Optimal Myocardial Protection Research Articles

Myocardial Protection in Cardiac Surgery: Exploring the Influence of Anesthetic Agents.

This review assesses the efficacy of inhalation anesthetics and propofol in cardiac surgery, primarily focusing on their impact on myocardial protection and subsequent clinical outcomes. The review provides a concise summary of the current scientific information regarding the protective efects of inhalation anesthetics and propofol, particularly in the context of ischemia-reperfusion injury during cardiac surgery. The review delves into the mechanisms of action and discusses clinical studies comparing the 2 anesthetic strategies regarding mortality, complication rates, and length of hospital stay. Inhalation anesthetics exhibit cardioprotective properties through many mechanisms, such as preconditioning, scavenging of free radicals, and stabilizing mitochondria. Propofol demonstrates certain protective benefits but does not possess the preconditioning capability of inhalation medications. Clinical investigations yield contradictory findings, as several studies indicate enhanced outcomes with inhalation anesthetics, while others observe no substantial disparity between the 2 approaches. The cardioprotective efcacy of propofol against ischemia-reperfusion injury remains limited. While its inherent antioxidant properties ofer direct myocardial protection, propofol demonstrably lacks the preconditioning-mediated signaling pathways triggered by inhalation anesthetics. As a result, propofol's protective efect may be slightly inferior to preconditioning strategies, and its potential to inhibit organ-protective impact of other interventions needs further investigation. The question of which anesthetic approach ofers superior myocardial protection remains debatable. Current evidence is inconclusive, potentially due to patient heterogeneity, surgical complexity, and methodological limitations of existing studies. Future research, including pharmacogenetic studies and large, welldesigned, randomized controlled trials, are necessary to provide definitive guidance on anesthetic selection for optimal myocardial protection in cardiac surgery.

Efficacy and Safety of Multidose del Nido Cardioplegia for Optimal Myocardial Protection in Isolated Coronary Artery Bypass Grafting Surgery: A Comparative Retrospective Cohort Study

Background: The perioperative outcomes of del Nido cardioplegia (DNC) as a single-dose solution have been investigated in cardiac surgical procedures. However, the optimal redosing interval for multiple doses of DNC remains an area of ongoing debate. The purpose of this study is to evaluate the safety and efficacy of multidose DNC administered according to our protocol in comparison to intermittent cold blood cardioplegia (BC) in isolated coronary artery bypass grafting (CABG) patients. Methods: A retrospective analysis was conducted on 79 consecutive isolated CABG patients between January 2022 and March 2023. The Patients were divided into two groups: the DNC group (n = 35), and the BC group (n = 44). Perioperative clinical characteristics, cardiac enzyme levels, and postoperative complications were compared between the groups. DNC was applied in a 1:4 (crystalloid:blood) ratio, with an initial dose of 20 mL/kg. Maintenance doses of 10 mL/kg were given every 45 to 50 minutes. A half dose was given if the aortic cross-clamp was expected to last less than 60 minutes. Warm blood was applied before releasing the aortic cross-clamp. Results: Both groups demonstrated comparable mean aortic cross-clamp and cardiopulmonary bypass times. At 24 hours postoperatively, troponin T levels were significantly lower in the DNC group (p ˂ 0.001), while creatine kinase-myocardial band (CK-MB) levels were higher (p ˂ 0.001). The DNC group required lower defibrillation rates than the BC group (p = 0.008). Multivariate logistic regression analysis revealed that the requirement for defibrillation (odds ratio (OR) = 10.9, 95% confidence interval (CI): 2.9–41.8, p < 0.001), cross-clamp time (OR = 1.04, 95% CI: 1.02–1.1, p = 0.002) and body mass index (BMI) (OR = 0.8, 95% CI: 0.7–0.9, p = 0.030) were independent risk factors for low cardiac output syndrome. DNC and left ventricle ejection fraction >40% were associated with a return to sinus rhythm (OR = 3.6, 95% CI: 1.3–10.1, p = 0.013 and OR = 3.1, 95% CI: 1.1–8.7, p = 0.035, respectively). No significant differences were found in terms of postoperative adverse events, and in-hospital mortality. Conclusion: Multidose DNC in CABG patients provides equivalent clinical outcomes and myocardial protection compared to BC. In addition, the findings suggest that the redosing interval strategy employed in the DNC protocol is acceptable.

