Is there a rationale for short cardioplegia re-dosing intervals?

Redosing of long acting cardioplegic solutions in adult cardiac surgery: A comparative study

INTRODUCTION

Despite promising results regarding using long-acting cardioplegia in the adult population, little data exists specifically for operations requiring prolonged aortic cross-clamp needing additional doses. In this pilot study, we evaluated the outcomes of patients undergoing surgery with prolonged cross-clamp time based on four different redosing compositions.

METHODS

During the period from January 2019 until June 2022, 288 patients undergoing cardiac surgery with an expected cross-clamp time over 60 min were prospectively randomized regarding the type of the cardioplegia used: Group 1 (N = 150)- single-dose del Nido antegrade cardioplegia and Group 2 (N = 138)- single-dose Histidine-Tryptophane-Ketoglutarate (HTK) antegrade cardioplegia. In patients with ischemic time over 60 min, needing a redosing were further analyzed separately in four subgroups: (A) Cold whole blood (CWB) (4:1) (N = 95); (A1: DN-CWB; A2: HTK-CWB) and (B) St Thomas Solution (N = 92) (B1: DN-St Thomas; B2: HTK-St Thomas. Control groups were C1 (DN redosed by DN) and C2 (HTK by HTK).

RESULTS

Troponin levels in A1 and B1 groups were significantly lower than in DN-control. Respiratory support time and incidence of atrial fibrillation were significantly lower in Group A1 versus DN-control.

CONCLUSIONS

Long-acting cardioplegic techniques are becoming widely utilized in the adult population, with minimal data on redosing methods/compositions for prolonged cases. Due to the small patient population, further investigation is needed to delineate optimal redosing methods, but this report brings to attention the initial success of multiple strategies.

Custodiol versus blood cardioplegia in pediatric cardiac surgery: a randomized controlled trial

BACKGROUND

Blood-based cardioplegia is the standard myocardial protection strategy in pediatric cardiac surgery. Custadiol (histidine-tryptophan-ketoglutarate), an alternative, may have some advantages but is potentially less effective at myocardial protection. This study aimed to test whether custadiol is not inferior to blood-based cardioplegia in pediatric cardiac surgery.

METHODS

The study was designed as a randomized controlled trial with a blinded outcome assessment. All pediatric patients undergoing cardiac surgery with cardiopulmonary bypass and cardioplegia, including neonates, were eligible. Emergency surgery was excluded. The primary outcome was a composite of death within 30 days, an ICU stay longer than 5 days, or arrhythmia requiring intervention. Secondary endpoints included total hospital stay, inotropic score, cardiac troponin levels, ventricular function, and extended survival postdischarge. The sample size was determined a priori for a noninferiority design with an expected primary outcome of 40% and a clinical significance difference of 20%.

RESULTS

Between January 2018 and January 2021, 226 patients, divided into the Custodiol cardioplegia (CC) group (n = 107) and the blood cardioplegia (BC) group (n = 119), completed the study protocol. There was no difference in the composite endpoint between the CC and BC groups, 65 (60.75%) vs. 71 (59.66%), respectively (P = 0.87). The total length of stay in the hospital was 14 (Q2-Q3: 10-19) days in the CC group vs. 13 (10-21) days in the BC group (P = 0.85). The inotropic score was not significantly different between the CC and BC groups, 5 (2.6-7.45) vs. 5 (2.6-7.5), respectively (P = 0.82). The cardiac troponin level and ventricular function did not differ significantly between the two groups (P = 0.34 and P = 0.85, respectively). The median duration of follow-up was 32.75 (Q2-Q3: 18.73-41.53) months, and there was no difference in survival between the two groups (log-rank P = 0.55).

CONCLUSIONS

Custodial cardioplegia is not inferior to blood cardioplegia for myocardial protection in pediatric patients. Trial registration The trial was registered in Clinicaltrials.gov, and the ClinicalTrials.gov Identifier number is NCT03082716 Date: 17/03/2017.

