This is a prospective, observational study that will examine endothelial dysfunction in atrial fibrillation before and after treatment with anti-arrhythmic agents and the extent to which baseline endothelial dysfunction improves after treatment.

This will be a prospective, observational study and roughly 60 patients will be recruited based on strict inclusion/exclusion criteria. Goal population includes adult patients with a diagnosis of paroxysmal or persistent atrial fibrillation seen in the electrophysiology clinic and admitted to the UPMC Presbyterian electrophysiology service for initiation of anti-arrhythmic medications.

The primary goal of the study will be to evaluate the degree of endothelial function recovery seen after initiating anti-arrhythmic medical therapy. We will assess genetic markers, arterial stiffness and vasodilation in response to acetylcholine iontophoresis, nitroprusside iontophoresis, local thermal hyperemia and reactive hyperemia. Laser speckle contrast imaging will be employed to evaluate the microvasculature. SphygmoCor (arterial tonometry) will be used to assess macrovasculature. Testing will be performed at baseline prior to the 1st dose of anti- arrhythmic therapy and repeated again 1-3 months later at outpatient follow-up visit. Additionally, follow-up phone calls or office visits will take place at 6 and 12 months after the initial data collection visit to document recurrence rate of atrial fibrillation.

Inclusion Criteria:

• Adult patients (18-75 years of age) with paroxysmal or persistent atrial fibrillation
• Patients who recovered from prior tachycardia induced cardiomyopathy will be allowed to enroll in the study.

Exclusion Criteria:

Exclusion criteria will include:

• age >75 years
• history of cardiomyopathy
• history of severe cardiac valvular disease
• history of coronary artery disease
• pulmonary artery hypertension
• congenital heart disease
• history of stroke
• chronic hypoxia
• recent worsening or flare up of obstructive or restrictive lung disease
• liver cirrhosis
• stage three or worse chronic kidney disease
• any major trauma or surgery within the preceding 3 months
• uncontrolled hyperthyroidism
• uncontrolled hypertension
• uncontrolled diabetes mellitus
• active malignancy
• poorly controlled connective tissue disease
• any acute or chronic inflammatory or infectious disease
• Patients who are already on class I or class III antiarrhythmic agents will be excluded from the study
• Patients on non-dihydropyridine calcium channel blockers and beta blockers will not be excluded from the study, as these agents are not considered anti-arrhythmics and are not hypothesized to affect endothelial function.

Adult patients with known or new diagnosis of either paroxysmal or persistent atrial fibrillation seen at the electrophysiology outpatient clinic and admitted to the electrophysiology service for initiation of anti-arrhythmic medications.