12.02: Variations of Wave Reflection Indexes Induced by Acute Blood Pressure Changes at Different Arm Heights

Abstract

Acute blood pressure (BP) changes might influence augmentation index (AIx), an integrated dimensionless measure of reflected wave timing and amplitude. In 30 healthy subjects (49±16 years, 43% men), supine brachial BP and radial-artery waveform (applanation tonometry, SphygmoCor) were obtained with the right arm supported in 3 different positions: at the heart level (0°), raised by 30° (+30°), and lowered by 30° (−30°). BP and tonometric measures were also obtained on the contralateral arm, which was held at the heart level during the examination.

Brachial systolic/diastolic BP was 121/67±18/8 mmHg. Radial AIx was 84±19%, and estimated central AIx 27±14%. As expected, changes in arm position modified substantially mean BP (96±12 mmHg at −30°, 85±11 mmHg at 0°, 74±11 mmHg at +30°, all p<0.001).

Radial and central AIx were both reduced at −30° (71±22% and 17±17%), and increased at +30° (97±21% and 30±14%, all p<0.001)vs corresponding values at 0°. Heart rate and contralateral BP and AIx did not change. Changes in radial and aortic AIx were strongly related each other (r=0.76, p<0.001). Percent variation in radial AIx (highest minus lowest, divided by AIx at heart level) had a strong inverse relationship with age (r=−0.43, p<0.001) and systolic BP (r=−0.37, p<0.001).

In conclusion, acute gravitational upper-limb BP changes generate opposite changes in radial AIx. Acute changes in radial Aix decrease with age and BP levels, and might represent a novel index of vascular aging. Artifactual changes in aortic AIx may arise in the presence of radial-aortic distending pressure gradient.