Background: Arterial stiffness, as measured by arterial pulse wave velocity (PWV) in large conduit arteries, is being increasingly accepted as a significant prognostic index of cardiovascular function. The significance of PWV in arteries in the microvasculature is not yet established, due mainly to the difficulty in obtaining reliable non-invasive measurements in vivo. The eye, as the only organ providing direct non-invasive imaging access to its internal anatomical structure, has the potential to be used to assess arterial stiffness at the level of the microcirculation. Aim: To develop signal processing and high-speed imaging techniques to measure pulse transit time (PTT) to determine retinal artery PWV (rPWV) in the rat eye. Methods: Measurements were performed in nine Wistar-Kyoto (280±30 g, 12 weeks) anesthetized male rats. Due to the high heart rate of rats, high-speed imaging was used to record retinal arterial pulsations without aliasing. Retinal video images were captured using a high speed camera (Optronis, Germany) at a rate of 250 frames per second for 10 seconds with a 50° field of view. A simultaneously recorded electrocardiogram was used in subsequent waveform analysis and heart rate (HR) calculation. Recorded video images were analysed with custom algorithms to measure arterial diameter pulsations at two sites 0.5 mm apart. PTT between the sites was calculated using the time delay of a fiducial point at 20% of the waveform height. Results: The average rPWV was 11.5±6.0 cm/s at a HR of 322±37 bpm, mean BP of 89±10 mmHg, and average retinal artery diameter of 54±11 μm. A positive correlation was obtained between arterial diameter and pulse amplitude (r²=0.52). The correlation between rPWV and HR was r²=0.32. Conclusion: This study confirmed the feasibility of a novel approach to measure rPWV in animal models. This technique is a promising accessible tool for microvascular assessment of PWV. The inter-individual variability is likely related to variations in depth of anesthesia and blood pressure which needs to be controlled to improve reproducibility. Future studies are required to assess the significance of PWV in the retinal microvasculature in rat models of cardiovascular disease.
|Number of pages||1|
|Publication status||Published - Jun 2014|
|Event||Annual Scientific Meeting of the High Blood Pressure Research Council of Australia (HBPRCA) (35th : 2013) / Annual Scientific Meeting of the Australian Atherosclerosis Society (AAS) (39th : 2013) - Melbourne, Australia, Australia|
Duration: 5 Dec 2013 → 7 Dec 2013