You have responded to a report of an abrupt collapse of a middle-aged man at a local office building. your bls assessment shows the man is unresponsive, not breathing normally, and has no carotid pulse. this condition is most likely caused by and treated with:

it is caused by cardiac arrest and could be treated with CPR and defribillation

Explanation:

Cardiac arrest is a sudden loss of unciousness because of sudden loss of heart function and breathing. This is exactly what happened to the middle age man.

Cardiac arrest can be treated by performing CPR and defibrillation.

''Cardiopulmonary resuscitation (CPR) is an emergency procedure that combines chest compressions with artificial ventilation in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person who is in cardiac arrest.'',(wikipedia)