Modified del Nido versus blood cardioplegia in congenital cardiac surgery

BACKGROUND

Lactated Ringer-based del Nido cardioplegia has been reported to be safe for acquired cardiac surgery. The original Plasma-Lyte-based solution has been proved for congenital cardiac surgery but its modification has not been adequately examined. We compared the clinical outcomes of congenital cardiac surgery using lactated Ringer-based del Nido cardioplegia versus cold blood cardioplegia.

METHODS

Between September 2018 and November 2020, 116 consecutive patients with congenital heart disease undergoing operations with cardioplegic arrest performed by a single surgeon at Faculty of Medicine Siriraj hospital; 66 with modified del Nido solution and 50 with institutional's blood cardioplegia. The patient risk profiles, operative details, mortality rates, care durations, inotrope use, blood transfusion and complications were compared.

RESULTS

Preoperative characteristics were similar between groups, including median age (2.5 vs. 3.1 years; p = 0.49), size, and gender. The Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery score of 3 to 5 was more prevalent in the del Nido group (24.2% vs. 10%; p = 0.049). There were 4 deaths in the modified del Nido group (risk category score of 4) but none in the cold blood group (p = 0.13). There was no significant difference in median intubation duration, length of intensive care unit stay, and vasoactive medications immediately and 24 h after the operation. The del Nido group required 70 to 100 ml less blood transfusion (p = 0.04). All complications were similar between the two groups.

CONCLUSIONS

Clinical outcomes of lactated Ringer-based del Nido cardioplegia were comparable to those of blood cardioplegia in congenital cardiac surgery.

Long-Term Protective Effects of Single-Dose Cardioplegic Solutions in Cell Culture Models

Despite the popularity of single-dose cardioplegic techniques, the time window and targeted population for successful reperfusion remain unclear. We tested currently available techniques based on cell viability and integrity to demonstrate long-term cardioprotection and clarify whether these solutions were performed on neonatal/adult endothelium and myocardium by examining different cell lines. Cell viability with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test proliferation assay and membrane integrity with the lactic dehydrogenase (LDH) cytotoxicity test were documented in a cell culture/microscopy setting on adult (human umbilical vein endothelium [HUVEC]), neonatal (H9C2-cardiomyocytes), and myofibroblast (L929) cell lines. Apoptotic cell activity and necrosis were evaluated by acridine orange/propidium iodide (AO/PI) staining. Twenty-four hours after seeding, cells were incubated in control (Dulbecco's modified Eagle), St. Thomas and blood cardioplegia (4:1), histidine-tryptophan-ketoglutarate (HTK), and del Nido solutions at 32°C followed by an additional 6, 24, and 48 hours in standard conditions (37°C, 5% CO2). Experiments were repeated eight times. In MTT cell viability analysis, HTK protection was significantly better than the control medium in L929 cell lines at 48th hours follow-up and acted markedly better on the HUVEC cell line at 24th and 48th hours. del Nido and HTK provided significantly better protection on H9C2 (at 24th and 48th hours). Apoptotic and necrotic cell scoring as a result of AO/PI staining was found consistent with MTT results. The LDH test demonstrated that the level of cell disruption was significantly higher for St. Thomas and blood cardioplegia in H9c2 cells. Experimental studies on cardioplegia aimed at assessing myocardial protection use time-consuming and often expensive approaches that are unrealistic in clinical practice. We have focused on identifying the most effective cell types and the direct consequences of different cardioplegia solutions to document long-term effects that we believe are the most underestimated ones in the cardioplegia literature.

Comparative Effects of Single-Dose Cardioplegic Solutions Especially in Repeated Doses During Minimally Invasive Aortic Valve Surgery

OBJECTIVE

This study aims to compare del Nido cardioplegia (DNC) and histidine-tryptophan-ketoglutarate (HTK) cardioplegic solutions in minimally invasive aortic valve replacement (mini-AVR) surgery to discuss the safety level of myocardial protection and rationale for redosing intervals.

