Myocardial protection during prolonged aortic cross-clamping. Comparison of blood and crystalloid cardioplegia

We compared the ability of blood and crystalloid cardioplegia to protect the myocardium during prolonged arrest. Twelve dogs underwent 180 minutes of continuous arrest. Group I (six dogs) received 750 ml of blood cardioplegic solution (potassium chloride 30 mEq/L) initially and every 30 minutes. Group II (six dogs) received an identical amount of crystalloid cardioplegic solution (potassium chloride 30 mEq, methylprednisolone 1 gm, and 50% dextrose in water 16 ml/L of electrolyte solution). Temperature was 10 degrees C and pH 8.0 in both groups. Studies of myocardial biochemistry, physiology, and ultrastructure were completed before arrest and 30 minutes after normothermic reperfusion. Biopsy specimens for determination of adenosine triphosphate were obtained before, during, and after the arrest interval. Regional myocardial blood flow, total coronary blood flow, and myocardial oxygen consumption were statistically unchanged in Group I (p greater than 0.05). Total coronary blood flow rose 196% +/- 49% in Group II (p less than 0.005), and left ventricular endocardial/epicardial flow ratio fell significantly in this group from 1.51 +/- 0.18 to 0.8 +/- 0.09, p less than 0.01 (mean +/- standard error of the mean. The rise in myocardial oxygen consumption was not significant in this group (34% +/- 36%, p greater than 0.05). Ventricular function and compliance were statistically unchanged in both groups. In Group II, adenosine triphosphate fell 18% +/- 3.4% (p less than 0.005) after 30 minutes of reperfusion; it was unchanged in Group I. Ultrastructural appearance in both groups correlated with these changes. We conclude that blood cardioplegia offers several distinct advantages over crystalloid cardioplegia during prolonged arrest.     

Myocardial preservation using lidocaine blood cardioplegia

Prevention of ventricular fibrillation after aortic unclamping using lidocaine hydrochloride as an additive to cold potassium blood cardioplegia was studied prospectively in 46 patients undergoing elective myocardial revascularization. Patients were similar with respect to age, ventricular function, severity of coronary artery disease, cross-clamp time, completeness of revascularization, frequency of internal thoracic artery grafting, systemic temperature at the time of cross-clamp removal, and mean infusate volume and temperature. Patients receiving lidocaine blood cardioplegia (group 1, 23 patients) had a significant reduction in the incidence of ventricular fibrillation (22% versus 74%; p less than 0.0005) and in the mean number of cardioversion attempts required to defibrillate the heart (0.5 +/- 1.3 versus 1.9 +/- 0.97; p less than 0.0005) after cross-clamp removal compared with controls (group 2, 23 patients). There were no differences between the two groups postoperatively with regard to cardiac enzyme release, hemodynamic measurements, or clinical outcome. Patients receiving lidocaine blood cardioplegia tended to have a lower incidence of new postoperative atrial fibrillation (9% versus 26%). Ventricular function was preserved equally in both groups. We conclude that lidocaine is a safe additive to potassium blood cardioplegia and significantly reduces the incidence of ventricular fibrillation after aortic unclamping.     

Myocardial oxygen tension during surgical revascularization. A clinical comparison between blood cardioplegia and crystalloid cardioplegia.

OBJECTIVE: The aim of this study was to assess the effect of cardioplegic solutions on myocardial oxygenation during surgical revascularization. METHODS: In 30 patients, randomized to receive crystalloid (CC) or blood (BC) cardioplegia, myocardial oxygen tension was measured continuously by polarography. RESULTS: The two groups were comparable in terms of patients' age, sex, pre-operative ejection fraction, coronary disease, perfusion time, and aorta cross-clamping time. However, the BC group required 22% more of cardioplegic solution to stop electrical activity of the heart. Throughout the pre- and post-cardiac arrest periods, oxygen tension between the two groups was similar. At the end of the observation (4th day), myocardial oxygenation increased over 200% in relation to the values before revascularization. During the first infusion of cardioplegia, oxygen tension in the CC group was lower compared to the BC group (0.1 mmHg vs 1.3 mmHg; P<0.05) being the only significant difference between the two groups during cardiac arrest. Throughout the cardiac arrest, myocardial oxygen tension was close to zero regardless of the type of cardioplegia used. Post-operatively, addition of oxygen to the respiratory air increased myocardial oxygenation by over 17% resulting in a positive correlation (r=0.94; P<0.05) between myocardial oxygen tension and peripheral saturation. CONCLUSIONS: In conclusion, the differences in myocardial oxygen tension between the CC and BC groups are trivial. Thus, any potential beneficial effect of blood cardioplegia compared to crystalloid cardioplegia must be due to other circumstances than its oxygen carrying capacity. An important observation is a significant increase in myocardial oxygenation during oxygen supplement to the respiratory air.     

