The definitive treatment for the end stage pediatric heart failure is the orthotopic heart transplantation (OHTx). However, because of the lack of organ donors, especially in very small children, the use of ventricular assist device (VAD) is a validated therapy to bridge patients to the OHTx with a success rate up to 84% (Ibrahim et al., 2000; Reinhartz et al., 2003; Chang and McKenzie, 2005; Stiller et al., 2005; Hetzer et al., 2006; Gandhi et al., 2008; Brancaccio et al., 2010, 2013; Potapov et al., 2011; Almond et al., 2013; Miera et al., 2014; Kirklin, 2015; Mascio, 2015; Sandica et al., 2016).

The use of left VADs (LVAD) could successfully support patients till the OHTx, increasing the cardiac output (CO), unloading the left ventricle (LV) and decreasing the left atrial pressure and the pulmonary arterial pressure. The LVAD decrease the LV volumes and the LV work because of the flow distribution between the native LV and the LVAD (Barbone et al., 2001). In fact, in the presence of the LVAD, the total cardiac output is the sum of the LV output and the LVAD output. Increasing the LVAD cardiac output (increasing the LVAD speed in the continuous flow LVAD or increasing the pump rate in pulsatility flow LVAD) it is possible to obtain an increment of the total cardiac output (untill a determined plateau) and a higher unloading of the LV with lower LV volumes, lower left atrial pressure, lower pulmonary pressure and lower LV output. In the case of total support, all the cardiac output is totally provided by the LVAD and the aortic valve remains closed. This condition is usually avoided to permit to the LV at least a slight ejection and to the aortic valve to open at least every three cardiac cycle.

The effects of the LVAD on the right ventricular function is controversial. In fact, one of the major complications in LVAD patients is the right ventricular (RV) failure with an incidence among 13–44% in adults and an incidence of 42% in children (Chen et al., 1996; Kukucka et al., 2011; Saraiva Santos et al., 2012; Karimova et al., 2014). Different explanations about the increased risk of the RV failure in LVAD patients were proposed:

On the contrary, it has been considered that the LVAD could decrease the RV afterload, decreasing the pulmonary arterial pressure, possibly leading to a better RV pump functioning (?). In literature, there are different opinions and several authors performed also animal experiments to study the interventricular interaction during LVAD assistance (Kawai et al., 1992; Mandarino et al., 1992; Morita et al., 1992; Hendry et al., 1994; Chen et al., 1996; Barbone et al., 2001; Omoto et al., 2002; de Jonge et al., 2005; Kukucka et al., 2011; Saraiva Santos et al., 2012; Umeki et al., 2012; Arakawa et al., 2014; Karimova et al., 2014).

Di Molfetta et al. (2016) summarized with a simulation the effects of the LVAD implantation and the effects of the increased LVAD contribution using a lumped parameter model (Figure 1). Increasing the LVAD contribution a decrement of the LV preload and volumes and an increment of the arterial systemic mean pressure can be obtained together with an increment of the RV preload and RV volumes and a decrement of the pulmonary mean pressure. Finally, a decrement of the LV work and an increment of RV work are obtained increasing the pump contribution.

Analyzing the infant population, only the Berlin Heart EXCOR (BHE; Berlin Heart, Berlin Heart AG, Berlin, Germany) is licensed as long term VAD to bridge children to OHTx (Ibrahim et al., 2000; Reinhartz et al., 2003; Chang and McKenzie, 2005; Stiller et al., 2005; Hetzer et al., 2006; Gandhi et al., 2008; Brancaccio et al., 2010, 2013; Potapov et al., 2011; Almond et al., 2013; Miera et al., 2014). The smallest patients are particularly demanding in terms of morbidity and mortality (Ibrahim et al., 2000; Reinhartz et al., 2003; Chang and McKenzie, 2005; Stiller et al., 2005; Hetzer et al., 2006; Gandhi et al., 2008; Brancaccio et al., 2010, 2013; Potapov et al., 2011; Almond et al., 2013; Miera et al., 2014) especially now that the LVAD staying is increasing over time. In particular, small body surface area, BHE size mismatch and younger age seems to be associated with an increased risk of thromboembolic complications (Almond et al., 2013; Miera et al., 2014).

In a recent study, Conway et al. reported about the outcome of a multicenter study on 97 pediatric patients under 10 kg undergoing Berlin Heart EXCOR VAD. In their study, the median LVAD stay was 26 days with a survival to heart transplantation less than 60% (Conway et al., 2015).

On the basis of these considerations, the aim of this study is to retrospectively review our single-center experience on the use of BHE in children under 10 Kg.

The use of BHE could successfully bridge pediatric patients till the OHTx, but the management of small patients is especially challenging. In fact, small body surface area seems to be associated with an increased risk of thromboembolic complications during VAD assistance and increased mortality as reported by Almond et al. (2013). In accordance with this consideration, Reinhartz et al. (2003) evidenced that an oversized device, which is simpler in smaller patients, could lead to an increased risk of thromboembolisms because of the stasis into the devices or systemic hypertension due to large stroke work. Similarly, Miera et al. (2014) demonstrated the influence of the BHE size in relation to patients weight on the clinical outcome. In fact, in their study Miera et al. evidenced that a large pump size in relation to body surface area is an independent risk factor for the occurrence of thromboembolic events (Miera et al., 2014). Moreover, they evidenced that younger age and smaller body surface area patients showed a trend of increased risk of thromboembolic events. In their work, Stiller et al. (2005) reported about the BHE implantation in 18 children less than 1 year underlying that the small children could be successfully bridged to OHTx, but the intensive care management and the anticoagulation strategy should be optimized to improve the outcome in terms of mobility and mortality. Gandhi et al. (2008) reported their experience on the use of BIVAD in 9 small children with an average weight of 9.4 kg (3 to 38 kg). Patients were supported for 35 days (1 to 77) and then 8 patients were successfully transplanted. It should be underlined that, as reported by Hetzer et al. (Potapov et al., 2011), the length of VAD staying is increasing over time and the management of small patients to achive long term event free VAD support is still challenging (Potapov et al., 2011). Finally, Conway et al reported about the outcome of a multicenter study on 97 pediatric patients under 10 kg undergoing Berlin Heart EXCOR VAD. In their study, the median LVAD stay was 26 days with a survival to heart transplantation less than 60% (Conway et al., 2015).

In our study, we reported our experience on the use of BHE in 30 patients under 10 kg. Patients were assisted for a median time of 132.8 ± 94.4 days that is a significantly longer time compared to the experiences reported in literature (Almond et al., 2013; Conway et al., 2015). Despite a longer period of support the complications and the outcomes of our population are comparable to the complications and the outcomes reported in literature. Sixty seven percentage of patients were successfully transplanted, 23% of patients required re-intervention for bleeding, 23% of patients experienced major neurological complication and 30% experienced BHE cannulas infection.

In conclusion, the use of BHE in small children is becoming of common use in recent years. Longer support time of several months requires a careful management of these fragile patients especially in terms of coagulation and infections. Good results in short and long term are possible, encouraging the use of this strategy as bridge to OHTx.

FG, Clinical data; AD, Statistical analysis and clinical data; SF, Surgical procedure analysis; LD, Post operative data analysis; RI, Pre-op Echo analysis; RA, Preoperative analysis data; GP, Post-op Echo analysis; MD, Post-op Intensice care analysis; IF, Anticoagulation protocol; AR, Anticoagulant data analysis; GT, Post operative data analysis; AA, Paper Overview.