The impact of venous outflow obstruction on venous return to the heart - preload, cardiac function and exercise tolerance (Dr Rachael Morris)

Post-Thrombotic Syndrome (PTS) affects up to 50% of patients who develop thrombosis in the proximal (inferior vena cava, IVC or iliofemoral, IFV) veins.

Chronic fibrotic changes, occurring from natural thrombus resolution, may result in partial or complete venous outflow obstruction (VOO).

Severe PTS (exercise-limiting leg pain and swelling) limits work and leisure activities, and significantly affects quality of life.

Patients with proximal VOO also become breathless on exertion, without evidence of pulmonary embolism or cardio-respiratory disease.

This may result from insufficient lower limb venous return, leading to inadequate preload and diminished cardiac output during exercise.

This project will explore: (i) the physiology of venous return during exercise; (ii) the changes after stenting of the IVC and IFVs; and (iii) the natural compensatory mechanisms that develop, including diversion of venous return through collateral pathways.

Results will inform assessment and treatment pathways for patients with VOO and expand knowledge on the importance of the venous system in preload reserve during exercise.

They may also indicate a need to investigate asymptomatic causes of impaired venous return (such as venous compression syndromes) in patients with cardiac disorders.