Cardiopulmonary Exercise Testing to Evaluate Pulmonary AVMs
Cardiopulmonary Exercise Testing to Evaluate Pulmonary AVMs
Pulmonary arteriovenous malformations (PAVMs) are a rare vascular condition affecting the
 lungs. PAVMs lead to low blood oxygen levels, yet are very well tolerated by patients. This
 study will examine the exercise capacity of PAVM patients using formal cardiopulmonary
 exercise tests performed on a stationary bicycle.
It is well known that the lung is the site at which oxygen enters the blood stream, diffusing
 from the alveolar air sacs into the pulmonary capillaries. This newly oxygenated blood is
 carried to the heart in the pulmonary veins, then passes into the systemic circulation to
 provide oxygen to the tissues.

 Patients with pulmonary arteriovenous malformations (PAVMs) have abnormal vascular
 connections between pulmonary arteries and pulmonary veins in the lung. Blood flowing through
 PAVMs therefore bypasses the oxygenation sites in the pulmonary capillaries. Low blood oxygen
 levels (hypoxemia) is frequent in PAVM patients but breathlessness (dyspnea) is not. The
 investigators have shown that dyspnea was not a common presenting complaint in a large UK
 series, and that there is little correlation between severity of dyspnea in PAVM patients,
 and blood oxygen levels.

 In this study the investigators will address the question "Why are hypoxemic PAVM patients
 not more dyspneic?"

 The investigators will address this by first performing standardised cardiopulmonary exercise
 testing, as used in the clinic, on age and sex matched patients with PAVMs and healthy
 controls. Physiological parameters will be compared, to test the null hypothesis that the
 impact of exercise on PAVM patients' cardiopulmonary systems does not differ to normal
 controls.

 If the expected differences are confirmed, the investigators will examine if there is any
 difference to normals by re-examining the exercise tolerance of the PAVM cohort after they
 have had their PAVMs treated by embolization.

 Most patients with PAVMs have an underlying hereditary vascular disorder, hereditary
 haemorrhagic telangiectasia. Assuming the expected differences between PAVM patients and
 controls are confirmed, the investigators will therefore also examine which pattern HHT
 patients without PAVMs display. Finally, cellular and molecular methods will be used to
 dissect mechanistic pathways.
Inclusion Criteria:

 -  Ability to provide informed consent

 -  Healthy volunteers: no concurrent health reason to avoid exercise

 -  Pulmonary AVMs: pulmonary AVMs confirmed by CT scan

 -  Hereditary hemorrhagic telangiectasia without pulmonary AVMs: HHT according to current
 international consensus criteria, with no evidence of PAVMs on dedicated thoracic CT
 scan.

 Exclusion Criteria:

 -  Inability to provide informed consent.

 -  Any known cardiovascular abnormality including a history of syncope (faintness,
 dizziness, lightheadedness or loss of consciousness due to an abnormality of the
 cardiovascular system).

 -  Current respiratory tract infection (eg a cold).

 -  Pregnancy.

 -  Claustrophobia or needle phobia