Effect of cold blood cardioplegia enriched with potassium-magnesium aspartate during coronary artery bypass grafting

AIM: The aim of this investigation is to evaluate the effect of enriched with potassium-magnesium aspartate cold-blood cardioplegia on early reperfusion injury and postoperative arrhythmias in patients with ischemic heart disease undergoing coronary artery bypass grafting (CABG), using measurements of cardiac troponin I (CTnI), hemodynamic indexes and clinical parameters. METHODS: Forty patients with three-vessel coronary artery disease (CAD) and stable angina, receiving first-time elective CABG, were randomly divided into 2 groups: patients in control group (C group n=20) received routine institutional cold blood cardioplegia (4 degrees C) concentration of Mg2+4 mmol/L, Ca2+1.2 mmol/L and K+ 24mmol/L during myocardial arrest. Patients in P group (n=20) received modified cold blood cardioplegia enriched with potassium-magnesium aspartate and maintained concentration of Mg2+10 mmol/L, Ca2+1.2 mmol/L and K+20mmol/L in the final blood cardioplegia solution. Clinical outcomes were observed during operation and postoperatively. Serial venous blood samples for CTnI were obtained before induction, after cardiopulmonary bypass (CPB), and postoperative 6, 24, and 72 hours. Hemodynamic indexes were obtained before and after bypass by the radial catheter and Swan-Ganz catheter. RESULTS: In both groups, there were no differences regarding preoperative parameters. There were no cardiac related deaths in either group. The time required to achieve cardioplegic arrest after cardioplegia administration was significantly shorter in P group (47.5+/-16.3 s) than in C group (62.5+/-17.6 s) (P<0.01). The number of patients showing a return to spontaneous rhythm after clamp off was significantly greater in P group (n=20, 100%) than in C group (n=14, 70%) (P<0.01). Eight patients in C group had atrial fibrillation (AF) compared with two patients in P group (P<0.05) in the early of postoperative period. The level of CTnI increased 6 hours and 12 hours postoperatively, and there was a significant difference between groups (P<0.05). P group also shortened the time of postoperative mechanical ventilation (P<0.05) after surgery. CONCLUSIONS: Cold blood cardioplegia enriched with potassium-magnesium aspartate is beneficial on reducing reperfusion injury.     

Experimental study on myocardial protection with verapamil and salvia miltiorrhiza Bunge cardioplegia

Myocardial 45Ca sequestration was studied in dogs during 60 minutes of global ischemia and 30 minutes of reperfusion using cardiopulmonary bypass (CPB) and myocardial function was studied before and after CPB. Group A (n = 5), as a control, received cold hyperkalemic cardioplegic solution, Group B (n = 5) received the same solution plus verapamil (150 micrograms/kg/L) and Group C plus specific activity (TSA = DPM x 10(4)/g) and plasma specific activity (PSA = DPM x 10(4)/ml) were determined by biopsy before and after release of the cross-clamp The results showed that myocardial function in Group B and C were better than that in Group A (P less than 0.01). It is suggested that verapamil and Salvia miltiorrhiza Bunge effectively control myocardial calcium sequestration during early reperfusion and reduce myocardial reperfusion injury As to myocardial protection, cardioplegia with verapamil and Salvia miltiorrhiza Bunge were superior to hyperkalemic alone. Verapamil cardioplegia was still better than Salvia miltiorrhiza Bunge.     

Regulation of coronary myoplasmic Ca(2+)-myosin light chain phosphorylation pathway and vasomotor tone: hyperpolarizing versus depolarizing cardioplegia

BACKGROUND: This study was designed to compare the effects of hyperpolarizing versus depolarizing cardioplegic solutions on the coronary vasomotor regulation, specifically focusing on coronary myoplasmic Ca2+-myosin light chain (MLC) phosphorylation pathway and beta-adrenergic signal transduction. METHODS: With the use of an in vitro cardioplegic model, rat coronary microvessels loaded with fura-2 were subjected to simulated cold (20 degrees C) cardioplegia and reperfused with Krebs solution for 60 minutes at 37 degrees C. Cardioplegia consisted of either (1) Krebs solution alone (control), (2) Krebs plus adenosine triphosphate-sensitive potassium channel opener (100 micromol/L pinacidil [PCO-CP]), (3) hyperkalemic cardioplegia (K(+) = 25 mmol/L [K-CP]), or (4) K-CP plus magnesium (Mg(2+) = 25 mmol/L; [K/Mg-CP]). RESULTS: At the endpoint of the cardioplegic period, K-CP resulted in a significant increase both in [Ca(2+)](i) and in MLC phosphorylation compared with control (both P <.05). In contrast, PCO-CP did not make any significant difference in these indices compared with control. After reperfusion, the relaxation responses to isoproterenol and forskolin after K-CP were significantly reduced (both P <.05 vs control) but were preserved after PCO-CP. K/Mg-CP provided comparable effects to PCO-CP. CONCLUSIONS: These results suggest that neither an activation of the coronary myoplasmic Ca(2+)-MLC phosphorylation pathway nor beta-adrenergic desensitization seen after exposure to depolarizing cardioplegia occurs with exposure to hyperpolarizing cardioplegia and magnesium-supplemented depolarizing hyperkalemic cardioplegia.     

