The cardiac tissue can adapt to stressful situations by increasing the heart rate and the volume of blood that reaches its tissues. Suppose any of the coronary arteries (arteries responsible for carrying oxygen and nutrients to the heart tissue) have obstruction due to the chronic deposit of cholesterol in their walls. In that case, the affected region will not be able to generate adequate contractions of the ventricular fibers due to the lack of oxygen and nutrients, putting the patient’s life at risk. 

The nuclear stress test allows detecting areas of the heart affected by poor blood supply as a consequence of a clogged coronary artery by inducing a stressful situation. In order to carry out this test, drugs with radioactive dye are used intravenously and allow visualization of all chambers and vessels of the heart through an imaging study.  

Indications 

• Patients with characteristic symptoms (chest pain, shortness of breath after exertion, dizziness, or weakness) are candidates to determine the presence of lesions in the coronary arteries. 
• Those patients who already have a diagnosis of a disease in the coronary arteries may undergo this test to determine in more detail the location of the lesions as well as the degree of severity and extension of the affected tissue. 
• Follow-up of patients who have already started treatment for block arteries and myocardial dysfunction. It allows the physician to compare past images with the current state of the heart. 

Preparation

• The patient must attend with comfortable clothing and sports shoes to carry out physical activities without injuries.  
• Avoid any beverage or food that may contain caffeine (such as coffee, tea, sodas or chocolate. Remember most decaffeinated products contain trace amounts of caffeine also). Caffeine blocks the effects of the chemical used to stress the heart and can lead to a falsely normal test (the test is truly abnormal and because of the caffeine it resulted in normal images).
• In the case of patients taking any medication, they must consult with their physician before the test to determine if they should suspend or not. 
• Asthmatic patients should bring their medications the day of the test in case of any eventualities. Let your doctor know before the test. 
• Notify your doctor in case of pregnancy. 

How is the test performed? 

• The test is normally done in the physician’s office. 
• A brief interview  will be carried out to determine the current medications consumed, the last food ingested, and if they present any physical injury or impediment to performing the test. This information will later be confirmed with the medical history previously made.
• The radioactive drug (radiopharmaceutical) will be injected through the vein. The patient has to wait 15-45 minutes and then proceed to the imaging study where photos of the heart will be taken with the radioactive drug during contraction and relaxation phases. 
• A medication that accelerates the heart rate and causes arterial vasodilation like Lexiscan is injected creating an increased workload  for the heart tissue. Then another sent of pictures is done. 

Results

Once the images of the heart are obtained (at rest and after a stress), the doctor should compare the images and evaluate the blood flow of the heart. In that case, the territory of the cardiac tissue supplied by this artery will receive little radioactive contrast. Correlating this finding with the patient’s clinic symptoms and their EKG will lead to an accurate diagnosis.