Adenosine Stress Test

It can be difficult to identify the symptoms of cardiac disease at rest. The cardiac stress test looks at the way the body, and the heart specifically, responds to stress/exercise.

However, for some patients it is not possible to walk on a treadmill or ride a stationary exercise bike and reach their target heart rate in a regular cardiac stress test.

Perhaps there are back problems, dizziness, or poor gait or balance which mean that they cannot do this.

If this is the case then an adenosine (or chemical) stress test is conducted.

What is an adenosine stress test

There are a number of different stress tests that a patient can have done.

The adenosine (or chemical) stress test combines an intravenous medication with an imaging technique.

The intravenous medication is used in place of exercise and increases the heart's load.

In a healthy heart this increased stress causes dilation of the coronary arteries and restricted blood flow may be observed in arteries that are partially or completely blocked.

This restricted blood flow is observed by the imaging technique.

This imaging technique typically involves the injection of an isotope (usually thallium and technetium) as is done in the nuclear stress test.

Areas of the heart that take up the isotope quickly have adequate blood flow compared to those areas that respond slowly if at all.

How is the adenosine stress test conducted?

Unlike the regular cardiac stress test which involves the walking on a treadmill or riding a stationary bike, in an adenosine test the patient lies down and an intravenous line is started in the arm.

The typical procedure for this heart stress test involves the following steps:

• The patient will come into the exam room and be asked to lie down.
• The heart rate, blood pressure, and EKG readings are recorded.
• The intravenous medication is given to increase the heart's load. This is done according to the protocol of the stress-producing medication.
• Following the stress-producing medication the patients heart rate increases. When the patients heart rate reaches the target rate (usually 85% of the maximal heart rate for their age) the isotope is given
• This isotope allows images of the heart and associated blood flow following the increased heart rate.

  These images allow the physician to identify the extent (if any) of coronary heart disease.

Is the chemical stress test an accurate measure of stress?

First it is important to understand that chemical stress test do not measure stress.

What they measure is the flow of blood in the heart and coronary artery following stress-provoking medication.

The accuracy of a chemical stress test is about 80%.

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