Effect of Intradialytic Exercise on Left Ventricular Diastolic Function in Hemodialysis Patients

Left Ventricular Diastolic Function worsens during the hemodialysis session mainly due to preload effects. However, studies in patients with advanced CKD (pre-dialysis) have shown benefits in diastolic function when subjected to exercise programs. Based on this, implementing a standardized and protocolized exercise regimen during the hemodialysis session could provide cardiovascular benefits, specifically in terms of improving left ventricular diastolic function in this population.

The implementation of intradialytic exercise in the hemodialysis unit of our Institute began in 1994. However, there is no standardized or systematic process for intradialytic exercise.

This leads us to ask the following question: What is the effect of performing systematic intradialytic exercise on the echocardiographic parameters of left ventricular diastolic function in hemodialysis patients?

Methodology

Study Design:

• Non-randomized clinical trial (quasi-experimental, before-and-after study).
• Purpose: Analytical
• Temporal sequence: Longitudinal
• Control of study factor assignment: Experimental
• Chronology: Prospective

Study Population Description:

The target population is patients with chronic kidney disease who are currently receiving hemodialysis at the National Institute of Cardiology (prevalent hemodialysis patients).

Eligible Population:

Patients with chronic kidney disease, prevalent in hemodialysis, who are treated in the hemodialysis unit at the National Institute of Cardiology, with left ventricular diastolic function determined by echocardiographic measurement within a 6-month period from September 2023 to September 2024.

Once the inclusion criteria are met, a baseline transthoracic echocardiogram will be performed to determine and record the parameters that evaluate left ventricular diastolic function. If the patient presents any degree of diastolic dysfunction, the study will begin with a 16-week hemodialysis period without exercise. All echocardiograms will be performed before the first dialysis session of the week (Monday or Tuesday according to the patient's session schedule). At the end of the 16 weeks, a final transthoracic echocardiogram will be performed. The second phase of the study, which consists of hemodialysis with intradialytic exercise for 16 weeks, will then begin, and at the end of this period, another final transthoracic echocardiogram will be performed to determine diastolic function parameters. All echocardiograms will be performed before the first dialysis session of the week (Monday or Tuesday according to the patient's session schedule).

Evaluation of Intradialytic Exercise:

The prescription of intradialytic exercise will be based on the FITT-VP protocol, validated by the American College of Sports Medicine, which consists of the following points:

• F: Frequency
• I: Intensity
• T: Time
• T: Type
• V: Volume or amount of exercise
• P: Progression

Based on this, a cardiopulmonary exercise test will be conducted by a sports medicine expert for all patients. Based on the results and according to Skinner's three-phase model, the prescribed workload will be determined by the first ventilatory threshold (VT1), which lies between training zones 1 and 2. Adjustments will be made according to the FITT-VP points as follows:

Frequency: Frequency: 3 times a week during the hemodialysis session (all patients)

Intensity: Low (no resistance), maintaining the VT1 watts throughout the session.

Time: Initially 45 minutes, increasing by 5 minutes each week, reaching 1 hour 30 minutes of exercise at the end of the study phase.

Type: Aerobic (stationary cycling).

Volume: Continuous pedaling during the hemodialysis session with work monitored in watts using power meters.

Progression: Progress will be recorded during the intradialytic exercise period.

Intradialytic exercise will be performed with a stationary bicycle model Urban fit PRO SH-612. Power meters (Favero Assioma UNO) will be inserted into the pedals and connected to a cycle computer (iGPSPORT BSC100S) to measure the workload in watts. The intradialytic exercise program will consist of pedaling during the hemodialysis session, with heart rate reserve monitored using the modified Karvonen method ((HRmax-HRrest)×(40-80%)+ HRrest) and Borg's Rating of Perceived Exertion Scale. A record will be kept for each session. Exercise prescription will be supervised by a sports medicine specialist, along with two medical interns trained in cardiopulmonary exercise testing, who will be responsible for registering and supervising the intradialytic exercise program.

