more than 2 mm horizontal or downsloping ST segment depression in non-Q wave leads, or marked axis shift
Arrhythmias other than sustained ventricular tachycardia e.g. Premature ventricular contractions, both multifocal or triplet; heart block; supraventricular tachycardia or bradyarrhythmias
Intraventricular conduction delay or bundle branch block or that cannot be distinguished from ventricular tachycardia
Increasing chest pain
Fatigue, shortness of breath, wheezing, claudication or leg cramps
Hypertensive response (systolic blood pressure > 250 mmHg or diastolic blood pressure > 115 mmHg)

Adverse effects
Side effects from cardiac stress testing may include
Palpitations, chest pain, myocardial infarction, shortness of breath, headache, nausea or fatigue. Adenosine and dipyridamole can cause mild hypotension. As the tracers used for this test are carcinogenic, frequent use of these tests carries a small risk of cancer. Pharmacological agents
Pharmacologic stress testing relies on coronary steal. Vasodilators are used to dilate coronary vessels, which causes increased blood velocity and flow rate in normal vessels and less of a response in stenotic vessels. This difference in response leads to a steal of flow and perfusion defects appear in cardiac nuclear scans or as ST-segment changes.The choice of pharmacologic stress agents used in the test depends on factors such as potential drug interactions with other treatments and concomitant diseases. Pharmacologic agents such as adenosine, Lexiscan (regadenoson), or dipyridamole is generally used when a patient cannot achieve adequate work level with treadmill exercise, or has poorly controlled hypertension or left bundle branch block.
The test is also common in sport science for measuring athletes VO2 max. Nuclear stress test
The best known example of a nuclear stress test is myocardial perfusion imaging. Typically, a radiotracer (Tc-99 sestamibi, Myoview or thallous chloride 201) may be injected during the test. After a suitable waiting period to ensure proper distribution of the radiotracer, scans are acquired with a gamma camera to capture images of the blood flow. Scans acquired before and after exercise are examined to assess the state of the coronary arteries of the patient.Showing the relative amounts of radioisotope within the heart muscle, the nuclear stress tests more accurately identify regional areas of reduced blood flow.Stress and potential cardiac damage from exercise during the test is a problem in patients with ECG abnormalities at rest or in patients with severe motor disability. Pharmacological stimulation from vasodilators such as dipyridamole or adenosine, or positive chronotropic agents such as dobutamine can be used. Testing personnel can include a cardiac radiologist, a nuclear medicine physician, a nuclear medicine technologist, a cardiology technologist, a cardiologist, and/or a nurse.The typical dose of radiation received during this procedure can range from 9.4 millisieverts to 40.7 millisieverts. Function
The American Heart Association recommends ECG treadmill testing as the first choice for patients with medium risk of coronary heart disease according to risk factors of smoking, family history of coronary artery stenosis, hypertension, diabetes and high cholesterol.