Myocardial protection in the neonatal heart. A comparison of topical hypothermia and crystalloid and blood cardioplegic solutions

Myocardial protection achieved during 2 hours of ischemic arrest was evaluated in 45 isolated, blood perfused, neonatal (1 to 5 days) piglet hearts. Comparisons were made among five methods of myocardial protection: Group I, topical cooling; Group II, hyperosmolar (450 mOsm) low-calcium (0.5 mmol/L) crystalloid cardioplegia; Group III, St. Thomas' Hospital cardioplegia; Group IV, cold blood cardioplegia with potassium (21 mmol/L), citrate-phosphate-dextrose (calcium level 0.6 mmol/L), and tromethamine; and Group V, cold blood cardioplegia with potassium alone (16 mmol/L) (calcium level 1.2 mmol/L). Hemodynamic recovery (percent of the preischemic stroke work) after 30 and 60 minutes of reperfusion was 82.9% and 86.7% in Group I, 35.7% (p less than 0.0001) and 43.7% (p less than 0.0001) in Group II, 76.1% and 77.7% in Group III, 67.4% (p less than 0.05) and 60.6% (p less than 0.05) in Group IV, and 110.7% and 100.6% in Group V. Conclusions: Topical cooling is an effective method of myocardial protection in the neonate. Cold blood cardioplegia with potassium alone and a normal calcium level provides optimal functional recovery. The improved protection obtained with both crystalloid and blood cardioplegia with normal calcium levels suggests an increased sensitivity of the neonatal heart to the calcium level of the cardioplegic solution.     

Improved myocardial protection with blood and crystalloid cardioplegia

Although the results of coronary artery bypass surgery have been excellent, recent studies have demonstrated transient alterations in myocardial function and metabolism in spite of apparently adequate cardioplegic protection. Blood cardioplegia may provide better protection than crystalloid cardioplegia, but clinical studies remain inconclusive. Critical coronary stenoses limit cardioplegic delivery, and myocardial protection would be improved with either blood or crystalloid cardioplegia if the solution could be delivered beyond the coronary stenosis. The construction of proximal as well as distal anastomoses during a prolonged cross-clamp period permits more uniform cardioplegic delivery and immediate reperfusion when the cross clamp is released. This technique was used in a prospective randomized trial comparing blood and crystalloid cardioplegia. The long cross-clamp technique eliminated temperature gradients induced when cardioplegia was delivered into the aortic root. The technique of cardioplegic delivery may be as important as the solution used for cardioplegic protection. (J VASC SURG 1984;1:656-9.)     

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

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

Myocardial metabolism during aortic valve replacement. I. Hypothermic crystalloid cardioplegia with mannitol

Myocardial energy metabolism during hypothermic potassium cardioplegia with addition of mannitol was studied in five patients undergoing aortic valve replacement. Myocardial biopsies were taken from the left ventricle 10 min after the aortic cross-clamping and immediately before declamping and were analyzed for ATP, lactate and glycogen. The ATP concentration fell (13.2 +/- 3.6-11.0 +/- 4.3 mmol X kg-1 dry muscle), the lactate concentration rose (61.5 +/- 17.6-86.6 +/- 13.3) and glycogen decreased (181 +/- 54-143 +/- 3 mmol X kg-1 d.m.). Use of mannitol in a crystalloid cardioplegia solution does not prevent pronounced anaerobic metabolism in the myocardium during aortic valve replacement.     

Myocardial preservation during anoxic arrest. Chemical cardioplegia

Two types of cardioplegic solution--the potassium arrest and the Bretschneider solution, both at 4 degrees C--were compared with regard to protective effect against ischemic damage during 60 min of anoxic cardiac arrest in the dog heart. Both solutions provided equally good protection, which was superior to that given by hypothermia alone.     

