A cannula for relieving the left side of the heart is provided, the cannula having a cannula shaft comprising a heart-side inlet and a pump-side outlet. A lumen extends between the inlet and the outlet, and a suture ring for connecting the cannula to a left atrium is arranged on an outer side of the cannula shaft. The outlet is configured such that the outlet can be connected to a pump and the length of the cannula shaft between the suture ring and the outlet is such that the cannula shaft can be guided outwards through an intercostal space.