METHODS

During the period from January 2017 to June 2019, 200 patients undergoing mini-AVR (solely or with concomitant procedures) were prospectively randomized to DNC (n = 100) andHTK (n = 100), both up to 90 minutes ischemic time. Patients with ischemic time over 90 minutes, needing a redosing, were further analyzed in 2 subgroups with DNC-R (n = 30) and HTK-R (n = 36). Sensitive biomarkers, in addition to routine biochemistry, were also documented at baseline (T1), after cessation of cardiopulmonary bypass (T2), and on the first postoperative day (T3). Transmural myocardial biopsies were sampled for staining.

RESULTS

No statistical differences could be demonstrated in DNC and HTK groups with up to 90 minutes cross-clamp times in routine biochemical measurements and basic perioperative clinical outcomes. DNC-R showed significantly more arrhythmia/AV block incidence resulting in more extended intensive care unit (ICU) stay. Interleukin-6 and syndecan-1 in DNC and DNC-R groups were substantially higher at T2. Aquaporin-4 levels were significantly lower in the DNC-R group, demonstrating unsatisfactory response of cells to an excessive volume at T2.

CONCLUSIONS

DNC and HTK provided acceptable myocardial protection as single-dose applications. DNC-R had significantly unbalanced levels of biomarkers, and more arrhythmia/AV block incidence resulting in more extended ICU stay. For patients who may need redosing HTK may be preferable to DNC.

Myocardial protection technique structured on cardiac mass

OBJECTIVE

Myocardial protection is crucial in cardiac surgery: quantification is often difficult as there is a significant mismatch between body weight and heart weight as per geometric remodeling. This study has the objective to compare two groups of patients on the administration of myocardial protection in valvular pathologies: the first group has indexed the administration with left ventricular mass index; the second has indexed it on the body weight or on the body surface area. The primary endpoint of double-blind case-control study is to detect the difference in incidence in terms of post-operative low cardiac output syndrome.

METHODS

A single-center double-blind case-control study in a specialized regional tertiary cardiac surgery center in Italy. Between March 2017 and September 2018, 200 adults (100 per Group A vs. Group B) were scheduled for elective procedures: Group A (50 aortic valve replacement-50 mitral valve repair in minimally invasive cardiac surgery) used blood cardioplegic solution with Saint Thomas I solution, with calculation of left ventricular mass index with echocardiographic measures (Formula Group A); Group B (50 aortic valve replacement-50 mitral valve repair in minimally invasive cardiac surgery) used blood cardioplegic solution with Saint Thomas I solution, with calculation indexed on the body surface area, Du Bois Method (Formula Group B).

RESULTS

A statistically significant difference was found for Student's t-test in patients who used myocardial indexed protection on left ventricular mass index versus control: aortic valve replacement procedures in aortic valve stenosis-ejection fraction (24 hours, p-value = 0.046), TnT (24 hours, p-value = 0.047), stroke volume shift (24 hours, p-value = 0.043), and infusion of epinephrine after cardiopulmonary bypass (p-value = 0.033); aortic valve replacement procedures in aortic valve insufficiency-ejection fraction (24 hours, p-value = 0.044), TnT (24 hours, p-value = 0.047), stroke volume shift (24 hours, p-value = 0.046), and infusion of Epinephrine after cardiopulmonary bypass (p-value = 0.029). No statistically significant differences in patients undergoing mitral valve repair surgery.

CONCLUSION

The study group in the aortic valve surgery that administered myocardial protection indexed for the left ventricular mass index and showed a statistically significant lower incidence for post-operative low cardiac output syndrome compared to the control group.

Does the type of cardioplegia used during valve surgery influence operative nadir hematocrit and transfusion requirements?

INTRODUCTION

Myocardial protection is performed using diverse cardioplegic (CP) solutions with various combinations of chemical and blood constituents. Newer CP formulations that extend ischemic intervals may require greater asanguineous volume, contributing to hemodilution.

METHODS

We evaluated intraoperative hemodilution and red blood cell (RBC) transfusion rates among three common CP solutions during cardiac valve surgery. Data from 5,830 adult cardiac primary valve procedures where either four-to-one blood CP (4:1), del Nido solution (DN) or microplegia (MP) was used at 173 United States surgical centers. The primary outcome was the nadir hematocrit (Hct) during cardiopulmonary bypass (CPB), with a secondary outcome of total units of RBC transfused intraoperatively. Outcomes were assessed using mixed-effects regression, with controls for patient size, age, first Hct in the operating room, ultrafiltration volume, net bypass circuit priming volume, anesthesia and perfusion asanguineous volumes, cross-clamp and total procedure times, procedure type, reoperation, hospital, surgeon and twelve other patient and procedural variables.

