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Determining optimal donor heart ischemic times in adult cardiac transplantation
Paul C Tang1, Xiaoting Wu1, Min Zhang2
1Department of Cardiac Surgery, University of Michigan Frankel Cardiovascular Center, Ann Arbor, Michigan, USA.
Insights
The optimal ischemic time (IT) for heart transplants is approximately 3 hours. Longer preservation times, especially for O blood type donor hearts, are associated with increased mortality risk and postoperative complications.
Area of Science:
- Cardiology
- Transplantation Surgery
- Biostatistics
Background:
- Heart transplantation is a life-saving procedure.
- Optimizing donor organ preservation is crucial for successful outcomes.
- Ischemic time (IT) is a critical factor influencing graft survival.
Purpose of the Study:
- To statistically determine the optimal ischemic time (IT) threshold for heart transplant recipients.
- To analyze the impact of IT on transplant outcomes across different ABO donor heart types.
Main Methods:
- Analysis of 36,145 heart transplants from the United Network for Organ Sharing database (2000-2018).
- Utilized Contal and O'Quigley univariable and Vito Muggeo multivariable segmented modeling for IT cutoff determination.
- Employed parametric and nonparametric statistical testing for variable analysis.
Main Results:
- A statistically determined optimal ischemic time (IT) cutoff of approximately 3 hours was identified.
- Increased IT beyond 3 hours was associated with higher early mortality risk (90 days to 1 year) and increased postoperative complications (stroke, dialysis, primary graft dysfunction).
- Transplantation with O blood type donor hearts and IT ≥3 hours showed significantly increased mortality risk across all time points compared to non-O types.
Conclusions:
- The unbiased statistical threshold for optimal donor heart ischemic time (IT) is approximately 3 hours.
- Longer ischemic times, particularly for O blood type donor hearts, negatively impact heart transplant survival.
- These findings underscore the importance of minimizing IT in heart transplantation to improve patient outcomes.
Objectives:
Unsupervised statistical determination of optimal allograft ischemic time (IT) on heart transplant outcomes among ABO donor heart types.
Methods:
We identified 36,145 heart transplants (2000-2018) from the United Network for Organ Sharing database. Continuous and categorical variables were analyzed with parametric and nonparametric testing. Determination of IT cutoffs for survival analysis was performed using Contal and O'Quigley univariable method and Vito Muggeo multivariable segmented modeling.
Results:
Univariable and multivariable IT threshold determination revealed a cutoff at about 3 h. The hourly increase in survival risk with ≥3 h IT is asymmetrically experienced at the early 90 days (hazard ratio [HR] = 1.29, p < .001) and up to 1-year time point (HR = 1.16, p < .001). Beyond 1 year the risk of prolonged IT is less impactful (HR = 1.04, p = .022). Longer IT was associated with more postoperative complications such as stroke (2.7% vs. 2.3, p = .042), dialysis (11.6% vs. 9.1%, p < .001) and death from primary graft dysfunction (1.8% vs. 1.2%, p < .001). O blood type donor hearts with IT ≥ 3 h has significantly increased hourly mortality risk at 90 days (HR = 1.27, p < .001), 90 days to 1 year (HR = 1.22, p < .001) and >1 year (HR = 1.05, p = .041). For non-O blood types with ≥3 h IT hourly mortality risk was increased at 90 days (HR = 1.33, p < .001), but not at 90 days to 1 year (HR = 1.09, p = .146) nor ≥1 year (HR = 1.08, p = .237).
Conclusions:
The donor heart IT threshold for survival determined from unbiased statistical modeling occurs at 3 h. With longer preservation times, transplantation with O donor hearts was associated with worse survival.