Reperfusion modification with a simplified blood cardioplegia system compared with oxygenated crystalloid cardioplegia

A simplified system was developed for administration of blood cardioplegia with reperfusion modification. This system utilizes a single pass stainless steel coil to eliminate the need for a separate heat exchanger circuit. This system was compared with an oxygenated crystalloid cardioplegia system which was utilized in a manner which allowed warm blood perfusion of the heart for the last three minutes of the crossclamp interval. Both of these systems were compared with regard to mortality, spontaneous defibrillation, myocardial temperature, blood usage and peak CK-MB levels. In this series of patients, no significant advantage of either system could be identified.     

Antegrade crystalloid cardioplegia vs antegrade/retrograde cold and tepid blood cardioplegia in CABG.

BACKGROUND: This study evaluated the myocardial protective strategies in isolated coronary bypass surgeries. METHODS: One hundred and twenty-eight patients were prospectively randomized to 3 techniques of myocardial protection; group I (n = 47) antegrade/retrograde tepid blood cardioplegia, group II (n = 40) antegrade/retrograde cold blood cardioplegia with topical cooling, group III (n = 41) antegrade crystalloid cardioplegia with topical cooling. RESULTS: The incidence of spontaneous defibrillation was significantly higher in group I (p < 0.001) while the incidence of low cardiac output was not different between the 3 groups. The incidence of ventricular arrhythmia was higher in group III (p < 0.016 group III vs I). There was no significant statistical difference in hemodynamic recovery between the 3 groups. CK-MB levels were significantly lower in group I versus the other 2 groups, (p = 0.0013, 0.04). Acid release and oxygen extraction were higher in group II than in group I (p = 0.06) during cardioplegia and reperfusion. Lactate release was less in group I at the release of aortic cross-clamp, and reperfusion. There was no significant difference between the 3 groups in ICU stay, ventilation time, or hospital complications. CONCLUSIONS: Tepid blood cardioplegia showed superiority in metabolic and functional recovery, whereas crystalloid cardioplegia had the highest incidence of postoperative arrhythmias. There was no significant statistical difference between the 3 groups in hospital mortality and morbidity.     

温血诱停及再灌注对缺氧未成熟心肌保护的实验研究

目的　探讨温血诱导心脏停跳及复跳前再灌注对缺氧未成熟心肌的保护作用。方法　构建缺氧幼兔模型 ,观察比较温血诱导心脏停跳及复跳前再灌注 (实验组 )与冷晶体停跳液灌注 (对照组 ) ,心肌丙二醛 (MDA)、超氧化物歧化酶 (SOD)及三磷酸腺苷 (ATP)含量 ,心肌含水量和心肌细胞超微结构的变化。结果　缺氧幼兔出现发绀 ,低氧血症和右室 / (左室 +室间隔 )比值 [RV/ (LV +S) ]增高等改变 ,与紫绀型先天性心脏病的病理生理改变相近。再灌注末心肌MDA、SOD、ATP含量分别为 :实验组( 32 6 39± 82 88)nmol/g、( 45 44± 4 76 )U/ 10 0mg、( 13 0 9± 1 5 0 ) μmol/g ;对照组 ( 5 37 88± 10 0 5 1)nmol/g、( 2 9 2 5± 5 40 )U/ 10 0mg、( 11 5 3± 2 17) μmol/g(P <0 0 1)。心肌含水量实验组 ( 5 9 95± 2 0 9) %、对照组 ( 79 77± 1 17) % (P <0 0 1)。实验组心肌细胞线粒体、细胞核等超微结构得到较好保护。结论　缺氧幼兔模型制作方法简单 ,可操作性和可重复性较强。温血诱导停跳及复跳前再灌注能减少缺血后未成熟心肌的氧自由基产生和再灌注损伤 ,对心肌能量代谢、超微结构等方面的保护效果较好。     

Blood cardioplegia: a review and comparison with crystalloid cardioplegia.

The Oxford International Symposium on myocardial preservation provided an appropriate milestone and impetus to survey one aspect of operative myocardial preservation, namely blood cardioplegia, and to contrast it with the more popular crystalloid cardioplegia. This review is by no means complete or exhaustive but represents my best effort to summarize important information that has accumulated in the literature as blood cardioplegia, and our understanding of it, has evolved. It is appropriate to compare blood and crystalloid cardioplegia with respect to biochemical and physiological differences. Clinical comparison has been limited, for the most part, to randomized studies, and a number of differences and details of clinical management of the two techniques have been omitted, either because they seemed unimportant or there was no good information that would allow an objective comparison of their significance. Hopefully, the reader will recognize the intent to focus on meaningful differences and similarities between the two techniques and to present them fairly.     

