Agreement between carotid and radial augmentation index: Does medication status affect the relation?

Central augmentation index (AI) is an index for arterial stiffness and wave reflection, but the measurement requires technical precision. We recently reported that AI obtained directly from radial arterial pressure waveforms (without using the general transfer function) could provide equivalent information to carotid AI in healthy adults. The aim of the present study was to determine whether such association would exist among patients on anti-hypertensive drugs. Forty-six hypertensive patients taking blood pressure lowering medications (62 ± 9 years, mean ± SD) and 78 age-matched apparently healthy adults (60 ± 9 years) were studied. Carotid and radial AI were obtained using arterial applanation tonometry, and radial AI was calculated using the equation [(second peak radial systolic pressure - diastolic pressure)/(first peak radial systolic pressure - diastolic pressure) × 100]. Radial AI was strongly and positively correlated with carotid AI in medicated patients (r = 0.73, P < 0.0001) as well as in healthy controls (r = 0.84, P < 0.0001). The Brand-Altman plot demonstrated that the difference and SD between carotid and radial AI were not different between medicated patients and healthy controls (61.8 ± 7.7 vs 63.0 ± 7.7%). These results suggest that radial AI may be able to provide qualitatively similar information to carotid AI even in patients on antihypertensive medications.