Which processes are during the latent period of ventricular contraction?
During the latent period of ventricular contraction, excitation-contraction coupling takes place.

There may be other processes, but I think most are these from Wikipedia:


An action potential is initiated by pacemaker cells in the Sinoatrial node or Atrioventricular node and conducted to all cells in the heart via gap junctions.
The action potential travels along the surface membrane into T-tubules (the latter are not seen in all cardiac cell types) and the depolarisation causes Ca2+
to enter the cell via L-type calcium channels (also known as Dihydropyridine receptors) and possibly sodium-calcium exchanger during the early part of the plateau phase. This Ca2+
influx causes a small local increase in intracellular Ca2+
.
The increase in Ca2+
is detected by ryanodine receptors in the membrane of the sarcoplasmic reticulum which releases Ca2+
in a positive feedback physiological response. This positive feedback is known as calcium-induced calcium release and gives rise to Calcium sparks.
The spatial and temporal summation of ~30,000 Ca2+
sparks gives a cell-wide increase in cytoplasmic calcium concentration.
Contractile mechanism similar as in skeletal muscle about cytoplasmic calcium binding to troponin C and so on. 


Note that to fully answer this question you should include figures about mechanisms of excitation-contraction coupling, cardiac action potential -figure and permeabilities of different ions.