac output (CO) reflected better myocardial recovery at 6 and 24 hours after CPB (p ⫽ 0.75). Abbreviations as in Figure 1.
Fig 5. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Stroke volume (SV) reflected better myocardial recovery at 6 and 24 hours after CPB (p ⫽ 0.37). Abbreviations as in Figure 1.
Transesophageal Echocardiography
PLASMA SAMPLES.
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Fig 6. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Central venous pressure (CVP) was similarly increased in both groups after CPB (p ⫽ 0.82). Abbreviations as in Figure 1.
Fig 8. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Pulmonary capillary wedge pressure (PCWP) showed minor differences between the groups (p ⫽ 0.26). Abbreviations as in Figure 1.
Change in ubiquinone (gradient between coronary sinus and aorta) was higher in the NC group (Table 4) ( p ⫽ 0.59). Change in LDL-TRAP gradient was higher at 5 minutes in the NC group ( p ⬍ 0.05) after declamping but decreased in the control group as shown in Figure 9. Also, change in LDL-TRAP-CHOL values were increased in the NC group, whereas the changes were minor in the control group (Table 4) ( p ⫽ 0.20). Change in LDL-DC (p ⫽ 0.02) and LDL-DC-CHOL (LDL-conjugated dienes in relation to the cholesterol concentration of the preparations) ( p ⬍ 0.05) were increased in the control group more after declamping than in the NC group, but thereafter decreased in the control group to a level below that of the NC group (Table 4).
Lactate concentrations were at their highest in both groups at 1 minute after declamping. As the reperfusion progressed, the concentration diminished gradually in the coronary sinus in both groups. The groups did not differ from each other significantly (Table 4). The glutathione level remained constant in the NC group but decreased in the control group during the first few minutes of reperfusion (Table 4) ( p ⫽ 0.34). Similarly, superoxide dismutase showed increasing values in the NC group ( p ⫽ 0.26) but decreased in the control group (Table 4).
MYOCARDIAL BIOPSIES.
Myeloperoxidase was determined in myocardial biopsies to evaluate the infiltration of leukocytes, ie, the activation of leukocytes during the first few minutes of reperfusion. Myeloperoxidase activity increased in the control group at 5 and 10 minutes of reperfusion, whereas it decreased in the NC group at the same time points (Fig 10). Myeloperoxidase activity was 3.2 times higher after 10 minutes of declamping in the control group than in the NC group ( p ⫽ 0.13).
GRANULOCYTE INFILTRATION.
Comment
Fig 7. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Pulmonary artery diastolic pressure (PAPD) showed no major differences between the groups (p ⫽ 0.05). Abbreviations as in Figure 1.
Postoperative ventricular arrhythmias are dangerous to myocardial function [1]. It has been shown that NC protects grafts after experimental heart transplantation in rats after 2 hours of ischemia [8]. The grafts treated with NC had fewer arrhythmias, and more grafts began to beat than in the control group. Atrial fibrillation frequency was almost the same in both groups, but a lower frequency of ventricular arrhythmic disorders could also be shown by the present study. Oxygen-derived free radicals produce lipid peroxidation of cell membrane polyunsaturated fatty acids, which generates conjugated dienes. The diene conjugation
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Table 3. Transesophageal Echocardiographic Values Parameter Left ventricular elastance (mm Hg/mL) Induction Before CPB After declamping Sternum closed 2 hours 3 hours End-diastolic volume recruitable stroke work (mm Hg) Induction Before CPB After declamping Sternum closed 2 hours 3 hours Ejection fraction (%) Induction Before CPB After declamping Sternum closed 2 hours 3 hours Fractional area change (%) Induction Before CPB After declamping Sternum closed 2 hours 3 hours Stroke work (mL䡠mm Hg) Induction Before CPB After declamping Sternum closed 2 hours 3 hours
Control Group
Nitecapone Group
1.748 ⫾ 0.251 1.939 ⫾ 0.298 1.493 ⫾ 0.204 1.764 ⫾ 0.219 1.931 ⫾ 0.343 2.196 ⫾ 0.674
1.736 ⫾ 0.240 2.059 ⫾ 0.313 1.878 ⫾ 0.375 1.988 ⫾ 0.412 1.782 ⫾ 0.231 1.565 ⫾ 0.185
0.386 ⫾ 0.031 0.380 ⫾ 0.026 0.314 ⫾ 0.032 0.345 ⫾ 0.032 0.409 ⫾ 0.031 0.391 ⫾ 0.029
0.395 ⫾ 0.036 0.393 ⫾ 0.030 0.359 ⫾ 0.032 0.367 ⫾ 0.024 0.385 ⫾ 0.027 0.378 ⫾ 0.025
52.0 ⫾ 3.3 56.7 ⫾ 3.4 54.7 ⫾ 3.5 55.0 ⫾ 3.8 56.5 ⫾ 3.0 56.4 ⫾ 3.3
61.3 ⫾ 4.2 60.2 ⫾ 3.8 63.2 ⫾ 4.1 60.1 ⫾ 4.8 61.3 ⫾ 3.6 61.1 ⫾ 3.2
39.1 ⫾ 2.9 43.3 ⫾ 3.0 41.6 ⫾ 3.1 41.9 ⫾ 3.3 43.1 ⫾ 2.7 43.1 ⫾ 3.2
47.9 ⫾ 3.9 46.7 ⫾ 3.5 49.6 ⫾ 3.7 47.1 ⫾ 4.3 47.6 ⫾ 3.3 47.2 ⫾ 2.8
47.6 ⫾ 5.2 43.5 ⫾ 4.3 37.9 ⫾ 4.9 40.1 ⫾ 5.0 51.8 ⫾ 5.0 48.7 ⫾ 4.5
55.0 ⫾ 6.4 49.8 ⫾ 8.2 49.5 ⫾ 5.1 48.5 ⫾ 5.5 49.2 ⫾ 4.0 52.8 ⫾ 4.4
No differences between groups were statistically significant. CPB ⫽ cardiopulmonary bypass.
