Polycythemia, Polycythemia Vera (PV)
Conditions
Keywords
Blood viscosity, polycythemia
Brief summary
Polycythemia vera (PV) is a rare haematological disorder characterized by an excessive production of red blood cells, associated with the somatic JAK2 V617F mutation. Clinical manifestations are varied and often include exercise intolerance but the underlying mechanisms remain poorly understood. Physical activity is recommended in the management of chronic diseases, but it must be tailored to the physiological profile of the patient. A cardiopulmonary exercise test (CPET) is essential to ensure safety, detect possible contraindications, and assess maximal oxygen uptake (VO₂max), a key indicator of aerobic performance. This prospective, experimental, non-randomized study will include patients with PV followed at Lyon Sud University Hospital and for which a CPET is scheduled in their routine clinical follow-up. The primary objective is to compare VO₂max between two groups of patients: moderate (\<10%) versus marked (≥10%) extent of blood viscosity increase after the completion of the CPET. The main hypothesis is that a significant increase in blood viscosity during exercise (≥10%) is a major limiting factor in oxygen transport and leads to a reduced VO₂max, reflecting impaired exercise tolerance. Secondary analyses will focus on hemorheological parameters, tissue oxygenation, and cardiorespiratory and metabolic responses. The study aims to better understand the biological and physiological determinants of exercise intolerance in this population.
Interventions
BIOLOGICALResearch samples blood viscosity and viscoelasticity:
Research samples: Blood rheology: hematocrit, blood viscosity, deformability and erythrocyte aggregation, viscoelasticity
Sponsors
Hospices Civils de Lyon
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE
Intervention model description
Prospective, experimental, single-center, non-randomized study.
Eligibility
Sex/Gender
ALL
Age
18 Years to 70 Years
Healthy volunteers
No
Inclusion criteria
* Patient aged at least 18 years and under 70. * Patient followed for a diagnosis of Polycytemia vera (confirmed JAK2 V617F mutation) and who were prescribed a CPET because of their wish to resume regular physical activity. * Patient affiliated with or benefiting from a social security scheme.
Exclusion criteria
* Any known history of heart disease or chronic respiratory illness likely to affect VO₂max independently of Polycytemia vera (e.g., asthma), according to the investigator's judgment. * Any known history of major thromboembolic complication, according to the investigator's judgment. * Body mass index (BMI) greater than 35, according to the investigator's judgment. * Participation in another interventional research protocol that may interfere with the present study, according to the investigator's judgment. * Adult subject under legal protection measures (guardianship, curatorship). * Subject currently receiving psychiatric care. * Subject deprived of liberty by judicial or administrative decision.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Blood viscosity (Centipoise) at 6 shear rates. | Measurements will be performed at baseline (pre-test), at 3 minutes post-CPET, and at 60 minutes post-CPET | Blood viscosity will be measured using a cone-plate viscometer (Brookfield, model LVDVII+ PRO, cone CPE 40) on native hematocrit blood, at 7 different shear rates: 2.25, 4.5, 11.5, 22.5, 45, 90, and 225 s-¹, using an ascending ramp shear protocol. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Rheological properties of blood: deformability and aggregation of erythrocytes | Measurements will be performed at baseline (pre-test), at 3 minutes post-CPET, and at 60 minutes post-CPET. | Analyses will be performed on EDTA tubes. Erythrocyte deformability will be measured by ektacytometry at 9 shear stresses (0.3-30 Pa) under isotonic conditions. Maximal elongation index (EImax) and shear stress for 50% deformation (SS₁/₂) will be recorded. Aggregation/disaggregation will be assessed by syllectometry at 40% hematocrit. Parameters include aggregation index (AI) and minimal shear rate (γmin) for full disaggregation |
| Viscoelasticity of blood | Measurements will be performed at baseline (pre-test), at 3 minutes post-CPET, and at 60 minutes post-CPET | Viscoelastic properties of blood will be assessed using rotational thromboelastometry (ROTEM delta) on citrated blood tubes. The following tests will be performed: NATEM, TEMACT, FIBTEM, and EXTEM. For each test, the following parameters will be measured: clotting time (CT, in seconds), clot amplitude at 5, 10, 20, and 30 minutes (A5, A10, A20, A30, in mm), alpha angle (indicating clot formation velocity, in degrees), maximum clot firmness (in mm), percentage of clot lysis at 30 minutes (LI30), as well as lysis onset time (LOT) and total lysis time (LT), both expressed in seconds |
| Tissue and haemoglobin oxygenation with near-infrared spectroscopy (NIRS) | Measurement will be performed during the CPET. | Near-infrared spectroscopy (NIRS) will be performed using the Portamon MKIII system (Artinis) with a sampling rate of 100 Hz. This non-invasive technique involves placing surface electrodes on the skin over the vastus lateralis muscle, halfway between the anterior superior iliac spine and the patella. NIRS enables continuous monitoring of changes in oxyhemoglobin (HbO₂) and deoxyhemoglobin (HHb) concentrations, allowing for the calculation of the tissue oxygenation index (TOI) |
Countries
France
Contacts
Primary ContactEmeric Stauffer, Dr
Outcome results
None listed