Heart transplantation (HTx) is the ultimate treatment for end-stage heart disease for adults and children, including ne-onates and pediatrics. Since Kantrowitz and colleagues'1 first HTx in infants in 1968 and Cooley and colleagues'2 first bridge to HTx in 1969, various mechanical circulatory support systems have been developed and used all over the world; nevertheless, the limitations are still the same, particularly, suitable sizes for pediatrics. Because of the shortage of donor organs, mechanical circulatory support is still the only alternative to bridge these patients to HTx. Compared with the systems used in adult cases, the selection of ventricular assist device (VAD) systems for adequate support for children is limited.
A number of devices have been developed to defeat these limitations. Some of the pioneers in this field are Del Nido et al., 3 who bridged to HTx by extracorporeal membrane oxygenation in 1985; Frazier et al., 4 who bridged to HTx in 1989 by a Biomedicus centrifugal pump; and Warnecke et al., 5 who did it with the Berlin Heart System in 1991.
The purpose of this study was to evaluate the overall outcome of transplanted pediatric patients after circulatory support.
Materials and Methods
We retrospectively analyzed 91 pediatric patients who underwent HTx from 1989 to 2004. Seven of these patients required support by a VAD system before HTx. Group A comprised 84 pediatric patients who underwent HTx electively as outpatients, whereas group B comprised 7 pediatric patients who were supported with VAD systems before HTx as a consequence of low-output or postcardiotomy syndrome after corrective congenital operations. Table 1 shows demographic data including age, weight, height, and diagnoses for all patients in group B.
The aim of VAD support was maintenance of systemic circulation, recovery of multiple organ failure, and bridge to transplantation. Criteria for receiving VAD support were clinical deterioration (despite optimal pharmacologic support and the use of an intraaortic balloon pump), low-output syndrome, mean arterial pressure <60 mm Hg, ejection fraction <25%, cardiac index <2 l/min, diuresis <1 ml/min/kg, central venous pressure >15 mm Hg, and left atrial pressure >18 mm Hg.
Routine evaluation of ejection fraction via echocardiography within 72 hours showed an improvement or an irreversible organ failure, so that we evaluated the patients according to HTx selection criteria to place them on the waiting list. HTx selection criteria were irreversible heart pathology, stability of major organ function, no neurologic defects, no active infection/sepsis, and family and social compliance. Normally, clinical improvement is seen immediately after VAD implantation. We achieved a sufficient circulation, preventing multiorgan failure by normalizing organ perfusion to wean off inotropes. Table 2 shows device type, indications for VAD, duration of support, and survival in group B.
The VAD systems used in our cohort were the Biomedicus centrifugal pump, Thoratec or Medos paracorporeal systems, and the Novacor LVAD. For short-term support up to 6 weeks, we used the Biomedicus centrifugal pump consisting of the pediatric pumphead (35 ml) and a 0.25-inch tubing set. Usually, this system is used for bridge to recovery or bridge to bridge.
We prefer Thoratec and Medos devices, especially for midterm support up to 1 month, and the Novacor device for long-term use (>6 months) if body surface area (BSA) is more than >1.5 m2. For a BSA of less than 1.5 m2 2 in pediatric cases, we prefer the Medos system because of its miniaturized chambers with various sizes from 10, 25, and 60 ml for the left side chamber and 9, 22.5, and 54 ml for the right side chamber. It can even be used in neonates with a BSA <0.3 m2. Figure 2 shows device variations of Medos. Thoratec can be used for patients with a body weight >40kg, especially in cases of biventricular heart failure.6 We found that the device-related patient selections are important for both the outcome and the duration of support.
Of the 91 patients, 75 survived transplantation. The overall mean survival rate was 82%. There were no significant differences in survival rates between groups. Actuarial survival in group A was 91% at 1 year, 88% at 5 years, and 84% at 10 years. Actuarial survival in group B was 71% at 1 year, 71% at 5 years, and 71% at 10 years. Figure 3 shows cumulative survival analysis of the groups as Kaplan-Meier survival function. Major complications were bleeding, thrombosis, and infection. There are no neurologic disorders in Group B survivors. No renal dysfunction was seen in either group.
Candidates for VADs are patients with postcardiotomy low-output syndrome, acute heart failure, and those on the waiting list who show deterioration in clinical condition despite maximum pharmacologic support. Organ shortage is the main cause of death for patients on the waiting list.
With VADs, patients can be bridged for weeks or months, so that they have the chance to receive a suitable organ. The average waiting time on the list of 304 days has not decreased since 1998,6 and the mortality rate, which is now up to 30%7 of those on the waiting list, can only be decreased with VADs.
End-organ recovery is the second major advantage in addition to VAD's lifesaving and time-gain functions. Satisfactory long-term survivals are associated with end-organ recovery, which is achieved before HTx. Duncan8 demonstrated that in-hospital survival rates of 40–80% are possible for children who require mechanical support, and described a border time interval of support of 72 hours for extracorporeal membrane oxygenation and 48 hours for VAD in which recovery of ventricle function must occur; otherwise, patients require HTx.9 Comparing our results with those of Pasic et al. 10 and Stiller et al., 11 who reported 1-year survival rates of 62% and 82%, respectively, our survival rates are acceptable.
Although neurologic complications are one of the major causes of morbidity during VAD support, successful management of anticoagulation can decrease the incidence of adverse events.
According to Reiss et al., 12 renal dysfunction is a predictor of high mortality in VAD patients, which emphasizes the importance of implantation timing. Early referral and elective implant result in better outcomes with regard to end-organ recovery.
Our results are comparable with those of other centers, and the best results seem to be related to end-organ recovery achieved with the correct VAD selection and implantation timing.
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