Potential Biological and Physiological Determinants for Exercice in Patients With Polycythemia Vera

N/ANot Yet RecruitingNCT07341048

Hospices Civils de Lyon54 enrolled

Overview

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.

Study Type

INTERVENTIONAL

Allocation

Purpose

BASIC_SCIENCE

Masking

NONE

Enrollment

Conditions

Polycythemia

Eligibility

Sex: ALLMin age: 18 YearsMax age: 70 Years

Medical Language ↔ Plain English

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.

Outcomes

Primary Outcomes

Blood viscosity (Centipoise) at 6 shear rates.

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.

Time frame: Measurements will be performed at baseline (pre-test), at 3 minutes post-CPET, and at 60 minutes post-CPET

Secondary Outcomes

Rheological properties of blood: deformability and aggregation of erythrocytes

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

Time frame: Measurements will be performed at baseline (pre-test), at 3 minutes post-CPET, and at 60 minutes post-CPET.

Viscoelasticity of blood

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

Time frame: Measurements will be performed at baseline (pre-test), at 3 minutes post-CPET, and at 60 minutes post-CPET

Tissue and haemoglobin oxygenation with near-infrared spectroscopy (NIRS)

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)

Time frame: Measurement will be performed during the CPET.