In this study the investigators will test the hypothesis that short-term consumption of inorganic nitrate (supplied in concentrated beetroot juice) enhances coronary blood flow responses, large artery hemodynamics, and leg oxygenation/exercise tolerance in patients with peripheral arterial disease (PAD). Understanding and improving blood flow regulation in the heart and skeletal muscles of patients with PAD is important because exercise triggers symptoms of leg pain and substantially raises blood pressure and myocardial demand in these patients.
Peripheral arterial disease (PAD) is a strong predictor of cardiovascular mortality and negatively affects functional capacity and quality of life for as many as 14 million patients in the U.S. alone. One open-label study showed that acute consumption of beetroot juice improved 6 min walk performance, reduced blood pressure, and enhanced leg muscle oxygenation in PAD patients. However, no studies have rigorously confirmed these findings in a double-blind manner, nor have the effects of this supplement been investigated (acutely or short-term) in the coronary circulation of PAD patients. In addition to studying its effects on graded treadmill walking performance and consequent large artery vasodilation, the present study will examine the effects of short-term beetroot juice consumption (twice/day) on both coronary and leg vasodilator (graded calf flexion) and vasoconstrictor (isometric handgrip, voluntary apnea) responses in patients with PAD. Participants will randomly consume either nitrate-rich or nitrate-depleted beetroot juice with a 7 to 14 day wash-out period between. Effects of beetroot juice consumption on plasma nitrate, nitrite and methemoglobin will also be assessed.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
11
This beverage contains 0.3 g of inorganic nitrate per 70 ml container, and is bottled and supplied by James White Drinks (UK).
This beverage is identical in look and taste to the Beet-It organic shot, but has the nitrate removed. It is also bottled and supplied by James White Drinks (UK).
Milton S. Hershey Medical Center
Hershey, Pennsylvania, United States
Peak Treadmill Time
Peak treadmill time was determined using the Gardner treadmill protocol, measured as the number of seconds the participant was able to walk until they asked to stop the test due to leg fatigue.
Time frame: 4 to 6 days after initiating daily ingestion of beetroot juice
Coronary Flow Velocity Response to Peak Plantar Flexion Exercise
Change in LAD coronary artery flow velocity, measured using transthoracic ultrasound, from baseline rest to peak plantar flexion exercise. Single leg plantar flexion exercise of the most symptomatic leg was performed at a rate of 20 contractions per minute, with increases in workload (1 kg) every minute until volitional fatigue, or until maximum exercise duration of 14 min was reached.
Time frame: 4 days after initiating daily ingestion of beetroot juice
Resting Blood Pressure
Resting mean arterial blood pressure (mmHg) obtained prior to the exercise treadmill test obtained using an automated arm blood pressure cuff.
Time frame: 4 to 6 days after initiating daily ingestion of beetroot juice
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