Increasing heart transplant donor pool by liberalization of size matching

Abstract

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.

Keywords: heart transplantation; left ventricular assist devices; mortality; size mismatch.

Figure 1

Analyzed for bodyweight matching there were no significant differences in 1-year survival between the groups. One-year survival was 88% for in range, 89% for oversize and 94% for undersized hearts (p = 0.65).

Figure 2

As seen in the overall cohort, there were no significant differences in survival for bodyweight matching in the subgroup analysis of left-ventricular-assist-devices bridging.

Figure 3

University of Chicago Transplant Size Matching Algorithm as part of an overall assessment of the donor’s heart. Our size matching starts with bodyweight matching. In case of an undersized donor per body weight definition we adjust by incorporating 2 additional factors: a donor left ventricular end diastolic diameter (LVEDD) of at least 4 cm and left posterior ventricular wall >0.9 cm but <1.2 cm. Especially in left-ventricular-assist-devices patients and female-male gender mismatch smaller donor LVEDDs should be avoided. In case of oversized hearts, it is essential to avoid donor hearts with a large LVEDD to avoid restrictive physiology and difficult chest wall closure. DRWR, donor-to-recipient weight ratio; LVEDD, left ventricular end diastolic diameter; PHM, predicted heart mass; LVPW, left ventricular posterior wall.