RESULTS

A total of 2,641 patients received 4:1 (45.3%), 1,864 received DN (32.0%) and 1,325 received MP (22.7%). There were only slight differences in the central tendency (mean (SD)) for crude nadir Hct on CPB: 4:1, 25.5 (4.5), DN, 26.0 (4.6) and MP, 26.5 (4.7). After controlling for numerous operative and patient characteristics, the regression-adjusted estimate of the nadir Hct on CPB for MP was 26.2%, compared to 25.7% for 4:1 and 25.7% for DN; differences between MP and the other methods were statistically significant (p<0.01). Unadjusted mean RBC units transfused per patient was very similar across the groups (4:1, 2.2; MP, 2.3; DN, 2.4). Regression-adjusted estimates for the number of units of RBC transfused intraoperatively showed no statistically significant differences between CP methods.

CONCLUSIONS

In patients undergoing cardiac valve surgery, the type of CP did not have a strong clinical impact on hemodilution or transfusion. Choice of a myocardial preservation solution can be made independently of its effect on intraoperative Hct.

Warm blood cardioplegia versus cold crystalloid cardioplegia for myocardial protection during coronary artery bypass grafting surgery

We retrospectively analyzed early results of coronary artery bypass grafting (CABG) surgery using two different types of cardioplegia for myocardial protection: antegrade intermittent warm blood or cold crystalloid cardioplegia. From January 2015 to October 2016, 330 consecutive patients underwent isolated on-pump CABG. Cardiac arrest was obtained with use of warm blood cardioplegia (WBC group, n = 297) or cold crystalloid cardioplegia (CCC group, n = 33), according to the choice of the surgeon. Euroscore II and preoperative characteristics were similar in both groups, except for the creatinine clearance, slightly lower in WBC group (77.33 ± 27.86 mL/min versus 88.77 ± 51.02 mL/min) (P < 0.05). Complete revascularization was achieved in both groups. In-hospital mortality was 2.0% (n = 6) in WBC group, absent in CCC group. The required mean number of cardioplegia’s doses per patient was higher in WBC group (2.3 ± 0.8) versus CCC group (2.0 ± 0.7) (P = 0.045), despite a lower number of distal coronary artery anastomoses (2.7 ± 0.8 versus 3.2 ± 0.9) (P = 0.0001). Cardiopulmonary and aortic cross-clamp times were similar in both groups. The incidence of perioperative myocardial infarction (WBC group 3.4% versus CCC group 3.0%) and low cardiac output syndrome (4.4% versus 3.0%) were similar in both groups. As compared with WBC group, in CCC group CK-MB/CK ratio >10% was lower during each time points of evaluation, with a statistical significant difference at time 0 (4% ± 1.6% versus 5% ± 2.5%) (P = 0.021). In presence of complete revascularization, despite the value of CK-MB/CK ratio >10% was less in the CCC group, clinical results were not affected by both types of cardioplegia adopted to myocardial protection. As compared with cold crystalloid, warm blood cardioplegia requires a shorter interval of administration to achieve better myocardial protection.

Does the Type of Cardioplegic Technique Influence Hemodilution and Transfusion Requirements in Adult Patients Undergoing Cardiac Surgery?

