A non-invasive cardiovascular index for the quantification of arterial load

Our aim is to quantify steady and pulsatile components of arterial load in a concise and sensitive way by means of a new non-invasive cardiovascular index (NICI).

NICI is based on non-invasively measured pressure (sphygmomanometer), stroke volume index and cardiac index (Doppler echocardiography and ECG) and yields a numerical value (in mm Hg). It expresses the difference between the actual arterial load and reference loading conditions as determined in a control group (29 M/35 F, age 34 +/- 13 yr.) of healthy subjects, with blood pressure 116/61 mm Hg (systolic/diastolic), stroke volume index (SVI) 34 +/- 18 ml.m-2 and cardiac index (CI) 2.1 +/- 0.5 l.min-1.m-2. NICI was calculated in the control group and in 23 borderline hypertensive subjects (10 M/13 F, age 65 +/- 12 yr.) with blood pressure 156/79 mm Hg, SVI 36 +/- 10 ml.m-2 and CI 2.4 +/- 0.6 l.min-1.m-2. NICI was higher in borderline hypertensives (33 +/- 51 vs. 0 +/- 34 mm Hg; P < 0.001) and was strongly correlated with total peripheral resistance index (r = 0.89; P < 0.001) and with the ratio of SVI and pulse pressure (r = -0.89; P < 0.001), expressing the combined effect of both known determinants of cardiac load. NICI was also correlated with effective arterial elastance index (r = 0.89; P < 0.001).

NICI quantifies, within a logical biomechanical framework, the arterial load as seen by the ejecting ventricle. It combines steady and pulsatile components of arterial load and has a single control value of zero mm Hg.