In-human Validation of a Technique for Measuring Central Aortic Hemodynamics With Peripheral Arterial Waveforms

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.

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.

Eligibility Criteria:
Inclusion Criteria:

* Written informed consent
* Age 18 through 80 years, inclusive
* Scheduled for coronary artery bypass surgery with CPB

Exclusion Criteria:

* Scheduled for heart surgery other than coronary artery bypass surgery
* Females of childbearing potential
* Emergency surgery
* BMI \> 35