Comparison between intermittent antegrade warm blood cardioplegia and cold crystalloid cardioplegia in patients performed reoperation for valvular heart disease

The purpose of this study was to compare the postoperative cardiac function and systemic effects between intermittent antegrade warm blood cardioplegia and cold crystalloid cardioplegia in patients performed reoperation for chronic acquired valvular heart disease. Group I consisted of 4 patients who underwent intermittent antegrade warm blood cardioplegia (MVR in 1, MVR + TAP in 2, DVR + TAP in 1), and Group II consisted of 5 patients who underwent intermittent antegrade cold crystalloid cardioplegia (MVR + TAP in 3, TVR in 2). There were no significant differences found between the two groups in operation time, perfusion time, aortic cross clamp time, spontaneous beating rate after declamping and reperfusion time. Also doses of inotropes required during weaning was almost the same for the both groups. But 24 hours after surgery, smaller doses of inotropes (4.4 +/- 2.1 gamma/kg/min) were required for Group 1, while larger doses (7.8 +/- 2.8 gamma/kg/min) were required for Group 2 (p < 0.05). As for the postoperative complications, none was noted in Group 1, while multiple organ failure in 2, hyperbilirubinemia in 2 and complete atrioventricular block in 1 patient was noted in Group 2. The above results suggest that, for reoperations of valvular heart disease, intermittent antegrade warm blood cardioplegia is a useful and reliable method with optimum myocardial protection as well as favorable systemic effects.     

Preservation of myocardial high-energy phosphates in open-heart surgery with deep general hypothermia and multidose crystalloid cardioplegia

Myocardial energy metabolism during deep general hypothermia (20 degrees C) and multidose crystalloid cardioplegia, and also during subsequent reperfusion, was studied in eight patients undergoing isolated aortic valve replacement. Six serial transmural biopsy samples from the left ventricular apex were analyzed for high-energy phosphates and their degradation products. Reductions in ATP, total adenine nucleotide content and energy charge were insignificant during cardioplegia, as were changes in adenosine and uric acid concentrations. During reperfusion, however, there was slight but significant reduction in total adenine nucleotide content, despite adequate oxygenation as indicated by reversal of lactate accumulation. These observations suggest that the reperfusion phase is accompanied by metabolic aberrations which are not overcome by good oxygenation in relation to the metabolic rate.     

Myocardial preservation in the neonate. Beneficial effects of cardioplegia and systemic hypothermia on piglets undergoing cardiopulmonary bypass and myocardial ischemia

This study examined anatomic differences between the adult and the newborn heart as they relate to myocardial preservation and compared standard techniques of myocardial preservation used in operations for congenital heart disease. The biventricular endocardial surface area/ventricular mass ratios were calculated in 10 neonatal (2.5 +/- 0.2:1) and 10 adult (0.6 +/- 0.1:1) pigs (p less than 0.001). Three groups of neonatal pigs underwent 1 hour of global myocardial ischemia while being supported by cardiopulmonary bypass. Myocardial protection was by deep systemic hypothermia (group 1), moderate systemic hypothermia and cardioplegia (group 2), or by deep systemic hypothermia and cardioplegia (group 3). Left ventricular end-systolic pressure-dimension and end-diastolic pressure-dimension relationships were measured before and after cardiopulmonary bypass. Septal temperatures remained below 20 degrees C in groups 1 and 3 but rose above 20 degrees C in group 2. Groups 1 and 2 had moderate and mild ventricular stiffening, respectively, whereas group 3 showed no diastolic dysfunction. Ventricular contractility was increased (p less than 0.05) in group 3. Techniques for myocardial preservation used during operations for congenital heart disease must consider the large endocardial surface area/mass ratio and the rewarming effects of systemic blood. The combination of deep systemic hypothermia and cardioplegia provided superior myocardial protection compared with the other techniques tested.     

