https://orcid.org/0000-0003-0613-8273
Figures
Abstract
This study aimed to evaluate the safety and efficacy of a modified, bloodless Del Nido (DN) cardioplegia solution in patients undergoing isolated aortic valve replacement (AVR). A total of 370 patients who underwent isolated AVR between 2015 and 2022 were retrospectively analyzed. Patients were categorized into two groups based on the cardioplegia solution used: the bloodless DN group (N = 180) and the histidine-tryptophan-ketoglutarate (HTK) group (N = 190). To reduce selection bias and adjust for baseline differences, inverse probability of treatment weighting analysis was performed. There was no significant difference in in-hospital mortality between the two groups (HTK vs. DN: 1.2% vs. 0.9%, P = 0.554). However, the rate of spontaneous sinus rhythm restoration without the need for defibrillation following aortic cross-clamp release was significantly higher in the DN group (40.0% vs. 75.2%, P < 0.001). Additionally, the initial postoperative lactate level (3.0 ± 2.6 mmol/L vs. 2.2 ± 1.4 mmol/L, P = 0.002), and the incidence of low cardiac output syndrome (9.4% vs. 1.7%, P < 0.001) were significantly lower in the DN group compared to the HTK group. Other postoperative morbidities did not differ significantly between the groups. The modified bloodless Del Nido cardioplegia demonstrated favorable myocardial protection and early clinical outcomes compared to HTK solution in patients undergoing isolated AVR. These findings suggest that the bloodless Del Nido technique may be a viable alternative, although further validation in larger, prospective studies is warranted.
Citation: Sohn B, Yoo JS, Kim DJ, Lee H (2025) The efficacy of modified bloodless del Nido cardioplegia in isolated aortic valve replacement. PLoS One 20(9): e0333083. https://doi.org/10.1371/journal.pone.0333083
Editor: Redoy Ranjan, Royal Holloway University of London, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
Received: May 18, 2025; Accepted: September 9, 2025; Published: September 29, 2025
Copyright: © 2025 Sohn et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript.
Funding: The author(s) received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Myocardial protection is an essential element for successful cardiac surgery since left ventricular failure resulting from ischemic myocardial damage is a major cause of mortality and morbidity following cardiac surgery [1]. Myocardial protection in aortic valve replacement (AVR) is particularly challenging because left ventricular hypertrophy and wall tension in aortic valve disease increase myocardial oxygen demand [2,3]. Although several myocardial protection strategies with different cardioplegia have been suggested, the optimal myocardial protection strategy is still controversial in aortic valve surgery [4–7].
The histidine-tryptophan-ketoglutarate (HTK) cardioplegia is a single-dose cardioplegia, offers over two hours of myocardial protection, and provides favorable clinical outcomes in various cardiac surgeries including aortic valve surgery [4,5,8]. However, several drawbacks of HTK solution including, hemodilution, disturb blood homeostasis, electrolyte imbalances have been reported [9,10].
The Del Nido (DN) cardioplegia, introduced in the 1990s as a singular cardiac protection solution primarily for congenital and pediatric heart surgeries, has exhibited a reliable duration of myocardial safeguarding exceeding 60 minutes [11–13]. Its application has extended to diverse adult cardiac surgeries with consistently positive outcomes [14–17]. It’s noteworthy that with the expiration of the patent for DN cardioplegia, there has been a proliferation of modified versions, and research endeavors have been reported to explore and optimize its formulation [18,19].
In our institution, DN was firstly adapted in congenital heart surgery. The original formulation requires mixing with blood, which adds complexity to the circuit setup. In certain cases, constructing the mixing circuit may be technically challenging, unavailable due to equipment limitations, or impractical if additional blood withdrawal is not feasible. This is particularly relevant in pediatric patients, who are more sensitive to changes in blood volume. Under these circumstances, we began using a bloodless version of the del Nido solution since early 2000s. Favorable outcomes of modified ‘bloodless’ DN formula for several years in congenital cardiac surgery have broadened usage of the modified version of DN cardioplegia into adult cardiac surgery in 2014. The aim of our study is to assess the effectiveness of our modified ‘bloodless’ DN cardioplegia in AVR, with a comparative analysis against HTK cardioplegia.
