Size and Gender Matching in Heart Transplantation – Optimizing Donor Utilization in an Era of Changing Donor and Recipient Characteristics

Donor heart selection: Evidence-based guidelines for providers

The proposed donor heart selection guidelines provide evidence-based and expert-consensus recommendations for the selection of donor hearts following brain death. These recommendations were compiled by an international panel of experts based on an extensive literature review.

Evaluation of donor heart for transplantation

Cardiac transplantation is considered the gold-standard treatment option for patients suffering from end-stage heart failure refractory to maximum medical therapy. A major determinant of graft function and recipient survival is a comprehensive evaluation of the donor allograft. Challenges arise when designing and implementing an evidence-based donor evaluation protocol due to the number of influential donor-specific characteristics and the complex interactions that occur between them. Here, we present our systematic approach to donor evaluation by examining the impact that relevant donor variables have on graft function and recipient outcomes.

Benefits of the Modified Bicaval Anastomosis Technique for Orthotopic Heart Transplantation From a Size-Mismatched Marginal Donor

BACKGROUND

Size-mismatched heart transplantation (HTx) is associated with a risk of stenosis of the caval anastomosis site or low cardiac output syndrome. We developed a modified bicaval anastomosis technique (mBCAT) that achieved an adjustable caval anastomosis to compensate for size mismatch. This study was performed to validate the rationale of the mBCAT for size-mismatched HTx.Methods and Results:This institutional consecutive series involved 106 patients who underwent HTx with the mBCAT during an 18-year period. The cohort was divided into 3 groups according to the donor-to-recipient body weight ratio: <0.8, undersized group (n=17); 0.8-1.3, size-matched group (n=68); and >1.3, oversized group (n=21); outcomes were compared. The undersized, size-matched, and oversized groups showed no significant differences in the rate of mild or worse echocardiographic tricuspid regurgitation at 1 month [1 (5.8%), 7 (10.2%), and 1 (4.8%), respectively; P=0.87] or the survival rate at 10 years [100%, 93.9%, and 100%, respectively; P=0.25]. The right heart catheter study revealed no pressure gradient across the orifices of both cavae in any patient. Additionally, the cardiac index immediately post-HTx was significantly low in the undersized group (P=0.008), but was similar to the other groups at 6 months post-HTx (P=0.16).

CONCLUSIONS

The mBCAT prevented caval anastomosis-related complications in size-mismatched HTx and achieved excellent hemodynamics regardless of donor size.

Alternative methods for virtual heart transplant-Size matching for pediatric heart transplantation with and without donor medical images available

BACKGROUND

Listed pediatric heart transplant patients have the highest solid-organ waitlist mortality rate. The donor-recipient body weight (DRBW) ratio is the clinical standard for allograft size matching but may unnecessarily limit a patient's donor pool. To overcome DRBW ratio limitations, two methods of performing virtual heart transplant fit assessments were developed that account for patient-specific nuances. Method 1 uses an allograft total cardiac volume (TCV) prediction model informed by patient data wherein a matched allograft 3-D reconstruction is selected from a virtual library for assessment. Method 2 uses donor images for a direct virtual transplant assessment.

METHODS

Assessments were performed in medical image reconstruction software. The allograft model was developed using allometric/isometric scaling assumptions and cross-validation.

RESULTS

The final predictive model included gender, height, and weight. The 25th-, 50th-, and 75th-percentiles for TCV percentage errors were -13% (over-prediction), -1%, and 8% (under-prediction), respectively. Two examples illustrating the potential of virtual assessments are presented.

CONCLUSION

Transplant centers can apply these methods to perform their virtual assessments using existing technology. These techniques have potential to improve organ allocation. With additional experience and refinement, virtual transplants may become standard of care for determining suitability of donor organ size for an identified recipient.

Selection of Patients for Initial Clinical Trials of Solid Organ Xenotransplantation

Several groups have reported extended survival of genetically engineered pig organs in nonhuman primates, varying from almost 10 months for life-supporting kidney grafts and more than 2 years for non-life-supporting heart grafts to less than 1 month for life-supporting liver and lung grafts. We have attempted to define groups of patients who may not have an option to wait for an allograft. These include kidney, heart, and lung candidates who are highly-allosensitized. In addition, some kidney candidates (who have previously lost at least 2 allografts from rapid recurrence of native kidney disease) have a high risk of further recurrence and will not be offered a repeat allotransplant. Patients with complex congenital heart disease, who may have undergone previous palliative surgical procedures, may be unsuitable for ventricular assist device implantation. Patients dying of fulminant hepatic failure, for whom no alternative therapy is available, may be candidates for a pig liver, even if only as a bridge until an allograft becomes available. When the results of pig organ xenotransplantation in nonhuman primates suggest a realistic potential for success of a pilot clinical trial, highly selected patients should be offered participation.