Tests for investigating people with suspected coronary artery disease
CT Angiography
What does CT angiography detect?
• Presence of significant coronary stenosis
• Presence, extent and composition of coronary artery plaque
• Evidence of global and/or regional left ventricular (LV) functional impairment
How accurate is the test for detection of coronary stenosis (narrowing)?
• CT accurately excludes significant stenosis (> 50%) with 95% sensitivity and 98% negative predictive value compared to invasive coronary angiography
• Specificity is 85% and positive predictive value is 80% if image evaluation is diminished by the presence of coronary artery calcification or motion
• CT is considered more accurate for the detection of stenosis morphology then functional testing
Can CT detect plaques in the arteries before they cause significant narrowing?
• CT is sensitive (85%) to detect non-calcified plaque larger than 1 mm
• Calcified plaque detection is very accurate
• CT is the most reliable method available to detect non-obstructive CAD non-invasively LV Function:
• CT accuracy is comparable to MR for global and regional function
Practical Tips:
• Patients with no coronary plaque have an extremely low risk for death over the next 5 years and typically do not require additional diagnostic evaluation unless there is a change in clinical status
• CT may overestimate the degree of stenosis, and some patients with moderate stenosis may appear to have a more significant stenosis than is found on invasive angiography
• Stress testing may be useful in determining the hemodynamic significance of stenoses identified on CT
• More aggressive prevention strategies and risk assessment modification may be considered in patients with non-obstructive disease
• Presence of significant coronary stenosis
• Presence, extent and composition of coronary artery plaque
• Evidence of global and/or regional left ventricular (LV) functional impairment
How accurate is the test for detection of coronary stenosis (narrowing)?
• CT accurately excludes significant stenosis (> 50%) with 95% sensitivity and 98% negative predictive value compared to invasive coronary angiography
• Specificity is 85% and positive predictive value is 80% if image evaluation is diminished by the presence of coronary artery calcification or motion
• CT is considered more accurate for the detection of stenosis morphology then functional testing
Can CT detect plaques in the arteries before they cause significant narrowing?
• CT is sensitive (85%) to detect non-calcified plaque larger than 1 mm
• Calcified plaque detection is very accurate
• CT is the most reliable method available to detect non-obstructive CAD non-invasively LV Function:
• CT accuracy is comparable to MR for global and regional function
Practical Tips:
• Patients with no coronary plaque have an extremely low risk for death over the next 5 years and typically do not require additional diagnostic evaluation unless there is a change in clinical status
• CT may overestimate the degree of stenosis, and some patients with moderate stenosis may appear to have a more significant stenosis than is found on invasive angiography
• Stress testing may be useful in determining the hemodynamic significance of stenoses identified on CT
• More aggressive prevention strategies and risk assessment modification may be considered in patients with non-obstructive disease
Stress Echocardiography
What does stress echo detect?
• Presence, extent and location of wall motion abnormality during rest and stress
• Global and regional left ventricular dysfunction
• High risk findings such as mult-ivessel disease, systolic dilation
• Valve disease
• Other cardiac abnormalities associated with chest pain
Test Characteristics
Stenosis Detection:
• Sensitivity of exercise echo is approximately 85% and the specificity is 88% and the sensitivity of dobutamine echo is 80% and the specificity is 84% as compared to invasive coronary angiography
• Stress echocardiography and nuclear perfusion imaging have similar diagnostic accuracy for the detection of coronary artery disease
Prognosis:
• A normal exercise echocardiogram is associated with an annual cardiovascular event rate of <1% and these patients typically do not require additional diagnostic evaluation unless there is a change in clinical status
• Patients with extensive stress induced wall motion abnormalities in a multivessel pattern are at high risk for cardiac event including mortality
Practical Tips
• False negative stress echocardiograms are most common in those who fail to achieve an adequate stress and those with single vessel disease particularly in the left circumflex coronary artery territory
• False positive stress echocardiograms can occur in any setting with mismatch of myocardial oxygen demand and myocardial perfusion (oxygen supply – i.e.: hypertension and cardiomyopathy)
• Conduction abnormalities may also cause false positive interpretations due to abnormal wall motion.
• Baseline LV dysfunction, failure to augment LV ejection fractionwith stress, wall motion abnormality at a low workload and wall motion abnormalities in the anterior territory (or left anterior coronary artery distribution) are other high risk findings
• The prognostic value of stress echocardiography in women is similar to that of men
• Presence, extent and location of wall motion abnormality during rest and stress
• Global and regional left ventricular dysfunction
• High risk findings such as mult-ivessel disease, systolic dilation
• Valve disease
• Other cardiac abnormalities associated with chest pain
Test Characteristics
Stenosis Detection:
• Sensitivity of exercise echo is approximately 85% and the specificity is 88% and the sensitivity of dobutamine echo is 80% and the specificity is 84% as compared to invasive coronary angiography
• Stress echocardiography and nuclear perfusion imaging have similar diagnostic accuracy for the detection of coronary artery disease
Prognosis:
• A normal exercise echocardiogram is associated with an annual cardiovascular event rate of <1% and these patients typically do not require additional diagnostic evaluation unless there is a change in clinical status
• Patients with extensive stress induced wall motion abnormalities in a multivessel pattern are at high risk for cardiac event including mortality
Practical Tips
• False negative stress echocardiograms are most common in those who fail to achieve an adequate stress and those with single vessel disease particularly in the left circumflex coronary artery territory
• False positive stress echocardiograms can occur in any setting with mismatch of myocardial oxygen demand and myocardial perfusion (oxygen supply – i.e.: hypertension and cardiomyopathy)
• Conduction abnormalities may also cause false positive interpretations due to abnormal wall motion.