Materials and methods
Study design
In a retrospective analysis, we examined the records of 370 patients who underwent isolated AVR at our institution from September 2015 to March 2022. These patients were categorized into two groups: HTK cardioplegia (N = 190) and DN cardioplegia (N = 180). The study protocol was approved by the Institutional Review Board of Bucheon Sejong Hospital, which waived the requirement for informed patient consent (IRB No. BSH 2023-04-001; approval date: April 19, 2023). Data used in this study were accessed for research purposes between 17/05/2023 and 16/05/2024. All procedures were conducted in accordance with relevant guidelines and regulations.
Surgical techniques and myocardial protection strategies
The patients in our study underwent AVR procedures through either a full median sternotomy or a minimally invasive approach, which included right mini-thoracotomy, right anterior thoracotomy, and partial sternotomy. The surgical operations were conducted under mild hypothermia. For myocardial protection, antegrade perfusion of a cardioplegic solution was employed. In patients without aortic regurgitation, antegrade cardioplegia was infused via aortic root cannula after aortic cross-clamping (ACC). In patients with significant aortic regurgitation, cardioplegic solution was administered directly to the coronary arteries after aortotomy following ACC. The aortic valve replacement was performed with the standard fashion. A biological, a sutureless, or a mechanical prosthesis was implanted based on age and choice of patient regarding to the clinical situations.
HTK cardioplegia
HTK solution was utilized in its commercially prepared, original form. The composition of the HTK solution is detailed in Table 1. The initial dose of the HTK solution was standardized at 2,000 mL. To achieve myocardial protection, the cardioplegia was administered antegradely into the aortic root, maintaining a 4 °C infusion temperature. In instances where the ACC time surpassed 120–180 minutes, an additional dose, equivalent to half of the initial dose, was administered to sustain effective cardioplegic protection.
The modified bloodless DN cardioplegia
The DN cardioplegia was carefully prepared by perfusionists, containing the same components as the original formulation, as outlined in Table 1. The formula contains components nearly consistent with those of the original del Nido solution, except that 15% mannitol was used instead of 20%. Unlike the conventional protocol, no blood components were mixed during administration, rendering it a fully crystalloid solution. Instead, 10 mL of 20% Dextrose solution was added as an energy substrate. The initial dose was standardized at 600 mL per body surface area (BSA) and delivered via antegrade perfusion into the aortic root at an infusion temperature of 4 °C. In cases where the ACC time exceeded 90 minutes, an additional dose—equivalent to half of the initial volume—was administered using the same technique to maintain effective myocardial protection.
Statistical analysis
Descriptive statistics for the entire study population were computed, with categorical variables presented as numbers and percentages, and continuous variables as means and standard deviations. To assess inter-group differences, the t-test (or the Mann–Whitney test when the normality assumption was in doubt) and Chi-square test (or Fisher’s exact test when the expected cell frequency was < 5) were employed for continuous and categorical variables, respectively. An inverse probability of treatment weighting (IPTW)-adjusted analysis was performed to balance the distribution of baseline risk factors between HTK and DN groups. The propensity score was derived through multiple logistic regression, considering preoperative baseline characteristics and operative parameters. They included chronic obstructive pulmonary disease, New York Heart Association (NYHA) class 3–4, Atrial fibrillation, previous open heart surgery, left ventricular ejection fraction, aortic stenosis, aortic steno-regurgitation, infective endocarditis, cardiopulmonary bypass time and aortic cross clamp time. Weights for the DN group were the inverse of the PS, and those for the HTK group were the inverse of 1-PS. Stabilized weights were used to reduce variability in the IPTW model. The love plot and the density plots before and after IPTW were included in S1 and S2 Figs, respectively. We also analyzed PS matching as an added robust analysis result. A total of 104 patients from the DN group were matched to 104 patients from the HTK group using nearest-neighbor matching without replacement and a matching tolerance (caliper) of 0.2. The Cox proportional hazards model analysis was employed to estimate the treatment effect of the two groups on long-term outcomes. The hazard ratios (HRs) of late clinical outcomes between the two groups were compared based on original unmatched data, IPTW models, and matched data. There was no missingness for data in our models and no imputation was performed for missing data. Statistical significance was set at P < 0.05. Statistical analysis was carried out using R 4.3.1 (R Foundation for Statistical Computing, Vienna, Austria).