Myocardial Protection in High-Risk Cardiopulmonary Bypass Support

The development of cardioplegia has facilitated complex cardiac surgery and allowed high-risk patients to safely tolerate life-saving procedures. By following the principles of electromechanical arrest, inducing hypothermia, and using adjunctive agents to help mitigate the effects of hypothermia and ischemia reperfusion injury, cardioplegia can be safely induced with various commercially available compositions, which can be delivered by several different surgical techniques. Although many studies have compared these methods, there is little consensus on whether any one method is superior to another. Just as a surgeon may need to modify technique according to individual patient factors, so too must a surgeon be flexible and be prepared to use different cardioplegia strategies according to the clinical circumstances. Increasing evidence shows the advantage of coronary artery bypass grafting (CABG) over percutaneous interventions in patients with low ejection fractions. Thus, optimal myocardial protection will continue to be necessary in this higher-risk cohort. Moreover, while patients in cardiogenic shock rarely present for CABG, the high mortality in this cohort demonstrates the need for ongoing efforts to improve myocardial protection. Lastly, there may be circumstances in which alternative approaches involving fibrillatory arrest or keeping the heart beating are more effective than conventional cardioplegia. These techniques should all be part of the surgeon’s armamentarium, enabling the surgeon to tailor the operation to the individual patient.

Microplegia in paediatric hearts.

A basic prerequisite for a good surgical outcome in heart surgery is optimal myocardial protection. However, cardioplegia strategies used in adult cardiac surgery are not directly transferable to infant hearts. Paediatric microplegia, analogous to Calafiore cardioplegia used in adult cardiac surgery, offers the advantage of safe myocardial protection without haemodilution. The use of concentration-dependent paediatric microplegia is new in clinical implementation. Paediatric microplegia has been in clinical use in our institution since late 2014. It is applied via an 1/8 inch tube of a S5-HLM roller pump (LivaNova, Italy). As cardioplegic additive, a mixture of potassium (K) 20mL (2mmol/mL potassium chloride 14.9% Braun) and magnesium (Mg) 10mL (4mmol/mL Mg-sulphate Verla® i. v. 50%) is fixed into a syringe-pump (B. Braun, Germany). This additive is mixed with arterial patient blood from the oxygenator in different flowdependent ratios to form an effective cardioplegia. After microplegia application of initially 25mmol/L K with 11mmol/L Mg for 2min, a safe cardioplegic cardiac arrest is achieved, which after release of the coronary circulation, immediately returns to a spontaneous cardiac-rhythm. In the case of prolonged aortic clamping, microplegia is repeated every 20min with a reduction of the application dose of K by 20% and Mg by 30% (20mmol/L K; 8.5mmol/L Mg) and a further reduction down to a maintenance dose (15mmol/L K; 6mmol/L Mg) after additional 20min. The microplegia adapted to the needs of paediatric myocardium is convincing due to its simple technical implementation for the perfusionist while avoiding haemodilution. However, the required intraoperative interval of microplegia of approx. 20min demands adapted intraoperative management from the surgeon.

Comparison of troponin 1 level among the patients who underwent coronary artery bypass grafting with and without adenosine as an adjunct to blood cardioplegia

Background: Cellular injury is not avoidable with current cardioplegic solutions. No method of cardioplegia has been shown to completely protect the myocardium against cellular injury. The objective of the study is to evaluate the safety and efficacy of adenosine as an adjunct to blood cardioplegia during CABG.Methods: A retrospective study at GMCT, Thiruvananthapuram in CABG patients for 3 years from January 1, 2016, to December 31, 2019, between the age of 40 and 70 years. Patients with other chronic diseases and pre-operative echo showing EF less than 40% were excluded. The study variables were level of troponin I intra and postoperative period, time taken for cardiac standstill, number of days in ventilator, ICU and on inotropic supports. Also, postoperative lactate levels, changes in RWMA and EF.Results: Of the total 75 subjects, 40 got adenosine while 35 didn’t. The mean post op EF for those who got adenosine is 55.30 and without is 56.46. The mean time of cardiac stand still with adenosine is 12.88 sec and without is 16.51 sec. The mean post op troponin I level in those who got adenosine is 6.43 and without is 12.94.Conclusions: Decreased level of troponin I and inotropic requirement suggests that an optimal myocardial protection. Adenosine usage helps in early extubation but doesn’t alter the number of days in ICU. Adenosine is safe, gives more rapid cardiac arrest but it will not alter the post op left ventricular function.

