Cardiac Imaging Flashcards
Types of Cardiac Testing
- EKG
- Ambulatory ECG Monitoring
- Stress test
- Exercise
- Pharmacologic
- Echocardiogram
- Stress echocardiogram
- CT scan
- MRI
EKG
Indications
-
Symptomatic patients
- CP, palpitations, fatigue w/SOB, syncope (pass out), seizure
-
Eval/monitoring of:
- Audible abnormalities (arrhythmia, murmur)
- Suspected electrolyte imbalance
- PE
- Congenital heart disorders
- CHF
- Cardiomyopathy (enlargement)
- Poisonings/electrocution
-
Drug monitoring - need regular EKG monitoring
- Drugs that prolong QT (lithium, psych meds)
- Presence of implanted defibrillator/pacemaker (yearly EKG
Screening EKGs
USPSTF
- Adults at low risk of CVD events: Recommend AGAINST EKG screening (Grade D) → can lead to unnecessary tests
- Adults at intermediate or high risk: Insufficient evidence for screening (Grade I)
-
Athletes - sports physical
-
History and physical most important
- Worried about electrical abnormalities (asymptomatic arrhythmias) while exercising)
-
History and physical most important
- Pre-operative exams
- Certain occupations may require screening EKG: cataract
If patient has no symptoms indicating an EKG → no need to test again
How to assess CVD risk by USPSTF?
Use Pooled cohort calculator
10-year ASCVD risk < 7.5% = low
“” >/= 7.5% elevated risk
Ambulatory EKG monitoring
Provides data over extended period of time
Ambulatory EKG monitoring Indications
- Arrhythmias s/s
- Eval effectiveness of arrhythmia therapy
- Screening for asymptomatic arrhythmia
- Eval prognosis post ACS
- Assess for silent ischemia in someone with known/suspected CAD
- DM, women
What arrhythmia s/s indicate for ambulatory EKG monitoring?
- Unexplained syncope/near syncope
- Episodic dizziness, unexplained recurrent palpitations
- Frequent palpitations/palpitations associated w/other s/s: SOB, dizziness, etc
- Vasovagal event precipitated by something (feel like I’m going to pass out)
- Passing out
Types of ambulatory Monitoring
- Continuous EKG (Holter)*
- Event (loop) monitors
- Patch monitors*
- Mobile Cardiac Outpatient Telemetry (MOCT)
- Insertable cardiac monitoring
*** = see in primary care
Holter monitor
- Best for daily or near daily symptoms and/or if continuous monitoring of all cardiac activity is required (gives you most info for shortest time)
- Daily palpitations or dizziness
- Assessment of rate control in afib (short time period to see rate) don’t need 30days, only snippet
- Continuously records heart rhythm
- Usually worn for 24-48 hrs
- 3-5 electrodes on chest
- Patient keeps symptom diary
- Hit a button
Patch monitor
- Good for pts w/less frequent s/s or need for longer monitoring
- Weekly or every other week s/s
- More convenient and easier for pt to tolerate than Holter
- Small all in one device - ONE electrode
- Record only single lead but can record continuously for up to 30 days
- 3, 7, 14, or 30d
Event Monitor
types
- Good for less frequent symptoms (weekly or bi-weekly)
- Not recording unless patient hits the button when they’re experiencing s/s → problem is the monitor may not be able to capture the duration while it’s occuring
- Pre-symptom memory loop recorders - “continuous loop event recorder” - always recording and erasing data
- Not for asymptomatic
- Post-event recorders - “non-looping event recorder”
- May miss rhythm problem
- Auto-detect - GOOD FOR ASYMPTOMATIC automatically sends data to provider to interpret
Insertable cardiac monitor
- May be needed if other event monitors can’t provide enough data
- Use if symptoms are infrequent
- Size of pack of gum
- Can be programmed to record when patient activates it or when s/s occur
Cardiac stress tests
Indications? What limitation and other option is there?
- Exercise stress testing used in symptomatic, intermediate-risk patients who can exercise and who have interpretable EKG results
- No exercise → pharmacologic stress test
When is stress testing NOT used?
- In high-risk patients actively evaluated or treated for ACS; it may be used once ruled out ACS for risk stratification
- Exercise stress testing not recommended in asymptomatic, low-risk patients
- None on pt w/acute MI, going to ER w/CP → have it later on
Stress testing indications (7)
- New CP or angina (not current) ASK THIS!
- Known CAD and new/worsening symptoms (cardiac disease)
- Hx of PCI/re-vascularization (stenting)
- Valvular heart disease - stress ECHO
- New HF or cardiomyopathy - evaluate ischemia as cause
- Pre-operatively in pts w/known cardiac conditions
- Assess heart health prior to cardiac rehab or new exercise regimen
Contraindications to Stress Testing
Absolute!