Results
Baseline characteristics
Patients of the DN group had a higher prevalence of New York Heart Association functional classification 3 or 4 (HTK vs. DN; 10.5% vs. 25.0%, P < 0.001) and higher European system for cardiac operative risk evaluation (EuroSCORE) (1.5 ± 3.4 vs. 3.3 ± 5.5, P < 0.001). However, after IPTW, no significant differences in demographic data were observed between the groups. Table 2 describes the baseline characteristics of the study patients.
Operative data
The operative data was shown in Table 3. The cardiopulmonary bypass time, ACC time and, percentage of minimally invasive cardiac surgery (MICS) did not differ between the two groups after IPTW. The DN group showed higher use of sutureless valve (0.0% vs. 17.4, P = 0.008), and higher rate of spontaneous rhythm recovery without electrical intervention (e.g., defibrillation) after aortic cross clamp release (40.0% vs. 75.2%, P < 0.001, Fig 1).
HTK; Histidine-tryptophan-ketoglutarate; DN, Del Nido.
Early outcomes
Early mortality after AVR was not different between the two groups (2 (1.2%) in HTK vs. 2 (0.9%) in DN group, P = 0.554). Postoperative left ventricular ejection fraction (LVEF) did not differ significantly between the two groups. However, the incidence of low cardiac output syndrome (LCOS) was significantly lower in the DN group compared to the HTK group (16 (9.4)% in HTK vs. 4 (1.7%) in DN, P < 0.001). Similarly, the immediate postoperative lactate level was significantly lower in the DN group (3.0 ± 2.6 mmol/L in HTK vs. 2.2 ± 1.4 mmol/L in DN, P = 0.002, Fig 2). Perioperative transfusion requirements and postoperative hemoglobin levels were comparable between the two groups (Table 4).
HTK; Histidine-tryptophan-ketoglutarate; DN, Del Nido.
Late outcomes
Fig 3 demonstrates that there was no statistically significant difference in overall mortality between the HTK and DN cardioplegia groups across all analytic approaches, including crude comparison, multivariable Cox regression, IPTW-adjusted analysis, and propensity score-matched analysis.
HTK; Histidine-tryptophan-ketoglutarate; DN, Del Nido; IPTW, inverse probability of treatment weighting; PS, propensity-score.
Discussion
The modified bloodless DN cardioplegia demonstrated favorable early and late outcomes in patients undergoing isolated AVR compared to the HTK solution. The incidence of low cardiac output syndrome and the initial postoperative lactate level were both significantly lower in the bloodless DN group. In addition, the bloodless DN group demonstrated a significantly higher rate of spontaneous restoration of sinus rhythm following aortic cross-clamp removal, further supporting the cardioprotective efficacy of the DN solution. These findings indicate that DN cardioplegia may provide superior myocardial protection and reduce the risk of myocardial injury relative to HTK. Other postoperative complications, including morbidity and mortality, were not significantly different between the two groups.
The comparison between the original DN cardioplegia and HTK solution in myocardial protection has been a topic of increasing interest, particularly as both solutions offer single-dose protection with prolonged ischemic times. Although previous studies suggested similar outcomes of myocardial protection in both the DN and HTK solution, the DN cardioplegia provides several advantages than HTK solution. It requires less volume which offer less hemodilution, higher rate of spontaneous rhythm recovery that suggesting a lower ischemia-reperfusion injury risk, and cost effectiveness [4]. The DN cardioplegia tends to show better early cardiac recovery and less myocardial edema in some studies, while HTK offers strong protection but might be associated with slower recovery postoperatively [20]. In addition, the cost of the DN solution is not expensive compared to HTK solution (1L DN: $ 8 vs 1L HTK: $ 105), it is more affordable for patients in financial difficulty.
