Pulmonary AVMs (PAVMs)

HHT is an autosomal dominant genetic disorder, meaning that an individual only needs one copy of the faulty gene from either parent to develop the condition. Mutations in the ENG (endoglin) or ACVRL1 (activin receptor-like kinase 1) genes are commonly associated with HHT.

PAVMs are abnormal connections between the pulmonary arteries and veins in the lungs. In individuals with HHT, these malformations often lack the normal capillary bed, leading to direct shunting of blood from the arteries to the veins. This can result in poorly oxygenated blood reaching the systemic circulation.

Patients with PAVMs may remain asymptomatic, or they may experience a range of symptoms. Common manifestations include dyspnea (shortness of breath), fatigue, and cyanosis (bluish discoloration of the skin and mucous membranes). Some individuals may develop complications such as stroke or brain abscess due to paradoxical emboli, where abnormal blood clots travel from the veins to the arteries.

Various imaging techniques are employed to diagnose and assess PAVMs in HHT patients. Contrast echocardiography, computed tomography (CT) angiography, and magnetic resonance imaging (MRI) are commonly used to visualize the abnormal blood vessels and assess the severity and distribution of PAVMs.

The primary goal of treating PAVMs in HHT patients is to prevent complications related to abnormal shunting of blood. Embolization, a minimally invasive procedure, is often employed to occlude the abnormal vessels using coils or other embolic materials. Regular follow-up is crucial to monitor the effectiveness of treatment and identify any new PAVMs that may develop over time.

Since HHT is a hereditary condition, genetic counseling is recommended for affected individuals and their families. Understanding the genetic basis can help in family planning decisions and early detection of the condition in at-risk relatives.

Managing PAVMs in HHT patients often requires a collaborative approach involving pulmonologists, interventional radiologists, cardiologists, and genetic counselors. Regular monitoring and coordination between specialists are essential for optimal patient care.

Orla Sills shares her insights on what advice she would like to tell the paramedics about HHT: Pulmonary Arteriovenous Malformations PAVMS

• Symptoms: often people with lung AVMs have low oxygen saturation. Mine was 90 and I’m a relatively fit woman of 37 years. The breathlessness had been on-going for years and I had never had childhood asthma. I was also constantly fatigued. 
• Misdiagnosis: often lung AVMs are misdiagnosed as asthma or an asthma attack- we too have difficulty breathing.
• Risks: People with undiagnosed lung AVMs or uncoiled lung AVMs are at high risk of a stroke, transient ischemic attack or brain abscess at any time. If the patient is coughing up blood this is a medical emergency.
• IV air filter (bubble trap): Perhaps, the most important but unknown piece of information is that an IV air filter (bubble trap) should be used when a patient has an intravenous line. 

This is to prevent any large air bubble from entering the bloodstream, going through a lung AVM, and then causing a temporary stroke. This is most effectively done by using a filter in the IV line as close to the patient as possible. A 0.22 micron filter is best if available, but a blood filter is also acceptable (about 260 microns) and will stop all large air bubbles. 

During a blood transfusion, a standard blood filter is all that is needed. Please note that filters often cannot be used for IV contrast injections like you might get for CT or MRI scans.

Personally, I wear a medical bracelet. It would make me feel much more secure to know our paramedics will understand what HHT means so I can get the best care possible. Thank you all and I wish you all the best in your future careers as paramedics.

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In summary, pulmonary AVMs are a significant clinical feature of HHT, and their management involves a combination of imaging studies, interventional procedures, and a multidisciplinary healthcare approach to improve patient outcomes and quality of life.