- Acute MI w/in 48hrs
- Acute myocarditis/pericarditis
- Rapid Afib or ventricular arrhythmias
- Symptomatic severe aortic stenosis
- Severe anemia, acute illness, infection
- Uncontrolled hyperthyroidism
- Acute aortic dissection, PE, recent CVA (stroke)
Contraindications to stress testing
Relative - cardiology would decide
- Hypertrophic obstructive cardiomyopathy
- Suspected L main disease > 50%
- Severe HTN, > 200/110 mmHg
- Congestive heart failure (CHF)
- Severe ST depression at rest (unstable angina)uPermanent Pacemakers/ LBBB
- Left bundle branch blocks
- Specific way to stress ppl with these to get data
What are the components of a stress test?
- Stressor: exercise or pharmacologic
- Imaging modality: EKG, Echo, Nuclear (myocardial perfusion imaging - MPI)
Exercise (2 imaging tests) vs Pharmacologic (drug) as stressor
Imaging for each type?
- Exercise as Stressor - PREFERRED
- EKG imaging only = Exercise Tolerance Test (ETT) Level 1 stress test
- Nuclear imaging = Treadmill Nuclear Stress Test
- Pharmacologic as Stressor (drug)
- Always includes either nuclear or echocardiogram imaging
- NOT EKG monitoring
Best way to stress the heart?
EXERCISE PREFERRED
When should a patient not utilize exercise as a stressor?
Limitations
- Not able to exercise to 85% of age-predicted max HR
- On BB or other AV blocking agents inhibiting HR increase needed
- Take these off - sensitivity to detect coronary stenosis reduced
Consider these patients for pharmacologic stress testing
Can your patient exercise to a satisfactory level?
Algorithm
If pt on BBs or other AV blocking agents, or have any conditions (LBBB, paced rhythm) that would inhibit HR increase needed to achieve stress or reduce stress test sensitivity → YES → Pharmacologic
Need to be mental and physical limitations (respiratory, elderly, dementia)
What do you always need before a stress test?
Baseline EKG
Bruce Protocol vs Modified Bruce Protocol (treadmill)
- Bruce Protocol - most common in office-based testing - extensively validated
- Modified Bruce Protocol - can be used in patients unable to complete Bruce protocol - going slowly
Who needs a Pharmacologic Stress Test?
- Any patient unable to exercise to a satisfactory workload
- Patients w/baseline LBBB or ventricular pacing
- Electric pathway not in line - make sure heart is getting adequate perfusion - need more tracing
Does Pharmacologic Testing include imaging?
YES
What kind of meds are involved in pharmacologic stress test?
Vasodilating agents
Ionotropes/chronotropes
Vasodilating agents
MOI
- Increase coronary blood flow by acting on Adenosine receptors in heart - primarily A2A
- When activated these receptors result in vasodilation
- Also present in brain, lungs, spleen
- Preferred agents for stress testing
- Can be combined w/low level exercise → decrease SEs from vasodilator + provide better assessment of exercise capacity
Vasodilating agents: which drugs
Adenosine
Regadenosen (selective for A2A receptors - best tolerated)
Dipyridamole (long ½ life; not used as frequently)
Vasodilating agents
Contraindications
- Significant reactive airway disease such as asthma (acting on beta receptors)
- Significant HoTN
- High degree AV block
- Unstable or complicated ACS
- Theophylline and caffeine should be withheld prior to vasodilator stress
- Theophylline hold for 48 hours; caffeine for 12 hours
Dobutamine
- (+) ionotrope and chronotrope → stimulates beta1 and beta2 receptors
- Rapid onset (1-2m) + short half-life
- Can be given w/ atropine to achieve target heart rate if needed
- Preferred agent in stress echos: 2nd in MPI - nuclear
Dobutamine
contraindications
- Sustained arrhythmias or Afib w/RVR
- Recent MI/unstable angina
- Aortic dissection
- Moderate to severe HTN (SBP > 180)
Purpose of imaging the heart
- Helps determine whether inducing stress (using exercise or pharmacologic agents) caused myocardial ischemia → significant coronary stenosis
- Imaging types: EKG, Echo, Nuclear
Which test(s) require a cardiac stress agent?
Nuclear stress/stress echo
Does the patient have an abnormal baseline EKG?
Yes → then what?
No → then what?
