This chapter describes in detail the mechanical events occurring during the interval from one heart beat to the other, known as Cardiac cycle. The relationship between chronological pressure changes in the left atrium, left ventricle, aorta and left ventricular volume changes, vis-a-vis electrocardiogram and phonocardiogram during one cardiac cycle, is shown as an illustrative diagram. This chapter also explains the work output of the heart, the ejection fraction, graphical analysis of ventricular pumping and the energetics and efficiency of cardiac contraction.