Myocardial protection of warm blood cardioplegic induction during cardiopulmonary bypass

In his prospective randomized clinical study, we evaluated the myocardial protection of warm blood cardioplegic induction and cold blood cardioplegic induction, respectively, during cardiopulmonary bypass. Twenty-eight adult patients who underwent valve replacement were randomly divided into two groups: group T (14 cases) received cold (6-8 degrees C) blood cardioplegic induction after ECG showed straight line induced by warm (35-37 degrees C) blood cardioplegia; whereas, group C (14 cases) received cold blood cardioplegic induction only. The effects of myocardial protection of both cardioplegic inductions were evaluated by clinical outcomes, myocardial biochemistry index (cardiac troponin T, cTnT), and myocardial automorphology. The ratio of myocardial auto resuscitation was significantly higher in group T (93%) than that in group C (50%). Only one case in group T (7%) and three cases in group C (21%) needed temporary pacemakers. No case in group T (0%) and five cases (36%) in group C received dopamine. The postoperative mechanical ventilation time and ICU stay time of group T were shorter than those of group C. Myocardial biochemistry indexplasma level of cTnT in group T was lower than that of group C immediately and 6 h after cardiopulmonary bypass. Myocardial morphology-group T had comparably better outcomes than group C. We concluded that warm blood cardioplegic induction during cardiopulmonary bypass, compared with cold blood cardioplegic induction, provides better myocardial protection.     

Superior myocardial protection with nicorandil cardioplegia.

OBJECTIVE: The ATP-sensitive potassium channel (K(ATP)) activator nicorandil used as cardioplegic agent may protect the left ventricle during cardiac arrest. Nicorandil in cold blood was compared with standard hyperkalemic blood and crystalloid cardioplegia. METHODS: Twenty-one pigs were randomly assigned to three groups: (1) cold hyperkalemic crystalloid (n=7); (2) cold hyperkalemic blood (n=7); and (3) nicorandil as cardioplegia in cold blood (n=7). Left ventricular mechanical performance, pressure-volume area (PVA) and myocardial oxygen consumption (MVO(2)) were measured before and at 1 and at 2 h after 60 min of cold global ischemia on cardiopulmonary bypass using intraventricular pressure-volume conductance catheters, coronary flow probes and O(2)-content difference. RESULTS: The slope (M(w)) of the stroke work end-diastolic volume relationship, the preload recriutable stroke work relationship, was unchanged after ischemia in the nicorandil group, but was reduced to averaged 62.5% (standard deviation 14) of baseline values in both hyperkalemic perfusions (P<0.05). The slope of the MVO(2)-PVA relationship was unchanged after nicorandil cardioplegia while the slope after hyperkalemic blood and crystalloid cardioplegia increased with 33% (P<0.02) and 52% (P<0.02) of baseline values, respectively. CONCLUSIONS: Nicorandil as sole cardioplegic agent in cold blood given intermittently preserves left ventricular contractility and myocardial energetics significantly better than traditional forms of cardioplegia after cardiac arrest.     

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.     

Risk of low calcium and high magnesium in continuous warm hyperkalemic cardioplegia.