- No → ETT
- Yes → add imaging to stress
List of abnormal baseline EKG reading conditions
- LVH - any wall abnormalities - echo (structural)
- LBBB
- Paced rhythm
- WPW syndrome
- ST-T wave changes > 1mm
- On digoxin
- Hx of revascularization, angiography
Nuclear Exercise Stress Test
What
- Stress radionuclide myocardial perfusion imaging (rMPI)
- Single photon emission CT (SPECT) - common IMAGE
- Can be used in exercise MPI or pharmacologic MPI
OR
- Positron emission tomography (PET) - more exepensive
- ONLY used in pharmacologic MPI
Nuclear Exercise Stress Test
Process
- IV Radioactive tracer administered → wait 30m → RESTING pictures taken 1st
- Exercise/stress inducer starts → 2nd tracer administered → STRESS pictures taken
- Total time 2-3hrs → longer than ETT
- Compare REST VS STRESS pictures → see how well heart is perfused → cardiologist interprets this
SPECT imaging interpretation
- Gamma radiation measured directly
- Images after 45 minutes of rest are compared to stress images
- Nuclear imaging - “cold spot” areas are considered areas of low or no blood flow → less activity
- Interpretation based on rest images
- Re-perfused (ischemic area) → reversible defect
- Fixed defect (infarct area)
ETT
Imaging vs. W/o imaging
- W/o imaging
- Provides ONLY EKG tracings
- Acceptable for most patients who are able to exercise
- W/imaging
- Provides EKG TRACING and IMAGING
- More sensitive
- For pt who is ABLE TO EXERCISE w/any of following
- WPW (ventricular pre-exication)
- ST-T wave changes
- LVH
- On digoxin
- Requires ischemia localization or assessment of viability
- For pt who is ABLE TO EXERCISE w/any of following
Stress test preparation (7 things)
- NPO 4hrs prior
- No caffeine for 24hrs prior
- Meds to hold day of test: Isosorbide, NTG, BBs, CCBs
- No smoking 4hrs prior
- No exercise day of test
- Comfortable shoes and clothing (no jumpsuit)
- No lotions to help electrodes stick
Two types of echocardiogram
- Transthoracic Echocardiogram (TTE) → on side, external
- Transesophageal echocardiogram (TEE) → going into behind the heart → need sedation
Can have both done to get bigger picture of heart. Both dependent on skill level of technician
Echocardiogram indications
-
Structural evaluation
- Pericardium (pericardial effusion)
-
Ventricles (hypertrophy, dilation, wall motion abnormalities, visualize thrombi)
- Pumping appropriately
- Valves (stenosis, prolapse
- Great vessels (aortic dissection)
- Atria and septa between chambers (congenital heart disease, trauma)
-
Hemodynamic evaluation - blood flowing and how it’s flowing
- Blood flow through valves (stenosis, regurgitation)
- Stenosis - blood not able to get through (only a little)
- Regurgitation - goes through but comes back
- Blood flow through chambers (ejection fraction)
- How efficient the heart is pumping and how it’s pumping out
- Blood flow through valves (stenosis, regurgitation)
Conditions to order an Echo for (8)
- New or monitoring
- Valvular disease (suspected)
- CHF
- LVH/cardiomyopathy
- New afib - look at valves
- Pulmonary HTN (suspected)
- Post ACS/pts w/CAD - remodeling of heart structure
- Congenital heart disease
- Endocarditis or thrombus or tumor
TTE
- Most common
- Less invasive with no prep
- Image quality affected by amount of tissue between transducer and chest
- Difficult to see posterior images
TEE and indications
- Clearer image - behind heart, not as optimal for front of heart
- Sedation
- Fasting 4-6hrs prior
- Esophagus can restrict transducer position
- Indications
- Concern for infective endocarditis/complications of
- Suspected acute aortic pathology
- IF TTE non-diagnostic w/high suspicion for cardiac etiology
- Complex congenital disease
Bubble study
Testing for?
Risk of having this?
Shake saline and pump BUBBLE into vein → if they see bubble travel to other side of heart (go into LV) - Patent Foramen Ovale
+PFO → clot → stroke
Stress echocardiogram
Purpose + Process
- Stress test + ECHO
- Allows eval of cardiac function to see if parts of heart not getting perfused
- Real-time eval of cardiac function from exercise
- Echo before and after exercise
- Same considerations and patient selection criteria
- Rest echo → Treadmill, bicycle, or pharmacologic stress → immediate post-exercise echo
Stress Echo indications
- THINK STRUCTURE OF HEART
- Detection and eval of intra-ventricular gradients in hypertrophic cardiomyopathy
- See how blood flow is through valves
- Can see ischemic changes
- Eval of LV wall motion abnormalities
- Eval pulmonary HTN, mitral regurgitation, mitral stenosis during exercise w/pulmonary artery systolic pressure - help w/surgical decision
- Can see ischemic changes w/ventircular hypokinesis, akinesis, or dyskinesis
