Disk method (SIMPSON method). Significantly more accurate results of calculating global LV contractility can be obtained by quantifying two-dimensional echocardiograms. The Simpson method (disc method) is most suitable for this purpose, based on planimetric determination and summation of the areas of 20 discs, which are peculiar LV cross sections at different levels. To calculate the volumes of the LV, two LV images are taken from the apical position (to systole and diastole), then the cursor traces its cavity and determines the long axis in each of the phases of the cardiac cycle (Figure 1.15).
Calculation of hemodynamic parameters of the LV according to the Simpson method and area-length.
Normally, the average values of PV are within 55 – 65%. With a decrease in EF below 55%, talk about a decrease in LV contractility, and EF above 70% indicates a hyperkinetic type of hemodynamics. At present, the rate of circular shortening of myocardial fibers is used less frequently than EF.It is calculated as follows:
Vcf = (KDR * KSR) / PI * KDR, where PI is the period of exile. Normally, this indicator exceeds 0.9 s.