The FDA classified a recall of Boston Scientific's catheters used in a type of minimally invasive surgery as "most serious".

The recall involves updating instructions for use rather than removing the device, POLARx Cryoablation Balloon Catheters, from where they are used or sold, the FDA said.

The company meanwhile is revising the use instructions of the catheter due to a higher-than-anticipated number of reports of esophageal injury, specifically a complication known as atrio-esophageal fistula, which can lead to air bubbles blocking blood vessels in the brain.

The FDA said the use of the affected products may also cause stomach and intestinal bleeding, a system-wide infection, and even death.

There have been seven reported injuries and four deaths, the health regulator added.

On Oct. 10, Boston Scientific sent an urgent medical device advisory to all affected customers with recommendations.

Boston's device is used in ablation procedures to treat recurrent symptomatic atrial fibrillation that causes irregular, fast heartbeats lasting up to seven days and not responding to medication.

Ablation is a minimally invasive procedure used to treat atrial fibrillation by creating scars on the heart tissue.