Cardioprotection with Adenosine during Coronary Revascularization

Background: Postoperative cardiac dysfunction is a common cause of mortality and morbidity associated with CABG Surgery. Adenosine enhances tolerance of the myocardium to ischemic arrest. Therefore, the study on adenosine pre-treatment as an adjunct to cardioplegia in patients undergoing CABG will definitely help to provide better myocardial protection for better postoperative outcome.
 Methods: Quasi experimental study was done in the Department of Cardiac Surgery, NICVD during July 2012 to June 2014 with patients who underwent conventional CABG surgery. Patients were divided in two groups. Group A: Patients received at regular institutional high-potassium ([K+] = 20 mol/ l) cold (12 °C) blood cardioplegia. and Group B: Patients received 250 μg /kg bolus dose of adenosine pre-treatment, which was immediately followed by high-potassium cold (12 °C) blood cardioplegia after clamp-on. Patients were followed up to evaluate the degree of myocardial damage by measuring perioperative Troponin I, amount of inotropic support, time of assisted ventilation, arrhythmia and mortality.
 Results: Most of the patients in each group belongs to 51-60 years of age range. There was no difference regarding operative parameters in two groups. Time to arrest was significantly shorter in group B compared to group A, indicating that adenosine has the potential to enhance the efficacy of cardioplegic arrest. Plasma level markers of myocardial damage: cardiac Troponin I (cTnI) obtained from serial venous blood samples post-operatively were significantly lower in group B than group A (p<0.05). There was significantly decreased requirement of inotrope in group B during first 24 hrs (p <0.05).
 Conclusion: Decreased level of cardiac enzymes and lower inotropic requirement suggests that an optimal myocardial protection with less cellular damage is obtained with adenosine pre-treatment as adjunct to cold blood cardioplegia.
 Cardiovasc. j. 2021; 13(2): 128-134

Ministernotomy aortic valve surgery in patients with prior patent mammary artery grafts after coronary artery bypass grafting.

Patients with patent internal thoracic artery (ITA) grafts after prior coronary artery bypass grafting surgery who require aortic valve replacement (AVR) pose unique technical challenges for safe and optimal myocardial protection. The purpose of this study is to review our short- and long-term outcomes with redo minimally invasive AVR in patients with patent in situ ITA grafts. From 2008 to 2016, 48 patients with at least 1 patent in situ mammary artery graft underwent minimally invasive AVR. Preoperative computed tomography was performed in all patients to evaluate the relationship of patent grafts to the sternum. Retrograde coronary sinus and pulmonary vent catheters were placed via the right internal jugular vein. The in situ ITA grafts were not clamped during AVR. Transverse aortotomy, taking care to avoid the grafts arising from the aorta, was performed to expose the aortic valve. The median age of the patients was 78 years [Quartile 1 (Q1)-Quartile 3 (Q3): 71-81]. Thirty-nine (81%) patients were men, and 46 (96%) patients had aortic stenosis. The median cardiopulmonary bypass and cross-clamp times were 124 (Q1-Q3: 108-164) and 92 (Q1-Q3: 83-116) min, respectively. Moderate hypothermia at 28-30°C was used in all patients. Most patients received cold blood cardioplegia with antegrade induction and continuous retrograde delivery. Four patients received only retrograde delivery due to some degree of aortic insufficiency. Thirty-day mortality was 4% (2 of 48 patients). There was no conversion to full sternotomy, and no reoperations were performed for postoperative bleeding or sternal wound infection. Excluding the 2 patients who died in the hospital, the median postoperative length of stay was 7 days (Q1-Q3: 5-8). Overall survival at 1, 5 and 10 years was 94%, 87% and 44%, respectively. Percutaneous retrograde cardioplegia combined with antegrade cardioplegia and moderate hypothermia, without interruption of ITA flow, is a safe and reliable strategy in patients with patent ITA grafts undergoing aortic valve replacement. This strategy combined with a minimally invasive approach may reduce surgical trauma, and is a safe and effective technique in these challenging patients.