method appears to be a better indicator of oxidative stress in the human body than thiobarbituric acid reactive substances [15]. Several investigations have demonstrated that lipid peroxidation occurs during cardiopulmonary bypass [17]. The gradient of the conjugated dienes between the coronary sinus and the aorta was highest in this study at 1 minute of reperfusion and decreased thereafter, which demonstrates that lipid peroxidation products are released into the coronary sinus. Nitecapone also reduced lipid peroxidation measured as conjugated dienes, which is in accordance with earlier findings on NC properties in scavenging free radicals [4, 5]. Radical-trapping antioxidative potential capacity has been used to demonstrate the protective capacity of
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Table 4. Biochemical Data Obtained From Plasma Samples and Myocardial Biopsies Parameter ⌬ LDL-DC-CHOL (mol/L) (plasma) Before CPB 1 min 5 min 10 min ⌬ LDL-DC (mol/L) (plasma) Before CPB 1 min 5 min 10 min ⌬ LDL-TRAP-CHOL (mol/L) (plasma) Before CPB 1 min 5 min 10 min ⌬ Ubiquinone (mol/L) (plasma) Before CPB 1 min 5 min 10 min ⌬ Lactate (mol/L) (plasma) Before CPB 1 min 5 min 10 min Glutathione (mol/L) (biopsy) 1 min 5 min 10 min Superoxide dismutase (mol/L) (biopsy) 1 min 5 min 10 min
C Group
NC Group
p
⫺0.105 ⫾ 0.313 ⫺0.355 ⫾ 0.340 1.903 ⫾ 2.249 0.491 ⫾ 0.756 0.247 ⫾ 0.398 0.011 ⫾ 0.419 ⫺1.153 ⫾ 0.459 0.693 ⫾ 0.606 ⬍ 0.05
0.107 ⫾ 1.216 ⫺0.747 ⫾ 2.361 4.093 ⫾ 4.911 0.480 ⫾ 1.535 0.553 ⫾ 0.601 1.573 ⫾ 0.772 ⫺1.753 ⫾ 1.209 1.360 ⫾ 0.920
⫺0.767 ⫾ 0.901 0.593 ⫾ 0.867 ⫺0.40 ⫾ 1.344 0.453 ⫾ 0.838
0.20 ⫾ 0.847 1.02 ⫾ 1.830 2.153 ⫾ 1.137 3.687 ⫾ 3.101
0.097 ⫾ 0.075 ⫺0.108 ⫾ 0.124 ⫺0.003 ⫾ 0.049 ⫺0.057 ⫾ 0.047 0.160 ⫾ 0.105 0.189 ⫾ 0.104 ⫺0.073 ⫾ 0.088 0.168 ⫾ 0.135
0.02
NS
NS
0.0 ⫾ 0.057 ⫺0.020 ⫾ 0.044 0.680 ⫾ 0.152 0.533 ⫾ 0.203 0.333 ⫾ 0.123 0.20 ⫾ 0.053 0.073 ⫾ 0.122 ⫺0.033 ⫾ 0.092
NS
1.175 ⫾ 0.092 0.989 ⫾ 0.098 1.121 ⫾ 0.045
1.211 ⫾ 0.10 1.179 ⫾ 0.079 1.176 ⫾ 0.080
NS
3.624 ⫾ 0.272 3.611 ⫾ 0.230 3.403 ⫾ 0.214
3.337 ⫾ 0.263 3.568 ⫾ 0.227 3.659 ⫾ 0.169
NS
CPB ⫽ cardiopulmonary bypass; ⌬ ⫽ gradient between coronary sinus and aorta; LDL-DC-CHOL ⫽ low-density lipoprotein– conjugated dienes in relation to cholesterol concentration; LDLTRAP-CHOL ⫽ low-density lipoprotein peroxyl trapping antioxidant potential in relation to cholesterol concentration; NS ⫽ not significant.
blood against free radicals by determining the total peroxyl radical-trapping antioxidative value, which is used to obtain information on the quantitative chainbreaking antioxidant capacity instead of measuring individual antioxidants separately [16]. Several sources of free radical production during CPB must be detoxified with endogenous mechanisms, which in turn consume alfatocopherol, glutathione, and superoxide dismutase. It has been shown that NC recycles ascorbate and alfatocopherol. The increase in LDL-TRAP gradient capacity
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Fig 9. Gradient between coronary sinus and aorta with regard to low-density lipoprotein–peroxyl radical trapping antioxidant potential in relation to cholesterol concentration. (LDL TRAP CHOL) (mol/L) showed that nitecapone (NC)-treated patients had better antioxidant potential than the control (C) group at 5 minutes after declamping (p ⬍ 0.05). 1 AD, 2 AD, and 3 AD ⫽ 1, 5, and 10 minutes after declamping, respectively.
during reperfusion in the NC group supports the view of NC’s preserving effect on antioxidative capacity. Ubiquinone is a vitamin-like substance with an important role in oxidative respiration, membrane stabilization, and free radical scavenging. It has been shown to prevent lipid peroxidation by acting as an antioxidant [18]. However, Taggart and associates [19] could not show any improvement in human myocardial function after short-term supplementation, but Sunamori and colleagues showed that intravenous administration of ubiquinone improved the postoperative stroke work index in patients who had coronary artery bypass grafting [20]. In our study, the ubiquinone gradient between the coronary sinus and the aorta decreased quickly in the control group at 1 minute of reperfusion and the value increased to over the level before CPB in the NC group at 5 minutes after declamping. However, there were no statistically significant differences. It was interesting that
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the gradient first clearly decreased and thereafter increased at 5 minutes and decreased at 10 minutes after declamping. This rebound effect could be explained by a fast regeneration of ubiquinone during the reperfusion period. There were only little changes between the time points in the NC group. Chello and colleagues [18] showed that pretreatment with ubiquinone 7 days before coronary artery bypass grafting reduced ventricular arrhythmias postoperatively. We had also fewer ventricular arrhythmias in the study group. However, because the differences in ubiquinone levels were not significant between the groups, the ubiquinone level probably was not related to the incidence of arrhythmias. Cardiopulmonary bypass and ischemia-reperfusion injury impair functional recovery of the myocardium after cross-clamping. Much of the tissue injury is caused by activated neutrophils, which are produced during CPB and ischemia. It has been shown experimentally to be beneficial to inhibit leukocytes with depletion [1, 21], inhibition of complement activation [22], arachidonic acid metabolism [23], and inhibition of proteases [24]. In the clinical setting, there is no ideal molecule available to restrict leukocyte activation and to reduce myocardial injury. It has been shown that leukocytes in deferoxamine-treated patients produced fewer radicals than in control group patients [25]. In our study, myeloperoxidase activity decreased after reperfusion but was lower in the NC group and higher in the control group. The decrease in MPO activity showed that CPB and ischemiaactivated leukocytes were less sequestered in the coronary circulation in the NC group. The dilemma of this study design was that we were not able to use NC as an additive in patients who would probably benefit most from it. Patients with normal myocardial function and a relatively short period of ischemia would respond similarly. However, NC significantly decreased the number of postoperative ventricular arrhythmias during the recovery period, lipid peroxidation in the myocardium, and the activation of leukocytes. Taken together these data suggest that NC might offer additional benefit for critically ill patients with preoperative myocardial dysfunction. This study was supported by a grant from Viipuris Tuberculosis Foundation and the Finnish Foundation for Cardiovascular Research. We thank the consultant statistician Juha Akkila, MSc, for statistical analysis, and Sirkku Haartti and the operating room personnel.
