Growth of oversized grafts in neonatal heart transplantation

Total ventricular mass oversizing +50% or greater was a predictor of worse 1-year survival after heart transplantation

OBJECTIVES

Current donor-recipient size matching guidelines rely primarily on body weight, with no specified oversizing cutoff values. Recent literature has explored predicted total ventricular mass matching over body weight matching. We aim to explore the impact of total ventricular mass oversizing on heart transplant outcomes.

METHODS

The United Network for Organ Sharing database was queried for adults who underwent primary heart transplant from 1997 to 2017. By using validated equations, donor-recipient total ventricular mass mismatch was calculated. Donor-recipient pairs were divided into 3 groups by total ventricular mass mismatch. Post-heart transplant 1-year survival was analyzed using the Kaplan-Meier method and Cox proportional hazards models. We also investigated post-heart transplant complications, independent predictors for mortality, donor-recipient sex mismatch, and donor-recipient body habitus in total ventricular mass mismatch greater than +50%.

RESULTS

A total of 34,455 donor-recipient pairs were included. Fractional polynomial regression demonstrated increased the risk of mortality with higher total ventricular mass mismatch. Total ventricular mass mismatch of +48.3% maximized the Youden Index. Donor-recipient pairs were subsequently grouped by total ventricular mass mismatch as -20% to +30%, +30% to +50%, and greater than +50%. Total ventricular mass mismatch greater than +50% was an independent risk factor for 1-year mortality (hazard ratio, 1.40, P = .004) and was associated with increased postoperative stroke (P = .002). Some 80.3% of these recipients were smaller female patients with male donors. Total ventricular mass mismatch from +30% to +50% was not associated with worse survival (P = .17).

CONCLUSIONS

Total ventricular mass mismatch greater than +50% is associated with worse 1-year survival, although this group comprises a small portion of heart transplant. total ventricular mass mismatch from +30% to +50% is not associated with worse survival. These outcomes should be considered in selecting donors and in efforts to expand the potential donor pool.

Extreme size mismatch: bronchus compression by an oversized donor heart in small children

Studies have suggested that a more liberal criterion of donor–recipient weight ratio (DRWR) is associated with superior waitlist survival without compromising posttransplant outcomes in selected critically ill patients. Successful transplantation of an extremely oversized donor heart into a small recipient is herein described. A 2-year-old girl accepted a size-mismatched adult donor heart offer (DRWR of 4.4) due to frequent complications with a left ventricular assist device. During the immediate postoperative period, spatial constraints within the thoracic cavity compromised graft function. Computed tomography revealed severe compression of the left bronchus due to the oversized allograft with lobar collapse of the left lung. With temporary extracorporeal membrane oxygenation support, graft function improved within 1 month after transplantation. Subsequent adaptive size remodeling of the transplanted heart with concomitant left bronchus re-expansion was observed within 6 months after transplantation. Despite a complicated posttransplant recovery, the patient was discharged home with minimal respiratory sequelae. Our report describes an alternative strategy for managing early morbidities related to an oversized graft and supports extending the criteria of size matching in pediatric heart transplantations.

Oversized donor heart transplantation-clinical experience with an underestimated problem

PURPOSE

Heart transplantation is the definitive treatment for end-stage heart failure. With respect to donor-recipient size matching, the problems with undersized heart transplantation have been widely discussed, but there is a paucity of information on oversized transplants due to the presumed advantage of large hearts. We intend to share our center's experience with oversized heart transplantation and its associated problems which would help to expand the knowledge on oversized cardiac allografts.

METHODS

Patients who underwent isolated heart transplantation at our hospital between March 1, 2008, and March 1, 2020, were included. For adults, a donor-recipient predicted heart mass percentage difference exceeding 30% and for children, a donor-recipient weight ratio < 0.8 and > 2.0 was considered a mismatch. We collected data from the in-patient medical records and analyzed the in-hospital outcomes and survival post-transplant among various other parameters.

RESULTS

Out of the 43 patients included in this study, 32 (74.4%) patients received a matched heart and 11 (25.6%) patients received oversized hearts. None of the patients received an undersized heart. The in-hospital mortality rate of oversized transplants was 18.2% whereas that of matched transplants was 9.4% (p = 0.432). The post-operative characteristics and 1-year survival were comparable between the groups. We encountered problems specific to oversizing in 5 of the 11 patients (45.4%) which are discussed.

CONCLUSION

With the liberalization of donor criteria to overcome organ shortage, oversized heart transplantation poses certain unique challenges, which when efficiently managed offers acceptable outcomes.

