EF = EDV-ESV/EDV= SV/EDV

Ventricular function is graded into four groups by two dimensional echocardiography according to ejection fraction as shown in fig 5 (*Conolly HM & Kohl J 2012*).


Fig. 5. LV Grade and Corresponding Ejection Fraction

**Diastolic volume index**: EDV indexed to the patients body surface area (BSA) is another measure of ventricular performance. A normal index is considered less than 100ml/m². In patients with regurgitant valves and volume overload, the end diastolic volume index (EDVI) may be high despite preserved LV function.

**The Fick Equation**: Defines the relationship between C.O and oxygen extraction.

O2 consumption= C.O X O2 content difference (sao2-svo2)

C.O = O2 consumption/O2 content difference (sao2-svo2)

Therefore CO is inversely proportional to O2 content difference, assuming that O2 consumption remains constant. A normal value for arterio-venous oxygen difference would be less than 5 ml/dl or 50ml/L. A low cardiac output state would encourage increased oxygen extraction, resulting in widening of arterio-venous o2 content of greater than 5ml/dl*. (Hensley et al.,1995 )*