During cardiac surgery, myocardial protection is performed using diverse cardioplegic (CP) solutions with and without the presence of blood. New CP formulations extend ischemic intervals but use high-volume, crystalloid-based solutions. The present study evaluated four commonly used CP solutions and their effect on hemodilution during cardiopulmonary bypass (CPB). Records from 16,670 adult patients undergoing cardiac surgery with CPB between February 2016 and January 2017 were reviewed. Patients were classified into one of four groups according to CP type: 4-1 blood to crystalloid (4:1), microplegia (MP), del Nido (DN) and histidine-tryptophan-ketoglutarate (HTK). Covariate-adjusted estimates of group differences were calculated using multivariable logistic and linear mixed effects regression models. The primary end point was intraoperative transfusion of allogeneic red blood cells (RBCs), with a secondary end point of intraoperative hematocrit change. Among all patients, 8,350 (50.1%) received 4:1, 4,606 (27.6%) MP, 3,344 (20.1%) DN, and 370 (2.2%) HTK. Both 4:1 and MP were more likely to be used in patients undergoing coronary revascularization surgery, whereas DN and HTK were seen more often in patients undergoing valve surgery (p < .001). The highest volume of crystalloid CP solution was seen in the HTK group, 2,000 [1,754, 2200], whereas MP had the lowest, 50 [32, 67], p < .001. Ultrafiltration usage was as follows: HTK-84.9%. DN-83.7%, MP-40.1%, and 4:1-34.0%, p < .001. There were no statistically significant differences on the primary outcome risk of intraoperative RBC transfusion. However, statistically significant differences among all but one of the pair-wise comparisons of CP methods on hematocrit change (p < .05 or smaller), with MP having the lowest predicted drift (-7.8%) and HTK having the highest (-9.4%). During cardiac surgery, the administration of different CP formulations results in varying intraoperative hematocrit changes related to the volume of crystalloid solution administered.

Novel cardioprotection strategies for the aged heart: evidence from pre-clinical studies

The incidence of cardiovascular disease is rising as the population ages. This has led to an increase in the need to perform cardiac surgery in older patients. However, aged hearts are particularly susceptible to reperfusion injury following periods of myocardial ischaemia that occur during cardiac surgery. Indeed, older adults experience myocardial dysfunction and reduced survival post-surgery compared to younger people and certain groups, including older women and frail older adults, are at particular risk. This highlights the need to design cardioprotective strategies specifically for the ageing heart. Cardioprotection during surgery is often accomplished by perfusing the heart with chemical arresting agents, known as cardioplegic solutions. New protective strategies have been developed and tested in animal models, where cardioplegic solutions have been modified by changing their temperature, chemical components and/or the frequency of delivery. In addition, drugs designed to activate cardioprotective mechanisms or to inhibit mechanisms involved in injury have been added to improve the efficacy of these solutions. However, most experimental studies have developed and optimized cardioplegic solutions in hearts from younger male animals. This review discusses pre-clinical models used to optimize cardioplegic solutions, with an emphasis on the few studies that have used hearts from older animals. Pharmacologic agents that have been shown to enhance the benefits of cardioplegia in younger hearts and could, in theory, protect vulnerable older hearts are also considered. We emphasize the need to conduct studies in frail older animals of both sexes to facilitate translation of laboratory-based observations to the clinic.

Rationale for Implementation of Warm Cardiac Surgery in Pediatrics

Cardiac surgery was developed thanks to the introduction of hypothermia and cardiopulmonary bypass in the early 1950s. The deep hypothermia protective effect has been essential to circulatory arrest complex cases repair. During the early times of open-heart surgery, a major concern was to decrease mortality and to improve short-term outcomes. Both mortality and morbidity dramatically decreased over a few decades. As a consequence, the drawbacks of deep hypothermia, with or without circulatory arrest, became more and more apparent. The limitation of hypothermia was particularly evident for the brain and regional perfusion was introduced as a response to this problem. Despite a gain in popularity, the results of regional perfusion were not fully convincing. In the 1990s, warm surgery was introduced in adults and proved to be safe and reliable. This option eliminates the deleterious effect of ischemia-reperfusion injuries through a continuous, systemic coronary perfusion with warm oxygenated blood. Intermittent warm blood cardioplegia was introduced later, with impressive results. We were convinced by the easiness, safety, and efficiency of warm surgery and shifted to warm pediatric surgery in a two-step program. This article outlines the limitations of hypothermic protection and the basic reasons that led us to implement pediatric warm surgery. After tens of thousands of cases performed across several centers, this reproducible technique proved a valuable alternative to hypothermic surgery.