Exercise Stress Test

Patient Prep:  Click Here

How does an Exercise (Regular) Stress Test Work? 

Patients with coronary artery blockages may have minimal symptoms and an unremarkable or unchanged EKG while at rest. However, symptoms and signs of heart disease may become unmasked by exposing the heart to the stress of exercise. During exercise, healthy coronary arteries dilate (develop a more open channel) than an artery that has a blockage. This unequal dilation causes more blood to be delivered to heart muscle supplied by the normal artery. In contrast, narrowed arteries end up supplying reduced flow to it's area of distribution. This reduced flow causes the involved muscle to "starve" during exercise. The "starvation" may produce symptoms (like chest discomfort or inappropriate shortness of breath), and the EKG may produce characteristic abnormalities. 

When is a Regular Stress Test ordered? 
A regular stress test is considered in the following circumstances:
  • Patients with symptoms or signs that are suggestive of coronary artery diseases (CAD). 
  • Patients with significant risk factors for CAD. 
  • To evaluate exercise tolerance when patients have unexplained fatigue and shortness of breath. 
  • To evaluate blood pressure response to exercise in patients with borderline hypertension. 
  • To look for exercise-induced serious irregular heart beats.

       Please remember that the regular stress test is heavily dependent upon interpretation of EKG changes produced by exercise. Therefore, the reliability drops drastically if there are significant EKG changes at rest (for example in patients with long standing high blood pressure, an artificial cardiac pacemaker, use of medications like digitalis, or presence of a bundle branch block pattern, etc.). In all such cases, the physician will usually order a Stress Echo or a Nuclear Stress Test, particularly if he or she is suspecting coronary artery disease. However, a regular stress may be sufficient in stable patients or those with a low suspicion of coronary artery disease who are being assessed for exercise tolerance (for example, prior to undergoing a structured exercise or rehab program).

How is a Regular Treadmill Stress Test Performed? 

The patient is brought to the exercise laboratory where the heart rate and blood pressure are recorded at rest. Electrodes are attached to the chest, shoulders and hips and connected to the EKG portion of the Stress test machine. A 12-lead EKG is recorded on paper. Each lead of the EKG represents a different portion of the heart, with adjacent leads representing a single wall. For example: 

  • Leads 2, 3, and aVF = bottom or inferior portion of the heart. 
  • Leads V1 and V2 = septum or partition of the heart. 
  • Leads V3, V4, V5 and V6 = anterior or front portion of the heart. 
  • Leads 1 and aVL = superior or top and outer left portion of the heart. 
  • Lead aVR looks at the cavity of the heart and has almost no clinical value in identifying coronary disease. 

 The treadmill is then started at a relatively slow "warm-up" speed. The treadmill speed and it's slope or inclination are increased every three minutes according to a preprogrammed protocol (Bruce). The patient's blood pressure is recorded during the second minute of each Stage. However, it may be recorded more frequently if the readings are too high or too low.

    The EKG is constantly displayed on the monitor. It is also recorded on paper at one minute intervals. The physician pays particular attention to the heart rate, blood pressure, changes in the EKG pattern, irregular heart rhythm, and the patient's appearance and symptoms. The treadmill is stopped when the patient achieves a target heart rate (this is 85% of the maximal heart rate predicted for the patient's age). However, if the patient is doing extremely well at peak exercise, the treadmill test may be continued further. The test may be stopped prior to achievement of the target heart rate if the patient develops significant chest discomfort, shortness of breath, dizziness, unsteady gait, etc., or if the EKG shows alarming changes or serious irregular heart beats. It may also be stopped if the blood pressure (BP) rises or falls beyond acceptable limits. Please note that the systolic BP (upper number) may normally rise to 200 at peak exercise. At the same time, the diastolic BP (lower number) remains unchanged or falls to a slight degree. In contrast, the BP of patients with hypertension or high BP will show a rise of both systolic and diastolic readings. The latter may rise above 90 - 100.