In-human Validation of a Technique for Measuring Central Aortic Hemodynamics With Peripheral Arterial Waveforms
Condition: Coronary Artery Disease
MeSH terms: Coronary Artery Disease
Study type: Observational

Summary: 
      Central aortic blood pressure (BP) and flow are generally more informative about the health
      condition of the heart and the arterial system compared with BP measured in peripheral
      locations (e.g. arm or leg). However, their clinical impact has been limited due to the cost,
      risk and discomfort associated with their measurements. Peripheral BP is attractive because
      it can be measured relatively easily than central aortic BP. However, peripheral BP is not as
      useful as central aortic BP since the shape of its waveform is different from that of central
      aortic BP. The applicant recently developed two innovative methods, the "Individualized
      Transfer Functions (ITF)," which is able to estimate the central aortic BP waveform of a
      patient using the measurements of peripheral BP waveform(s). The methods were successfully
      validated using animal and simulated human subjects. The objective of the proposed research
      project is to examine the validity of these innovative methods in human subjects.

      Cardiovascular disease accounts for 1/3 of all deaths and more than $22 billion
      healthcare-related cost in Canada every year. The proposed research project will make
      significant contribution in improving clinical care by the potential of ITF in detection and
      diagnostics of cardiovascular disease. In fact, the proposed research project is a key
      initial step towards our long-term research objective of non-invasive cardiovascular disease
      diagnostics. The success of the proposed research project will demonstrate that ITF can serve
      as a low-cost, non-invasive and convenient alternative for central aortic BP measurement,
      which can further be used for the development of detection and diagnostics methods for a
      number of cardiovascular diseases (e.g. aortic valve impairment and peripheral arterial
      disease) by virtue of the relevant health and disease conditions of central and peripheral
      arterial vessels that ITF can deliver.
    

Detailed description: 
      Central aortic blood pressure (BP) and flow are generally more informative about cardiac
      dynamics and global circulation compared with cardiovascular parameters measured in the
      periphery [1,2]. However, their clinical impact has been limited due to significant clinical
      risk and substantial cost associated with their measurements. Peripheral arterial BP's are
      easily obtained non-invasively, but they cannot serve as direct substitutes for central
      aortic BP due to the distortion of arterial BP waveform caused by pressure wave propagation
      and reflection. Recently, two innovative model-based methods, the "Individualized Transfer
      Functions (ITF)," have been developed by Dr. Hahn to estimate central aortic BP waveform
      using the measurements of peripheral BP waveform(s) [3-6]. These techniques have been
      validated in animal and simulated human subjects. The objective of the proposed research
      project is to 1) examine the feasibility and validity of these innovative methods in human
      subjects, and 2) compare the performance of these methods against direct peripheral BP and
      existing non-individualized (NITF) methods.

      The proposed research project consists of two major parts: 1) collection of central aortic
      and peripheral BP data, and 2) evaluation of ITF methods using these data. BP data will be
      collected from the patients already undergoing procedures with cardiopulmonary bypass.
      Central aortic, radial and femoral BP waveforms will be simultaneously recorded. A
      non-invasive finger BP waveform will also be recorded. The pair of radial-femoral or
      finger-femoral BP recordings will be analyzed by the two-measurement ITF [3-5] to estimate
      individual-specific central aortic BP waveform. In addition, radial or finger BP recording
      will be analyzed by the single-measurement ITF [6] to estimate individual-specific central
      aortic BP waveform. The feasibility and validity of the methods in human subjects will be
      assessed by comparing the estimated central aortic BP waveforms with the measured central
      aortic BP waveforms. Its relative performance with respect to direct peripheral BP and
      existing NITF methods will be analyzed by comparing the difference between measured central
      aortic versus ITF-derived central aortic BP waveforms with those between measured central
      aortic versus direct peripheral and NITF-derived central aortic BP waveforms.

      Cardiovascular disease accounts for 1/3 of all deaths and more than $22 billion
      healthcare-related cost in Canada every year [7]. The proposed research project will make
      significant contribution in improving clinical care through the use of ITF in detection and
      diagnostics of cardiovascular disease. In fact, the proposed research project is a key
      initial step towards our long-term research objective of non-invasive cardiovascular disease
      diagnostics. The success of the proposed research project will be a milestone to demonstrate
      that ITF can serve as minimally invasive and/or non-invasive approach whose individually
      estimated central aortic BP waveform and cardiovascular system model can be exploited for
      detection and diagnostics of a number of cardiovascular disease, e.g. aortic valve impairment
      and peripheral arterial disease, by virtue of diagnostically relevant health and disease
      conditions of central and peripheral arterial vessels that ITF can deliver.
    

Intervention name(s): BP Measurements at aorta, radial and femoral locations
Intervention type(s): Procedure
Intervention description(s): The following additional research related procedures will be performed in patients recruited into the study: 1) a small cuff will be placed on one the finger of each subject to measure the pulse in the finger (Finapres); 2) a cannula will be placed in the femoral artery by the surgeon to measure femoral artery pressure; 3) for a period of two minutes immediately before and after the cardiopulmonary bypass a small cannula (the size of a pencil tip) will be inserted by the surgeon under direct vision into the aorta and 4) the information from each of these cannula will be recorded on a computer for later study.
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        This study is looking at those individuals undergoing Coronary Artery Bypass surgery
        requiring CPB, between the age of 18-80, with a BMI < 35.
      
Keywords: CABG; Coronary Artery Bypass; Central Aortic Pressure; Peripheral Arterial Waveform