CV Imaging Flashcards
Atherosclerotic Plaque Development
Risk Factor Stage: fatty streaks that can accumulate WBCs and RBCs due to slight inflammation
Subclinical Stage CAD: lumen is starting to narrow with calcifications and scarring with inflammation
Clinical Stage CAD: the plaque can rupture and cause acute coronary system with you can get thrombi; platelets and fibrin try to repair ruptures and cause MI and more obstruction
Goals of Cardiac Imaging
Augment the History and Physical
Identify Anatomic Disease
Assess functional significance of pathologic disease
Predict cardiac and overall prognosis
Clarify cardiac etiology of symptoms
Guide management (medical, surgical, percutaneous, device)
Cardiac Imaging Types
X-Ray/CT: x-rays used with detector to create an image
Nuclear: inject dye and emit photons and the camera tracks these; marker of perfusion of myocardium
Echo: least costly other than chest x-ray; transducer uses sound to image the heart
MRI: great images; uses magnet and electromagnetic signals
Resting Imaging
Resting Imaging
2D & 3D Echocardiography
Transesophageal echocardiography (TEE)
Stress Imaging
Stress Imaging
Stress EKG
Stress Echocardiography
Stress Nuclear Perfusion Imaging
Advanced Imaging
Advanced Imaging
Coronary Calcium Scoring
Computed Tomography (CT)
Cardiovascular Magnetic Resonance Imaging (CVMRI)
2D Echocardiography
High frequency waves generated by a pizoelectric crystal travel through body tissue and then are reflected by tissues based on the acoustic impedence of various tissues. The reflected waves return to the transducer causing mechancal deformations of the crystal. Based on the time from generation of the impulse to receiving the reflected impulse back, calcuations are made to determine the distance from the probe. Images are thus reconstructed.
2D Echocardiography + Doppler
-Doppler studies can help assess blood flow direction, velocity and turbuence. Also helps estimate pressure gradients.
-Principle is that waves reflected from moving objects undergo a phase shift relative to the velocity of the moving object.
Doppler gives blood flow
Orange, yellow, red = towards transducer
Blue = away from transducer (systole)
2D Echocardiography Advantages
Advantages:
- Noninvasive
- No radiation exposure
- Real time imaging
- Portable
- Quantitative
- > 30 years of research and validation
Clinical Indications for 2D Echocardiography Advantages
Assess LV Function: CHF, acute MI, chronic heart disease
Assess Valves: acute/chronic valve disease, prosthetic valves, heart murmur, CHF/CAD
Pericardial Effusion: chest pain, dyspnea, hypotension
Assess for Structural Disease: dyspnea, chest pain, syncope, palp CVA, shock/hypotension
2D Echocardiography Limitations
- Technician / Interpreter dependent
- Limited by lung, soft tissue interference; COPD, obesity
- Impractical in certain settings (e.g. OR)
TEE
Transesophageal Echo
There isn’t much tissue in the way so see image well
Portable and immediate
Requires conscious sedation
Requires special training
TEE: Specific Indications
Pre-cardioversion for atrial arrhythmias Valvular disease and endocarditis Improved imaging of mechanical valves Cardiac masses and thrombi Cardiac source of thromboembolism Aortic pathology Septal defects and congenital disease Nondiagnostic transthoracic echo Special settings: ICU, OR
Cardioburn: shock someone to normal rhythm; do TEE first to make sure there is not a clot in L appendage that formed during an atrial fibrillation it can cause systemic emboli or stroke
Agitated Saline Study (Bubble Study)
Agitated saline is injected (bubbly looking) into a vein and go to right atrium; if shows up in L atrium there must be a hole somewhere
Direct Imaging
Direct imaging:
Cardiac calcium scoring
Coronary CTA or MRA
Coronary angiography
Indirect Imaging
Stress EKG
Ultrasound: stress echocardiography
Nuclear perfusion imaging: Nuclear stress test
Tc-99m: Cardiolite, Myoview
Thallium
Pathogenesis of CAD
Normal
Early Plaque
Complex Plaque
Acute MI
Coronary Artery Disease: Evaluation Strategies
Invasive Anatomic Imaging: direct imaging of the heart by coronary angiography
Non-invasive Functional Imaging: indirect imaging of the heart by stress EKG, echo, or nuclear; also anatomic direct imaging via CT r MRI
Stress Testing: Technique
Induce Cardiac “Stress”: Exercise, Dobutamine, Vasodilatiors
Assess for Ischemia: EKG, Echocardiography, Nuclear Imaging, MRI
Sometimes don’t even image the patient especially if low suspicion so stress them on treadmill by getting their HR to target for their age, time for HR, etc. and if possible then they are fine
ST changes that tell about ischemia, so look for that on treadmill EKGs
Exercise EKG
Graded exercise protocol
Continuous EKG monitoring
Inexpensive, practical
Standardized, with extensive database
Exercise EKG: Advantages and Disadvantages
Advantages:
Inexpensive, fast, widely-available
Objective assessment of exercise capacity
Assess exercise-induced symptoms, arrhythmias
Disadvantages:
Requires ability to exercise
Reduced accuracy in patients with abnormal baseline ECG
Does not localize disease
Exercise Stress Echocardiography
