Assessment of endothelial function using digital pulse amplitude tonometry

Abstract

The importance of endothelial dysfunction in the development and clinical expression of cardiovascular disease is well recognized. Impaired endothelial function has been associated with an increased risk of cardiovascular events. Endothelial function may be evaluated in humans by assessing vasodilation in response to stimuli known to induce the release of nitric oxide. A novel pulse amplitude tonometry device noninvasively measures vasodilator function in the microcirculation of the finger. This article reviews the recent studies that support the utility of digital pulse amplitude tonometry as a relevant test of peripheral endothelial function.

Figures

Figure 1

As shown at the top left, the thimble-like PAT device is placed on a finger from each hand. Tubing connects the device to a recording unit that transmits data directly to a computer. As shown in the diagram on the right, the device contains air-filled chambers that are inflated to approximate diastolic pressure throughout the study. Sensors allow detection of changes in finger volume with each arterial pulsation. A typical setup for a research study is shown in the bottom left panel. While the device is on the fingertip, the hand is elevated to allow the fingers to hang freely without touching any surfaces. A cuff is placed on one forearm that will be inflated to suprasystolic pressures to induce hyperemia.

Figure 2

As shown, the tracings on the left are from an individual with a high PAT hyperemic response whereas the tracings on the right are from an individual with a low PAT hyperemic response. The study has three phases. Phase 1 records the baseline pulse amplitude from the probes on both fingers. Phase 2 is during the cuff inflation on one arm. In the test finger flow is occluded but continues in the control finger. Phase 3 is recorded after cuff release. In the test finger pulse amplitude rises rapidly in the healthy individual but not in the patient with coronary artery disease. In the control finger flow, there is minimal change in pulse amplitude after cuff release.