Anti-hypertensive treatment in the immediate post-operative period and 1 year after pediatric heart transplantation

Hypertension is a known complication of pediatric heart transplantation. We sought to identify factors associated with anti-hypertensive use in pediatric heart transplant recipients immediately post-transplant and oral anti-hypertensive use at discharge and 1-year post-transplant. Retrospective chart review was conducted of patients ≤18 years who underwent heart transplantation at two major heart transplant centers between August 1, 2009 and December 31, 2017 with ≥1-year follow-up. Exclusion criteria included re-transplant, multi-organ recipients, survival <1 year, and comorbidities associated with hypertension. Anti-hypertensive use was recorded during initial ICU stay, at discharge, and 1-year post-transplant. Univariate and multivariate analyses determined associations of demographic and diagnostic factors and need for anti-hypertensives. There were 188 patients that met inclusion criteria. Anti-hypertensive infusions were required in the ICU post-transplant in 46 patients (24.5%) for a median of 3 days (1-21 days). Oral anti-hypertensives were required in 58 patients (30.9%) at discharge and 1-year post-transplant. Anti-hypertensive infusion in the ICU post-transplant was associated with donor-to-recipient weight ratio. Oral anti-hypertensive use at discharge was associated with weight ratio and pretransplant VAD use, and at 1-year, post-transplant was associated with age at transplant, steroid use at discharge, and oral anti-hypertensive use at discharge. Hypertension is common immediately following and 1-year post-transplant. Weight ratio was the only independent predictor of anti-hypertensive use in the early post-transplant period, whereas VAD use was also associated with anti-hypertensive use at discharge. Anti-hypertensive use 1-year post-transplant was not associated with those factors, but rather with age at transplant and steroid use.

Reduced Biventricular Volumes and Myocardial Dysfunction Long-term After Pediatric Heart Transplantation Assessed by CMR

BACKGROUND

Long-term cardiac remodeling after heart transplantation (HT) in children has been insufficiently characterized. The aim of our study was to evaluate ventricular size in HT patients using cardiovascular magnetic resonance (CMR) imaging, to find underlying factors related to potentially abnormal cardiac dimensions and to study its impact on functional class and ventricular function.

METHODS

Seventy-five pediatric HT recipients (age 14.0 ± 4.2 y) were assessed by using CMR 11.2 ± 5.4 years after HT. Right ventricular (RV) and left ventricular (LV) volumes and mass were derived from short-axis cine images and myocardial strain/strain rate was assessed using myocardial feature tracking technique. Results were compared with a healthy reference population (n = 79, age 13.7 ± 3.7 y).

RESULTS

LV end-diastolic ventricular volumes were smaller (64 ± 12 versus 84 ± 12 mL/m; P < 0.001) while mass-to-volume ratio (0.86 ± 0.18 versus 0.65 ± 0.11; P < 0.001) and heart rate (92 ± 14 versus 78 ± 13 beats/min; P < 0.001) were higher in HT patients. LV-ejection fraction (EF) was preserved (66% ± 8% versus 64% ± 6%; P = 0.18) but RV-EF (58 ± 7 versus 62% ± 4%, P = 0.004), LV systolic longitudinal strain (-12 ± 6 versus -15% ± 5%; P = 0.05), diastolic strain rate (1.2 ± 0.6 versus 1.5 ± 0.6 1/s; P = 0.03), and intra and interventricular synchrony were lower in the HT group. Smaller LV dimensions were primarily related to longer follow-up time since HT (β = -0.38; P < 0.001) and were associated with worse functional class and impaired ventricular systolic and diastolic performance.

CONCLUSIONS

Cardiac remodeling after pediatric HT is characterized by reduced biventricular size and increased mass-to-volume ratio. These adverse changes evolve gradually and are associated with impaired functional class and ventricular dysfunction suggesting chronic maladaptive processes affecting allograft health.

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.

Early Result of Heart Transplantation in Japan: Osaka University Experience

Since the new organ transplantation law was established in 1997, 17 heart transplantations have been performed in Japan, 7 of which were carried out at Osaka University Hospital. Recipient diagnosis was dilated cardiomyopathy in 2, dilated phase of hypertrophic cardiomyopathy in 4, and post-myocarditis cardiomyopathy in 1. Ages ranged from 8 to 49 years with a mean of 35.3 years. Five patients were bridged with a left ventricular assist device. The waiting period was 182–977 days (mean, 643 days). There was no early or late death during follow-up of 1–4.8 years. Under a standard triple-drug regimen using mycophenolate, there were 3 rejection episodes greater than grade 3 in 2 patients, and humoral rejection requiring plasmapheresis in one. A young boy whose donor was a hemodynamically compromised adult developed neurological sequelae after resuscitation following ventricular tachycardia. All patients were discharged and went back to work or their regular daily life. Although the donor shortage is still severe in Japan, the resumption of heart transplantation has been satisfactory, and left ventricular assist devices have played a crucial role.