Effect of Adenosine on Myocardial Protection as an Adjunct to Cardioplegia during Coronary Artery Bypass Surgery

Background: Adenosine (ADO) has been known to have beneficial effects against tissue injury after myocardial ischemia. So, this study was carried out to investigate the cardio protective effect of exogenous ADO pretreatment as an adjunct to cold blood cardioplegia during coronary artery bypass surgery.Materials and methods: 50 patients (25 in each group) with coronary artery disease undergoing CABG were randomly assigned to both groups: Group A received regular institutional high-potassium ([K+] 20 mol/ 1) cold (12 °C) blood cardioplegia and Group B received 250 ug/ kg adenosine pretreatment followed by antegrade high-potassium cold (12 °C) blood cardioplegia after clamp-on. Clinical outcomes were observed before, during and after the operation.Results: There was no difference regarding operative parameters in two groups. Time to arrest was significantly shorter in group B compared to Group A, indicating that adenosine has the potential to enhance the efficacy of cardioplegic arrest. Plasma level markers of myocardial damage: cardiac Troponin I (cTnl) obtained from serial venous blood samples were significantly lower in group B during cTnl at 10 min after declamping of cross clamp and 12 hours post-operative period than group A. There was significantly decreased requirement of inotrope in group B during 1st 24 hrs. Other postoperative outcomes (mechanical ventilation, ICU stay, postoperative arrhythmia and in hospital mortality were similar in both groups.Conclusion: Decreased level of cardiac enzymes and lower inotropic requirement suggests that a optimal myocardial protection with less cellular damage is obtained with adenosine pretreatment as adjunct to cold blood cardioplegia.University Heart Journal Vol. 14, No. 1, Jan 2018; 21-23

Mechanisms of Cardioprotection of Halogenated Agents During Extracorporeal Circulation in Cardiac Surgery.

The implementation of cardioprotective strategies involving pre-, intra-, and postoperative interventions is key during cardiac surgery requiring extracorporeal circulation (ECC). The primary goal of this study was to review the physiopathology and protection strategies against myocardial damage secondary to ECC during cardiac surgery. The administration halogenated anesthetics for cardiac anesthesia is common place due to their well-known cardioprotective effects and their capacity to ensure hypnosis. An optimal myocardial protection strategy requires that a comprehensive approach should be adopted to cover pre-, intra-, and post-operative interventions. Pre-conditioning and post-conditioning share numerous pathways, mainly based on mitochondrial signaling, antiapoptotic pathways, and reduced inflammatory mediators. However, volatile anesthetic can also be administered during ECC, in which mechanism of action has been scantly investigated, during this period and its biology is still unknown.

Custodiol versus blood cardioplegia in pediatric cardiac surgery, two-center study

BackgroundCold blood cardioplegia is widely used as a method of myocardial protection in pediatric cardiac surgery. Operative interruption to administer cardioplegia and need for repeated administration and occasional direct coronary ostial cannulation are considered a drawbacks of this technique. Custodiol, a crystalloid solution, has been used in children as an alternative cardioplegia solution with the potential advantage of single dose administration with equivalent myocardial protection. We sought to compare the outcomes of cold blood cardioplegia versus Custodiol cardioplegia in pediatric cardiac surgery. MethodsA retrospective cohort study was performed between November 1st, 2013 and June 30th, 2014. All children who underwent heart surgery at two institutions with the use of cardiopulmonary bypass and cardioplegia were included. Patients were identified from a prospective database and additional data were collected from operative report and electronic and paper charts. Continuous data were represented as median and interquartile range, and tested with Wilcoxon rank-sum test. Categorical data were represented as proportions, and tested with Pearson test. A composite endpoint of all cause death, Low Cardiac Output Syndrome (LCOS), Acute Kidney Injury (AKI), and significant arrhythmia was analyzed with a multiple logistic regression model adjusted for complexity using the Risk Adjustment of Congenital Heart Surgery -1 (RACHS-1) categories. A p-value of less than 0.05 was considered to be significant. ResultsBlood cardioplegia was administered in 88 (57.1%) patients, and Custodiol cardioplegia was administered in 66 (42.9%) patients according to surgeon's preference. In the risk adjusted comparison of the composite outcome of all-cause death, LCOS, AKI and significant arrhythmia, Custodiol cardioplegia was found to be an independent predictor of an adverse outcome, OR 3.17 (95% CI 1.41–7.14, P-value = 0.0054). ConclusionsCustodial cardioplegia is associated with less optimal myocardial protection and higher adverse outcomes compared to cold blood cardioplegia in children undergoing cardiac surgery. A randomized comparison is warranted.