References
Fig 10. Myeloperoxidase activity of the myocardial biopsy (mU/mg of protein) was higher in the control (C) group but lower in the nitecapone (NC) group (p ⫽ 0.13).
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nitecapone are potentiated by glutathione. Biochem Mol Biol Int 1995;35:387–95. Marcocci L, Suzuki YJ, Tsuchiya M, Packer L. Antioxidant activity of nitecapone and its analog OR-1246: effect of structure modification on antioxidant action. Methods Enzymol 1994;234:526– 41. Valenza M, Serbinova E, Packer L. Nitecapone protects the Langendorff-perfused heart against ischemia-reperfusion injury. Biochem Mol Biol Int 1993;29:443–9. Haramaki N, Stewart DB, Aggarwal S, Kawabata T, Packer L. Role of ascorbate in protection by nitecapone against cardiac ischemia-reperfusion injury. Biochem Pharmacol 1995;50:839–43. Vento AE, Ra¨mo¨ OJ, Nemlander AT, Nissinen E, Holopainen A, Mattila SP. Nitecapone, a new antioxidant, has beneficial effect on functional performance in experimental heart transplantation. Res Exp Med 1997;197:137– 46. Vento AE, Ra¨mo¨ OJ, Pesonen EJ, et al. The effect of nitecapone, a new antioxidant, on myocardial function after aortic cross-clamping in experimental heart ischemia. Int J Angiol 1999;8:16–21. Sundberg S, Scheinin M, Ojala-Karlsson P, Kaakkola S, Akkila J, Gordin A. Exercise hemodynamics and catecholamine metabolism after cathechol-O-methyltransferase inhibition with nitecapone. Clin Pharmacol Ther 1990;48: 356– 64. Suzuki K, Ota H, Sasagawa S, Sakatoni T, Fujikura T. Assay method for myeloperoxidase in human polymorphonuclear leukocytes. Ann Biochem 1983;132:345–52. Laihia JK, Jansen CT, Ahotupa M. Lucigenin and linoleate enhanced chemiluminescent assay for superoxide dismutase activity. Free Radical Biol Med 1993;14:457– 61. Saville B. A scheme for the colorimetric determination of microgram amounts of thiols. Analyst 1985;83:670–2. Takada M, Ikenoya S, Yuzuhira T, Katayama K. Simultaneous determination of reduced and oxidized ubiquinones. Methods Enzymol 1985;105:147–55. Vasankari T, Kujala U, Heinonen O, Kapanen J, Ahotupa M. Measurement of plasma lipid peroxidation during exercise using three different methods: diene conjugation, thiobarbituric acid reactive material and fluorescent chromolipids. Clin Chim Acta 1995;234:63–9. Uotila JT, Kirkkola AL, Rorarius M, Tuimala RJ, Metsa¨-
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Ketela¨ T. The total peroxyl radical-trapping ability of plasma and the cerebrospinal fluid in normal and preeclamptic parturients. Free Radical Biol Med 1994;16:581–90. Toivonen HJ, Ahotupa M. Free radical reaction products and antioxidant capacity in arterial plasma during coronary artery bypass grafting. J Thorac Cardiovasc Surg 1994;108: 140–7. Chello M, Mastroroberto P, Romano R, et al. Protection by coenzyme Q10 from myocardial reperfusion injury during coronary artery bypass grafting. Ann Thorac Surg 1994;58: 1427–32. Taggart DP, Jenkins M, Hooper J, et al. Effects of short-term supplementation with coenzyme Q10 on myocardial protection during cardiac operations. Ann Thorac Surg 1996;61: 829–33. Sunamori M, Tanaka H, Maruyama T, Sultan I, Sakamoto T, Suzuki A. Clinical experience of coenzyme Q10 to enhance intraoperative myocardial protection in coronary artery revascularization. Cardiovasc Drugs Ther 1991;5:297–300. Ichihara T, Yasuura K, Maseki T, et al. The effects of using a leukocyte removal filter during cold blood cardioplegia. Jpn J Surg 1994;24:966–72. Weisman HF, Bartow T, Leppo MK, et al. Soluble human complement receptor type 1: in vivo inhibitor of complement suppressing post-ischemic myocardial inflammation and necrosis. Science 1990;249:146–51. Amsterdam AA, Pan HL, Rendig SV, Symons JD, Fletcher MP, Longhurst SC. Limitation of myocardial infarct size in pigs with a dual lipoxygenase-cyclo-oxygenase blocking agent by inhibition of neutrophil activity without reduction of neutrophil migration. J Am Coll Cardiol 1993;22: 1738– 44. Nicolini FA, Mehta JL, Nichols WW, Donnelly WH, Luostarinen R, Saldeen TGP. Leukocyte elastase inhibition and t-PA-induced coronary artery thrombosis in dogs: beneficial effects on myocardial histology. Am Heart J 1991;122: 1245–51. Menasche´ P, Pascuier C, Bellucci S, Lorente P, Jaillon P, Piwnica A. Deferoxamine reduces neutrophil-mediated free radical production during cardiopulmonary bypass in man. J Thorac Cardiovasc Surg 1988;96:582–9.
