Stress ECG

What is a cardiac stress test?

The term cardiac stress test refers to a modified method of an electrocardiogram. A normal ECG detects electrical impulses generated by the heart via electrodes placed on the skin surface. By interpreting the results, doctors can evaluate the cardiac rhythm as well as the conduction system and identify rhythm abnormalities, myocardial infarctions and other diseases of the heart. However, certain diseases of the heart will remain undetected at rest and only show up on an ECG under physical activity.

When is cardiac stress testing carried out?

The most common indication to perform a cardiac stress test is to evaluate pain in the thorax and to assess patients with increased cardiovascular risk or after treatment for myocardial infarction. In such patients it not only helps to evaluate the response to physical activity but also establish a prognosis and fine-tune individual medication regimens.

Coronary artery disease (that means narrowing of the vessels supplying the heart) is another reason to perform cardiac stress testing. Also the assessment of heart frequency in patients who either have an implanted pacemaker or are suspected to suffer from arrhythmias, may be more conclusive under physical activity. However, it may also be a prophylactic diagnostic measure, for instance in middle-aged patients that wish to return to doing sports after a longer period of inactivity.

How are cardiac stress tests carried out?

First, blood pressure is measured and ECG at rest is obtained. Patients will then be exposed to physical stress under controlled circumstances. Patients may be asked to work against a progressively increasing resistance, mostly a treadmill or ergometer.

Once physical stress goes up, the body must adapt by increasing heart frequency and stroke volume. A level of physical stress that should be well tolerated by healthy people without abnormal ECG results is initiated, which may be enough to produce suspicious findings in patients with heart diseases. During the exercise, also fatigue, breathing pattern and signs of oxygen deficiency (paleness, cyanosis) are evaluated aside from blood pressure and ECG findings. By precisely documenting the stepwise increase in stress, finally a stress test protocol is established.

To sum up: cardiac stress tests are a useful tool for assessing the individual stress tolerance and how blood pressure as well as heart frequency react to it.

Under what circumstances can cardiac stress testing not be performed?

Cardiac stress tests are not entirely free of risk. Potential risks are, however, very rare if all diseases associated with the patient are taken into account. Heart attacks and rhythm disturbances are possible complications, which is why patients suffering from certain diseases should not be subjected to stress tests.

The following conditions are examples for reasons not to perform the test:

• Suspected myocardial infarction
• Instable angina
• Arrhythmias with symptoms
• Akute inflammatory heart diseases
• Severe heart insufficiency

All in all, cardiac stress test can assist in diagnosing heart diseases but after obtaining an abnormal ECG at rest which points to an ongoing heart disease, one should refrain from this test and rather initiate therapeutic steps.