BACKGROUND: The recent introduction of operations on a warm heart has prompted clinical reports on the usefulness of continuous blood cardioplegia, but no in-depth basic evaluation of continuous cardioplegia has been done. The cardioprotective effects of magnesium (Mg) and calcium (Ca) in continuous warm hyperkalemic crystalloid cardioplegic solutions were investigated in an isolated rat heart model. METHODS: Isolated rat hearts were arrested for 180 minutes at 37 degrees C with a continuous warm hyperkalemic (20 mmol/L) modified Krebs-Henseleit bicarbonate buffer solution containing 1.2, 8.0, or 16.0 mmol/L of Mg and 0.1 to 2.5 mmol/L of Ca in different concentrations. Recovery of cardiac function and tissue damage were estimated. RESULTS: For each Mg concentration, the percentage recovery of aortic flow generated dose-response curves depending on Ca concentration. However, as Mg concentration increased, the recovery of aortic flow decreased in the groups with 0.5 mmol/L of Ca or less. CONCLUSIONS: In continuous warm cardioplegia the combination of low Ca and high Mg concentration caused severe cardiac injury, and normal Ca concentration avoids cardiac injury regardless of Mg concentrations.     

Influence of ischemic preconditioning and blood cardioplegia protection on postischemic endothelial activation in coronary bypass surgery

Summary Background Hypothermic ischemia in open heart surgery and cardiopulmonary bypass involve a postischemic in-flammatory reaction caused by an activation of leukocytes and endothelia with the systemic release of cytokines and adhesion molecules. The present study addresses the question, if an amelioration of postischemic endothelial activation in the heart could be achieved by means of cardioplegic protection or ischemic preconditioning. In a randomized prospective study patients underwent a normothermic preconditioning procedure either followed by crystalloid or blood cardioplegia during coronary bypass surgery. Methods Patients (n=28) were included and randomized in the study according to defined criteria: Group A received St. Thomas cardioplegia, group B cold blood cardioplegia. Ischemic precon-ditioning was performed twice at normothermia under a cardiopulmonary bypass (CPB) for 5 min followed by 10 min of reperfusion before coronary aortic bypass graft (CABG) using St. Thomas (group C) or blood cardioplegia (group D) hypothermic protection. In coronary sinus blood and arterial blood myocardial (creatine-kinase myoglobin [CK-MB]) and endothelial activation (endothelin, IL-6, IL-8, sE-selectin, soluble vascular adhesion molecule-1 [sVCAM-1], soluble intercellular adhesion molecule-1 [sICAM-1]) parameters were investigated 1, 3, 6, 9, 12, and 24 h after coronary reperfusion. Results 1) Parameters of myocardial injury (CK-MB, myoglobin) revealed increased levels at 1 h and 9 to 12 h after CABG. Levels at 12 h were lower in group B and D as compared to A and C. 2) Cytokines (IL-6, IL-8) showed increased levels 3 h after reperfusion with no difference between study groups. 3) Soluble adhesion molecules (E-selectin, VCAM-1, ICAM-1) were found increased in all groups 6 to 12 h after reperfusion. Lower levels were present in group D for E-selectin and VCAM-1. Conclusions The results indicate a sequence of cytokine and adhesion molecule release as a potential pathomechanism of myocardial reperfusion injury. Gradual decrease in the release of endothelial adhesion molecules in late myocardial injury was noted for blood cardioplegia and ischemic preconditioning. Amelioration of endothelial activation by means of preconditioning and blood cardioplegia may improve heart muscle recovery in open heart surgery with borderline ischemia time and organ dysfunction.      

冷温血停搏液联合灌注对瓣膜置换术中炎性细胞因子和自由基的影响

目的　评价冷温血停搏液联合灌注在瓣膜置换术中对血浆促炎性细胞因子和自由基代谢水平的影响 ,探讨更有效的心肌保护方法。方法　将 30例瓣膜病病人随机分为两组 :温血组 (A组 ,n =15 ) ,采用温血诱导心脏停搏、冷血维持与终末温血灌注心肌保护方法 ;冷血组 (B组 ,n =15 ) ,采用冷氧合血停搏液进行心肌保护。分别于心肺转流 (CPB)前 (T1)、CPB 30min(T2 )、CPB结束后30min(T3 )、4h(T4)、2 4h(T5)测定血浆白细胞介素 6 (IL 6 )、IL 8和MDA浓度及SOD活性。结果B组IL 6于T2 即升高 ,持续至T5;A组无明显变化 ,于T3 明显低于B组 (P <0 0 5 )。B组IL 8于T2升高 (P <0 0 1) ,至T3 达峰值 (P <0 0 1) ,于T5下降至基础值水平 ;A组在T3 ～T4较基础值明显升高 (P <0 0 5 ) ,于T2 ～T4均显著低于B组 (P <0 0 5 )。两组MDA均在T2 升高 ,持续至T4,但A组于T3 、T4显著低于B组 (P <0 0 5 )。B组SOD活性自T2 开始降低 ,持续至T4(P <0 0 1) ;A组无明显变化 ,且在T3 与B组比较有显著性差异 (P <0 0 5 )。结论　冷温血停搏液联合灌注对瓣膜病病人的心肌再灌注损伤的抑制效应优于冷血心脏停搏液。     