The Society of Thoracic Surgeons: Thirty-sixth Annual Meeting Mark your calendars for the Thirty-sixth Annual Meeting of The Society of Thoracic Surgeons, which will be held at the Greater Fort Lauderdale Broward County Convention Center in Fort Lauderdale, Florida, January 31– February 2, 2000. The Postgraduate Course will provide in-depth coverage of thoracic surgical topics selected to enhance and broaden the knowledge of practicing thoracic and cardiac surgeons. Advance registration forms, hotel reservation forms, and details regarding transportation arrangements, as well as the complete meeting program, will be mailed to Society members. Also, complete meeting information will be available on The Society’s Web site located at http://www.sts.org. Nonmembers wishing to receive information on attending the meeting may contact the Society’s Secretary, Peter C. Pairolero. Abstracts for the meeting may also be submitted elec-
© 1999 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
tronically. The electronic submission form may be accessed at http://www.ctsnet.org/abstracts/sts. There is no charge for submitting your abstract electronically. The electronic abstract submission deadline is August 7, 1999, at 12 Midnight, CDT, five days later than the paper submission deadline. Any questions may be directed to the STS headquarters. Peter C. Pairolero, MD Secretary The Society of Thoracic Surgeons 401 N Michigan Ave Chicago, IL 60611-4267 Telephone: (312) 644-6610; fax: (312) 527-6635 e-mail: [email protected] website: http: //www.sts.org.
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Background. Nitecapone has been shown to have a protective effect against ischemia-reperfusion injury in experimental heart transplantation and in Langendorff preparations. This prospective, randomized study assessed the effects of nitecapone in patients who had coronary artery bypass grafting. Methods. Thirty patients with normal myocardial function were randomly divided into control patients (n ⴝ 15), who received crystalloid (Plegisol) cardioplegia, and nitecapone patients, who received nitecapone in a 50 M solution (n ⴝ 15) in Plegisol. Cardioplegia was administered as an initial dose of 15 mL/kg of body mass after cross-clamping and 2 mL/kg every 15 minutes. Simultaneous coronary sinus and aortic blood samples, and myocardial biopsies were taken at 1, 5, and 10 minutes after unclamping. Hemodynamics were measured invasively for 24 hours and with transesophageal echocardiography for 3 hours after cardiopulmonary bypass.
Results. There were no adverse effects. The incidence of ventricular arrhythmias was significantly lower in the treatment group during the recovery period (p ⴝ 0.02). Cardiac output and stroke volume did not differ significantly between the groups. The conjugated dienes gradient between the aorta and the coronary sinus increased significantly during the first minute of reperfusion in the control group (p ⴝ 0.02) compared with the nitecapone group. Myeloperoxidase activity in myocardial biopsies was higher in the control group (2.3 times higher at 5 minutes and 3.2 times higher at 10 minutes) than in the nitecapone group (p ⴝ 0.13). Conclusions. Nitecapone did not exert any significant hemodynamic effects in patients with normal ejection fraction.
I
Nitecapone’s toxicology has been studied by OrionFarmos Corporation (Certificate of Analysis 1995, Analytical Department, Orion-Farmos Corporation, Espoo, Finland). In addition, before the present human studies NC has also been tested in volunteers without any effect on hemodynamics itself [10]. Despite its potentially beneficial properties for abating ischemia-reperfusion injury, it has not yet been studied in a clinical setting. This study was designed to clarify the effects of NC on myocardial metabolism and functional recovery by adding NC to a cold crystalloid cardioplegia in patients with normal left ventricular function who had coronary artery bypass grafting.
schemia-reperfusion injury impairs myocardial recovery after cross-clamping during heart operations by causing arrhythmias and decreases myocardial function [1]. Myocardial protection is the key element to preventing this injury, and various methods and molecules have been examined to discover a drug capable of preserving the myocardium [2, 3]. In vitro, nitecapone (NC) (3-[3,4-dihydroxy-5-nitrophenyl]methylene-2,4-pentanedione) is a molecule with good antioxidative properties [4, 5]. It has also been tested in Langendorff preparations [6, 7], in a heterotopic transplantation model [8], and in pigs using a model resembling clinical heart ischemia in our own laboratory [9]. Nitecapone has been shown to recycle ascorbate and alfatocopherol [6, 7], to scavenge free radicals [4, 5], and to inhibit xanthine oxidase enzyme [5]. In addition, recent findings from our laboratory showed that one of the most important mechanisms is an inhibition of myeloperoxidase, indicating neutrophil inhibition.
Accepted for publication Feb 16, 1999. Address reprint requests to Dr Ra¨mo¨, Department of Thoracic and Cardiovascular Surgery, Helsinki University Central Hospital, Haartmaninkatu 4, 00290 Helsinki, Finland.
© 1999 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
(Ann Thorac Surg 1999;68:413–20) © 1999 by The Society of Thoracic Surgeons
Patients and Methods Thirty men who had coronary artery bypass grafting were prospectively entered into this study, which was approved by the ethics committee of our hospital and the Ministry of Health of Finland. All patients gave their informed consent. The patients were randomly assigned to receive nitecapone (n ⫽ 15) or to serve as controls (n ⫽ 15). The surgical procedures consisted of coronary artery bypass grafting alone with venous or arterial grafts or both. 0003-4975/99/$20.00 PII S0003-4975(99)00514-7
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Anesthesia Patients were premedicated with lorazepam. Patients with a normal morning dosage of long-acting nitrates, beta- or calcium-channel blockers received their medication. Anesthesia was induced with 30 g/kg fentanylcitrate and 0.1 mg/kg midazolam and maintained with 0.3 g/kg per minute fentanylcitrate and 0.8 g/kg per minute midazolam infusions.
