A generalized arterial transfer function derived at rest underestimates augmentation of central pressure after exercise

OBJECTIVES Peripheral exercise blood pressure and resting central blood pressure are considered more relevant to cardiovascular health than resting peripheral blood pressure. Central exercise blood pressure may well be an even more useful measure, but there is no simple non-invasive means of determining it. The aim of the present study was to establish whether the estimation of central blood pressure from peripheral blood pressure using a transfer function derived at rest, would hold after aerobic exercise. METHODS Thirty healthy young men were studied before and immediately (< 1 min) and 10 min after 15 min bicycle exercise at 65-70% of maximum heart rate. Simultaneous carotid and radial artery waveforms were recorded, and radial-to-carotid generalized transfer functions (GTF) were calculated using Fourier analysis for rest and immediately postexercise. Central systolic blood pressure (SBP) and augmentation index (AIx) were calculated for measured and derived waves. RESULTS The resting GTF underestimated central SBP and AIx immediately (-5.8 +/- 2.1 mmHg, P = 0.01; -8.3 +/- 2.9%, P = 0.008) and 10 min after (-2.0 +/- 0.7 mmHg, P = 0.008; -7.0 +/- 2.1%, P = 0.003) exercise. No significant bias was found between measured and derived (using resting GTF) carotid values at rest. The use of an exercise-specific GTF resulted in no specific bias immediately or 10 min after exercise, although it overestimated blood pressure and AIx at rest (2.5 +/- 1.0 mmHg, P = 0.02; 11.3 +/- 3.0%, P = 0.001). CONCLUSION A peripheral-to-central arterial GTF derived at rest significantly underestimates key measures of central arterial pressure immediately after exercise, and pressure estimations may be improved by the use of an exercise-specific GTF.