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The Safety and Late Hemodynamics of Donor Cardiac Undersizing in Heart Transplantation
Chetan Pasrija1, Alexandra Debose-Scarlett1, Daniel K Ragheb1
1Department of Cardiac Surgery, Vanderbilt University Medical Center, Nashville Tennessee.
Insights
Small donor hearts (predicted heart mass ratio <0.86) increase 1-year mortality risk in complex heart transplant patients. However, for noncomplex cases, undersized hearts show similar outcomes to matched or oversized grafts, suggesting selective safety.
Area of Science:
- Cardiology
- Transplantation Surgery
- Medical Engineering
Background:
- Predicted heart mass (PHM) ratio is the standard for donor-recipient size matching in heart transplantation.
- While small PHM ratio hearts are linked to higher 1-year mortality, the reasons and duration of this risk are unclear.
Purpose of the Study:
- To investigate the impact of donor-recipient size matching using PHM ratio on heart transplant outcomes.
- To determine if the increased mortality associated with undersized hearts differs between complex and noncomplex transplant recipients.
Main Methods:
- A single-institution analysis of 334 heart transplant recipients from January 2019 to July 2022.
- Patients were stratified by PHM ratio: undersized (<0.86), matched (0.86-1.15), and oversized (>1.15).
- Survival was analyzed, stratified by complex (preoperative LVAD, ACHD, ECMO) and noncomplex transplant groups.
Main Results:
- Overall 30-day and 1-year survival were significantly worse in the undersized group.
- This survival difference was only observed in complex transplant recipients, not in noncomplex recipients.
- Hemodynamic parameters like mixed venous oxygen saturation and cardiac index were maintained across all groups.
Conclusions:
- Small PHM ratio hearts are associated with increased 1-year mortality, primarily driven by complex transplant operations.
- Undersized hearts in noncomplex transplant operations demonstrated similar hemodynamic profiles and survival rates compared to matched or oversized hearts.
- These findings suggest that small PHM ratio hearts may be safely used in select noncomplex heart transplant cases.
Background:
Predicted heart mass (PHM) ratio has become the standard donor-recipient size matching method in heart transplantation. Although use of small PHM ratio hearts is associated with increased 1-year mortality, the underlying mechanisms and time horizon of mortality remain uncertain.
Methods:
A single-institution analysis of 334 isolated heart transplant recipients (January 2019-July 2022) was performed. Patients were stratified by PHM ratio: undersized (<0.86; n = 106), matched (0.86-1.15; n = 175), and oversized (>1.15; n = 53). Survival within PHM ratio groups was further stratified by complex transplant group (preoperative left ventricular assist device, adult congenital, or preoperative extracorporeal membrane oxygenation) and noncomplex transplant group (all others).
Results:
Donor and recipient variables were similar. However, undersized patients were more likely to have a durable left ventricular assist device (P = .022). Although postoperative primary graft dysfunction and inotrope score were similar between groups, there was a trend toward increased need for postoperative dialysis with undersized hearts (P = .056). Overall, 30-day (P = .012) and 1-year survival (P = .002) was significantly worse in the undersized group compared with the matched or oversized groups. However, subset analysis showed these differences only remained among the complex transplant recipients (P = .013) but not the noncomplex transplant recipients (P = .428). Median mixed venous oxygen saturations at serial time points were maintained between 65% and 70% in all heart size groups, with cardiac indices between 2.4 and 2.8 L/min/m2.
Conclusions:
Small PHM ratio hearts are associated with increased 1-year mortality, driven by complex transplant operations. Recipients who received undersized PHM ratio hearts from noncomplex transplant operations had a similar hemodynamic profile and survival as those who received matched and oversized hearts. Small PHM ratio hearts may be selectively safe for transplantation.