IMPACT OF A WHOLE BODY PERFUSION STRATEGY DURING CIRCULATORY ARREST FOR AORTIC ARCH RECONSTRUCTIVE SURGERY

During aortic arch reconstructive surgery, continuous coronary and antegrade cerebral perfusion (ACP) has been shown to provide optimal myocardial and cerebral protection. However, hypothermia alone without perfusion is frequently trusted for lower body protection. When prolonged, visceral and lower body ischemia can result in metabolic debt, leading to significant lactic acidosis and end organ dysfunction. Between January 2008 and April 2014 a single surgeon at London Health Sciences Centre performed 83 consecutive proximal aortic arch reconstructive surgeries requiring hypothermic circulatory arrest (HCA). All operations were performed using ACP and moderate hypothermia (21°C to 28°C). Forty-two patients had their surgery using only ACP and HCA. Forty-one patients had their surgery using a whole body perfusion (WBP) strategy (ACP, HCA, and additional lower body perfusion through femoral artery cannulation or direct descending aorta cannulation). Baseline characteristics, clinical outcomes, and metabolic data were analyzed. There were no significant differences in patient demographics or comorbidities between the 2 groups. The WBP group contained a significantly higher number of patients undergoing total arch reconstruction (56% versus 19%, p<0.01) with a concomitant need for significantly longer bypass time (268±79 versus 205±55 minutes, p<0.01), cross clamp time (203±60 versus 131±57 minutes, p<0.01), and HCA time (43±29 versus 30±15 minutes, p=0.01). Both groups contained a similar proportion of aortic dissections and emergent cases. Despite the complexity of surgeries performed in the WBP group, there was not a significant increase in intraoperative or postoperative peak lactate levels. Similarly, there were no differences in bicarbonate levels; however intra-operative pH values were significantly lower in the WBP group but recovered within hours of ICU admission (see figure). Use of platelets (39% versus 59%, p=0.06) and FFP (37% versus 69%, p<0.01) was less in the WBP group, as was ICU length of stay (mean 5 days versus 8 days p=0.01). There were no differences between the groups in terms of postoperative outcomes including death (4.9% versus 7.1%, p=0.67) and any of 10 major postoperative complications (27% versus 31%, p=0.68). Aortic arch reconstructive surgery can be safely performed using a WBP strategy that combines moderate HCA and ACP with additional lower body perfusion. The technique may reduce metabolic debt in more complex arch cases and may be contributory to a reduction in the use of blood products and ICU length of stay. Further study is warranted.

Sevoflurane at 1 MAC provides optimal myocardial protection during off-pump CABG

Objective. We investigated the myocardial protective effect of sevoflurane in patients receiving off-pump coronary artery bypass grafting (OPCABG) and the role of brain natriuretic peptide (BNP). Design. Forty-eight patients receiving elective OPCABG were randomly assigned to a control group, and to 0.75 MAC, 1.0 MAC and 1.5 MAC sevoflurane groups. Blood samples were collected and levels of BNP and cardiac troponin I (cTnI) were measured before anesthesia, and immediately, 24, 48 and 72 h after surgery. Results. Dopamine was necessary to maintain blood pressure in the sevoflurane groups, but not in the control group (p < 0.002). 1.0 MAC sevoflurane significantly decreased post-surgical cTnI levels (p < 0.001). 0.75 MAC had no significant effect, and increasing sevoflurane concentrations to 1.5 MAC caused no further decrease in cTnI concentrations. There was no significant difference in BNP level among the groups (p = 0.227) or between any two groups, although values of BNP showed a significant correlation with cTnI values in control subjects immediately after (r = 0.847) and 24 h after (r = 0.661) surgery. Conclusions. Our results demonstrated that 1.0 MAC and 1.5 MAC sevoflurane can exert a significant myocardial protective effect. BNP cannot be used to predict the myocardial protective effect of sevoflurane in OPCABG.