Operative Technique Patients were ventilated with a Siemens Servo Volume Ventilator (Siemens-Elema AB, Solna, Sweden). The aorta and right atrium were cannulated for cardiopulmonary bypass (CPB). Left ventricular pressure was measured with a 4F pediatric Swan-Ganz catheter (Arrow AI-07122; Arrow International Inc, Reading, PA) and a single-use transducer (Deltran II; Utah Medical Co, Midvale, UT). The catheter was introduced into the left ventricle through the right superior pulmonary vein and the mitral valve. A catheter was inserted into the coronary sinus through the right atrium with a 14F coronary sinus cannula (Research Medical Inc, Salt Lake City, UT). Cardiopulmonary bypass equipment consisted of a roller pump, a membrane oxygenator, and a cardiotomy reservoir. The extracorporeal circuit was primed with 2,000 mL of a crystalloid solution containing 5,000 IU of heparin. Before cannulation, patients received heparin at a dose of 3 mg/kg of body weight. Bypass was conducted at a flow rate of 2.0 to 2.4 L/m2 and mean arterial pressure was maintained at 40 to 80 mm Hg with nonpulsatile perfusion in mild hypothermia (30° to 32°C as a nasopharyngeal temperature). The rectal temperature was rewarmed to a minimum of 34°C and the nasopharyngeal temperature to 36° to 37°C before weaning from the CPB. The fraction of inspired oxygen was 100% during the perfusion and mixed venous saturation (SVO2) was maintained at over 75%. Lung ventilation was discontinued after the beginning of the perfusion and was subsequently resumed after declamping. After the discontinuation of CPB heparin was neutralized by using protamine sulfate. The duration of the reperfusion period before weaning from CPB was 30% of the aortic crossclamping time. An initial dose of 15 mL/kg of body weight of 4°C Plegisol solution was delivered into the aortic root in the control group or with 50 M of nitecapone in the treatment group through the aortic root cannula after application of the aortic clamp. Two milliliters of cardioplegic solution per kilogram of body weight was reinfused every 15 minutes and if ventricular fibrillation was present. Nitecapone was a gift from Orion-Pharma (Espoo, Finland) and was provided in the form of a sterile powder which was dissolved in sodium bicarbonate (NaHCO3) and then added to Plegisol solution.
Hemodynamic Measurements Invasive hemodynamics were measured through an 8F Swan-Ganz catheter (Baxter Health Corp, Santa Ana,
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CA) using the AS\3 monitor (Datex, Helsinki, Finland), radial artery pressure, and through a left ventricular pressure catheter. Hemodynamic variables were recorded after the induction of anesthesia and after the insertion of the left ventricular catheter before venous and coronary sinus cannulation. The hemodynamic surveillance was continued after declamping, sternum closure, and at 2, 3, 6, and 24 hours after CPB. The left ventricular pressure catheter was pulled back into the left atrium after 3 hours of CPB and removed after the final measurements 24 hours after CPB. Left ventricular internal diameter was measured at the midpapillary level with a 5-MHz biplane transesophageal echocardiography probe (Aloka SSD-880; Aloka Co, Tokyo, Japan). Left ventricular function values were calculated in a blinded fashion offline on videotape. The measurements were made at six different time points. The first two measurements were, after the induction of anesthesia and immediately before cannulation of the great vessels, and the last four were after decannulation, and at 1, 2, and 3 hours after CPB. At the first measurement point, left ventricular pressure was estimated by systolic arterial pressure. Three pressure points were used to calculate left ventricular elastance and enddiastolic volume recruitable stroke work. Ejection fraction, fractional area change, and stroke work (SW) were calculated using the baseline values.
Blood Sampling Blood samples were obtained from the coronary sinus and aorta before the onset of CPB, and at 1, 5, and 10 minutes after declamping. Blood specimens were drawn with a 20-mL syringe and collected into heparinized tubes which were immediately capped and stored in ice-cold water. The samples were centrifuged in a temperature controlled centrifuge (Minifuge, RF, HeraeusChrist GmbH, Hanau, Germany) at 3,000 ⫻ g at a temperature of 4°C, for 15 minutes. The supernatant was placed in Eppendorff tubes and kept at ⫺70°C until assayed. Myocardial biopsies were taken with biopsy needle (Gallini, Mirandola, Italy) from the wall of the left ventricle for glutathione, superoxide dismutase, ubiquinone, and myeloperoxidase measurements at the same period of time. Biopsy samples were immediately frozen and stored at ⫺70°C until assayed.
Biochemistry Myeloperoxidase activity was determined using a modification of the method described by Suzuki and associates [11] in which the enzyme catalyzes the oxidation of 3,3⬘, 5,5⬘-tetramethylbenzidine by H2O2 to yield a blue chromogen with a maximum wavelength of 655 nm. Superoxide dismutase activity was determined using the method described by Laihia and colleagues [12] in which the xanthine or xanthine oxidase-dependent chemiluminescence was enhanced by both lucinogenin and linoleate. Glutathione content was estimated by the method described by Saville [13].
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Table 1. Patient and Operative Data Parameter Age (y) Preoperative ejection fraction Degree of coronary disease ⬎ 50% Left coronary main stem Left anterior descending artery Left circumflex artery Right coronary artery Previous myocardial infarction Number of bypasses Cross-clamp time (min) Perfusion time (min)
Control Group
Nitecapone Group
59.7 ⫾ 2.1 55.2 ⫾ 3.5
60.5 ⫾ 2.6 56.9 ⫾ 2.3
1 15 12 12 6 3.1 ⫾ 0.19 57.6 ⫾ 4.1 92.8 ⫾ 5.2
2 14 12 12 10 3.4 ⫾ 0.16 62.0 ⫾ 4.7 98.5 ⫾ 5.8
There were no statistically significant differences between the groups.
Ubiquinone concentration was analyzed using standard high pressure liquid chromatography (HPLC) procedures with ultraviolet detection [14]. Low-density lipoprotein (LDL) oxidation products and conjugated dienes (LDL-DC) were measured as previously described by Vasankari and coworkers [15]. Lowdensity lipoprotein oxidation was estimated by the baseline level of diene conjugation in the lipid fraction of LDL (LDL-BDC). Low-density lipoprotein–total peroxyl radical trapping antioxidant potential (LDL-TRAP) was estimated in vitro by the plasma potency in resisting 2,2’ azobis (2-amino propane) hydrochloride (ABAP)-induced peroxidation. A solution of 0.45 mL of 0.1 mmol sodium phosphate buffer, pH 7.4, containing 0.9% NaCl, 0.02 mL of 120 mmol linoleic acid, 0.05 mL of luminol (0.5 mg/mL), and 100-L low-density lipoprotein samples was mixed in the cuvette and the assay was initiated with 0.05 mL of ABAP (83 mg/mL). Chemiluminescence in duplicate cuvettes at 37°C was measured until a peak value for each sample was detected. Peroxyl radical trapping capacity was defined by the half-peak time point. ␣-tocopherol analogue served as a standard radical scavenger. To obtain an estimation of the relative antioxidant power of given LDL preparations, the results were expressed in relation to the cholesterol concentration of the preparations (LDLTRAP-CHOL) [16].
