1. An essential amino acid found in proteins that is important for the growth and repair of tissue.
2. An amino acid involved in the repair of tissues that is also the precursor of histamine.

1. A test that measures electrical activity in a part of the heart which carries the signals that control the time between heartbeats or contractions.
2. The recording of an electrogram from the His bundle (arioventricular bundle or a group of fibers that carry electrical impulses through the center of the heart) usually by an intravenous introduction of an electrode.

Risks of the procedure include:

• Arrhythmias or any disorder of the heart rate or rhythm during which the heart beats too quickly, too slowly, or with an irregular pattern.
• Cardiac tamponade or the compression of the heart that occurs when blood or fluid builds up in the space between the myocardium (the muscle of the heart) and the pericardium (the outer covering sac of the heart).
• Embolism from blood clots at the tip of the catheter.
• Heart attack which takes when blood vessels that supply blood to the heart are blocked, preventing enough oxygen from getting to the heart.
• Hemorrhage or the escape of blood from a ruptured vessel.
• Infection, an invasion by and multiplication of pathogenic microorganisms in a bodily part or tissue, which may produce subsequent tissue injury and progress to an overt disease through a variety of cellular or toxic mechanisms.
• Injury to the vein or artery.
• Low blood pressure.
• Stroke or the interruption of the blood supply to any part of the brain