Even a cursory look at the map will make one realise that there is North Atlantic and South Atlantic Ocean to the northern and eastern coasts of Brazil respectively.
The southern Brazil is occupied by an extensive plateau. The height (altitude) decreases gradually to its north. A number of rivers take off from the terminal portion of the highlands and flow northwards to meet Atlantic Ocean. The only major river Sao Francisco flows towards the north for a distance and then takes a sharp eastward turn to enter the coastal strip along the Atlantic Ocean.
Moreover, Amazon which is the longest river in Brazil, originates from the eastern slopes of Andes Mountains in Peru, flows eastward and meet North Atlantic ocean.
Likewise, Parana, Paraguay and Uruguay originate from southern slopes of the Highlands and flows through the south-western part of Brazil. Therefore, there are no west-flowing rivers in Brazil.