Research on modified versions of DN cardioplegia has been expanding, particularly since its patent expired. Studies are investigating various modifications to improve outcomes, especially in adult cardiac surgeries. There are reports of cardiac surgery cases where increasing the proportion of blood was applied. A study reported the outcomes of coronary artery bypass grafting with left ventricular dysfunction patients using modified DN cardioplegia with increased amount of blood rather than original form. They demonstrated advantages such as significant reduction in postoperative epicardial edema, suggesting improved myocardial protection [21]. The approach they used was to add the cardioplegic additives directly to the patient’s whole blood rather than in a crystalloid base. Another study showed the results with the need for defibrillation was found to be significantly less in the modified versions of DN cardioplegia group compared with the classical DN group. There was no statistically significant difference between modified group and classical DN in all parameters related to myocardial protection [22]. There have also been studies published using different base solutions from the original formula. Due to the unavailability of the original ingredients (Plasmalyte A®), they used a modified version of the DN cardioplegia using Ionosteril as base solution. Modified version of DN cardioplegia based on Ionosteril® solution showed equivalent protection compared to Custodiol for isolated mitral valve repair [23].
The effect of blood in the original DN cardioplegia solution is multifaceted and contributes to enhanced myocardial protection during cardiac surgery. It optimizes myocardial protection by supporting oxygen delivery, buffering capacity, nutrient supply, reduced hemodilution, and improved rheology [24]. These are similar to the well-known benefits of blood cardioplegia. However, in DN cardioplegia, blood is mixed with the crystalloid solution in a 1:4 ratio (blood to crystalloid), and there is a lack of scientific evidence that this dose is sufficient to provide the benefits of blood for myocardial protection. Some studies suggested that adding blood to cardioplegia may not provide favorable influences, especially at lower temperatures [25,26]. Dr. Pedro J. DN, who is the pioneer of development of the DN cardioplegia solution, has also commented that the inclusion of blood in the solution may not provide significant additional safety or efficacy in terms of myocardial protection for the short-term myocardial ischemia in pediatric or simpler adult cardiac cases [27]. In our institution, a modified bloodless cardioplegia technique has been utilized since the early 2000s for congenital heart surgeries. After achieving positive results in congenital heart surgery [28], it was subsequently incorporated into adult cardiac surgery in 2014. Our institutional experiences including this study, also advocate the hypotheses that blood components may not be essential for DN cardioplegia. Considering the simplicity and resource efficiency of the operation, eliminating the blood mixing procedure could be a viable option. Bloodless DN cardioplegia eliminates the need for specialized circuits or additional resources to mix blood with the solution, making it an attractive option in resource-constrained settings. In addition, it could be beneficial in particular patients such as, small neonates, infants, or even small adults, for whom incorporating even small amount of the patient’s blood into the cardioplegia can be discouraging. Our study demonstrated that the key benefits traditionally attributed to the original Del Nido cardioplegia were maintained despite the exclusion of blood components from the solution.
Our study has several limitations. First, as a retrospective, non-randomized study conducted at a single institution, it may be subject to selection bias. Although IPTW analysis (with some variables still showing high standardized mean differences) and other statistical methods were employed to mitigate potential biases in patient selection, unidentified confounding factors could still affect the results. Second, data on key cardiac biomarkers, such as troponin and creatine kinase-muscle/brain, were not available, as these markers were not routinely measured following cardiac surgery at our institution except coronary artery bypass grafting. Instead, we included postoperative lactate levels, which may serve as an indirect indicator of postoperative LCOS. Third, in complex or extended cardiac surgeries that multi-dose administration of cardioplegia is necessary due to prolonged ACC time, it would be valuable to investigate whether the use of bloodless DN cardioplegia yields a distinct impact compared to other cardioplegia strategies. To validate our findings, multi-center, randomized controlled trials with a larger patient cohort would be required to better assess the myocardial impact of the modified bloodless DN cardioplegia compared to original formula.
