Cardiac CT arthrography
CT angiography is a non-invasive method to obtain images of the coronary arteries, but it is not the gold standard to visualize the coronary arteries. It also cannot be used to assess for stent failure or patency, only cardiac catheterization can provide those answers definitively.
In CT angiography, It should be used in patients for whom you anticipate will only require medical management and would likely not required stent placement. E.g. very mild increases in troponin not in keeping with an ischemic picture but the patient has risk factors for CAD, so a CT angiogram can be ordered to rule out CAD.
Cardiac catherization (coronary angiography vs ventriculography vs PCI)
Cardiac catherization: invasive procedure in which a catheter is inserted into a coronary vessel or ventricular chamber via a femoral or radial artery
Coronary catherization: If the catheter is inserted into a cardiac vessel, it is referred the procedure is referred to as coronary catherization or coronary catherization
Ventriculography: If the catheter is inserted into a chamber and the procedure is used to visualize the ventricles, then the procedure is referred to as ventriculography
PCI: If during the procedure, a stent is placed, then this is referred to as percutaneous coronary intervention
Stress test
How to stress the heart?
There are 2 ways to stress the heart: exercise and pharmacologically. Exercise is the preferred method to stress the heart since it most closely mimics stressors that typically induce ischemia. Exercise is achieved via increasing treadmill speed and slope incrementally (also referred to as the Bruce protocol) until the patient reaches their target heart rate required to detect ischemia. But sometimes patients are unable to ambulate easily or cannot walk for long enough on the treadmill to reach their target heart rate. For this patients we use pharmacological agents instead:
- Dipyridamole
- Coronary artery vasodilator in normal coronary arteries but NOT in coronary arteries that are distal to a stenosis
- This results in blood being “stolen” (steal phenomenon) from stenosed arteries which induces ischemia that can be picked up on stress test
- Adenosine
- Coronary artery vasodilator
- Dobutamine
- Used as third line after adenosine and dipyridamole
- Inotrope, chronotrope and vasodilator
How to detect/document ischemia after the heart has been stressed?
Nuclear stress test vs EKG stress test vs Echo stress test
- EKG stress test
- Used with intermediate probability of CAD based on risk factors and when the patient has a normal EKG at rest
- Assess for ST deviations after heart is stressed either using exercise or pharmacological agents
- Echo stress test
- Perform echocardiogram first, then stress the heart using exercise or pharmacological agents and then perform an echocardiogram afterwards
- You will see a pre and post stress LVEF reported and can look for wall motion abnormalities that become more apparent when the heart is stressed
- Nuclear stress test
- Also known as radionuclide myocardial perfusion imaging
- More specific and sensitive than EKG stress test
- Radioactive tracer is injected into a vein and then the patient is placed inside the scanner which contains the gamma camera which can detect radiation released by the tracer
- Next the patient is stressed either using exercise or pharmacological agents and then the patient is again placed into the scanner with the gamma camera to see whether the heart is being adequately perfused even after stressed