Feasibility Study of Arterial Stiffness in Hemodialysis Patients

Arterial Stiffness in Healthy Subjects and Patients With End-Stage- Renal Disease: A Feasibility Study

People with kidney failure have a higher chance of getting disease in the blood vessels and this result in a decreased elasticity of the arteries of their body which make them very stiff or hard. It appears that stiffer arteries with a decreased elasticity increase the risk of stroke and heart disease. A novel way to know the stiffness of blood vessels is by a method called "applanation tonometry", which measures the "pulse wave velocity" of major blood vessels such as the aorta, carotid and femoral arteries. The purpose of our study is to determine if we can measure arterial stiffness reliably and accurately using this method in healthy people and in people with kidney failure receiving hemodialysis treatments at our centre. Also, we would like to know how stiff these arteries in healthy people are. If we demonstrate that the method is reliable and accurate in these 2 groups of participants at our centre, a future larger study is planned to determine if we can use measures of arterial stiffness to evaluate the risk of stroke and heart disease in people with kidney failure receiving hemodialysis. The research study will take place at the Ottawa Hospital-Riverside Campus.

Background:

Cardiovascular (CV) disease is a major cause of morbidity and mortality in patients with end-stage renal disease (ESRD). Arterial stiffness measured by pulse-wave velocity (PWV) has been identified as an independent predictor of fatal CV events in these patients. Our long-term goal is to study the impact of interventions that decrease progressive arterial stiffness on CV mortality in ESRD patients. Thus, we postulate that measurements of PWV during these interventions will predict CV outcome. Before studying this relationship, establishing the feasibility of PWV measurements at our centre is necessary.

Objectives:

i) To demonstrate the reliability and accuracy of arterial PWV measurements in healthy subjects and patients with ESRD at our centre, ii) To assess subject satisfaction and level of discomfort associated with the testing procedure, iii) To characterize normative values for the PWV in our two subject groups, and iv) To determine the feasibility of recruitment of patients with ESRD, as a pre-requisite for a larger trial focused on CV outcomes.

Methods:

PWV will be measured consecutively by 2 research assistants in: a) a group of 20 healthy subjects; and b) a group of 20 patients with ESRD on chronic hemodialysis at The Ottawa Hospital. Two consecutive sets of PWV measurements with a time-interval of 1 week (± 2 days) will be obtained in the healthy and ESRD groups (pre-hemodialysis, between 2 consecutive mid-week hemodialysis sessions). To determine the impact of hemodialysis on PWV measures, in a sub-group of 10 ESRD subjects measurements will be taken before and after hemodialysis. The order of testing by the 2 assistants will be randomized.

HEALTHY SUBJECT GROUP

Inclusion criteria:

• Age: >18 years
• Able to provide informed consent

Exclusion criteria

• History of cardiovascular disease and/or hypertension (blood pressure >140/90 mm Hg)
• History of diabetes mellitus
• History of liver or kidney disease, cancer and/or any lymphoproliferative disease
• Currently receiving medication for any medical condition or illness
• Body Mass Index (BMI) ≥ 30 Kg/m2
• Pregnancy
• Any condition that limits functional ability and precludes participation
• Current smoker (>15 cigarettes per day) in the last 6 months.
• Former smoker (> 20 cigarettes per day) who stopped smoking < 2 years ago.
• Excessive alcohol intake (men >14 drinks per week; women: > 9 drinks per week).
• Psychoactive or performance-enhancing drug abuse.

END-STAGE RENAL DISEASE (ESRD) GROUP

Inclusion Criteria:

• Adult patient (age: >18 years) with ESRD (estimated glomerular filtration rate: <15 ml/min/m2)
• Receiving hemodialysis treatments, with no expected renal recovery
• Having received regular in-Centre Hemodialysis at TOH for at least the past 3 weeks
• Able to provide informed consent.

Exclusion Criteria:

• Atrial fibrillation (as it frequently results in transient or persistent rapid heart rates and these changes overestimate aortic stiffness).
• Active cancer or history of cancer in the past 5 years.
• Pregnancy
• Any condition that limit the patient's ambulatory ability and preclude participation on this basis
• Mechanical, bioprosthetic heart valves or mechanical assisting devices (these conditions may change myocardial stiffness and the volumetric properties of the left ventricle leading to diastolic dysfunction and these physiologic changes may modify the waveforms of the cf- APWV).
• Pre-dialysis systolic blood pressure ≥ 200 mm Hg recorded in the last 6 dialysis treatments (2 weeks).
• Inability to measure blood pressure in at least one arm.
• Current smoker (>15 cigarettes per day) in the last 6 months [Daily cigarette consumption (>15 cigarettes per day) adjusted by age, education level and other confounders has been found to be independently associated with the risk of hypertension].