Statistical Analysis Patients were randomizly assigned to treatment group. Data are expressed as the mean ⫾ the standard error of Table 2. Arrhythmias Type of Arrhythmia Ventricular arrhythmia Postoperative day 1 Postoperative day 2 After postoperative day 3 Total Atrial fibrillation
Control Group
Nitecapone Group
6 5 5 9 3
2 0 0 2 4
p 0.21
0.02 NS
Fig 1. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Heart rate (HR) was increased in both groups and was lower in the nitecapone (NC) group than in the control (C) group (p ⫽ 0.06). (ind ⫽ induction of anesthesia).
mean. The 2 test was used for clinical variables. Differences between the treatment groups in hemodynamics were statistically evaluated using repeated measures analysis of variance, which included the baseline value as a covariate. The biochemical parameters (gradients) were analyzed by the Wilcoxon rank sum test at each timepoint. Statistical calculations were carried out with SAS software (SAS Institute, Cary, NC). A p value less than 0.05 was considered statistically significant.
Results Patients from the two groups did not differ significantly with respect to age, preoperative ejection fraction, degree of coronary artery disease, or the operation as shown in Table 1. There were no technical complications related to myocardial biopsies.
Hemodynamics There were no significant differences in the use of inotropic agents between the groups. The incidence of atrial fibrillation (Table 2) was almost the same in both groups, but the incidence of ventricular arrhythmias (extrasystoles) was four times greater in the control group than in the NC group ( p ⫽ 0.02). Heart rate remained at a lower level in the NC group throughout the follow-up time (Fig 1). Mean arterial pressure values were stable during the follow-up period and showed no significant differences between the two groups (Fig 2). Cardiac output (CO) increased up to 60% in the NC group but only 43% in the control group after 24 hours of CPB (Fig 3) (p ⫽ 0.75). Cardiac index (CI) values naturally showed a similar trend during the follow-up period (Fig 4) (p ⫽ 0.67). Stroke volume values decreased in both groups during the first 3 hours, but after 6 hours the values increased
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Fig 2. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Mean arterial pressure (MAP) was over 60 mm Hg in both groups (p ⫽ 0.66). Abbreviations as in Figure 1.
Fig 4. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Cardiac Index (CI) reflected better myocardial recovery at 6 and 24 hours after CPB (p ⫽ 0.67). Abbreviations as in Figure 1.
more in the NC group than in the control group (Fig 5) ( p ⫽ 0.37). The filling pressures, central venous pressure, pulmonary artery diastolic pressure, and pulmonary capillary wedge pressure, were lower in the NC-group than in the control group. (Figs 6 – 8). Systemic vascular resistance and pulmonary vascular resistance values were not significantly different between the groups. Data not shown here.
after the termination of CPB. After that stroke work increased close to the preoperative level. Ejection fraction and fractional area change values showed a curve almost parallel to the X-axis without any significant changes at any time points. Elastance values in the NC group were higher up to 1 hour after CPB (Table 3).
Biochemistry
The myocardial function was examined during the operation with esophageal echocardiography. Stroke work decreased in both groups after induction up to 1 hour
Creatine kinase-MB values showed no significant differences between the groups on the first and the second postoperative days. Plasma creatinine values did not differ between the groups. Coronary sinus ubiquinone values were decreased in both groups at both 5 and 10 minutes after declamping.
Fig 3. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Cardiac output (CO) reflected better myocardial recovery at 6 and 24 hours after CPB (p ⫽ 0.75). Abbreviations as in Figure 1.
Fig 5. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Stroke volume (SV) reflected better myocardial recovery at 6 and 24 hours after CPB (p ⫽ 0.37). Abbreviations as in Figure 1.
Transesophageal Echocardiography
PLASMA SAMPLES.
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417
Fig 6. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Central venous pressure (CVP) was similarly increased in both groups after CPB (p ⫽ 0.82). Abbreviations as in Figure 1.
Fig 8. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Pulmonary capillary wedge pressure (PCWP) showed minor differences between the groups (p ⫽ 0.26). Abbreviations as in Figure 1.
Change in ubiquinone (gradient between coronary sinus and aorta) was higher in the NC group (Table 4) ( p ⫽ 0.59). Change in LDL-TRAP gradient was higher at 5 minutes in the NC group ( p ⬍ 0.05) after declamping but decreased in the control group as shown in Figure 9. Also, change in LDL-TRAP-CHOL values were increased in the NC group, whereas the changes were minor in the control group (Table 4) ( p ⫽ 0.20). Change in LDL-DC (p ⫽ 0.02) and LDL-DC-CHOL (LDL-conjugated dienes in relation to the cholesterol concentration of the preparations) ( p ⬍ 0.05) were increased in the control group more after declamping than in the NC group, but thereafter decreased in the control group to a level below that of the NC group (Table 4).
Lactate concentrations were at their highest in both groups at 1 minute after declamping. As the reperfusion progressed, the concentration diminished gradually in the coronary sinus in both groups. The groups did not differ from each other significantly (Table 4). The glutathione level remained constant in the NC group but decreased in the control group during the first few minutes of reperfusion (Table 4) ( p ⫽ 0.34). Similarly, superoxide dismutase showed increasing values in the NC group ( p ⫽ 0.26) but decreased in the control group (Table 4).
MYOCARDIAL BIOPSIES.
Myeloperoxidase was determined in myocardial biopsies to evaluate the infiltration of leukocytes, ie, the activation of leukocytes during the first few minutes of reperfusion. Myeloperoxidase activity increased in the control group at 5 and 10 minutes of reperfusion, whereas it decreased in the NC group at the same time points (Fig 10). Myeloperoxidase activity was 3.2 times higher after 10 minutes of declamping in the control group than in the NC group ( p ⫽ 0.13).
GRANULOCYTE INFILTRATION.
Comment
Fig 7. Hemodynamics in induction, before cross-clamping, after cross-clamping, when the sternum was closed, and 2, 3, 6, and 24 hours after cardiopulmonary bypass (CPB). Pulmonary artery diastolic pressure (PAPD) showed no major differences between the groups (p ⫽ 0.05). Abbreviations as in Figure 1.