Rest and stress images
Post exercise will get enhancement of L ventricular function
If see one area that was contracting well pre test and then see abnormality after stress = must be experiencing vasospasm, coronary bridge (artery is compressed by myocardium), or blockage present
Exercise Stress Echocardiography Advantages
- Assessment of valvular, pericardial, and aortic disease
- Results are immediately available
- No radiation exposure
- Less expensive, less “hassle” than nuclear
- Higher diagnostic accuracy than stress ECG
- Can be combined with pharmacologic stress
- Can localize disease (identify “culprit vessel”)
- Assessment of myocardial viability
- Allows measurement of LVEF
Nuclear Perfusion Imaging
Different slices of heart from different planes
Perfusion defect from rest to stress indicative of ischemia
If perfusion defect with both rest and stress indicative of infarct/MI
Best dx tool is nuclear scan, which is baded on 14 studies
Grated Nuclear Imaging: End systole and diastole to estimate EF
SPECT Perfusion Imaging Advantages
Single photon emission computed tomography aka myocardial perfusion imaging (nuclear imaging)
- Feasible in virtually all patients
- Can be combined with pharmacologic stress
- Slightly higher sensitivity than stress echo
- Better able to identify residual “borderzone” ischemia
- Extent & severity of ischemia can be objectively quantified
- Prognostic value is well established
- Can localize disease (identify “culprit vessel”)
- Assessment of myocardial viability
- LVEF can be automatically quantified
- Less false negatives, so sensitivity is higher
Strategy for Evaluation of Chest Pain
Low: stress test CCS or no workup = no therapy (-) or imaging stress test (+)
Intermediate: imaging stress test = no therapy (-) or medical tx (+) or angiography (+)
High: angiography = medical tx or PTCA/CABG
Steps in Selecting a Stress Test
- Is stress testing indicated?
- Is supplemental imaging required in addition to the ECG?
- Which imaging modality is preferable (Echo or SPECT?)
- Which stressor should be used?
Preferred Clinical Settings: Nuclear Imaging
Prior MI Prior PTCA or CABG Expect suboptimal echo windows Intermediate-high clinical suspicion for CAD LBBB or Pacemaker
Preferred Clinical Settings: Echocardiographic Imaging
No known prior CAD
Good echo windows
Low-intermediate clinical suspicion for CAD
Valve, pericardial, aortic information also desired
Expert readers available
Cardiac Imaging: Emerging Noninvasive Techniques
Coronary Calcium Scoring
CT angiography
MRI and MRA
Cardiac PET imaging
Coronary Calcium Score
Electron-beam computed tomography (EBCT) is used for detecting calcium build up in arteries
reflects total coronary plaque burden
a reliable and reproducible value
compared to “normals” for age and sex
does not predict individual stenosis severity
Potential Candidates for Calcium Scoring
- Asymptomatic patients with risk factors, to predict future cardiac risk
- Patients with “low risk” chest pain, as an alternative to stress testing
- Patients with known CAD, to monitor progression of disease and response to therapy (needs validation)
CT Angiography
Imaging of the vessels of the heart
Visualize occlusions, calcifications, plaques, etc.
CT Angiography Disadvantages
Calcium = hard to tell if lack of blood flow or calcium build up, therefore usually get calcium score first
Stents also make it hard to see whats going on
Difficult or impossible with irregular heart beat- give BB to slow HR to visualize heart bettter
Metal clips
Radiation exposure
MRI and MRA
Use for infiltrating disease of the heart; amyloid and sarcoidosis
Also for fat deposition ARVD – arrythmigenic right ventricular dysplasia; genetic condition where R ventricular lateral wall is replaced with fatty tissue and causes death
Stress MRI: Scarring in heart from old MI – see well with MRI
Cardiac PET Imaging
-PET employs positron emiting isotopes attched to metabolic or flow tracers
Perfusion tracers: blood flow to the heart, should all be white, but not in these images
Old MI with scarring is possibility for this or such a chronic blockage the physiology has shut itself down to minimize processes; if wall is alive to some extent must use glucose to stay alive, so inject glucose and if takes it up it tells it is not scarring and need to save the tissue before too late
Coronary Angiography: Technique
Most invasive
If want to do a L heart catheterization, have to be in L ventricular chamber; can do coronary angiography without being in L ventricle; femoral route causes more bleeding and complications; now radial route
Dye is injected and see vessels
Left Ventriculography
Pig tail catheter that is less damaging than others
Femoral to aorta to L ventricle = LV pressure and pull it back to see if aortic stenosis
Inject dye and see EF level as well
Strategies of Choosing Chest Pain Diagnostic Imaging
Cheapest is stress ECG, but not best prognosis significance or dx determination
Nuclear is best prognosis significance
EBCT: new test, but not used widely yet; just looking at calcium without looking at the heart
Catheterization is most invasive and costly, but good dx determination