Which Is the Better Option During Neonatal Cardiopulmonary Bypass

The optimal myocardial protection strategy for newborns/infants undergoing congenital heart surgery remains controversial. The purpose of this study was to compare myocardial protection using histidine-tryptophan-ketoglutarate (HTK) and cold blood cardioplegia in a neonatal piglet model. Twenty-one piglets were randomized to three groups: the control group (C group, n = 7), a single dose of HTK group (H group, n = 7), and multidose cold blood cardioplegia group (B group, n = 7). Animals in the two experimental groups were placed on hypothermic cardiopulmonary bypass, after which the ascending aorta was clamped for 2 hours. Immediately after declamping, both the difference between arterial and coronary sinus blood lactate concentrations and the oxygen extraction did not differ between the H group and the B group. At 3 hours after declamping, rise in serum troponin-T and creatine kinase isoenzyme MB levels showed no significant differences between the H group and the B group (p = 0.735 and p = 0.103, respectively). No significant differences were noted in the myocardial lactate content, ATP content, and histopathological score between the H group and the B group (p = 0.810, p = 0.158, and p = 0.399, respectively). Transfusion requirement in the B group was significantly more than that in the H group (p = 0.003). HTK solution provides equivalent myocardial protection to multidose cold blood cardioplegia for the neonatal heart with less transfusion requirement.

Results of Reoperation on the Aortic Root and the Ascending Aorta

Reoperations on the aortic root and the ascending aorta after previous aortic valve and proximal aortic surgery are increasingly frequent and highly demanding. The scarce comparability of the published series and the heterogeneity of clinical pictures contribute to the challenges of this subgroup. Forty-one patients (2004 to 2010) who were reoperated on the aortic root and the ascending aorta for aneurysmal, pseudoaneurysmal, or infectious disease were retrospectively analyzed from a prospectively filled-in database. Mean logistic European system for cardiac operative risk evaluation was 29.8%. At index reoperation, procedures were classic Bentall (51%), prosthesis-sparing operation (17%), supracoronary ascending aortic replacement plus aortic valve replacement-repair (22%), and root replacement using valved homografts (9.7%). Distally, the operation involved the arch in 51% of cases (17 hemiarch replacement, 4 total transverse arch, 3 elephant trunk). Operative mortality was 12% and rate of major operative morbidity was 17%. At a mean 26-months follow-up, the patients surviving the operation had a good survival and functional class. The rate of adverse events during the follow-up was acceptable. Reoperations on the aortic root-ascending aorta in the elective patients have respectable operative mortality-morbidity despite the high-risk profile, and are justified by the excellent follow-up survival. The mortality can be diminished by integrated surgical strategies and optimal myocardial protection. Our findings encourage complete resection of borderline dilated ascending aortic-root tissue at primary and redo operation.

Continuous coronary perfusion in redo aortic valve replacement following prior coronary surgery; an old trick for new dogs?

The optimal myocardial protection method for aortic valve replacement in the setting of prior coronary artery bypass surgery remains a subject of debate. Protection is particularly challenging when a patent pedicled internal thoracic artery graft supplies a proximally obstructed left anterior descending artery. Herein, we describe a modification of an old technique; continuous coronary perfusion, which can be used in selected, anatomically suitable cases.

The effect of using microplegia on perioperative morbidity and mortality in elderly patients undergoing cardiac surgery

Old age is a significant risk factor for perioperative morbidity and mortality following cardiac surgery and optimal myocardial protection strategy should be sought in this group of patients. We, therefore, reviewed the data on 295 consecutive patients older than 75 years who underwent any cardiac surgical procedure. Microplegia was used in 144 patients compared to 151 patients who had the standard 4:1 blood cardioplegia. Logistic regression analysis was used for propensity matching to balance the differences between the two groups. The microplegia group included more females and sicker patients as indicated by higher Parsonnet scores. There were differences in the pump time, aortic cross-clamp time, procedure type and surgeons between the two groups. These differences were balanced using the propensity matching. In-hospital mortality, acute renal injury and confusion were higher in the microplegia group (17%, 34%, 35%, respectively) compared to the standard 4:1 cardioplegia group (9%, 23%, 24%, respectively) (P=0.04, 0.04, 0.04, respectively). These differences were not statistically significant after propensity matching. These results demonstrate that the use of microplegia is safe in patients older than 75 years who are undergoing cardiac surgery and results in similar in-hospital morbidity and mortality to the standard 4:1 blood cardioplegia.

