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Vessel diameter changes during the cardiac cycle
1Diabetic Retinopathy Unit, Royal Postgraduate Medical School, Hammersmith Hospital, London, UK.
Insights
Retinal vessel diameter changes with the cardiac cycle, impacting blood flow measurements. Synchronizing fundus photography with electrocardiograms is crucial for accurate retinal blood flow assessment.
Area of Science:
- Ophthalmology
- Physiology
- Medical Imaging
Background:
- Retinal vessel diameter is key for measuring blood flow.
- Cardiac pulsation and vasomotion influence these diameters.
- Accurate retinal blood flow assessment is vital for diagnosing various conditions.
Purpose of the Study:
- To investigate the dynamic changes in retinal vessel diameter during the cardiac cycle.
- To quantify the impact of pulsation and vasomotion on retinal blood flow.
- To establish optimal timing for fundus photography for accurate measurements.
Main Methods:
- Analysis of three monochromatic fundus photographs.
- Images captured at eight points within the cardiac cycle.
- Study conducted on 10 healthy subjects.
Main Results:
- Venous diameter decreased in early systole, peaked in early diastole (4.82% change, p=0.03), affecting volumetric flow by 9.83%.
- Arterial diameter peaked in mid-late systole (3.46% change, p=0.01), increasing flow by 7.04%.
- Vasomotion caused 3.71% arterial and 2.61% venous diameter changes.
Conclusions:
- Retinal vessel diameter exhibits significant, measurable changes throughout the cardiac cycle.
- These dynamic changes directly influence volumetric blood flow calculations.
- Synchronizing fundus photography with electrocardiography is essential for precise retinal blood flow quantification.
Abstract:
Retinal vessel diameter, which is an important parameter in blood flow measurement, is affected by pulsation during the cardiac cycle and by vasomotion. This project studied these changes by analysing three monochromatic fundus photographs taken in eight arbitrary parts of the cardiac cycle of 10 healthy subjects. It was found that the venous diameter decreased in early systole, increasing thereafter to a maximum level in early diastole and then declined towards end diastole. The maximum change of 4.82% (between early systole and early diastole) (p = 0.03) represents a 9.83% change in volumetric blood flow. The arterial diameter peaked in mid-late systole, increasing by 3.46% (p = 0.01); this represents a blood flow increase of 7.04%. Vasomotion led to changes of 3.71% and 2.61% in arteries and veins respectively. It is concluded that for accurate measurement of retinal blood flow, fundus photographs should be taken synchronised with the electrocardiogram.