Effect of induction and reperfusion with warm substrate-enriched cardioplegia on ventricular function

BACKGROUND: This study tested the hypothesis that induction and reperfusion with warm substrate-enriched (IRWSE) blood cardioplegia improves postoperative left ventricular (LV) function in patients undergoing elective coronary bypass surgery (CABG). METHODS: After giving informed consent, 67 patients scheduled for CABG surgery were randomized to either IRWSE + cold blood (CB) or CB alone. IRWSE cardioplegia consisted of 37 degrees C substrate-enriched (glutamate, aspartate, hyperkalemic) anterograde and retrograde blood cardioplegic solution followed by non-substrate-enriched cardioplegic solution given at 4 degrees C to 8 degrees C. LV function was measured with ventriculograms, volume conductance catheters, echocardiography, and multiple gated (image) acquisition. RESULTS: The end-systolic pressure-volume relationship was improved postbypass in the IRWSE + CB group (CB, 1.5 +/- 0.74 mm Hg/mL vs IRWSE + CB, 2.1 +/- 1.2 mm Hg/mL; p = 0.042). The postoperative ejection fraction (EF%) was better preserved in the CB group (CB, 65 +/- 11.53% vs IRWSE + CB, 58.62 +/- 11.75%; p < 0.04). CONCLUSIONS: Our results demonstrate a transient improvement in LV systolic function in the immediate postbypass period in CABG patients in the IRWSE + CB group. The intraoperative benefits of the IRWSE + CB technique did not persist in the postoperative period.     

Methods of cardiac preservation alter the function of the endothelium in porcine coronary arteries

This study was undertaken to determine whether clinical methods for preservation and storage of hearts explanted for transplantation affect the responsiveness of coronary arteries to vasoactive agents. Porcine hearts were perfused with crystalloid or blood cardioplegic solution. Rings of coronary arteries were suspended in organ chambers for measurement of isometric force (1) immediately after perfusion and (2) after 5 hours' storage of the hearts at 4 degrees C in the same cardioplegic solution (n = 6 in each group). The maximal contraction of the smooth muscle to potassium chloride, 40 mmol/L, was reduced significantly after perfusion with crystalloid cardioplegic solution (10.8 +/- 1.2 gm) compared with blood cardioplegic solution (17.3 +/- 0.8 gm) and nonperfused coronary arteries (control group 16.9 +/- 1.8 gm). The sensitivity of the arteries with endothelium to the contractile effects of prostaglandin F2 alpha increased after perfusion with crystalloid cardioplegic solution (ED50, [-log mol/L] 5.8 +/- 0.04) compared with blood cardioplegic solution (5.3 +/- 0.02) and the control group (5.7 +/- 0.03). In addition, relaxations to the calcium ionophore A23187, bradykinin, and the alpha 2-agonist BHT-920, which depend on the presence of endothelial cells, were significantly reduced after perfusion with crystalloid compared with blood cardioplegic solution or the control group. The responsiveness of the endothelium and smooth muscle after 5 hours' cold storage was unaltered in the blood cardioplegia group, whereas storage resulted in functional recovery in the crystalloid cardioplegia group, with the result that all groups were comparable. These data suggest an immediate and reversible change in vascular function with crystalloid cardioplegia, which was not apparent with blood cardioplegia.     

Magnesium in cardioplegia: Is it necessary?

Objective

To study the effectiveness of magnesium in cardioplegic solution in preventing postoperative arrhythmias and perioperative ischemia.

Design

Randomized, control study.

Setting

The cardiovascular surgery division of a major referral centre for the maritime provinces of Canada.

Patients

Fifty patients scheduled to undergo coronary artery bypass who had a normal ejection fraction, normal preoperative serum magnesium level and no history of atrial or ventricular arrhythmia were randomized into two groups of 25 patients. One group received magnesium sulfate (15 mmol/L) in the cardioplegic solution (group 1), the other (control) group did not receive magnesium sulfate in the cardioplegic solution (group 2).

Intervention

Coronary artery bypass grafting during which myocardial protection was provided by intermittent cold blood cardioplegia.