Myocardial protection in cyanotic neonatal lambs

To investigate the susceptibility of cyanotic neonatal myocardium to ischemia and the effectiveness of cardioplegia for protection, we induced cyanosis in 2- to 5-day-old lambs (n = 16) by connecting the left atrial appendage to the main pulmonary artery with a 4 mm polytetrafluoroethylene graft, which produced an arterial oxygen tension of 34.1 +/- 1.2 torr. Seven to 10 days after creation of the model, isolated perfused hearts from cyanotic animals were subjected to 2 hours of ischemia with topical cooling or crystalloid cardioplegia (K = 30 mEq/L) for myocardial protection (both at 15 degrees C). Identical studies were performed on hearts from 16 normoxemic neonatal lambs 5 to 14 days old. The overall effect of cyanosis was to produce a significant impairment in recovery of maximum developed pressure (p less than 0.05) after ischemia. The overall effect of cardioplegia was to produce a significant improvement in recovery of maximum developed pressure, developed pressure at V10 (the balloon volume to produce an end-diastolic pressure of 10 mm Hg during the preischemic period), and peak rate of pressure rise at V10 (p less than 0.05). The protective effect of cardioplegia was more prominent in cyanotic hearts than in normoxemic hearts for recovery of maximum of peak rate of pressure rise and peak rate of pressure rise at V10 (p less than 0.05). End-diastolic pressure at V10 and the diastolic stiffness constant at 10 and 20 mm Hg were all significantly higher after ischemia in the cyanotic hearts than in the normoxemic hearts (p less than 0.05). We conclude that in neonatal hearts cyanosis may increase the vulnerability to ischemia and cardioplegia appears to enhance the recovery of systolic but not diastolic function in these hearts.     

Release of cardiac troponin I in antegrade crystalloid versus cold blood cardioplegia.

OBJECTIVE: The purpose of this study was to assess the efficacy of myocardial protection, comparing antegrade crystalloid cardioplegia with cold blood cardioplegia, in patients with preserved left ventricular function who were undergoing elective first coronary artery bypass grafting. Release of cardiac troponin I was used as a marker for the effectiveness of myocardial protection. METHODS: A consecutive series of 62 patients were randomly assigned to receive crystalloid or blood cardioplegia. Cardiac troponin I concentrations were determined in venous blood samples before the operation, immediately after unclamping, at 6, 9, 12, and 24 hours, and daily thereafter for 5 days. RESULTS: Rising levels of troponin I were found in all patients. The time course and peak release were similar in the crystalloid cardioplegia and the blood cardioplegia groups. No patients in either group had electrocardiographic evidence of perioperative myocardial infarction. Cardiac troponin I was able to detect small areas of myocardial damage, not revealed by electrocardiography or creatine kinase MB release. Aprotinin administration was associated with lower cardiac troponin I release in both groups. Cardiac troponin I was lower in patients whose conditions did not require electrical defibrillation after aortic unclamping, irrespective of cardioplegia type. The presence of a main stem lesion was associated with higher cardiac troponin I release only in the crystalloid cardioplegia group. CONCLUSIONS: Antegrade cold blood cardioplegia is equally effective as antegrade crystalloid cardioplegia in a randomized group of patients with preserved left ventricular function who were undergoing elective first coronary artery bypass grafting. Aprotinin administration resulted in lower cardiac troponin I release, whereas electrical defibrillation was related to a higher release irrespective of cardioplegia type. The presence of a main stem lesion resulted in higher cardiac troponin I release in the crystalloid cardioplegia group.     

Induction of cardioplegia with blood and crystalloid potassium solutions during prolonged aortic cross-clamping

Recent controversy concerns the proper vehicle for delivery of potassium cardioplegia. In the present study, adult dogs supported by cardiopulmonary bypass were subjected to 2 hours of multidose, hypothermic potassium cardioplegic arrest with 30 minutes of reperfusion with either autologous blood or crystalloid solution as the cardioplegic vehicle. Preservation of myocardial high-energy nucleotide stores was assessed by serial left ventricular biopsies assayed for adenosine triphosphate (ATP) and creatine phosphate. Preischemic and postischemic ventricular function was assessed by the use of an isovolumic intraventricular balloon. ATP stores were equally maintained at preischemic levels after ischemia and reperfusion by both autologous blood and crystalloid solution. Although creatine phosphate stores significantly declined (P less than 0.01, both groups) after 2 hours of arrest, reperfusion allowed equal restoration of preischemic levels. Maximum first derivative of left ventricular pressure and measured velocity were not depressed by either mode of protection. Similarly, myocardial compliance, as assessed by length-tension curves, showed no change following either autologous blood or crystalloid solution. The data show equal and significant myocardial protection by multidose, hypothermic potassium cardioplegia when both delivery vehicles were used.