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What is adenosine?
Adenosine is a substance produced in humans that helps
protect against ischemia (lack of blood flow). It's produced
in blood vessels, heart and skeletal muscle, and other organs.
What does adenosine
do?
When the demand for oxygen increases, as during exercise,
adenosine is produced in the muscle and vessels. It has these
effects:
- Provides more energy to the exercising
muscle.
- Enlarges blood vessels to improve
the blood and oxygen supply.
- Helps raise
blood pressure, which also increases oxygen supply.
- Produces pain that tells us to stop
exercising and rest, because our muscles aren't getting
enough energy and need to recover.
What does adenosine
do for the heart?
Adenosine helps protect the heart muscle from damage when
myocardial ischemia occurs. Myocardial ischemia happens when
the heart muscle (myocardium) doesn't get as much blood and
oxygen as it needs.
When this happens, adenosine is released in the heart vessels
and myocardium and has these effects:
- Enlarges vessels to increase blood
and oxygen supply.
- Improves energy supply for the myocardium
and helps decrease energy needs.
- Produces angina pectoris chest pain
or discomfort due to coronary heart disease). This symptom
of myocardial ischemia warns us to rest.
What are the clinical
applications for adenosine?
The sinoatrial node, located in the atrium (upper chamber)
of the heart, produces the electrical impulses that cause
the heart to beat. Adenosine has a depressant effect on sinoatrial
node activity. This is called an arrythmogenic effect of adenosine.
This makes adenosine effective in treating tachyarrhythmias(extremely
fast heart rates) involving the sinoatrial node.
Adenosine is also used
in diagnosing and treating supraventricular tachycardias.
These are extremely fast heart rates that originate above
the ventricles (lower heart chambers). It's also used in nuclear
medicine and during stress tests to detect coronary artery
disease. Ongoing research suggests that adenosine will be
important in protecting the heart during open-heart surgery. |
