In a patient with Subarachnoid Haemorrhage, between 3rd to 15th days of haemorrhage; there is chances of arterial narrowing called vasospasm.

Due to Vasospasm, patient may have transient ischemic attacks or stroke. These patients are treated with intra-arterial Nimodipine & Milrinoneinfusion. To dilate arteries chemical (drug) is infused so this process is called as chemical angioplasty.