Postoperative ventricular arrhythmias are dangerous to myocardial function [1]. It has been shown that NC protects grafts after experimental heart transplantation in rats after 2 hours of ischemia [8]. The grafts treated with NC had fewer arrhythmias, and more grafts began to beat than in the control group. Atrial fibrillation frequency was almost the same in both groups, but a lower frequency of ventricular arrhythmic disorders could also be shown by the present study. Oxygen-derived free radicals produce lipid peroxidation of cell membrane polyunsaturated fatty acids, which generates conjugated dienes. The diene conjugation
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Table 3. Transesophageal Echocardiographic Values Parameter Left ventricular elastance (mm Hg/mL) Induction Before CPB After declamping Sternum closed 2 hours 3 hours End-diastolic volume recruitable stroke work (mm Hg) Induction Before CPB After declamping Sternum closed 2 hours 3 hours Ejection fraction (%) Induction Before CPB After declamping Sternum closed 2 hours 3 hours Fractional area change (%) Induction Before CPB After declamping Sternum closed 2 hours 3 hours Stroke work (mL䡠mm Hg) Induction Before CPB After declamping Sternum closed 2 hours 3 hours
Control Group
Nitecapone Group
1.748 ⫾ 0.251 1.939 ⫾ 0.298 1.493 ⫾ 0.204 1.764 ⫾ 0.219 1.931 ⫾ 0.343 2.196 ⫾ 0.674
1.736 ⫾ 0.240 2.059 ⫾ 0.313 1.878 ⫾ 0.375 1.988 ⫾ 0.412 1.782 ⫾ 0.231 1.565 ⫾ 0.185
0.386 ⫾ 0.031 0.380 ⫾ 0.026 0.314 ⫾ 0.032 0.345 ⫾ 0.032 0.409 ⫾ 0.031 0.391 ⫾ 0.029
0.395 ⫾ 0.036 0.393 ⫾ 0.030 0.359 ⫾ 0.032 0.367 ⫾ 0.024 0.385 ⫾ 0.027 0.378 ⫾ 0.025
52.0 ⫾ 3.3 56.7 ⫾ 3.4 54.7 ⫾ 3.5 55.0 ⫾ 3.8 56.5 ⫾ 3.0 56.4 ⫾ 3.3
61.3 ⫾ 4.2 60.2 ⫾ 3.8 63.2 ⫾ 4.1 60.1 ⫾ 4.8 61.3 ⫾ 3.6 61.1 ⫾ 3.2
39.1 ⫾ 2.9 43.3 ⫾ 3.0 41.6 ⫾ 3.1 41.9 ⫾ 3.3 43.1 ⫾ 2.7 43.1 ⫾ 3.2
47.9 ⫾ 3.9 46.7 ⫾ 3.5 49.6 ⫾ 3.7 47.1 ⫾ 4.3 47.6 ⫾ 3.3 47.2 ⫾ 2.8
47.6 ⫾ 5.2 43.5 ⫾ 4.3 37.9 ⫾ 4.9 40.1 ⫾ 5.0 51.8 ⫾ 5.0 48.7 ⫾ 4.5
55.0 ⫾ 6.4 49.8 ⫾ 8.2 49.5 ⫾ 5.1 48.5 ⫾ 5.5 49.2 ⫾ 4.0 52.8 ⫾ 4.4
No differences between groups were statistically significant. CPB ⫽ cardiopulmonary bypass.
method appears to be a better indicator of oxidative stress in the human body than thiobarbituric acid reactive substances [15]. Several investigations have demonstrated that lipid peroxidation occurs during cardiopulmonary bypass [17]. The gradient of the conjugated dienes between the coronary sinus and the aorta was highest in this study at 1 minute of reperfusion and decreased thereafter, which demonstrates that lipid peroxidation products are released into the coronary sinus. Nitecapone also reduced lipid peroxidation measured as conjugated dienes, which is in accordance with earlier findings on NC properties in scavenging free radicals [4, 5]. Radical-trapping antioxidative potential capacity has been used to demonstrate the protective capacity of
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Table 4. Biochemical Data Obtained From Plasma Samples and Myocardial Biopsies Parameter ⌬ LDL-DC-CHOL (mol/L) (plasma) Before CPB 1 min 5 min 10 min ⌬ LDL-DC (mol/L) (plasma) Before CPB 1 min 5 min 10 min ⌬ LDL-TRAP-CHOL (mol/L) (plasma) Before CPB 1 min 5 min 10 min ⌬ Ubiquinone (mol/L) (plasma) Before CPB 1 min 5 min 10 min ⌬ Lactate (mol/L) (plasma) Before CPB 1 min 5 min 10 min Glutathione (mol/L) (biopsy) 1 min 5 min 10 min Superoxide dismutase (mol/L) (biopsy) 1 min 5 min 10 min
C Group
NC Group
p
⫺0.105 ⫾ 0.313 ⫺0.355 ⫾ 0.340 1.903 ⫾ 2.249 0.491 ⫾ 0.756 0.247 ⫾ 0.398 0.011 ⫾ 0.419 ⫺1.153 ⫾ 0.459 0.693 ⫾ 0.606 ⬍ 0.05
0.107 ⫾ 1.216 ⫺0.747 ⫾ 2.361 4.093 ⫾ 4.911 0.480 ⫾ 1.535 0.553 ⫾ 0.601 1.573 ⫾ 0.772 ⫺1.753 ⫾ 1.209 1.360 ⫾ 0.920
⫺0.767 ⫾ 0.901 0.593 ⫾ 0.867 ⫺0.40 ⫾ 1.344 0.453 ⫾ 0.838
0.20 ⫾ 0.847 1.02 ⫾ 1.830 2.153 ⫾ 1.137 3.687 ⫾ 3.101
0.097 ⫾ 0.075 ⫺0.108 ⫾ 0.124 ⫺0.003 ⫾ 0.049 ⫺0.057 ⫾ 0.047 0.160 ⫾ 0.105 0.189 ⫾ 0.104 ⫺0.073 ⫾ 0.088 0.168 ⫾ 0.135
0.02
NS
NS
0.0 ⫾ 0.057 ⫺0.020 ⫾ 0.044 0.680 ⫾ 0.152 0.533 ⫾ 0.203 0.333 ⫾ 0.123 0.20 ⫾ 0.053 0.073 ⫾ 0.122 ⫺0.033 ⫾ 0.092
NS
1.175 ⫾ 0.092 0.989 ⫾ 0.098 1.121 ⫾ 0.045
1.211 ⫾ 0.10 1.179 ⫾ 0.079 1.176 ⫾ 0.080
NS
3.624 ⫾ 0.272 3.611 ⫾ 0.230 3.403 ⫾ 0.214
3.337 ⫾ 0.263 3.568 ⫾ 0.227 3.659 ⫾ 0.169
NS
CPB ⫽ cardiopulmonary bypass; ⌬ ⫽ gradient between coronary sinus and aorta; LDL-DC-CHOL ⫽ low-density lipoprotein– conjugated dienes in relation to cholesterol concentration; LDLTRAP-CHOL ⫽ low-density lipoprotein peroxyl trapping antioxidant potential in relation to cholesterol concentration; NS ⫽ not significant.
