Final answer:
The patient's brother's sudden cardiac arrest is most likely an acquired condition caused by factors such as ischemia, diseases of the heart, metabolic disorders, or recreational drug use.
Step-by-step explanation:
Based on the information provided, the patient's brother's sudden cardiac arrest is most likely an acquired condition rather than a genetic predisposition. Acquired conditions can be caused by various factors such as ischemia to the heart muscle, diseases of the heart vessels or valves, metabolic disorders, neurological disorders, autoimmune pathologies, over-prescription of certain medications, recreational drug use, or prolonged bed rest. Treatment for acquired conditions relies on identifying the underlying cause and may involve supplemental oxygen.