Cardiac Stress Testing

Question 1

Used for …

Answer 1

• validated diagnostic tool for CAD in symptomatic patients
• premise of stress testing is provocation of transient myocardial ischemia (evidence of underlying CAD)
• exercise is the ptimary recommended method of stressing the heart

Question 2

Positive cardiac stress test

Answer 2

• may reproduce the pt’s symptoms AND provides some objective evidence of cardiac ischemia in the form of EKG abnormalities (i.e. ST segment changes

Question 3

usual indications for cardiac stress testing

Answer 3

• establishing dx of CAD in patients with CP or a possible “anginal equivalent” and some idea of the extent/severity of CAD
• Assessing prognosis and functional capacity in patients with chronic stable angina or after MI or after a revascularization procedure
• NOT RECOMMENDED IN asymptommatic CAD pt

Question 4

Regular exercise stress test

Answer 4

• Utilizes continuous HR and BP recording and continuous EKG monitoring while heart is “stressed” (usually by walking on a treadmill)

Question 5

Adequate Results from exercise stress test

Answer 5

• The age-predicted maximum heart rate is a useful measurement for safety purposes and for estimating the adequacy of the stress to evoke inducible ischemia.
• A patient who reaches 80% of the age-predicted maximum is considered to have a good test result, and an age-predicted maximum of 90% or better is considered excellent
• HR is 220-person’s age

Question 6

Bruce protocol

Answer 6

• employs 3 minutes of exercise at each stage
• With advancing stages, both the speed and incline of the belt increases

Question 7

Modified Bruce Protocol

Answer 7

• generally used for older, more overweight, or more debilitated patients
• incorporates two beginning stages with slower speeds and lesser inclines than are used in the standard Bruce protocol

Question 8

When to stop stress test?

Answer 8

• severe dyspnea, chest pain
• significant ischemic EKG changes
• significant dysrhythmias
• severe hypertension (>220 systolic) or hypotension
• Otherwise test proceeds until pt feels he/she has reached his/her maximal capacity (“patient fatigue”)

Question 9

Interpreting the Exercise Stress Test

• Normal

Answer 9

• Normal response to exercise – the HR and BP will go up, the ST segment will remain UNCHANGED

Question 10

Interpreting the Exercise Stress Test

• ischemic response

Answer 10

• consists of >1 mm ST segment depression in at least 3 consecutive depolarizations

Question 11

Interpreting the exercise stress test via EKG

Answer 11

Question 12

Do not send the pt for a regular exercise stress test if the patient’s baseline EKG shows

Answer 12

• Left ventricular hypertrophy
• Left bundle branch block
• Preexcitation Syndrome (Wolff-Parkinson-White Syndrome)
• Paced rhythm (patient has pacemaker)
• Severe uncontrolled hypertension or decompensated heart failure
• Severe valvular heart disease, e.g. symptomatic aortic stenosis
• Symptomatic or hemodynamically significant cardiac arrhythmias
• significant comorbid illness, e.g. pneumonia

Question 13

Pretest Probability of CAD

Answer 13

Question 14

Indications for adding imaging to cardiac stress test

Answer 14

• baseline EKG abnormalities present making “plain” exercise stress testing difficult to interpret
• sometimes for f/u of the results of exercise EKG when they are contrary to the clinical impression (i.e. a negative test in a patient with a reasonably high pre-test probability / no alt. diagnosis)
• pt cannot exercise and thus needs “pharmacologic” stress

Question 15

Exercise Stress Testing with Imaging: how its done?

Answer 15

• Still stress the patient’s heart with exercise and still obtain continuous EKG recording, but add cardiac imaging to the procedure – images taken both at rest and during peak stress – and compare the rest and stress images
• Two options for imaging:
  
  • Nuclear medicine perfusion imaging (more common)
  • Echo imaging

Question 16

Myocardial Perfusion Imaging

Answer 16

• Nuclear medicine imaging, aka “nuclear stress test”
• Utilizes radioactive isotope (thallium 201 or technetium-99m) attached to a cardiac-specific pharmaceutical - injected IV – concentrates in heart
• At peak exercise “stress images” taken and at rest “rest images” taken (pts get an injection before both)
• Functionally significant CAD suspected when an area of relative hypoperfusion is detected on peak stress images compared with resting images
• Note that resting images may also be abnormal if there is a permanently under-perfused territory

Question 17

Imaging stress test results + meaning

Answer 17

Question 18

Myocardial Perfusion Imaging

** Poaitive Test result

Answer 18

• one that demonstrates reversible ischemia.
• The size of the perfusion defect obviously has additional prognostic value….a “fixed defect” indicates prior MI / scarring

Question 19

Stress Echo procedure

Answer 19

• ¨Pt gets baseline echo at rest
• walks on a treadmill
• then gets re-echoed at peak exercise

Question 20

Stress echo results

Answer 20

• Ischemia indicated by new or worsening “wall motion abnormalities” during the stress images
• Segments that are hypokinetic or akinetic at baseline likely represent permanent ischemic damage
• areas of hypokinesis or dyskinesis only during stress likely represent “myocardium at risk” due to CAD

Question 21

more on how to read stress echo results

Answer 21

Question 22

advantages of stress echo

Answer 22

• better evaluation of valve function
• relatively portable
• lower cost than nuclear medicine protocols
• entire study completed in < 1 hr
• no radiation exposure

Question 23

disadvantages of stress echo

Answer 23

• suboptimal image quality with some pts
• image interpretation requires considerable expertise

Question 24

“Pharmacologic” Stress Testing is used for?

Answer 24

• those unable to exercise sufficiently due to
  
  • LE arthritis
  • neurologic compromise
  • significant physical deconditioning
  • advanced lung disease

Question 25

pharmalogic stress test protocol

Answer 25

• the most common pharmacologic agents used for non-exercise stress testing are IV dobutamine, dipyridamole, adenosine, and adenosine receptor agonists
  
  • ​coronary vasodilators that increase blood flow in normal arteries without significantly changing the flow in diseased vessels
• All pharmacologic stress tests require imaging
• Still comparing rest to stress images, but the “stress” is obtained via pharmaceuticals rather than exercise

Question 26

coronary angiography

Answer 26

• Invasive “gold standard” for CAD dx
• Catheter introduced into arterial circulation (usually femoral or radial artery) and advanced to heart
• Contrast is injected into the coronary arteries and can also be injected into left heart to visualize chambers.
  
  • Intracardiac pressures may also be obtained and cardiac output can be determined
• Most often, catheterization proceeds some type of intervention, such as angioplasty, CABG, or valvular surgery

Question 27

Cardiac cath

*Important findings

Answer 27

• ¨Atherosclerotic lesions appear as narrowing of the internal diameter (lumen) of the vessel; a hemodynamically important stenosis is defined as 70% or more narrowing of the luminal diameter (50% for proximal LAD)

Question 28

indications for cardiac cath

Answer 28

• Abnormal cardiac stress test results indicating high likelihood of extensive or significant disease
• Pt with a high pre-test probability of CAD (go straight to cath, bypass stress testing)
• Myocardial infarction, unstable angina

Question 29

cardiac cath for dx and therapy

Answer 29