In this manuscript, we provided for the first time a detailed description of hemodynamic changes after the use of levosimendan in neonates with intracranial AVSs. Although transiently, it allowed us to transfer both our patients to the operating theatre for embolization. Embolization by endovascular treatment has become the standard treatment for cerebral arteriovenous shunts, in particular for VGAM [2]. When possible, the procedure should be postponed after 3 months of age, considering the worse outcomes reported in infants weighing less than 5 kg, including adverse cardiac effects and major cerebral complications due to rebleeding [6].

However, high-output cardiac heart failure is the most common presentation of intracranial AVSs in the neonatal period (Fig. 3) [2], with features overlapping to those of congenital heart disorders that characterize the clinical picture: cyanosis, compromised peripheral pulses, and a cardiac murmur (often audible also through the fontanelle) [7, 8]. Intracranial AVSs often determine high-output heart failure characterized by increased venous return and increased afterload to the right ventricle (RV), resulting in a distended and non-compliant RV and increased pulmonary blood flow with pulmonary hypertension. The left ventricle (LV) often has normal or hyperdynamic function; however, the cardiac output (CO) is unable to meet the metabolic demand of the systemic organs resulting in lactic acidosis [9]. The prognosis is much worse than in those presenting later in childhood, with a higher risk of death due to cardiac failure [10]. Furthermore, survivors with previous heart failure had significantly worse neurodevelopmental outcomes [2].

Cardiac hemodynamic findings and physiological considerations in intracranial AVSs

On the other hand, these infants present with severe unstable conditions and require ventilatory support, inotropes and diuretics to improve hemodynamics, thus allowing them to undergo an embolization procedure.

The main aim of medical treatment of AVS-related hemodynamic changes is represented by ensuring blood flow to non-cerebral circulation through decreasing pulmonary overflow, reducing cardiac preload, and improving myocardial function (Table 4).

Diuretics and adequate fluid balance management are essential to reduce cardiac preload. Inotropic and vasopressor agents can support ventricular dysfunction (especially low-dose epinephrine and dobutamine), but they should be cautiously used to avoid excessive systemic vasoconstriction and to increase cardiac oxygen consumption.

The use of direct pulmonary vasodilators therapy (i.e. inhaled Nitric oxide - iNO) has been reported [11, 12] in order to reduce pulmonary vascular resistance (PVR). On the contrary, in the setting of pulmonary venous hypertension, the literature suggests that the use of pulmonary vasodilators to decrease PVR can lead to clinical deterioration [13] due to a further increase in pulmonary flow with the potential for lung edema or hemorrhage.

Prostaglandin infusion may be useful in patients with intracranial AVSs, presenting with refractory heart failure and suprasystemic pulmonary hypertension [14], to decompress right-to-left ductal shunting and thereby maintain an adequate systemic blood flow while awaiting definitive treatment. However, given the typical pulmonary venous hypertension of these infants and their pulmonary hemorrhages, we did not consider the use of pulmonary vasodilators or prostaglandin infusion.

Cardiopulmonary dysfunction could also be managed with inodilators such as milrinone, although it can cause an increase in heart rate and a decrease in blood pressure [15]. Intravenous milrinone has a pulmonary vasodilator effect but significantly improves myocardial performance: however, literature still lacks in-vivo measurements of cardiac output and systemic vascular resistance (SVR) after milrinone administration in newborn animal models with pulmonary hypertension due to the difficulty of performing double thoracotomies [16].

Despite the use of milrinone, both our patients persisted in having clinically relevant pulmonary hypertension (PH) and required the administration of levosimendan in order to stabilize them and allow the transport to the operating theatre.

De Rosa et al. previously reported the use of levosimendan in two of 12 neonates with VGAM who underwent endovascular embolization: both survived, whereas all-cause mortality of 58.3% (7/12) was reported in this cohort [17]. However, the aim of their paper was to describe the global outcome of their neonates with VGAM, and full details of levosimendan use were not reported. Conversely, herein we documented changes in hemodynamics parameters after levosimendan infusion at beat-by-beat analysis through PRAM with better cardiac output.

Levosimendan is a new inotropic agent belonging to calcium sensitizers, that improve myocardial contractility by increasing the sensitivity of troponin C for calcium, without increasing myocardial oxygen consumption, like the other inotropes [18]. First studies on levosimendan use are related to neonates with congenital heart disorders and congenital diaphragmatic hernia [19, 20]. Levosimendan can be used alone or in combination with other inotropic or vasopressor medications; however, given the risk of hypotension due to vasodilation by opening ATP-dependent potassium channels, careful monitoring is required [9].

The introduction of levosimendan in our two patients constituted the “bridge” to endovascular treatment of intracranial AVSs, whereas milrinone was not sufficient. These data are in line with Lechner’s findings, who previously studied the effects of levosimendan and milrinone in infants with congenital heart disorders: they observed an increase in the cardiac index in the levosimendan group, whereas cardiac index remained stable in the milrinone group [21]. In our two neonates, the use of PRAM monitoring allowed us to demonstrate significantly improved hemodynamic parameters, with a higher cardiac index (CI) after levosimendan infusion. The main hemodynamic parameters can also be obtained using other non-invasive devices, such as the cardiac index using echocardiography and the oxygen delivery index (DO2I) using Ultrasonic Cardiac Output Monitor (USCOM): however, we found that the main advantage of PRAM monitoring is the availability of a beat-by-beat analysis for all clinicians who take care of these neonates, especially those who are not able to perform functional echocardiography, and without stressing these fragile infants with evaluations with multiple devices.

Conversely, our findings warn of the limitations of NIRS monitoring in detecting changes during regional monitoring in these patients: we observed controversial results about cerebral FTOE before and after levosimendan infusion. We speculated that the presence of AVSs influences cerebral fractional tissue oxygen extraction, but the sole introduction of a drug could not be sufficient to compensate for the continuous typical “steal” phenomenon of these anomalies. In most severe cases, only the endovascular treatment can minimize flow shunt and significantly modify regional oxygen extraction. Furthermore, NIRS trends over time are more important than single values and can inform about hemodynamic instability.

To our knowledge, this is the first case series investigating in detail the changes in hemodynamics in levosimendan-treated neonates with intracranial AVSs.

Neonates with intracranial AVSs require multidisciplinary care, from preoperative stabilization to endovascular embolization, and pharmacological treatment should be discussed with different involved specialists [9]. The use of levosimendan could improve hemodynamics when conditions under conventional drugs are too unstable to allow neonates to undergo endovascular procedures. Multicenter randomized studies would need to provide evidence about its utility, but the rarity of intracranial Avs limits this type of research. Considering these disorders are life-threatening, even the use of off-label drugs in neonatal age should be promoted. Therefore, our experience could be a starting point for discussing the role of levosimendan in these congenital malformations.