Size matching in heart transplantation donor selection: "Too big to fail"?

Utility of Recipient Cardiothoracic Ratio in Predicting Delayed Chest Closure after Heart Transplantation

BACKGROUND

 Predicted cardiac mass (PCM) has been well validated for size matching donor hearts to heart transplantation recipients. We hypothesized that cardiothoracic ratio (CTR) could be reflective of recipient-specific limits of oversizing, and sought to determine the utility of donor to recipient PCM ratio (PCMR) and CTR in predicting delayed chest closure after heart transplantation.

METHODS

 A retrospective review of prospectively collected data on 38 consecutive heart transplantations performed at our institution from 2017 to 2020 was performed. Donor and recipient PCM were estimated using Multi-Ethnic Study of Atherosclerosis predictive models. Receiver operating characteristic analysis was performed to determine the discriminatory power of the ratio of PCMR to CTR in predicting delayed sternal closure.

RESULTS

 Of the 38 patients, 71.1% (27/38) were male and the median age at transplantation was 58 (interquartile range [IQR]: 47-62) years. Ischemic cardiomyopathy was present in 31.6% of recipients (12/38). Median recipient CTR was 0.63 [IQR: 0.59-0.66]. Median donor to recipient PCMR was 1.07 [IQR: 0.96-1.19], which indicated 7% oversizing. Thirteen out of 38 (34.2%) underwent delayed sternal closure. Primary graft dysfunction occurred in 15.8% (6/38). PCMR/CTR showed good discriminatory power in predicting delayed sternal closure [area under the curve: 80.4% (65.3-95.6%)]. PCMR/CTR cut-off of 1.7 offered the best trade-off between the sensitivity (69.6%) and specificity (91.7%).

CONCLUSION

 CTR could be helpful in guiding the recipient-specific extent of oversizing donor hearts. Maintaining the ratio of PCMR to CTR below 1.7 could avoid excessive oversizing of the donor heart.

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.

Increasing heart transplant donor pool by liberalization of size matching

BACKGROUND

The heart transplant (HT) guidelines recommendation to match recipient and donors within 30% of body weight lacks a strong evidence base and is not well established in patients bridged to transplant with left ventricular assist devices (LVAD). In light of the scarcity of donor hearts, we investigated the effect of size mismatch on hemodynamics, one-year survival and length of stay (LOS) following HT.

METHODS

Single-center retrospective analysis of consecutive HT patients from April 2007 to September 2017. Recipients were divided into 3 cohorts based on donor-to-recipient weight ratio (DRWR): (1) undersized (<0.7), (2) size-matched, (0.7-1.3); (3) oversized (>1.3).

RESULTS

288 consecutive patients were identified (mean age 53 ± 11 years; 76% male), 46 were undersized (0.61 ± 0.05), 210 size-matched (0.94 ± 0.16), and 32 oversized (1.65 ± 0.38). There was no significant difference in donor left ventricular end diastolic diameter (LVEDD) between the 3 groups (p = 0.11). The donor/recipient (D/R) predicted heart mass (PHM) was lowest in the undersized group (0.92 ± 0.13). There were no significant differences in 1-year survival in the overall and LVAD cohort (p = 0.65 and 0.59, respectively). Neither donor LVEDD nor D/R PHM differed among survivors or non-survivors. LOS was longer in the undersized group than the size-matched cohort (p = 0.004). The undersized group had hearts with the highest filling pressures and lowest cardiac index at 1 week among the remaining groups (p = 0.009, 0.017, and p = 0.05, respectively). There were no clinically significant differences in hemodynamics at 1 or 6 months.

CONCLUSIONS

HT undersizing affects hemodynamics early but not later in the course and does not impact 1-year survival. The liberalization of size matching may increase the HT donor pool significantly.

Improved long-term outcomes after heart transplantation utilizing donors with a traumatic mode of brain death

Background

The donor’s mode of brain death (BD), being associated with impairment of myocardial function and hemodynamic performance, impacts the prognosis of the heart transplantation (HTx) recipient.

Methods

All patients who underwent HTx between 1996 and 2017 were categorized according to donor’s BD mechanism: traumatic BD (TBD) versus non-traumatic BD (NTBD).

Results

The TBD group included 105 recipients, and the NTBD group, 85 recipients. Kaplan-Meier survival analysis showed that overall survival was significantly higher for recipients of TBD hearts (10-year survival 58.1 vs. 37.6%, p = 0.044). Consistently, multivariate analysis showed that TBD was independently associated with a significant 43% reduction in mortality [95% confidence interval (CI) 0.42–0.75, p = 0.033]. Rejection rate was lower in the TBD group (total rejection score 0.44 ± 0.32 vs. 0.51 ± 0.38, p = 0.04; any rejection score 0.38 ± 0.26 vs. 0.45 ± 0.31, p = 0.030), and freedom from cardiac allograft vasculopathy (CAV) was significantly higher in recipients of traumatic vs. non-traumatic donors (10 years: 82.9 vs. 62.4%, log-rank p-value = 0.024). Multivariate analysis showed a significant 42% reduction in CAV [hazard ratio (HR) = 0.58, 95% CI 0.51–0.85, p = 0.022).

Conclusion

Mode of brain death significantly impacts HTx outcomes, with TBD being associated with reduced mortality, rejections and CAV.