Is a venous varix (dilated vein) the same as an arteriovenous malformation (AVM) in a patient with suspected Hereditary Hemorrhagic Telangiectasia (HHT)?

No, a Venous Varix is NOT the Same as an Arteriovenous Malformation

A venous varix is simply a dilated vein, while an arteriovenous malformation (AVM) is a direct abnormal connection between arteries and veins that bypasses the normal capillary bed—these are fundamentally different vascular lesions with distinct pathophysiology, clinical implications, and management approaches. 1

Key Structural Differences

Arteriovenous Malformations (AVMs)

• AVMs are direct connections of artery to vein via abnormal dilated vascular channels (the "nidus") without a normal intermediary capillary bed, resulting in high-flow arteriovenous shunting. 1
• The abnormal dilated vascular channels in AVMs create pathological arteriovenous shunting that fundamentally alters hemodynamics. 1
• AVMs demonstrate fast-flow with arterialized venous waveforms on Doppler ultrasound, which is the hallmark diagnostic finding. 2

Venous Varices

• A venous varix is simply an abnormally dilated vein without arteriovenous shunting—it represents venous dilation rather than an arteriovenous connection. 1
• Venous varices show low-velocity or absent flow on Doppler evaluation, in stark contrast to the high-flow characteristics of AVMs. 2
• The presence of a venous varix was NOT predictive of hemorrhage in AVM studies, indicating these are distinct entities with different risk profiles. 1

Critical Distinction in HHT Context

AVMs in HHT

• Between 10-20% of HHT patients will develop at least one AVM during their lifetime, most commonly in the lungs, brain, or liver. 1
• HHT-associated AVMs carry significant morbidity and mortality risks: the annual rupture risk is 1.3% for previously unruptured brain AVMs and up to 4.8% for previously ruptured lesions. 1
• Multiple AVMs in the same individual, particularly in different organ systems, strongly suggest hereditary HHT rather than sporadic disease. 3

Telangiectasias vs. AVMs in HHT

• Telangiectasias are small mucocutaneous vascular lesions characteristic of HHT, while AVMs are larger visceral malformations—both can coexist in HHT but represent different points on the vascular malformation spectrum. 1
• HHT is defined by widespread cutaneous, mucosal, and visceral arteriovenous malformations ranging from tiny telangiectases to discrete AVMs of variable size. 1

Clinical Implications of the Distinction

Diagnostic Approach

• Doppler ultrasound is the critical first-line imaging study to distinguish these lesions based on flow characteristics: AVMs show high-velocity arterialized flow while venous varices show low-velocity venous flow. 2
• For suspected AVMs, cervicocerebral angiography remains the reference standard, providing high spatial and temporal resolution critical for characterizing feeding vessels, nidus architecture, and venous drainage. 1

Risk Stratification

• Imaging findings associated with higher hemorrhage risk in AVMs include intranidal aneurysm, deep venous drainage, deep location, or venous outflow obstruction—none of these apply to simple venous varices. 1
• The presence of a venous varix alone does not confer the same hemorrhage risk as an AVM with arteriovenous shunting. 1

Important Clinical Pitfall

Venous Varix as AVM Drainage

• In rare cases, a venous varix can develop as a consequence of serving as the draining vein for an adjacent AVM, representing a secondary phenomenon rather than a primary lesion. 4
• A huge varix can develop following endovascular embolization of an AVM with impaired venous outlets, particularly when there is stenosis in the draining venous system. 5
• When an AVM uses a venous malformation as its draining vein, treating the AVM alone (without treating the venous varix) can result in complete obliteration of the AVM with the venous malformation remaining unchanged. 4

Screening Recommendations for HHT Patients

• All HHT patients should undergo screening for pulmonary AVMs using contrast echocardiography or chest CT, as these can be treated presymptomatically to prevent stroke and cerebral abscess. 1, 6
• Brain MRI should be performed to detect cerebral AVMs in all HHT patients, as cerebral AVMs occur in approximately 7.7% of HHT patients screened with 3-T MRI/MRA. 6, 7
• Doppler ultrasonography is recommended as first-line imaging for liver involvement in all HHT patients, though most hepatic vascular malformations are asymptomatic. 1, 6
• Never perform liver biopsy in any patient with proven or suspected HHT due to catastrophic hemorrhage risk from vascular malformations. 1, 6