Donor chimera model for tolerance induction in transplantation

Tolerance induction is the basis of a successful transplantation with the goal being the re-establishment of homeostasis after transplantation. Non-autograft transplantation disrupts this maintenance drastically which would be avoided by administration of a novel procedure. At present, the blood group antigens and the genotypes of the donor and recipient are cross-matched before transplantation combined with a drug regimen that confers general immunosuppression. But the 'specific' unresponsiveness of the recipient to the donor organ, implied by 'tolerance', is not achieved in this process. This article introduces the 'donor chimera model' via the concept of the 'closed transplantation loop' approach for tolerance induction which seeks to limit the use of immunosuppressive therapy after transplantation.

Geometric Disproportion of Cardiac Structure and Graft Ischemia Affect Tricuspid Valve Regurgitation Early After Neonatal Heart Transplantation

BACKGROUND

Although tricuspid valve regurgitation (TR) after heart transplantation is a known complication, there has been little discussion of this subject in neonatal heart transplantation. We aim to elucidate the prevalence, etiology, and evolution of TR early after transplant in neonates.

METHODS

Eighty-five neonatal recipients were studied retrospectively by two-dimensional and Doppler echocardiography. The semiquantitative grading of TR was based on the ratio of regurgitation jet area to right atrial area.

RESULTS

Immediately after neonatal heart transplantation, TR was recognized in 47 patients (grade 1, n = 18; grade 2, n = 22; grade 3, n = 7; and grade 4, n = 0). Tricuspid regurgitation prevalence diminished from 55% to 19% with reduction in severity 1 year after transplantation. The prevalence of TR (grade 2 and grade 3) was affected by a donor/recipient body weight ratio of more than 2.0 (p = 0.004) and graft ischemia for more than 3 hours (p = 0.014). The ratio of donor and recipient right atria portion, which had a correlation with donor/recipient body weight ratio (r2 = 0.415, p < 0.0001), separated the four subgroups in terms of TR grade immediately after transplantation (p = 0.0064) and also at 1 year after transplantation in all surviving grafts from 1.48 +/- 0.54 to 0.8 +/- 0.32 (p < 0.0001). The Cox model found no significance for early posttransplant TR as a risk factor for graft survival.

CONCLUSIONS

Early posttransplant TR was affected by atria geometrical disproportion and by graft ischemia. Tricuspid regurgitation was not a risk factor for graft survival because of its amelioration over time, perhaps induced by recipient growth and recovery of myocardial injury relating to graft procurement.

Effect of oversizing cardiac allografts on survival in pediatric patients with congenital heart disease

BACKGROUND

There are few published data regarding the long-term outcome of "large" cardiac allografts in children. This study examines the effect of cardiac graft oversizing on the survival of pediatric patients with congenital heart disease (CHD).

METHODS

Two hundred ninety-one children, age 1 day to 17 years (median 50 days), with CHD underwent primary cardiac transplantation between 1985 and 2002. Patients were analyzed according to donor-recipient weight ratio (D-R): Group (Gp) I (n = 252) with D-R <2.5 (range 0.59 to 2.49, median 1.4), and Gp II (n = 39) with D-R >/=2.5 (range 2.5 to 4.65, median 2.78). CHD diagnoses included hypoplastic left heart syndrome (138 in Gp I, 13 in Gp II), single ventricle (29 in Gp I, 1 in Gp II) and other (85 in Gp I, 13 in Gp II). Patients with cardiomyopathy were excluded. Pre-transplant cardiac palliation was performed in 36% of Gp I and 15% of Gp II patients. The average graft ischemic times (minutes) were 266 +/- 7.5 and 283 +/- 18.9 for Gp I and Gp II, respectively (p < 0.2).

RESULTS

The operative mortality for Gp I was 10.3% and 10.2% for Gp II (p < 0.99). There was no significant difference between the 2 groups in length of hospital stay (p < 0.15) or duration of ventilator support (p < 0.6) post-transplantation. However, the incidence of open chest was higher (p < 0.003) in Gp II (28%) compared with Gp I (8%). The survival rates for Gp I and Gp II were: 82 +/- 2.4% vs 84 +/- 5.7% at 1 year; 71 +/- 2.9% vs 72 +/- 7.2% at 5 years; and 63 +/- 3.2% vs 65% +/- 7.4 at 10 years.

