is high blood pressure considered pre-existing condition for atrial fibrillation?

My father has been taking medications (atenolol) for high blood pressure for the last 4-5 years.
Recently he visited USA with a traveller's medical insurance. On his trip to US, he fainted once and was hospitalized. Doctors diagnosed it as atrial fibrillation. He was hospitalized for 4 days mainly to observe him till his heart rhythm came back to normal.
He has never had atrial fibrillation before.
My question is - given that he had high blood pressure previously, can the insurance company deny the claim citing high blood pressure as a pre-existing condition for atrial fibrillation?

[Amir Mostafaie]

Dear Mach10,

Atrial fibrillation (or AF) is not a disease as such, but it is a form of arrhythmia (the most common form in fact) which is a common arrhythmia in patients with hypertensive heart disease.

If the Emergency room physicians determined your father's AF to be a result of hypertensive heart disease or hypertension generally; and the insurance carrier considers his hypertension to be pre-existing, they may question the claim but it is hard to forecast exactly how it will be perceived by the insurance company.

Sincerely,

Amir Mostafaie