Cross-sectional relations of digital vascular function to cardiovascular risk factors in the Framingham Heart Study

Abstract

Background: Digital pulse amplitude augmentation in response to hyperemia is a novel measure of peripheral vasodilator function that depends partially on endothelium-derived nitric oxide. Baseline digital pulse amplitude reflects local peripheral arterial tone. The relation of digital pulse amplitude and digital hyperemic response to cardiovascular risk factors in the community is unknown.

Methods and results: Using a fingertip peripheral arterial tonometry (PAT) device, we measured digital pulse amplitude in Framingham Third Generation Cohort participants (n=1957; mean age, 40+/-9 years; 49% women) at baseline and in 30-second intervals for 4 minutes during reactive hyperemia induced by 5-minute forearm cuff occlusion. To evaluate the vascular response in relation to baseline, adjusting for systemic effects and skewed data, we expressed the hyperemic response (called the PAT ratio) as the natural logarithm of the ratio of postdeflation to baseline pulse amplitude in the hyperemic finger divided by the same ratio in the contralateral finger that served as control. The relation of the PAT ratio to cardiovascular risk factors was strongest in the 90- to 120-second postdeflation interval (overall model R(2)=0.159). In stepwise multivariable linear regression models, male sex, body mass index, ratio of total to high-density lipoprotein cholesterol, diabetes mellitus, smoking, and lipid-lowering treatment were inversely related to PAT ratio, whereas increasing age was positively related to PAT ratio (all P<0.01).

Conclusions: Reactive hyperemia produced a time-dependent increase in fingertip pulse amplitude. Digital vasodilator function is related to multiple traditional and metabolic cardiovascular risk factors. Our findings support further investigations to define the clinical utility and predictive value of digital pulse amplitude.

Figure 1

Panel A displays the pulse amplitude tracing in a participant with a PAT ratio in the highest tertile. Panel B displays the pulse amplitude tracing in a participant with a PAT ratio in the lowest tertile. As shown, in the arm undergoing hyperemia (upper tracing in A and B) baseline amplitude is recorded; subsequently during cuff inflation flow is occluded and rapidly rises after release during the hyperemic period in an individual with a high response (panel A), but in an individual with a low response (panel B). In the contralateral, control finger (lower tracing in A and B) flow continues throughout and there is minimal change in pulse amplitude.

Figure 2

Pulse amplitude response shown for the hyperemic finger and contralateral finger in women and men. Men had lower responses throughout in both fingers. Values are means. The minimum and maximum standard errors were 0.01 to 0.04.

Figure 3

Multivariable relation between cardiovascular risk factors including age, sex, systolic blood pressure, diastolic blood pressure, heart rate, body mass index, total/HDL cholesterol, triglycerides, glucose, diabetes, current smoking, hormone replacement therapy, hypertension treatment, lipid-lowering treatment, and prevalent cardiovascular disease, and the digital hyperemic response (PAT ratio) in the 30 second time intervals after cuff occlusion. As displayed, the strongest relation occurs in the 90-120 second post-deflation interval.

Figure 4

Boxplot of age-adjusted baseline and hyperemic pulse amplitude according to body mass index category and sex (Normal, <25 kg/m²; Overweight, 25 to <30 kg/m²; Obese ≥30 kg/m²). For men n=283, 471, 249 and for women n=501, 253, 200 for normal, overweight and obese, respectively, P for trend <0.0001.