Do You Need to Clamp a Patent Left Internal Thoracic Artery–Left Anterior Descending Graft in Reoperative Cardiac Surgery?

Dogma suggests optimal myocardial protection in cardiac surgery after prior coronary artery bypass graft surgery (CABG) with patent left internal thoracic artery (LITA) pedicle graft requires clamping the graft. However, we hypothesized that leaving a patent LITA-left anterior descending (LAD) graft unclamped would not affect mortality from reoperative cardiac surgery. Data were collected on reoperative cardiac surgery patients with prior LITA-LAD grafts from July 1995 through June 2006 at our institution. With the LITA unclamped, myocardial protection was obtained initially with antegrade cardioplegia followed by regular, retrograde cardioplegia boluses and systemic hypothermia. The Society of Thoracic Surgeons National Database definitions were employed. The primary outcome was perioperative mortality. Variables were evaluated for association with mortality by bivariate and multivariate analyses. In all, 206 reoperations were identified involving patients with a patent LITA-LAD graft. Of these, 118 (57%) did not have their LITA pedicle clamped compared with 88 (43%) who did. There were 15 nonsurvivors (7%): 8 of 188 (6.8%) in the unclamped group and 7 of 88 (8.0%) in the clamped group (p = 0.750). Nonsurvivors had more renal failure (p = 0.007), congestive heart failure (p = 0.017), and longer perfusion times (p = 0.010). When controlling for independently associated variables for mortality, namely, perfusion time (odds ratio 1.014 per minute; 95% confidence interval: 1.004 to 1.023; p = 0.004) and renal failure (odds ratio 4.146; 95% confidence interval: 1.280 to 13.427; p = 0.018), an unclamped LITA did not result in any increased mortality (odds ratio 1.370; 95% confidence interval: 0.448 to 4.191). Importantly, the process of dissecting out the LITA resulted in 7 graft injuries, 2 of which significantly altered the operation. In cardiac surgery after CABG, leaving the LITA graft unclamped did not change mortality but may reduce the risk of patent graft injury, which may alter an operation.

Mitochondrial oxidative and structural damage in ischemia-reperfusion in human myocardium. Current knowledge and future directions

The sequence of events in heart ischemia-reperfusion has been clearly documented in experimental animal models but not in cardiac surgery patients. The evidence in human studies had not been gathered in a systematic and comprehensive fashion, so as to provide an encompassing picture of the phenomenon. This limits our ability to devise appropriate strategies for optimal perioperative myocardial protection. We present here a review or our experience in myocardial ischemia-reperfusion in a historical perspective. From our previous studies we conclude that, although several issues still remain unsolved, there is no doubt that oxygen-free radicals are important contributors to myocardial injury during the reperfusion period of coronary artery bypass surgery. Yet, in spite of this wealth of information, both clinical and experimental, subsequent clinical trials conducted over the last several years with a variety of antioxidant strategies have been largely disappointing. Therefore, the whole paradigm of oxidative stress in cardiac injury needs to be re-evaluated. In this regard, differences between past and current knowledge are discussed, and future directions are traced. We concluded that patients subjected to elective bypass surgery undergo oxidative stress upon reperfusion after cardioplegic arrest; the magnitude of the phenomenon, however, is at present small and may not justify widespread antioxidant therapy.

Optimal myocardial protection strategy for coronary artery bypass grafting without cardioplegia: prospective randomised trial

