How HHT Affects Blood Pressure
HHT does not typically cause systemic hypertension; instead, it creates complex hemodynamic effects through vascular shunting that can lead to high-output cardiac failure and portal hypertension, while pulmonary arteriovenous malformations actually reduce pulmonary vascular resistance. 1
Cardiovascular Hemodynamic Effects
High-Output Cardiac State
- The most significant blood pressure-related effect in HHT is the development of high-output cardiac failure, not elevated systemic blood pressure. This occurs when hepatic arteriovenous malformations create left-to-right shunts, forcing the heart to pump increased volumes to maintain adequate tissue perfusion 1, 2
- High-output heart failure presents with exertional dyspnea, ascites, and edema—symptoms appearing around age 30, predominantly in females with ALK-1 mutations 1
- The underlying mechanism involves direct artery-to-vein connections that bypass capillary beds, resulting in increased cardiac output to compensate for ineffective tissue perfusion 3, 2
Portal Hypertension (Not Systemic Hypertension)
- HHT causes portal hypertension through two distinct mechanisms: hepatic artery-to-portal vein shunting and nodular regenerative hyperplasia, leading to variceal hemorrhage and ascites 1
- This represents elevated pressure in the portal venous system specifically, not systemic arterial hypertension 1
- The condition can mimic cirrhosis ("pseudocirrhosis") but occurs without liver insufficiency 1
Pulmonary Vascular Effects
Reduced Pulmonary Vascular Resistance
- Pulmonary arteriovenous malformations in HHT actually reduce pulmonary vascular resistance by creating right-to-left shunts, which is the opposite of pulmonary hypertension 1, 2
- These shunts cause systemic hypoxemia, paradoxical embolism, stroke risk, and cerebral abscess risk—not elevated pulmonary pressures 1
Rare Pulmonary Hypertension
- While pulmonary hypertension can occur in some HHT patients with specific ALK1 mutations, this is uncommon and represents a distinct complication rather than the typical hemodynamic pattern 1, 4
- When present, pulmonary hypertension may result from increases in either pulmonary vascular resistance or cardiac output, with the high-output state being more characteristic of HHT 4
Clinical Implications for Blood Pressure Management
Monitoring Priorities
- Focus cardiovascular monitoring on detecting high-output heart failure (elevated cardiac output with normal or low systemic vascular resistance) rather than systemic hypertension 1, 2
- Screen for portal hypertension complications (varices, ascites) using Doppler ultrasonography as first-line imaging 1, 5
Critical Pitfall
- Never perform liver biopsy in HHT patients due to catastrophic hemorrhage risk from hepatic vascular malformations, even when evaluating portal hypertension 1, 5
- Avoid invasive hepatic procedures unless intensive medical therapy has failed 5
Anticoagulation Considerations
- The decision to use antiplatelet or anticoagulant therapy in HHT patients requires careful balance, as these patients have both bleeding risks (from telangiectasias) and thrombotic risks (from paradoxical embolism through pulmonary AVMs) 6