Cardiac Imaging Flashcards
What is Appropriate Use Criteria (UAC)?
An appropriate diagnostic or treatment procedure is one where the expected benefit exceeds the risks by a generally acceptable margin.
What is a MET?
Metabolic Equivalent of Task
1 MET= O2 consumed at rest
3-4 METs: walking
10 METS: running for 10 minutes
What does an Exercise Treadmill Test (ETT) tell you?
It provides data about exercise capacity and duration, BP and heart rate responses, provoked symptoms and EKG changes concerning limitations of flow.
What is the Standard Bruce Protocol?
During an ETT, you increase the speed and incline of the treatmill by a set amount every 3 minutes
What are the 5 indications for an Exercise Treadmill Test?
- 1st line test to diagnose Coronary Artery Disease (if patient is capable of doing the test)`
- Risk assessment and prognosis re known CAD
- Progosis after MI
- Evaluation of exercise induced tachycardia
- Prescription for future exercise regimen re safe levels.
What are the Cons and contraindications for ETT?
Patient cannot exercise >5 METS
Many disease states: Acute MI (2 days), Unstable Angina, Acute endo-, myo-, pericarditis, Severe aortic stenosis, Uncontrolled arrhythmia w hemodynamic compromise, Acute PE
Con: Cannot detect early stenosis
How does a Cardiac Ultrasound (Echocardiogram) work?
Peizoelectric crystals emit ultrasound (>20K Hz)
when stimulated with electric current,
then produce current when stimulated by returning sound.
What is Ejection Fraction?
A measure of what percentage of blood is ejected at contraction.
LVEDV minus LVESV divided by LVEDV
LVEDV = Left Ventricular End Diastolic Volume
LVEDV = Left Ventricular End Systolic Volume
What is considered normal Ejection Fraction?
> 55%
What are the indications for an ECHO?
- 1st line test to assess left ventricular structure and function (ejection fraction)
- Assess cardiac valves
- Identify pericardial effusion
- detect intracardiac masses
- Assess aortic dsease
- Guide treatment re HF
- Prognosis about many heart problems
- Select patients for implantable defibrillator
What are the benefits/pros of an ECHO?
No radiation
Inexpensive
Easy
Done in real time
Noninvasive
How does nuclear cardiac imaging work?
AKA: Single Photon Emission Computed Tomography (SPECT)
Perfusion Imaging: radioactive tracer is injected to evaluate blood flow in coronary arteries to see if vessels can meet demand.
Done at rest and after exercise.
What are the indications for SPECT?
- Dx re Coronary Artery Disease
- Assess physiologic signs of CAD
- Prognosis of CAD
- Evaluate ventricular function
- Determine myocardial viability (dead or alive tissue?)
What are the pros of SPECT?
Can detect very early problems with coronary arteries long before Sx and while still treatable with meds.
Can help with prognosis
What are the Cons of SPECT?
It takes 4 hours, the patient cannot have beta blockers (will suppress heart rate), caffeine, or food (re nausea)
How does a cardiac CT work?
It is like a big 3D xray.
They use Gallium via IV for contrast, Metoprolol to decreases heart rate to decrease blurriness of image, dilate blood vessels to see better, and patient must hold breath for 10 seconds.
What is a new development re Cardiac CT?
Prospective ECG Triggering: the CT is synched to your heartbeat so it only takes an image at diastole and this also minimizes the amount of radiation exposure.
What are indications for Cardiac CT?
- Noninvasive anatomic assessment of CAD
- Evaluation of structure of heart
- Risk stratification using coronary calcium scoring
- Rapid evaluation re acute chest pain
What are the pros of Cardiac CT?
Very fast!
Newer developments have decreased radiation, amount of contrast needed, and enable 3-D rendering.
What are the cons or contraindications of Cardiac CT?
Radiation exposure
Patient must have BMI under 35
Patient must have GFR >30 and if 30-45 must evaluate risk/benefit ratio
How does cardiac catheterization work
They thread a catheter through an artery in your leg or arm, through aorta and into the coronary arteries to take a look.
What are the indications of cardiac catheterization?
Gold standard re Dx of CAD
What are the cons of cardiac catheterization?
1/2000 risk of
death, MI, stroke or procedural complications
How does a cardiac MRI work?
It uses magnets to line up the spinning, angular momentum of protons and uses “math” to translate this into images.
What are the indications for Cardiac MRI?
Assess:
- Myocardial viability
- Cardiomyopathy
- Inflammation/myocarditis
- Congenital Heart Disease such as septal defects
- Cardiac Tumors
- Pericardium
- Great Vessels
What are Cons/Contraindications of Cardiac MRI?
Can cause nephrogenic systemic fibrosis if pt has moderate to mild kidney disease
Danger re metal objects, such as shrapnel in tissues or wheelchair in room.
(Orthopedic implants, stents and valves are usually safe though)
Who are prime candidates for noninvasive cardiac imaging?
Those patients in the middle in terms of pretest probability.
What are the Cons/Contraindications of ECHO
Not sensitive to small blockages
Need a trained technician
What do you know if your patient has a negative ETT and a negative SPECT?
Paitne has a 4-5 year “warranty” in the absense of new Sx
How many heart attack patients had LDL levels at NCEP goal?
75%
What are the chances a 40 yo will get CAD?
1 in 3 women
1 in 2 men
(1 in 8 women will get breast cancer)
What is the most dangerous part of coronary artery disease/atherosclerosis?
If it ruptures and creates a thrombus
What are the two types of vulnerable plaques?
Erosion prone
Critically Stenotic
