Why have a stress test?

Stress tests are designed to show obstructive blockage

STRESS TESTS ARE FOR SYMPTOMS:

When the blood can't pass through the artery due to narrowing, symptoms like chest pain result. We call narrowing "stenosis" or "obstruction" to flow. Look at the difference (above) in the small red arrow depicting poor blood flow in obstructive disease and the large red arrow where vulnerable disease has great blood flow. Obstructive disease causes symptoms. Vulnerable arteries do not.

Designed for patients who have symptoms of chest pain or shortness of breath, stress tests are done to ask this question: Is the chest pain caused by severe stenosis, obstructing the blood flow? When the blood can't flow through the artery, stenting or bypass surgery is performed.

A screening test is a test we do when someone is having no symptoms. We do screening to find out who is at risk. Stress tests were not designed for screening to find someone at risk for heart attack, and are not recommended for that purpose (1).

Stress tests are for people having symptoms like chest pain. Stress tests can never predict heart attacks.

if your doctor recommends a stress test:

Get it done. Your doctor knows you and has reasons to order the test. Heart disease can sometimes cause odd symptoms like neck or jaw pain or excessive fatigue or leg swelling or nausea or sweating. It's not always the typical chest tightness radiating to the left arm. You should feel free to ask your doctor why. If it's because you have a high calcium score, that's a valid reason, too. If it's because you've already had a heart attack or by-pass or stenting, that may also be a valid reason (although it's somewhat controversial in the cardiology community). But if it's to ask the question "Are you at risk for a heart attack?" then ask for a better screening test, like the heart calcium scan.  

a Stress test can never predict who's at risk for heart attacks.

Because most heart attacks (over 80%) occur in blockages that are not severely narrowed, most heart attack victims would pass their stress test the day before the heart attack (2,3).

Passing a stress test does not mean that your risk for heart attack is low. It only means you don't need a stent or bypass surgery (4).

Half of men and about 2/3 of women who die suddenly from heart disease had no previous symptoms (5).

references:

  1. A recent task force paper reviewed the evidence for screening by using EKGs, nuclear stress tests and stress echocardiograms to find coronary disease in low-risk patients with no symptoms. They found no evidence supporting the use of these methods. They failed to address the well-documented evidence for screening by using CT heart calcium scans, but they did recommend using risk calculators.  Chou, Cardiac screening with electrocardiography, stress echocardiography or myocardial perfusion imaging: Advice for high-value care from the American College of Physicians. Ann Intern Med. 2015;162:438-447
  2. Screening by heart calcium scans, which identify calcium scores higher than 400, are often used as the basis of further testing with stress tests even in patients with no symptoms, owing to a higher risk of severe narrowing requiring surgical procedures like stents in patients with high scores.
  3. E. Falk, PK Shah, V Fuster, Coronary Plaque Disruption. Circulation 1995;92:657
  4. There are exceptions. Most institutions doing nuclear stress tests have a sensitivity of about 80%. That means out of 100 people who need bypass or stent, the nuclear stress test finds 80, and misses 20. President Bill Clinton passed his nuclear stress test, and then flunked the angiography, which confirmed that he did indeed need a by-pass procedure,
  5. Roger VL, et al. Heart disease and stroke statistics-2012 update: a report from the American Heart Association. Circulation. 2012;125(1):e2-220