Case February 2025
Hepatic Hemangioma

Case Report: Hemodynamic and Multisystem Evolution of a Preterm Infant with a Massive Hepatic Vascular Malformation (AVM)

March 2025 - Gabriel Altit

Discussion: 

This month’s case highlights a hepatic hemangioma associated with high-output right ventricular failure. These patients often present with a component of pulmonary hypertension, primarily flow-mediated, but it may also be influenced by high pulmonary vascular resistance due to fetal remodeling of the pulmonary vasculature. This remodeling occurs in response to elevated pulmonary blood flow during fetal life, at a critical stage of pulmonary vascular development. Patients with hepatic hemangiomas exhibit a large left-to-right shunt through the vascular malformation in the liver, leading to torrential flow into the IVC, right atrium (RA), and right ventricle (RV). This results in RA, RV, and pulmonary artery (PA) dilation. There is frequently a right-to-left shunt at the atrial and ductal levels. When the ductus arteriosus closes, these patients are at high risk of significant RV failure, as the RV is unable to adequately unload the excessive flow, which is now restricted to the pulmonary circulation—paradoxically often constricted. Additionally, retrograde flow in the aorta is often observed beyond the arterial feeders supplying the vascular malformation. This case has been previously published as a case report, which is available below. The case was also reviewed in the context of NH-TNE teaching for the McGill University program, and I have included the recording of this session above, where we analyzed both the imaging findings and physiological implications. Interestingly, this pathology is analogous to Vein of Galen malformation (VOGM). However, VOGM typically drains blood from the upper aortic arch via the carotid arteries, leading to torrential flow into the SVC and RA. In VOGM, retrograde flow in the aorta is often diffuse, originating at the carotid level, whereas in hepatic vascular malformations, the steal phenomenon typically occurs more distally.

Detailed review: In the presence of a large hepatic arteriovenous malformation (AVM), arteriovenous shunting within the liver diverts a substantial proportion of cardiac output away from the systemic circulation, creating a physiology similar to that observed in vein of Galen malformations (VOGM). The liver acts as a low-resistance vascular bed, functioning like a "vascular vacuum" that siphons blood directly from the post-ductal aorta and systemic circulation into the venous system, bypassing effective capillary exchange. This leads to profound systemic steal, overwhelming the right heart with excessive venous return while simultaneously reducing effective perfusion to systemic organs.

Due to the excessive venous return, right atrial (RA) pressure rises with progressive volume overload, leading to right-to-left shunting at the atrial level via a patent foramen ovale (PFO) or atrial septal defect (ASD). The size of the inter-atrial defect and the balance between RA and left atrial pressure dictates the degree and voluem of shunting at the atrial level. This shunt worsens systemic hypoxemia by bypassing pulmonary oxygenation, contributing to persistent pre-ductal cyanosis. The continuous volume/flow overload into the pulmonary circulation elevates pulmonary arterial pressures (Pressure ~ Flow x Resistance; increasing the flow significantly increases the pressure depending on the resistance level). this leads to sprogressive right ventricular (RV) dysfunction. 

The patent ductus arteriosus (PDA) typically shunts right to left, primarily due to underfilling of the descending aorta, which is being "vacuumed" by the hepatic AVM shunt. Additionally, the RV is exposed to torrential venous return, leading to an overwhelmed right ventricle during diastole and, ultimately, RV failure. Furthermore, increased pulmonary blood flow during fetal life compared to the expected norm may contribute to abnormal pulmonary vascular remodeling. Normally, only 10% of the RV output perfuses the lungs in utero; however, in these patients, excessive pulmonary blood flow during fetal development may stimulate increased vascular smooth muscle proliferation, predisposing them to heightened pulmonary vascular resistance (PVR) in the postnatal period, even in the setting of high pulmonary blood flow. Further, there may be a component of pulmonary hypoplasia secondary to the RV dilatation during fetal life, as well as the compressive effect from the large liver. 