Outcome Measures

Postoperative serum magnesium levels, cardiac-related death, infarction and arrhythmias.

Results

All group 2 patients had a lower postoperative serum magnesium level than group 1 patients. There were no cardiac-related deaths in either group. More group 2 patients had ischemic electrocardiographic changes than group 1 patients (p < 0.03). Non-Q-wave myocardial infarction occurred in two patients (one in each group). Eight patients in group 2 had atrial fibrillation compared with five patients in group 1. Ventricular ectopia occurred significantly (p < 0.01) more frequently in group 2 than in group 1.

Conclusion

The addition of magnesium to the cardioplegic solution is beneficial in reducing the incidence of perioperative ischemia and ventricular arrhythmia in patients who undergo coronary bypass grafting.     

氨基酸对未成熟心肌保护作用的实验研究

研究天门冬氨酸或（和）谷氨酸强化血停搏液对未成熟心肌的保护效果。将２４只出生３～４周新西兰幼兔随机均分成４组：Ｉ组为冷血停搏液组，Ｉ组天门冬氨酸（２０ｍｍｏｌ／Ｌ）强化组，ＩＩ组谷氨酸（２０ｍｍｏｌ／Ｌ）强化组，ＩＶ组谷氨酸加天门冬氨酸（各２０ｍｍｏｌ／Ｌ）强化组。结果表明，心功能指标心输出量（ＣＯ）恢复百分率ＩＶ组、Ｉ组明显少于Ｉ组（Ｐ＜０．０１）；左室收缩压（ＬＶＳＰ）恢复百分率Ｉ、ＩＩ、ＩＶ组明显少于Ｉ组（Ｐ＜０．０１）；左室舒张压（ＬＶＤＰ）及左室压力微分（ｄｐ／ｄｔ）恢复百分率Ｉ、ＩＩ、ＩＶ组优于Ｉ组（Ｐ＜０．０５）。乳酸脱氢酶（ＬＤＨ）和磷酸肌酶（ＣＫ）漏出量（Ｕ／Ｌ）中，ＬＤＨ漏出量Ｉ组优于Ｉ组（Ｐ＜０．０５），ＩＩ、ＩＶ组明显优于Ｉ组（Ｐ＜０．０１）；ＣＫ漏出量ＩＩ、ＩＶ组明显优于Ｉ组（Ｐ＜０．０１）。Ｉ、ＩＩ、ＩＶ组心肌含水量（％）明显优于Ｉ组（Ｐ＜０．０１）。Ｉ、ＩＩ、ＩＶ组心肌结构保护明显优于Ｉ组。结论：谷氨酸或（和）天门冬氨酸强化血停搏液能明显增强对未成熟心肌的保护作用。氨基酸强化组间之所以差别不显著可能与模型有关     

Intracellular free calcium accumulation in ferret vascular smooth muscle during crystalloid and blood cardioplegic infusions.

OBJECTIVE: The effects of magnesium- and potassium-based crystalloid and blood-containing cardioplegic solutions on coronary smooth muscle intracellular free calcium ([Ca2+]i) accumulation and microvascular contractile function were examined. METHODS: Isolated ferret hearts were subjected to hyperkalemic (25 mmol/L K+) blood cardioplegic infusion, hypermagnesemic (25 mmol/L Mg2+, K+-free) crystalloid cardioplegic infusion, or hyperkalemic crystalloid cardioplegic infusion for 1 hour. Coronary arterioles were isolated, cannulated, and loaded with fura 2. Reactivity and [Ca2+]i were assessed with videomicroscopy. [Ca2+]i was measured at baseline and after application of 50 mmol/L KCl. In addition, [Ca2+]i and vascular contraction were measured during exposure to Mg2+ and K+ cardioplegic solution at both 4 degrees C and 37 degrees C. RESULTS: From a baseline [Ca2+]i of 177 +/- 52 nmol/L, K+ cardioplegic infusion (302 +/- 80 nmol/L potassium) markedly increased [Ca2+]i, whereas blood cardioplegic infusion (214 +/- 53 nmol/L) and Mg2+ cardioplegic infusion (180 +/- 42 nmol/L) did not alter [Ca2+]i. Although a difference between groups in percentage contraction after application of 50 mmol/L KCl was not observed, [Ca2+]i increased significantly more in vessels in the control group (764 +/- 327 nmol/L) and the K+ crystalloid cardioplegic infusion group (698 +/- 215 nmol/L) than in vessels in the blood cardioplegic infusion group (402 +/- 45 nmol/L) and the Mg2+ cardioplegic infusion group (389 +/- 80 nmol/L). Mg2+ cardioplegic solution induced no microvascular contraction at either 4 degrees C or 37 degrees C, nor was an increase in [Ca2+]i observed. K+ cardioplegic solution induced microvascular contraction at 37 degrees C but not at 4 degrees C; it increased [Ca2+]i at both 4 degrees C and 37 degrees C. CONCLUSION: An Mg2+-based cardioplegic solution, or appropriate Mg2+ or blood supplementation of a K+ crystalloid cardioplegic solution, may decrease the accumulation of [Ca2+]i in the vascular smooth muscle during ischemic arrest.     