Supporting information
S1 Fig. Love Plot demonstrating covariate balance before and after IPTW adjustment.
https://doi.org/10.1371/journal.pone.0333083.s001
(PDF)
S2 Fig. Density Plot of propensity score distributions showing overlap between the HTK and DN groups.
https://doi.org/10.1371/journal.pone.0333083.s002
(PDF)
References
- 1. Cheng X-F, Wang K, Zhang H-T, Zhang H, Jiang X-Y, Lu L-C, et al. Risk factors for postoperative myocardial injury-related cardiogenic shock in patients undergoing cardiac surgery. J Cardiothorac Surg. 2023;18(1):220. pmid:37415183
- 2. Schwitter J, Eberli FR, Ritter M, Turina M, Krayenbuehl HP. Myocardial oxygen consumption in aortic valve disease with and without left ventricular dysfunction. Br Heart J. 1992;67(2):161–9. pmid:1531759
- 3. Oliveros RA, Boucher CA, Groves BM, Uhl GS. Myocardial supply-demand ratio in aortic regurgitation. Chest. 1979;76(1):50–5. pmid:446174
- 4. Duan L, Hu G-H, Wang E, Zhang C-L, Huang L-J, Duan Y-Y. Del Nido versus HTK cardioplegia for myocardial protection during adult complex valve surgery: a retrospective study. BMC Cardiovasc Disord. 2021;21(1):604. pmid:34922443
- 5. Gunaydin S, Akbay E, Gunertem OE, McCusker K, Kunt AT, Onur MA, et al. Comparative Effects of Single-Dose Cardioplegic Solutions Especially in Repeated Doses During Minimally Invasive Aortic Valve Surgery. Innovations (Phila). 2021;16(1):80–9. pmid:33155876
- 6. Lee C-H, Ju MH, Kim JB, Chung CH, Jung SH, Choo SJ, et al. Myocardial injury following aortic valve replacement for severe aortic stenosis: risk factor of postoperative myocardial injury and its impact on long-term outcomes. Korean J Thorac Cardiovasc Surg. 2014;47(3):233–9. pmid:25207220
- 7. Nardi P, Vacirca SR, Russo M, Colella DF, Bassano C, Scafuri A, et al. Cold crystalloid versus warm blood cardioplegia in patients undergoing aortic valve replacement. J Thorac Dis. 2018;10(3):1490–9. pmid:29707299
- 8. Reynolds AC, Asopa S, Modi A, King N. HTK versus multidose cardioplegias for myocardial protection in adult cardiac surgery: A meta-analysis. J Card Surg. 2021;36:1334–43.
- 9. Lindner G, Zapletal B, Schwarz C, Wisser W, Hiesmayr M, Lassnigg A. Acute hyponatremia after cardioplegia by histidine-tryptophane-ketoglutarate--a retrospective study. J Cardiothorac Surg. 2012;7:52. pmid:22681759
- 10. Stammers AH, Tesdahl EA, Mongero LB, Stasko AJ, Weinstein S. Does the Type of Cardioplegic Technique Influence Hemodilution and Transfusion Requirements in Adult Patients Undergoing Cardiac Surgery? J Extra Corpor Technol. 2017;49(4):231–40.
