Central blood pressure is a determinant of cardiovascular outcome; however, it can be described by parameters other than systolic and diastolic pressure with central augmentation index (AIx) often utilized. Although generally considered as determined by peripheral pressure wave reflection, not all data are consistent with this interpretation of AIx. We hypothesized that the motion of the heart during systole may influence central pressure waveform morphology, including the AIx.
We studied the carotid pressure waveform, aortic stiffness and endothelial function in 20 healthy young men (full data available in 19). Arterial stiffness was measured by carotid femoral pulse wave velocity (cfPWV), endothelial function by peripheral arterial plethysmography (PAPl) and central blood pressure waveform by carotid applanation tonometry. Basal cardiac motion was assessed with pulsed wave tissue Doppler imaging of the septal mitral annulus.
Carotid AIx decreased after the administration of glyceryl trinitrate by 11.3 ± (sem) 4.6% (P = 0.02); however, time to the inflection point (Ti) did not change. During systolic contraction at both baseline and after glyceryl trinitrate, time to peak annular systolic velocity was directly related to, and always preceded, carotid Ti (R2 = 0.81; P < 0.01). Carotid Ti and AIx were not related to cfPWV or endothelial function.
In fit young men, rather than only being a consequence of arterial properties Ti, and therefore central AIx, may be substantially determined by left ventricular systolic function. These findings question the interpretation of central AIx as a measure of pressure wave reflection and aortic stiffness and potentially impact its interpretation in diagnosis and treatment of cardiovascular risk.
Monash Cardiovascular Research Centre, MonashHeart and Monash University Department of Medicine, Monash Medical Centre, Melbourne, Australia
Correspondence to Professor James Cameron, Director, Monash Cardiovascular Research Centre, MonashHeart, Monash Medical Centre, 256 Clayton Rd, Clayton, Victoria, Australia. Fax: +61 3 9594 6295; e-mail: email@example.com
Abbreviations: AIx, augmentation index; cfPWV, carotid femoral pulse wave velocity; ECG, electrocardiogram; GTN, glyceryl trinitrate; PAPl, peripheral arterial plethysmography; RH-PAPI, reactive hyperaemia- peripheral arterial plethysmography; TDI, tissue Doppler imaging; Ti, time to inflection point
Received 6 November, 2011
Revised 18 July, 2012
Accepted 31 July, 2012