[The isovolumetric index: a new index of left ventricular function]

The isovolumic index (IVI%), a new parameter of left ventricular function defined as (isovolumic contraction + isovolumic relaxation time)/left ventricular ejection time, is easily obtained from a routine echocardiogram. By simultaneous recordings of an electrocardiogram, a carotid arterial pulse tracing and the mitral valve echocardiogram, we calculated the IVI% as (time from R wave to MV opening-LVET)/LVET %. 90 normal subjects, mean age 38.32 +/- 11.8 years (range 20-60), underwent an echocardiographic study in order to calculate this index. The value of the IV% was 39.75% +/- 6.82 (range 21.4%-52.3%). The index was heart rate independent and showed a weak positive correlation with age (y = 32.4 + 0.19x; r = 0.33; p less than 0.01). The intraobserver and interobserver variability were 2.6% and 3.6%. The methodologic aspects of the calculation of the IVI% are discussed.