Although hypothermia and ischaemic preconditioning (IP) are independently recognised mechanisms of cardioprotection, interactions between myocardial temperature and preconditioning have not been investigated. Therefore, this study explored the possibility of inducing IP during hypothermia and quantifying its effects at two temperature regimens commonly used in clinical practice. One hundred and four patients undergoing coronary artery bypass grafting (CABG) with intermittent cross-clamping and ventricular fibrillation were randomised to four groups: N=normothermia (36.5+/-0.5 degrees C); NP=normothermia+preconditioning, H=hypothermia (31.5+/-0.5 degrees C), HP=hypothermia+preconditioning. The primary outcome measure was release of cardiac Troponin I (cTnI), measured at 6 time points from pre- to 72 h after the end of CPB. There were no hospital deaths and no significant differences in pre- and intra-operative variables (P>or=0.05). There were significant differences in cTnI release between all groups, as follows: N: 117+/-12 microg/l (P<or=0.05 vs. all groups), NP: 87+/-8 microg/l (P<or=0.05 vs. groups N and HP), H: 76+/-6 microg/l (P<or=0.05 vs. groups N and HP), HP: 44+/-6 microg/l (P<or=0.05 vs. all groups). In conclusion, IP can be induced at both normothermia and moderate hypothermia, where it significantly reduces myocardial damage. Further studies are warranted to investigate the effects of the addition of hypothermia to pharmacological myocardial preconditioning.

Myocardial protection with oxygenated esmolol cardioplegia during prolonged normothermic ischemia in the rat

Objective: We previously showed that arrest with multidose infusions of high-dose (1 mmol/L) esmolol (an ultra-short-acting β-blocker) in oxygenated Krebs-Henseleit buffer (esmolol cardioplegia) provided complete myocardial protection after 40 minutes of normothermic (37°C) global ischemia in isolated rat hearts. In this study we investigated the importance of oxygenation for protection with esmolol cardioplegia, compared it with that of St Thomas' Hospital cardioplegia, and determined the protective efficacy of multidose esmolol cardioplegia for extended ischemic durations. Methods: Isolated rat hearts (n = 6/group) were perfused in the Langendorff mode at constant pressure (75 mm Hg) with oxygenated Krebs-Henseleit bicarbonate buffer at 37°C. The first part of the first study had four groups: (i) multidose (every 15 minutes) oxygenated (95% oxygen/5% carbon dioxide) Krebs-Henseleit buffer during 60 minutes of global ischemia, (ii) multidose deoxygenated (95% nitrogen/5% carbon dioxide) Krebs-Henseleit buffer during 60 minutes of global ischemia, (iii) multidose oxygenated esmolol cardioplegia during 60 minutes of global ischemia, and (iv) multidose deoxygenated esmolol cardioplegia during 60 minutes of global ischemia. The second part of the first study had three groups: (v) multidose St Thomas' Hospital solution during 60 minutes of global ischemia, (vi) multidose oxygenated St Thomas' Hospital solution during 60 minutes of global ischemia, and (vii) multidose oxygenated esmolol cardioplegia during 60 minutes of global ischemia. In the second study, hearts were randomly assigned to 60, 75, 90, or 120 minutes of global ischemia and at each ischemic duration were subjected to multidose oxygenated constant flow or constant pressure infusion of (i) Krebs-Henseleit buffer (constant flow), (ii) Krebs-Henseleit buffer (constant pressure), (iii) esmolol cardioplegia (constant flow), or (iv) esmolol cardioplegia (constant pressure). All hearts were reperfused for 60 minutes, and recovery of function was measured. Results: Multidose infusion of oxygenated esmolol cardioplegia completely protected the hearts (97% ± 5%) after 60 minutes of 37°C global ischemia. Deoxygenated esmolol cardioplegia was significantly less protective (45% ± 8%). Oxygenation of St Thomas' Hospital solution did not alter its protective efficacy in this study (70% ± 4% vs 69% ± 7%). Infusion of esmolol cardioplegia at constant pressure provided complete protection for 60, 75, and 90 minutes (104% ± 5%, 95% ± 5%, and 95% ± 3%, respectively), whereas protection with constant-flow esmolol cardioplegic infusion was significantly decreased at ischemic durations longer than 60 minutes. This decrease in efficacy of constant-flow esmolol cardioplegia was associated with increasing coronary perfusion pressure leading to myocardial injury. Conclusions: Oxygenation of esmolol cardioplegia (Krebs-Henseleit buffer plus 1.0 mmol/L esmolol) was essential for optimal myocardial protection. Multidose infusion of oxygenated esmolol cardioplegia provided good myocardial protection during extended periods of normothermic ischemia. Esmolol cardioplegia may provide an efficacious alternative to hyperkalemia.J Thorac Cardiovasc Surg 2002;124:340-51