CONCLUSIONS

Post-transplant morbidity and short- and long-term survival of pediatric recipients with CHD are not adversely influenced by the use of oversized cardiac allografts.

Transoesophageal echocardiographic monitoring of pulmonary venous obstruction induced by sternotomy closure during infant heart transplantation

A case of an infant receiving orthotopic heart transplantation with over-sized donor heart was reported. Left lower pulmonary venous obstruction after sternotomy closure was detected by transoesophageal echocardiography (TOE) and the decision to delay sternal closure was made and the clinical outcome was very satisfactory. The usefulness of intraoperative TOE monitoring and postoperative TOE follow-up for infant heart transplantation, especially in those cases of size mismatch, was well demonstrated.

Early detection of acute allograft rejection by linear and nonlinear analysis of heart rate variability

OBJECTIVE

The first months after orthotopic heart transplantation are associated with the highest risk of acute allograft rejection. This study explores the utility and reliability of linear and novel nonlinear metrics of heart rate variability as predictors of graft rejection. The underlying hypothesis is that the transplanted heart, in response to inflammatory mediators, alters the dynamic properties of its rhythm-generating system.

METHODS

In a cross-sectional study of 45 patients who had undergone heart transplantation, spanning a period of 4 months after the operation, heart rate variability was examined by time- and frequency-domain analysis. The nonlinear features of heart rate variability were studied by computing a pointwise correlation dimension of R-R interval time series. The results of heart rate variability analysis were compared with those of endomyocardial surveillance biopsy studies using the International Society for Heart and Lung Transplantation scoring system.

RESULTS

Duration of heart transplantation itself exhibited a significant (P<.05) association with the onset of rejection. Specific predictors of acute rejection based on heart rate variability were identified, including shortening of the R-R interval (from 700 +/- 68 to 648 +/- 72 ms), an increase in the ratio of low-frequency (0.04-0.15 Hz) to high-frequency (0.15-0.40 Hz) spectral power (from 0.3 +/- 0.2 to 0.6 +/- 0.4), and a decrease in pointwise correlation dimension values (from 1.7 +/- 0.7 to 0.9 +/- 0.3 units). Multivariable logistic regression analysis (R (2) = 0.4) revealed that the only significant independent risk predictors were pointwise correlation dimension (odds ratio, 2.2 per 0.1 unit) and duration of heart transplantation (odds ratio, 1.7 per week).

CONCLUSION

Nonlinear measures of heart rate variability provide noninvasive means for identifying patients undergoing cardiac transplantation with acute rejection, thereby enabling the assessment of the time-dependent adaptive response of the donor heart to its host.

Evolution in functional complexity of heart rate dynamics: a measure of cardiac allograft adaptability

The capacity of self-organized systems to adapt is embodied in the functional organization of intrinsic control mechanisms. Evolution in functional complexity of heart rate variability (HRV) was used as measure of the capacity of the transplanted heart to express newly emergent regulatory order. In a cross-sectional study of 100 patients after (0-10 yr) heart transplantation (HTX), heart rate dynamics were assessed using pointwise correlation dimension (PD2) analysis. A new observation is that, commencing with the acute event of allograft transplantation, the dynamics of rhythm formation proceed through complex phase transitions. At implantation, the donor heart manifested metronome-like chronotropic behavior (PD2 approximately 1.0). At 11-100 days, dimensional complexity of HRV reached a peak (PD2 approximately 2.0) associated with resurgence in the high-frequency component (0.15-0.5 Hz) of the power spectral density. Subsequent dimensional loss to PD2 approximately 1.0 at 20-30 mo after HTX was followed by a progressive near-linear gain in system complexity, reaching PD2 approximately 3.0 7-10 yr after HTX. The "dynamic reorganization" in the allograft rhythm-generating system, seen in the first 100 days, is a manifestation of the adaptive capacity of intrinsic control mechanisms. The loss of HRV 2 yr after HTX implies a withdrawal of intrinsic autonomic control and/or development of an entrained dynamic pattern characteristic of extrinsic sympathetic input. The subsequent long-term progressive rise in dimensional complexity of HRV can be attributed to the restoration of a functional order patterning parasympathetic control. The recognition that the decentralized heart can restitute the multidimensional state space of HR generator dynamics independent of external autonomic signaling may provide a new perspective on principles that constitute homeodynamic regulation.