Superiority of magnesium cardioplegia in neonatal myocardial protection

Background. We have shown that magnesium can offset the detrimental effects of normocalcemic cardioplegia in hypoxic neonatal hearts. It is not known, however, whether magnesium offers any additional benefit when used in conjunction with hypocalcemic cardioplegia.

Methods. Twenty neonatal piglets underwent 60 minutes of ventilator hypoxia (FiO₂ 8% to 10%) followed by 20 minutes of normothermic ischemia on cardiopulmonary bypass (hypoxic-ischemic stress). They then underwent 70 minutes of multidose blood cardioplegic arrest. Five (Group 1), received a hypocalcemic (Ca⁺² 0.2 to 0.4 mM/L) cardiologic solution without magnesium, whereas in 10, magnesium was added at either a low dose (5 to 6 mEq/L, Group 2) or high dose (10 to 12 mEq/L, Group 3). In the last 5 (Group 4), magnesium (10 to 12 mEq/L) was added to a normocalcemic cardioplegic solution. Function was assessed using pressure volume loops and expressed as percentage of control.

Results. Compared to hypocalcemia cardioplegic solution without magnesium (Group 1), both high- and low-dose magnesium enrichment (Groups 2 and 3) improved myocardial protection resulting in complete return of systolic (40% vs 101% vs 102%) (p < 0.001 vs Groups 2 and 3) and global myocardial function (39% vs 102% vs 101%) (p < 0.001 vs Groups 2 and 3), and reduced diastolic stiffness (267% vs 158% vs 154%) (p < 0.001 vs Groups 2 and 3). Conversely, even high-dose magnesium supplementation could not offset the detrimental effects of normocalcemic cardioplegia resulting in depressed systolic (End Systolic Elastance [EES] 41% ± 1%) (p < 0.001 vs Groups 2 and 3) and global myocardial function (40% ± 1%) (p < 0.001 vs Groups 2 and 3), and a marked rise in diastolic stiffness (258% ± 5%) (p < 0.001 vs Groups 2 and 3). Hypocalcemic magnesium cardioplegia has now been used successfully in 247 adult and pediatric patients.

Conclusions. Magnesium enrichment of hypocalcemic cardioplegic solutions improves myocardial protection resulting in complete functional preservation. However, magnesium cannot prevent the detrimental effects of normocalcemic cardioplegia when the heart is severely stressed. This study, therefore, strongly supports using both a hypocalcemic cardioplegic solution and magnesium supplementation as their benefits are additive.     

Does warm antegrade intermittent blood cardioplegia really protect the heart during coronary surgery?