- 11. Govindapillai A, Hua R, Rose R, Friesen CH, O’Blenes SB. Protecting the aged heart during cardiac surgery: use of del Nido cardioplegia provides superior functional recovery in isolated hearts. J Thorac Cardiovasc Surg. 2013;146(4):940–8. pmid:23953721
- 12. Harvey B, Shann KG, Fitzgerald D, Mejak B, Likosky DS, Puis L, et al. International pediatric perfusion practice: 2011 survey results. J Extra Corpor Technol. 2012;44(4):186–93. pmid:23441558
- 13. Kotani Y, Tweddell J, Gruber P, Pizarro C, Austin EH 3rd, Woods RK, et al. Current cardioplegia practice in pediatric cardiac surgery: a North American multiinstitutional survey. Ann Thorac Surg. 2013;96(3):923–9. pmid:23915588
- 14. Timek T, Willekes C, Hulme O, Himelhoch B, Nadeau D, Borgman A, et al. Propensity Matched Analysis of del Nido Cardioplegia in Adult Coronary Artery Bypass Grafting: Initial Experience With 100 Consecutive Patients. Ann Thorac Surg. 2016;101(6):2237–41. pmid:27016843
- 15. Ota T, Yerebakan H, Neely RC, Mongero L, George I, Takayama H, et al. Short-term outcomes in adult cardiac surgery in the use of del Nido cardioplegia solution. Perfusion. 2016;31(1):27–33. pmid:26228274
- 16. Mick SL, Robich MP, Houghtaling PL, Gillinov AM, Soltesz EG, Johnston DR, et al. del Nido versus Buckberg cardioplegia in adult isolated valve surgery. J Thorac Cardiovasc Surg. 2015;149(2):626–34; discussion 634-6. pmid:25483897
- 17. Garcia-Suarez J, Garcia-Fernandez J, Martinez Lopez D, Reques L, Sanz S, Carballo D, et al. Clinical impact of del Nido cardioplegia in adult cardiac surgery: A prospective randomized trial. J Thorac Cardiovasc Surg. 2023;166:1458–67.
- 18. Nakao M, Morita K, Shinohara G, Kunihara T. Modified del nido cardioplegia and its evaluation in a piglet model. Semin Thorac Cardiovasc Surg. 2021;33:84–92.
- 19. D’Angelo AM, Nemeth S, Wang C, Kossar AP, Takeda K, Takayama H, et al. Re-dosing of del Nido cardioplegia in adult cardiac surgery requiring prolonged aortic cross-clamp. Interact Cardiovasc Thorac Surg. 2022;34(4):556–63. pmid:34788429
- 20. Talwar S, Chatterjee S, Sreenivas V, Makhija N, Kapoor PM, Choudhary SK, et al. Comparison of del Nido and histidine-tryptophan-ketoglutarate cardioplegia solutions in pediatric patients undergoing open heart surgery: A prospective randomized clinical trial. J Thorac Cardiovasc Surg. 2019;157:1182–92.
- 21. Brown S, Nassar K, Razzouk J, Kashyap AK, Won M, Shehadeh T, et al. Outcomes of coronary artery bypass surgery using modified del Nido cardioplegia in patients with poor ventricular function. J Cardiothorac Surg. 2023;18(1):346. pmid:38031138
- 22. Karaarslan K, Erdinc I. Is Modified Del Nido Cardioplegia as Effective as Del Nido Cardioplegia in Patients With Isolated Coronary Artery Bypass Surgery? Heart Surg Forum. 2022;25(1):E163–7. pmid:35238295
- 23. Kang J, Hoyer A, Dieterlen M-T, Oetzel H, Otto W, Ginther A, et al. Comparison of modified Del Nido and Custodiol® cardioplegia in minimally invasive mitral valve surgery. Eur J Cardiothorac Surg. 2024;65(4):ezae161. pmid:38627243
- 24. Matte GS, del Nido PJ. History and use of del Nido cardioplegia solution at Boston Children’s Hospital. J Extra Corpor Technol. 2012;44(3):98–103. pmid:23198389
- 25. Magovern GJ Jr, Flaherty JT, Gott VL, Bulkley BH, Gardner TJ. Failure of blood cardioplegia to protect myocardium at lower temperatures. Circulation. 1982;66(2 Pt 2):I60-7. pmid:6805979
- 26. Heitmiller RF, DeBoer LW, Geffin GA, Toal KW, Fallon JT, Drop LJ, et al. Myocardial recovery after hypothermic arrest: a comparison of oxygenated crystalloid to blood cardioplegia. The role of calcium. Circulation. 1985;72(3 Pt 2):II241-53. pmid:4028363
- 27. Barner HB. Blood cardioplegia: a review and comparison with crystalloid cardioplegia. Ann Thorac Surg. 1991;52(6):1354–67. pmid:1755697
- 28. Kim ER, Lee CH, Kim WH, Lim JH, Kim YJ, Min J, et al. Primary versus staged repair in neonates with pulmonary atresia and ventricular septal defect. Ann Thorac Surg. 2021;112(3):825–30.