Tonometry waveforms were signal-averaged using the electrocardiographic R-wave as a fiducial point. Systolic and diastolic cuff blood pressures obtained at the time of the tonometry acquisition were used to calibrate the peak and trough of the signal-averaged brachial pressure waveform. Diastolic and integrated mean brachial pressures were used to calibrate carotid pressure tracings.24 (link) Calibrated carotid pressure was used as a surrogate for central pressure.24 (link) Central pulse pressure was defined as the difference between the peak and trough of the calibrated carotid pressure waveform. Carotid-brachial pulse pressure amplification was defined as brachial pulse pressure divided by central pulse pressure. Augmentation index was computed from the carotid pressure waveform as previously described.25 (link) Carotid-femoral (aortic) and carotid-radial (muscular artery) pulse wave velocities were calculated from tonometry waveforms and body surface measurements, which were adjusted for parallel transmission in the brachiocephalic artery and aortic arch by using the suprasternal notch as a fiducial point.26 (link) The carotid-femoral transit path spans the aorta, making carotid-femoral PWV a measure of aortic stiffness. In contrast, the carotid-radial transit path spans the subclavian, brachial and radial arteries, making carotid-radial PWV a measure of muscular artery stiffness.