blood against free radicals by determining the total peroxyl radical-trapping antioxidative value, which is used to obtain information on the quantitative chainbreaking antioxidant capacity instead of measuring individual antioxidants separately [16]. Several sources of free radical production during CPB must be detoxified with endogenous mechanisms, which in turn consume alfatocopherol, glutathione, and superoxide dismutase. It has been shown that NC recycles ascorbate and alfatocopherol. The increase in LDL-TRAP gradient capacity
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Fig 9. Gradient between coronary sinus and aorta with regard to low-density lipoprotein–peroxyl radical trapping antioxidant potential in relation to cholesterol concentration. (LDL TRAP CHOL) (mol/L) showed that nitecapone (NC)-treated patients had better antioxidant potential than the control (C) group at 5 minutes after declamping (p ⬍ 0.05). 1 AD, 2 AD, and 3 AD ⫽ 1, 5, and 10 minutes after declamping, respectively.
during reperfusion in the NC group supports the view of NC’s preserving effect on antioxidative capacity. Ubiquinone is a vitamin-like substance with an important role in oxidative respiration, membrane stabilization, and free radical scavenging. It has been shown to prevent lipid peroxidation by acting as an antioxidant [18]. However, Taggart and associates [19] could not show any improvement in human myocardial function after short-term supplementation, but Sunamori and colleagues showed that intravenous administration of ubiquinone improved the postoperative stroke work index in patients who had coronary artery bypass grafting [20]. In our study, the ubiquinone gradient between the coronary sinus and the aorta decreased quickly in the control group at 1 minute of reperfusion and the value increased to over the level before CPB in the NC group at 5 minutes after declamping. However, there were no statistically significant differences. It was interesting that
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the gradient first clearly decreased and thereafter increased at 5 minutes and decreased at 10 minutes after declamping. This rebound effect could be explained by a fast regeneration of ubiquinone during the reperfusion period. There were only little changes between the time points in the NC group. Chello and colleagues [18] showed that pretreatment with ubiquinone 7 days before coronary artery bypass grafting reduced ventricular arrhythmias postoperatively. We had also fewer ventricular arrhythmias in the study group. However, because the differences in ubiquinone levels were not significant between the groups, the ubiquinone level probably was not related to the incidence of arrhythmias. Cardiopulmonary bypass and ischemia-reperfusion injury impair functional recovery of the myocardium after cross-clamping. Much of the tissue injury is caused by activated neutrophils, which are produced during CPB and ischemia. It has been shown experimentally to be beneficial to inhibit leukocytes with depletion [1, 21], inhibition of complement activation [22], arachidonic acid metabolism [23], and inhibition of proteases [24]. In the clinical setting, there is no ideal molecule available to restrict leukocyte activation and to reduce myocardial injury. It has been shown that leukocytes in deferoxamine-treated patients produced fewer radicals than in control group patients [25]. In our study, myeloperoxidase activity decreased after reperfusion but was lower in the NC group and higher in the control group. The decrease in MPO activity showed that CPB and ischemiaactivated leukocytes were less sequestered in the coronary circulation in the NC group. The dilemma of this study design was that we were not able to use NC as an additive in patients who would probably benefit most from it. Patients with normal myocardial function and a relatively short period of ischemia would respond similarly. However, NC significantly decreased the number of postoperative ventricular arrhythmias during the recovery period, lipid peroxidation in the myocardium, and the activation of leukocytes. Taken together these data suggest that NC might offer additional benefit for critically ill patients with preoperative myocardial dysfunction. This study was supported by a grant from Viipuris Tuberculosis Foundation and the Finnish Foundation for Cardiovascular Research. We thank the consultant statistician Juha Akkila, MSc, for statistical analysis, and Sirkku Haartti and the operating room personnel.
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Fig 10. Myeloperoxidase activity of the myocardial biopsy (mU/mg of protein) was higher in the control (C) group but lower in the nitecapone (NC) group (p ⫽ 0.13).
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The Society of Thoracic Surgeons: Thirty-sixth Annual Meeting Mark your calendars for the Thirty-sixth Annual Meeting of The Society of Thoracic Surgeons, which will be held at the Greater Fort Lauderdale Broward County Convention Center in Fort Lauderdale, Florida, January 31– February 2, 2000. The Postgraduate Course will provide in-depth coverage of thoracic surgical topics selected to enhance and broaden the knowledge of practicing thoracic and cardiac surgeons. Advance registration forms, hotel reservation forms, and details regarding transportation arrangements, as well as the complete meeting program, will be mailed to Society members. Also, complete meeting information will be available on The Society’s Web site located at http://www.sts.org. Nonmembers wishing to receive information on attending the meeting may contact the Society’s Secretary, Peter C. Pairolero. Abstracts for the meeting may also be submitted elec-
© 1999 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
tronically. The electronic submission form may be accessed at http://www.ctsnet.org/abstracts/sts. There is no charge for submitting your abstract electronically. The electronic abstract submission deadline is August 7, 1999, at 12 Midnight, CDT, five days later than the paper submission deadline. Any questions may be directed to the STS headquarters. Peter C. Pairolero, MD Secretary The Society of Thoracic Surgeons 401 N Michigan Ave Chicago, IL 60611-4267 Telephone: (312) 644-6610; fax: (312) 527-6635 e-mail: [email protected] website: http: //www.sts.org.
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