Relationship between augmentation index obtained from carotid and radial artery pressure waveforms

OBJECTIVE: Increased aortic and carotid arterial augmentation index (AI) has been directly linked with cardiovascular disease risk, mortality and morbidity. The aim of this study was to examine whether AI obtained directly from radial artery pressure waveforms (radial AI) can provide information comparable with carotid arterial AI measurements. METHODS: In a cross-sectional study of 204 apparently healthy subjects (88 men and 116 women) aged 19-76 years (51 ± 15 years, mean ± SD), carotid AI [(second peak carotid systolic pressure - first peak carotid systolic pressure)/carotid pulse pressure*100] and radial AI [(second peak radial systolic pressure - diastolic pressure)/(first peak radial systolic pressure - diastolic pressure)*100] were measured using applanation tonometry. RESULTS: Radial AI was strongly correlated with carotid AI (r = 0.86, P < 0.0001, SD of difference 10.0%), although radial AI was consistently approximately 66% higher than carotid AI. In 16 apparently healthy young adults (11 men and five women, aged 23 ± 3 years) handgrip exercise was immediately followed by post-exercise muscle ischaemia (PEMI) to compare changes in carotid and radial AI during increased sympathetic nervous activity. PEMI caused parallel increases in carotid and radial AI (26 and 19%). Accordingly, changes in radial AI with PEMI were strongly correlated with corresponding changes in carotid AI (r = 0.86, P < 0.0001, SD of difference 7.3%). CONCLUSION: These results suggest that AI obtained directly from radial arterial pressure waveforms could provide equivalent information to carotid arterial AI, and has potential as a surrogate marker of cardiovascular disease.