• Baseline LV dysfunction, failure to augment LV ejection fractionwith stress, wall motion abnormality at a low workload and wall motion abnormalities in the anterior territory (or left anterior coronary artery distribution) are other high risk findings
• The prognostic value of stress echocardiography in women is similar to that of men
Exercise ECG
Stress ECG is able to detect:
• Normal rest ECG
• ST changes consistent with ischemia
• High risk findings such as very poor exercise tolerance, severe ventricular arrhythmia/hypotension
Test Characteristics
Stenosis Detection:
• Sensitivity of 67% and a specificity of 72% for the detection of significant stenosis in patients with an intermediate pretest likelihood of CAD as compared to invasive coronary angiography
Prognosis:
•“Early positive” exercise test result (inability to complete 1st two stages of Bruce protocol, exercise induced angina and treadmill time) have been identified as independent predictors of survival
• The Duke Treadmill score can identify a high risk group (score less than or equal to -11) with an average annual cardiovascular mortality greater than or equal to 5%.
Practical Tips
• ETT accuracy is slightly worse in women compared to men
• Patients with LVH by ECG criteria and ST depression have a lower specificity 70% ( vs 84%) with no change in sensitivity
• Exercise-induced ST depression usually occurs with right bundle-branch block in the anterior chest leads (V1 through V3) and is not associated with ischemia. Lateral leads (V4 through V6 ) and inferior leads (II and aVF) can be used to identify ischemia
• Computer processing of the exercise ECG can result in a false-positive indication of ST depression
• Normal rest ECG
• ST changes consistent with ischemia
• High risk findings such as very poor exercise tolerance, severe ventricular arrhythmia/hypotension
Test Characteristics
Stenosis Detection:
• Sensitivity of 67% and a specificity of 72% for the detection of significant stenosis in patients with an intermediate pretest likelihood of CAD as compared to invasive coronary angiography
Prognosis:
•“Early positive” exercise test result (inability to complete 1st two stages of Bruce protocol, exercise induced angina and treadmill time) have been identified as independent predictors of survival
• The Duke Treadmill score can identify a high risk group (score less than or equal to -11) with an average annual cardiovascular mortality greater than or equal to 5%.
Practical Tips
• ETT accuracy is slightly worse in women compared to men
• Patients with LVH by ECG criteria and ST depression have a lower specificity 70% ( vs 84%) with no change in sensitivity
• Exercise-induced ST depression usually occurs with right bundle-branch block in the anterior chest leads (V1 through V3) and is not associated with ischemia. Lateral leads (V4 through V6 ) and inferior leads (II and aVF) can be used to identify ischemia
• Computer processing of the exercise ECG can result in a false-positive indication of ST depression
Nuclear Perfusion Scan
SPECT/PET is able to detect:
• Presence, extent and location of reversible or irreversible myocardial ischemia/scar
• High-risk findings such as transient ischemic dilatation
• Global and regional left ventricular dysfunction
Test Characteristics
Stenosis Detection:
• Reversible ischemia on exercise/pharmacologic SPECT or PET has been found to have sensitivities of 87% and 90%, respectively, and in contemporary protocols (Tc agents and incorporation of gated images, or PET perfusion) specificities are 85-90% for the detection of significant stenosis as compared to invasive coronary angiography
Prognosis:
Annual risks for MI/death based on stress SPECT and PET findings are:
Normal: 0.3/0.5%; 0.2/0.5%
Mildly abnormal: 0.8/2.7%; 1.3/1.4%
Moderately abnormal: 2.3/2.9%; 3.6/3.0%
Severely abnormal stress: 2.9/4.2%; 6.4/5.8%
Practical Tips
• Ideally, medications should be held if possible so as to give best chance of reaching maximum stress
• Pharmacologic stress can be used if patients do not reach an adequate symptomatic or heart rate end
• Presence, extent and location of reversible or irreversible myocardial ischemia/scar
• High-risk findings such as transient ischemic dilatation
• Global and regional left ventricular dysfunction
Test Characteristics
Stenosis Detection:
• Reversible ischemia on exercise/pharmacologic SPECT or PET has been found to have sensitivities of 87% and 90%, respectively, and in contemporary protocols (Tc agents and incorporation of gated images, or PET perfusion) specificities are 85-90% for the detection of significant stenosis as compared to invasive coronary angiography
Prognosis:
Annual risks for MI/death based on stress SPECT and PET findings are:
Normal: 0.3/0.5%; 0.2/0.5%
Mildly abnormal: 0.8/2.7%; 1.3/1.4%
Moderately abnormal: 2.3/2.9%; 3.6/3.0%
Severely abnormal stress: 2.9/4.2%; 6.4/5.8%
Practical Tips
• Ideally, medications should be held if possible so as to give best chance of reaching maximum stress
• Pharmacologic stress can be used if patients do not reach an adequate symptomatic or heart rate end