The right-to-left PDA shunt results in pre- and post-ductal saturation differences. However, the blood entering the descending aorta remains essential to maintain systemic perfusion. As a compensatory mechanism, a fraction of this systemic flow recirculates through the hepatic malformation, exacerbating the hemodynamic imbalance. Embolization may interrupt this vicious cycle, but complete occlusion of the vascular anastomoses in a single procedure may significantly alter hemodynamics and destabilize a precarious balance. Therefore, embolization is typically performed in multiple stages to gradually reduce arteriovenous shunting while allowing for hemodynamic adaptation.

These patients frequently exhibit liver dysfunction leading to:

• Consumptive coagulopathy, with thrombocytopenia and hypofibrinogenemia, contributing to an increased risk of bleeding.

• Hypoalbuminemia, causing systemic edema and low oncotic pressure, further worsening volume overload.

• Hyperammonemia and hypoglycemia due to impaired hepatic metabolism/function.

• Hepatorenal syndrome, as well as acute kidney injury due to severe systemic steal resulting in renal hypoperfusion by a pre-renal pathophysiology.

• Severe hepatomegaly may contribute to thoracoabdominal restriction, impairing lung expansion and further complicating respiratory management.

Congenital Hepatic Hemangioma (CHH) vs. Kaposiform Hemangioendothelioma (KHE)

A crucial distinction must be made between congenital hepatic hemangiomas (CHH) and kaposiform hemangioendotheliomas (KHE):

Congenital Hepatic Hemangioma (CHH)

• GLUT1-negative (unlike infantile hemangiomas which is GLUT-1 positive)

• Can be focal, multifocal, or diffuse

• Often presents prenatally and may cause high-output cardiac failure due to large arteriovenous shunts.

• Does not cause a Kasabach-Merritt Phenomenon (KMP) - which is a phenomenon specific to hemangioendothelioma. Congenital hemangiomas (CH) can present with thrombocytopenia and coagulation abnormalities, but these changes are typically milder, transient, and self-limited. Unlike KMP, which is progressive and does not resolve spontaneously, the coagulation disturbances associated with CH tend to improve as the lesion stabilizes or regresses.

• Does not regress spontaneously. May require embolization, corticosteroids, or supportive care.

Kaposiform Hemangioendothelioma (KHE) & Tufted Angioma (TA)

• Locally aggressive vascular tumors

• GLUT1-negative

• Classically associated with Kasabach-Merritt Phenomenon (KMP): KPM is a severe consumptive coagulopathy characterized by thrombocytopenia, microangiopathic hemolytic anemia, and disseminated intravascular coagulation (DIC) in the context of a rapidly growing vascular tumor. It is exclusively associated with kaposiform hemangioendothelioma (KHE) and tufted angioma (TA), which belong to the same neoplastic continuum. Platelet transfusion is generally contraindicated, as it can aggravate platelet sequestration within the tumor, further worsening thrombocytopenia and coagulopathy. KMP is characterized by severe thrombocytopenia, consumptive coagulopathy, and hypofibrinogenemia due to platelet trapping within the tumor.

• Often treated with vincristine, sirolimus, corticosteroids, or anti-fibrinolytic therapy.

Physiology Review

Electrocardiogram

Pertinent publications and Case report

Echo Day 1

Echo Day 2

Bubbles are observed as something is being injected through a central venous access. This often happens despite the presence of filters. The bubbles are crossing through the PFO, indicating that there is still likely a component of right to left atrial shunt.

Echo Day 7

There is significant LV hypertrophy. The LV is pancaked in systole. There is systolic anterior motion of the mitral valve. The LV is underfilled. LA is small likely due to decreased preload. The combination of pulmonary hypertension and septal hypertrophy can further worsen the risk of LVOT obstruction in systole due to unfavourable septal positioning relative to the LVOT. The RV is dilated anteriorly. 

Here we appreciate the significant LV hypertrophy with kissing walls in systole. There is intra-cavitary acceleration of flow with some LVOT obstruction. There is barely flow seen in the middle panel for the LVOT.

Liver Ultrasound

The below images are outlining the hypervascular hepatic lesion that is corresponding to a congenital hepatic hemangioma.