Indices of cardiovascular function derived from peripheral pulse wave analysis using radial applanation tonometry: a measurement repeatability study

Abstract

Pulse wave analysis (PWA) using applanation tonometry is a non-invasive technique for assessing cardiovascular function. It produces three important indices: ejection duration index (ED%), augmentation index adjusted for heart rate (AIX@75), and subendocardial viability ratio (SEVR%). The aim of this study was to assess within- and between-observer repeatability of these measurements. After resting supine for 15 minutes, 20 ambulant patients (16 male) in sinus rhythm underwent four PWA measurements on a single occasion. Two nurses (A & B) independently and alternately undertook PWA measurements using the same equipment (Omron HEM-757; SphygmoCor with Millar hand-held tonometer) blind to the other nurse's PWA measurements. Within- and between-observer differences were analysed using the Bland-Altman `limits of agreement' approach (mean difference ± 2 standard deviations, 2SD). Mean age was 56 (blood pressure, BP 136/79; pulse rate 64). BP/PWA measurements remained stable during assessment. Based on the average of two PWA measurements the mean ± 2SD between-observer difference in ED% was 0.3 ± 2.0; AIX@75 1.0 ± 3.9; and SEVR% 1.7 ± 14.2. Based on a single PWA measurement the between-observer difference was ED% 0.3 ± 3.3; AIX@75 1.7 ± 6.9; and SEVR% 0.6 ± 22.6. Within-observer differences for nurse-A were ED% 0.0 ± 5.4; AIX@75 1.5 ± 7.0; and SEVR% 1.7 ± 39.0 (nurse-B: 0.1 ± 3.8; 0.1 ± 8.0; and 0.6 ± 23.3, respectively). PWA demonstrates high levels of repeatability even when used by relatively inexperienced staff and has the potential to be included in the routine cardiovascular assessment of ambulant patients.