woman with vascular malformation on face

Simply put, a vascular malformation is an abnormal communication between the arteries and veins. 

For doctors, the most important assessment for vascular malformations involves their classification into high flow and low flow malformations. This clinical classification helps guide further treatment decisions.

Dr. Manish Taneja

Vascular Specialist, Supreme Vascular and Interventional Clinic

Understanding Vascular Malformations: A Doctor’s Practical Approach to Diagnosis and Treatment

A vascular malformation occurs when there is an abnormal communication between the arteries and veins. It can be a simple lump and cause abnormal growth. These malformations can occur in any part of the body, ranging from simple birthmarks to complex life-threatening conditions. Vascular malformations are generally categorized into two types: vascular malformations and hemangiomas

The Types of Vascular Malformations

This article aims to provide a doctor’s practical approach to what vascular malformations are. Specifically, it is a deeper dive into the clinical treatment of vascular malformations from a doctor’s professional point of view (POV). Dr. Manish Taneja discusses how he aids patients to manage and treat vascular malformations. Moreover, these are his thoughts, work process, and patients’ success case studies regarding vascular malformations treatments. Read our other blog post “Vascular Malformations, Hemangioma, and Treatment Options Explained” for patients as well. 

Arteriovenous malformations (AVMs) occur when the arteries and veins are connected abnormally. These are usually large pulsating masses tending to more localised in nature. Read about our treatment options for AVM

Venous malformations (VMs) are caused by abnormal vein growth, whereas the abnormal growth of lymphatic vessels causes lymphatic malformations (LMs). VMs are abnormal enlargements of the wall of veins, appear as bluish or skin-coloured, soft lumps under the skin. These are usually more diffuse.

LMs are usually localised skin-coloured soft tissue masses that are composed of abnormal lymphatic channels.

Hemangioma is a benign tumor of blood vessels. This is commonly known as  red birthmark on infants, which can be anywhere on the body (often on the face, scalp, back or chest).

The Doctor’s Practical Approach to Vascular Malformations


In the context of vascular malformations, slow flow and high flow refer to the rate of blood flow within the abnormal vessels. According to the ISSVA’s (International Society for the Study of Vascular Anomalies) Classification of Vascular Anomalies, vascular malformations fall under slow flow and high flow.

Distinguishing between slow flow and high flow vascular malformations is important as it influences the diagnostic approach, treatment options, and potential risks associated with each type. The classification helps guide further management decisions and determines the appropriate interventions for each specific type of vascular malformation.

Click on the corresponding tabs to learn more about the types of slow flow and high vascular malformations as well as the definition for sclerotherapy and embolization treatment options. 

MRI is the best imaging tool for assessment with specific sequences and CTA may be useful in certain situations especially when planning treatment.

  • Venous malformations
  • Lymphatic malformations
  • Mixed malformations

These vascular malformations exhibit slower blood flow and involve abnormal dilation or enlargement of veins, capillaries, or lympathic vessels.

Low flow malformations lack the direct connection between artiers and veins.


Sclerotherapy involves a fine needle to inject the sclerosing agent into the targeted blood vessels with solution or foam that irritates the lining of the blood vessels. It causes them to become inflamed and stick together. As a result, the treated vessels close off and are gradually reabsorbed by the body over time.

Sclerotherapy usually doesn’t require anesthesia. The number of sessions needed depends on the size and extent of the vascular condition being treated. Following the procedure, patients may be advised to wear compression stockings or bandages to promote healing and prevent blood clots.

Sclerotherapy is considered a safe and effective treatment option for various vascular conditions, including spider veins, small varicose veins, and certain types of vascular malformations. However, like any medical procedure, it carries some potential risks and side effects, which can be discussed with a healthcare professional prior to undergoing the treatment.

  • Arteriovenous malformations

High flow vascular malformations involve abnormal connections between arteries and veins creating a direct pathway for blood to flow rapidly from arteries to veins without the presence of capillaries. These malformations are characterized by arterial blood pressure and a pulsatile flow pattern. 

Embolization is performed using image guidance, such as fluoroscopy or angiography. A catheter (a thin, flexible tube) is inserted into a blood vessel, usually through a small incision in the groin or wrist, and guided to the desired location. Once the catheter is properly positioned, embolic agents (tiny small beads, liquids, or metallic coils) are delivered through the catheter and released into the blood vessels.

The embolic agents used in the procedure can vary depending on the specific condition being treated. These agents cause the blood vessels to become blocked or narrowed, effectively preventing blood flow to the area. Over time, the blocked vessels are absorbed or replaced by scar tissue.

Embolization is employed to treat vascular malformations, stop bleeding, reduce the size of tumors by cutting off their blood supply (known as embolization therapy for tumors), manage aneurysms, or prepare for surgical procedures by blocking blood flow to certain areas. The procedure is generally safe and should be discussed with a healthcare professional before undergoing embolization.

Slow Flow Vascular Malformations


As mentioned above, slow flow vascular malformations exhibit slower blood flow and involve abnormal dilation or enlargement of veins, capillaries, or lymphatic vessels. Unlike high flow malformations, low flow malformations lack the direct connection between arteries and veins. Low flow malformations include venous malformations (VMs), and lymphatic malformations (LMs).

    Left foot venous malformation case study of a 30 year old male.

    30 year old male with left foot slow flow venous malformation


    • Majority of these are venous, lymphatic or mixed malformations.
    • Most common location: head and neck region, limbs and trunk.
    • The treatment used to be surgery.
    • Regrowth rate is very fast with incomplete resection.
    • Most lesions use sclerotherapy and embolization+/- surgery in selected cases.
    • Multiple sessions may be required.

    High Flow Vascular Malformations

    On the other hand, high flow vascular malformations involve abnormal connections between arteries and veins, creating a direct pathway for blood to flow rapidly from arteries to veins without the presence of capillaries. These malformations are characterized by arterial blood pressure and a pulsatile flow pattern. Examples of high flow malformations include arteriovenous malformations (AVMs).

    47 year old female with left thigh high flow AVM

    47 year old female with left thigh high flow AVM


    • These are classic arterio-venous malformation.
    • They can occur anywhere with brain being one of the most common and serious sites.
    • Treatment options:
      • Combination techniques: surgery/embo/radiosurgery
      • Embolization is a good curative option with advent of Onyx

    Surgery is done in conjunction with interventional treatment in certain causes and surgery as stand alone treatment is rarely done nowadays. 

    Complete cure is possible with interventional therapy depending on the type of vascular malformation.

    As is the case with the 40 year old male with the onset of seizures. Embolization for this high flow vascular malformation was used for treatment. Slide images for before and after treatment.

    At Supreme Vascular and Interventional Clinic, we specialize in interventional/endovascular treatments. Apart from these treatments at our clinic, there are more several types of vascular conditions we offer to treat different problems.

    The Supreme Vascular and Interventional Clinic, is your “go-to” facility for various vascular conditions and pain management as well as the premiere clinic in Singapore for vascular malformations treatments. Our state-of-the-art facilities and dedication to patient satisfaction ensure we help you best with a positive outcome. To learn more about how to deal with the issue, contact us to arrange an appointment on our website with our vascular specialist, Dr. Manish Tanejaor call us at +65 6904 8084.