Coronary Artery Disease in Patients With Friedreich's Ataxia

"Forearm blood flow (FBF) measurements in both arms will be made using venous occlusion strain-gauge plethysmography prior to the initiation of any intra-arterial infusions. All FBF measurements will be expressed as mL/min per 100-1 mL forearm volume according to prior studies and the Whitney method.1, 2 Resting baseline FBF will be measured at least 30 minutes after venous and arterial catheter placement to ensure that blood flows in the cannulated arms are stabilized. We will measure FBF during the last 2 minutes of each infusion period. Infusions of individual vasoactive medications will occur over a 15-minute interval. There will be a 25-minute washout between vasoactive medications. Cumulative dose response curves will be constructed over 5-minute incremental infusions. We will proceed in the following order:~* SNP 0.8, 1.6 and 3.2 mcg/min~* ACh 7.5, 15 and 30 mcg/min~* Normal saline"