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Updated: May 28, 2025
Optimization of the Cuff Technique for Murine Heart Transplantation
Published on: June 26, 2020
Relationship between body mass index and traditional size-matching in heart transplantation
Ahad Firoz1, Huaqing Zhao2, Eman Hamad3
1Department of Internal Medicine, University of California Davis Medical Center, Sacramento, CA, USA.
Insights
Obese heart transplant recipients show reduced mortality risk from undersized donor hearts, unlike normal or overweight patients. This finding could expand donor pool access for obese individuals.
Area of Science:
- Cardiology
- Transplantation Medicine
- Biostatistics
Background:
- Donor-recipient size matching is critical in heart transplantation.
- Predicted heart mass (PHM) ratio is an optimal metric, but its validation in obese recipients is lacking.
- Investigating acute survival across Body Mass Index (BMI) and PHM ratio categories is essential.
Purpose of the Study:
- To validate the Predicted Heart Mass ratio (PHMR) formula in obese heart transplant recipients.
- To analyze acute survival rates in relation to PHMR categories across different BMI groups.
- To provide data supporting expanded donor pool utilization for obese patients.
Main Methods:
- Analysis of adult heart transplant recipients from the United Network for Organ Sharing database.
- Categorization of recipients into BMI groups: normal, overweight, obese class I, and obese class II+.
- Classification of Predicted Heart Mass Ratio (PHMR) into five categories: severely undersized (U2), undersized (U1), approximately equally sized (R), oversized (O1), and severely oversized (O2).
- Evaluation of all-cause acute mortality as the primary outcome.
Main Results:
- A total of 46,141 recipients were analyzed, with increasing percentages of obese patients and donors over time.
- A stepwise reduction in mortality risk was observed for severely undersized grafts as BMI increased in normal and overweight groups.
- Mortality risk associated with graft size mismatching became insignificant in obese groups across all PHMR categories.
Conclusions:
- Normal to overweight BMI patients are susceptible to increased mortality with severely undersized grafts.
- Obese recipients demonstrate resistance to the adverse effects of organ size mismatching as defined by PHMR.
- Findings suggest potential for broader donor pool utilization and improved outcomes for obese transplant candidates.
Background:
Donor-recipient size matching is an important consideration for heart allocation, of which predicted heart mass (PHM) ratio has been found to be the most optimal metric. However, the PHM formula has not been validated in a cohort that included obese recipients. Therefore, our study seeks to add further granular data on this topic by investigating acute survival in PHM categories across multiple body mass index (BMI) groups.
Methods:
Adult heart transplant recipients were analyzed using the United Network for Organ Sharing database. BMI groups included: normal (18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2), obese class I (30.0-34.9 kg/m2), and obese class II+ (≥35.0 kg/m2). PHM ratio (PHMR) categories were: severely undersized (U2): <0.85, undersized (U1): 0.85-0.95, approximately equally sized (R): 0.95-1.05, oversized (O1): 1.05-1.25, and severely oversized (O2): ≥1.25. All-cause acute mortality was the primary outcome of interest.
Results:
A total of 46,141 recipients were included in our analysis. The percentage of obese patients and donors increased over the years, from 21.5 % and 17.2 % in 2000 to 34.4 % and 33.1 % in 2022, respectively. Survival analysis found a stepwise reduction in mortality risk for severely undersized grafts as BMI increased (normal: HR = 1.59, p < 0.001; overweight: HR = 1.20, p = 0.029), until ultimately reaching insignificant levels in obese groups across all PHMR categories.
Conclusion:
Patients with a normal to overweight BMI were susceptible to increased mortality with a severely undersized graft. Conversely, obese groups appeared to be resistant to the hazards of organ size mismatching by PHMR. The clinical implications of this study may enable recruitment from a larger donor pool and improve challenges in transplantation for obese patients.
