Besides an arrow shape, you can setup a line shape and change the ends to be arrow heads. You can create an arrow from a line shape in code or in the Spread Designer.

When you create a line in the Spread Designer you can then set the start cap and end cap using the shape properties as shown here. Create a shape in the designer using the Insert menu and shape option, then right-click on the shape to set additional properties.

The cap types are listed in this table, shown with a simulated image that roughly illustrates the appearance.

For more details on the line shape in code, refer to the LineShape class in the Assembly Reference.