OBJECTIVE: Intermittent antegrade blood cardioplegia (IABC) has been standardized as a routine technique for myocardial protection in coronary surgery. However, if the myocardium is known to tolerate short periods of ischemia during hypothermic arrest, it may be less tolerant of warm ischemia, so the optimal cardioplegic temperature of intermittent antegrade blood cardioplegia is still controversial. The aim of this study was to compare the effects of warm intermittent antegrade blood cardioplegia and cold intermittent antegrade blood cardioplegia on myocardial pH and different parameters of the myocardial metabolism. METHODS: Thirty patients undergoing first-time isolated coronary surgery were randomly allocated into two groups: group 1 (15 patients) received warm (37 degrees C) intermittent antegrade blood cardioplegia and group 2 (15 patients) received cold (4 degrees C) intermittent antegrade blood cardioplegia. The two randomization groups had similar demographic and angiographic characteristics. Total duration of cardiopulmonary bypass (108+/-17 and 98+/-21 min) and of aortic cross-clamping (70+/-13 and 65+/-15 min) were similar. The cardioplegic solutions were prepared by mixing blood with potassium and infused at a flow rate of 250 ml/min for a concentration of 20 mEq/l during 2 min after each anastomosis or after 15 min of ischemia. Intramyocardial pH was continuously measured during cardioplegic arrest by a miniature glass electrode and values were corrected by temperature. Myocardial metabolism was assessed before aortic clamping (pre-XCL), 1 min after removal of the clamp (XCL off) and 15 min after reperfusion (Rep) by collecting coronary sinus blood samples. All samples were analyzed for lactate, creatine kinase (MB fraction), myoglobin and troponin I. Creatine kinase and troponin I were also daily evaluated in peripheral blood during 6 days post-operatively. RESULTs: The clinical outcomes and the haemodynamic parameters between the two groups were identical. In group 1, XCL off and Rep were associated with higher coronary sinus release of lactate (5.5 +/- 1.8 and 2.2 +/- 0.5 mmol/l) than in group 2 (2.0 +/- 0.7 and 1.6 +/- 0.3 mmol/l, P < 0.05). Mean intramyocardial pH was lower in group 1 (7.23 +/- 0.08) than in group 2 (7.65 +/- 0.30, P < 0.05). There were no significant differences between the two groups with respect of creatine kinase (MB fraction) either after Rep or during the post-operative period. Lower coronary sinus release of myoglobin was detected at Rep in group 1 (170 +/- 53 microg/l) than in group 2 (240 +/- 95 microg/l, P < 0.05). At day 1, a lower release of troponin I was found in group 1 (0.11 +/- 0.07 g/ml) compared to group 2 (0.17 +/- 0.07 ng/ml, P < 0.05). CONCLUSION: With regards to similar clinical and haemodynamic results, myocardial protection induced by warm IAEX is associated with more acidic conditions (intramyocardial pH and lactate release) and less myocardial injury (myoglobin and troponin I release) than cold intermittent antegrade blood cardioplegia during coronary surgery.     

Intermittent antegrade warm myocardial protection compared to intermittent cold blood cardioplegia in elective coronary surgery--do we have to change?

OBJECTIVE: Intermittent antegrade warm blood cardioplegia (IAWBC) is a simple and cost-effective method of myocardial preservation. However, there are only few prospective trials comparing this type of cardioplegia to established cardioplegic strategies in elective on-pump coronary surgery with respect to myocardial protection and outcome. METHODS: In a prospective, randomized trial IAWBC (33 degrees C) (n=100) was compared to intermittent antegrade cold (4 degrees C) blood cardioplegia (n=100), regarding clinical outcome and myocardial protection using cardiac troponin-I (cTNI) and creatine kinase MB isoenzyme (CK-MB) measurements to assess ischemia. RESULTS: Preoperative parameters were comparable in both groups. Results demonstrated no differences in-between the groups regarding mortality (2.0% both), incidence of perioperative myocardial infarction (2 versus 3%), need for intra-aortic balloon pump (3 versus 4%), length of ICU stay (2.0+/-2.5 versus 2.1+/-3.0 days) and incidence of postoperative atrial fibrillation (41 versus 34%). However, the necessity of defibrillation after cardiac arrest (18 versus 43%, P<0.001) was significantly less frequent and of lower intensity (3.4+/-10.8 versus 10.8+/-20.6 J, P<0.001) in the IAWBC-group. Postoperatively the ischemia markers were significantly lower in the IAWBC-group, cTNI within the first 72 h (from P<0.001 to P=0.013) and even CK-MB within the first 24 h (from P=0.004 to P<0.011). CONCLUSION: IAWBC is a safe and simple method in elective on-pump coronary artery bypass surgery. Significantly lower ischemic markers suggest an improved myocardial protection compared to cold blood cardioplegia in these patients.     

