If you have lung disease, you may find it difficult to breathe in enough oxygen or breath out enough carbon dioxide. Therefore, there is less oxygen in your blood and your heart will have to work harder to deliver the available oxygen around your body. This increased demand on your heart can cause heart failure. Heart failure caused by lung disease usally affects the right side of the heart and is therefore called right-sided heart failure. It usually causes fluid accumulation in your legs and abdomen.