Evaluation of Diastolic Function:

Diastolic function will be measured based on the international recommendations of the American and European Societies of Echocardiography published in 2016. The two-dimensional echocardiography study will be performed by two experienced cardiologists with current certification in echocardiography, using the Vivid Q GE ultrasound machine with a 3.5 MHz transducer. The following measurements will be taken:

• Early transmitral flow velocity (E wave)
• Late diastolic transmitral flow velocity (A wave)
• E/A ratio in an apical 4-chamber view with pulsed Doppler, placing the sample volume at the tips of the mitral valve leaflets.
• Tissue Doppler imaging (TDI) will be performed in an apical 4-chamber view to determine septal e' and lateral e' waves, with the pulsed Doppler sample volume placed 5 mm in the medial and lateral regions of the mitral annulus. The E/e' ratio will be calculated.
• Left atrial (LA) volume will be measured in an apical 4-chamber view and indexed to body surface area.
• Tricuspid regurgitation velocity (TR) will be measured with continuous Doppler in the apical 4-chamber approach focused on the right ventricle.

Based on these parameters, measurements will be categorized into grades of diastolic dysfunction (1, 2, 3, or indeterminate) according to current guidelines for patients with either reduced or preserved LVEF as appropriate. Left atrial strain will be measured using tissue Doppler in an apical 4-chamber view with the speckle tracking method.

6-Minute Walk Test: The test will be conducted on the first day of the hemodialysis session (Monday or Tuesday) before the session, every 4 weeks. The test will be performed based on the guidelines of the American and European Thoracic Societies by two medical interns trained to administer the test.

General Practice Physical Activity Questionnaire (GPPAQ):

The GPPAQ questionnaire will be administered to each patient at the beginning and every 4 weeks thereafter, on the same day and before the 6-minute walk test. The GPPAQ is a self-administered questionnaire for adults consisting of 3 questions. The first question measures the type and amount of physical activity (PA) at work, the second asks about the time spent on different types of PA during the last week, and the third asks about the usual walking pace. The scoring system classifies patients into 4 levels of PA: inactive (sedentary work and no physical exercise or cycling), moderately inactive (sedentary work and <1 hour of physical exercise or cycling, or standing work without physical exercise or cycling), moderately active (sedentary work and 1-2.9 hours/week of physical exercise or cycling, or standing work and <1 hour/week of physical exercise or cycling, or physically active work without physical exercise or cycling), and active (sedentary work and ≥3 hours/week of physical exercise or cycling, or standing work and 1-2.9 hours/week of physical exercise or cycling, or physically active work and <1 hour of physical exercise or cycling, or work with vigorous PA).

Adverse Event Monitoring Adverse events will be monitored exclusively during the Intradialytic Exercise Phase (Intervention Period, 16 weeks). No exercise-related adverse events are expected during the Control Phase, as no exercise will be performed during that period. Arm for adverse event assessment: Intervention Period (Intradialytic Exercise). Adverse events during exercise, such as transient muscle fatigue or mild hemodynamic changes, will be recorded and classified. Any adverse event requiring session discontinuation will be documented and reported.

Ethics The study protocol was approved by the local Research and Ethics Committees under approval number PT 23-1378. This study was registered at ClinicalTrials.gov (NCT06584734). Written informed consent was obtained from all participants.

Inclusion criteria

• Adults ≥ 18 years
• Both genders
• Patients currently enrolled in the hemodialysis program at the National Institute of Cardiology unit
• Patients on hemodialysis for at least 3 months prior to enrollment
• Echocardiographic evidence of left ventricular diastolic dysfunction
• Patients with sufficient cognitive ability to understand and follow study instructions
• Patients with a good echocardiographic window that allows for the determination of parameters evaluating left ventricular diastolic function
• Patients capable of performing stationary cycling during hemodialysis sessions
• Patients who agree to participate and provide written informed consent prior to enrollment

Exclusion criteria

• Patients who have had a major cardiovascular event (MI, stroke) in the 3 months prior to the start of the study
• Patients who have visited the emergency room for symptoms of decompensated heart failure in the 3 months prior to the start of the study
• Patients diagnosed with atrial fibrillation and/or atrial flutter
• Patients with a mechanical mitral valve prosthesis
• Patients with orthopedic conditions or physical limitations that preclude lower-limb stationary cycling
• Pregnant women