Calcium-induced ventricular contraction during cardioplegic arrest

Cardiac arrest induced by hyperkalemic perfusion is generally considered to represent a state of complete electromechanical arrest. However, high-energy phosphate concentrations and ventricular function decrease with increasing cardioplegic calcium concentrations, possibly because of elevated resting muscle tone produced by calcium influx. We examined isolated rat hearts containing an isovolumic intraventricular balloon for the presence of contractile activity during the administration at 10 degrees C of a cardioplegic solution containing potassium, 20 mEq/L. Significant left ventricular pressure was developed (35.6% +/- 4.3% of prearrest systolic pressure) during administration of a solution containing a calcium concentration of 1.0 mmol/L and far less (9.7% +/- 1.6% of prearrest systolic pressure) with a calcium-free cardioplegic solution. The muscle contraction diminished with repeated doses, was increased by increasing cardioplegic calcium content, and was inhibited by magnesium. Adenosine triphosphate and creatine phosphate concentrations were 9.0 +/- 1.4 and 7.0 +/- 0.9 nmol/mg dry weight immediately after infusion of 15 ml of a hypoxic cardioplegic solution containing calcium, versus 13.3 +/- 1.3 (p less than 0.02) and 31.9 +/- 3.5 nmol/mg dry weight (p less than 0.0001) after a hypoxic acalcemic solution was given. When repeated doses of a hypoxic cardioplegic solution containing calcium in a concentration of 1.0 mmol/L were given at 15 minute intervals at 10 degrees C, ischemic contracture (a sustained development of ventricular pressure, mean 51% +/- 4% of prearrest systolic pressure) resulted within 1 hour. Coronary vascular resistance was increased during the muscle contractions induced by calcium-containing solutions, markedly so during contracture. Calcium-related mechanical activity was also observed during hypothermic cardioplegic arrest in five of six isolated isovolumic canine hearts. We conclude that hearts remain potentially active mechanically during cold hyperkalemic arrest and undergo energetically wasteful contraction when stimulated with calcium-containing hyperkalemic cardioplegic solutions.     

1，6—二磷酸果糖和巯甲丙脯酸对心脏术后心肌缺血—再灌注损伤的保护

目的：探讨1，6－二磷酸果糖（FDP）和巯甲丙腈酸（CAP）增强心脏停搏液对缺血心肌保护的临床效果，方法：将60例患者随机分成三组，I组：作为对照组，应用我院体外循环下心肌保护方法，即首剂应用冷钾晶体心脏停搏液，从第二剂量开始改用15度稀释氧合血灌注，Ⅱ组：在冷钾晶体心脏停搏液中加入FDP（5mmol/L)；Ⅲ组：在冷钾晶体心脏停搏液中加FDP（5mmol/L)和CAP（12．5mg/L)。观察血浆丙二醛（MDA），肌酸磷酸激酶同工酶（CPK－MB），血栓素B2（TXB2），6－酮－前列腺素F1（6－酮－PGF1a)及电子显微镜检查结果：结果：与I组比较，Ⅱ组和Ⅲ组MDA，CPK－MB明显降低，且Ⅲ组较好地维持了TXB2和6－酮－PGF1a二者的比例平衡，Ⅱ组和Ⅲ组对线粒体也有较好地保护及提高毛细血管通畅率的作用。结论：FDP和CAP能明显增加心脏停搏液对缺血心肌保护的效果。     

The efficacy and safety of extending the ischemic time with a modified cardioplegic technique for coronary artery surgery

Abstract   Background and Aim: The need to intermittently discontinue the administration of cardioplegia in order to complete the surgical procedure is a major drawback of antegrade warm blood cardioplegia. An ischemic time of 15 minutes is generally considered safe based on empirical observation. The aim of this study was the evaluation of the efficacy and safety of an intermittent warm blood cardioplegia with intervals between administrations prolonged to 25 minutes. Methods: Ninety-seven patients undergoing primary elective coronary artery revascularization were prospectively randomized into two groups. The first, Intermittent Antegrade Warm Blood Cardioplegia (IAWBC) group, comprising 49 patients, received standard intermittent antegrade warm blood cardioplegia repeated every 15 minutes. The second, Modified Intermittent Antegrade Warm Blood Cardioplegia (M-IAWBC) group, comprising 48 patients, received intermittent antegrade warm blood cardioplegia supplemented with magnesium sulfate (MgSO₄), delivered in volumes proportional to the ventricular mass and repeated every 25 minutes. The clinical outcomes were evaluated. The levels of creatine kinase-MB (CK-MB) isoenzyme, in addition to the echocardiographic assessment of septal dyskinesia and tricuspid annulus plane systolic excursion (TAPSE), have been used as markers of myocardial damage. Results: There were no statistically significant differences in clinical outcomes, need for inotropes and vasodilators, length of stay in the intensive care unit, and postoperative levels of CK-MB between the two groups. Likewise, postoperative echocardiographic assessment showed no relevant differences. Conclusions: Administration of warm antegrade cardioplegic solution supplemented with MgSO₄, delivered in volumes proportional to ventricular mass every 25 minutes, provides adequate myocardial protection for coronary artery surgery.