Abstract
Purpose: :
To develop and test a novel method for exploring vessel pulsatility in retinal circulation.
Methods: :
By connecting an external ECG device to the Retinal Vessel Analyzer - RVA (via the Finometer interface) it is possible to simultaneously record the ECG and the diameter of retinal vessels. We (RK) devised software able to recognise each R-peak from the ECG-signal and based on this gating to construct an average pulse curve for the chosen vessel segment. Retinal Vessels of five healthy subjects were examined at baseline und under flicker light stimulation. Additionally six healthy subjects underwent the above mentioned examination in sitting and then in Trendelenburg head-reclination position. Inferior temporal segment of retinal vessels was chosen for analysis.
Results: :
Pulse curves for each vessel segment were based on the standard 350 seconds RVA recording, comprising 420-480 heart cycles. With flicker light stimulation average diameter of vessels were increased from 127.9 µm to 135.4 µm and from 163.9 µm to 171.3 µm in arterioles and venules receptively (p=0.04 for both). Amplitude of pulsations was also increased from 2.8% to 3.1% of baseline diameter and from 1.7% to 2.7% in arterioles and venules receptively (p=0.02, and p=0.04). In reclination position both type of vessels were constricted from 114.0 µm to 106.3 µm and from 155.1 µm to 146.7 µm in arterioles and venules receptively, and their amplitude was also significantly reduced from 1.9% to 1.4% and from 2.5% to 1.2% (all p<0.03 ). The arteriolar and retinal pulsations were shifted out of phase at baseline, with venule peaks lagging and arteriole peaks leading. This shift, while not changing under flicker light stimulation, was in the reclination position significantly shortened in all subjects (0.98 radians to 0.52 radians, p=0.009).
Conclusions: :
ECG-gated analysis of vessel pulse curve is a novel feasible method to explore the amplitude and the phase of vessel wall pulsations in the retina. It could provide new insights into the state of small vessel wall rigidity, and into origin and possible pathophysiological relevance of retinal venous pulsations.
Keywords: blood supply • electrophysiology: clinical • retina