Ischemic Heart Disease Part 2 Flashcards
If a patient is at high risk of major CAD events or has ACS, what cardiac tests would you do in acute chest pain evaluation?
- Invasive coronary angiography
If a patient is at a high risk of major CAD events and is being evaluated for stable chest pain outpatient, what tests would be run?
Anatomic or functional testing
If a patient is at intermediate risk for major CAD events, what testing would be done for acute chest pain or stable chest pain?
Anatomic or functional testing
If a patient is low risk for major CAD events, how would they be tested for acute chest pain evaluation or stable chest pain evaluation?
No testing or defer testing
If a patient is asymptomatic, what tests should be done?
No testing
How is risk for major adverse cardiac event determined?
HEART score
If a patient has a HEART score of 0-3, what is their risk of MACE in 6 weeks? What intervention should be performed?
- Risk of MACE: 2.5%
- Intervention: discharge
If a patient has a HEART score of 4-6, what is their risk of MACE? What intervention should be performed?
- 22.3%
- Admit for observation
If a patient has a HEART score of 7-10, what is their risk of MACE in 6 weeks? What intervention should be performed?
- 72.7%
- Admit with early invasive strategies
What are uses for a 12-lead EKG?
- Assess for MI
- Ischemia
- Cardiac rhythm
- Conduction abnormalities
- Chamber hypertrophy
An EKG should be obtained in all adults who have what?
Chest discomfort without an obvious non-cardiac cause
Who is a 12 lead EKG routinely ordered for?
- Elderly patients
- Patients with DM (with dyspnea, nausea, malaise)
- Syncopal patients
- Arrhythmia suspected
What are best practices for a 12-lead EKG?
- Should be performed and evaluated for ischemic changes for anyone with symptoms of ACS within 10 mins of patient’s arrival at ED
- If initial EKG not diagnostic, but patient still symptomatic and high clinical suspicion for ACS, serial ECGs (15 to 30 min intervals during first 1-2 hrs) should be performed to detect ischemic changes
What is sometimes the earliest presentation of AMI?
Hyperacute T waves
How long are hyperacute T waves found on EKG after the beginning of AMI? What must they be distinguished from?
- 20-30 minutes after onset
- Peaked T waves associated with hyperkalemia
What is the interpretation of non-specific or normal EKG findings in the presence of ACS symptoms?
Does not exclude ACS
What is the interpretation of ST segment depression or T wave inversion in >2 contiguous leads in the presence of ACS symptoms?
Suspicious for NSTEMI or USA
USA = unstable angina
What is ST segment elevation or new LBBB on EKG suspicious for?
STEMI
What are the steps of STEMI evolution of an EKG?
- ST elevation (minutes to hours)
- ST elevation, pathological Q wave, inverted T waves, and scar formation (1-2 days)
- ST flattening, pathological Q wave (7-10 days)
- Normalization with a persistent Q wave (months)
What is the second step in evaluation of possible MI (for patients without ST-segment elevations)?
Cardiac biomarkers
What is the purpose of cardiac biomarkers?
Evaluate for myocardial damage
What are the cardiac biomarkers?
- Myoglobin
- CK-MB
- Troponin I, T
When would troponin be elevated?
When myocardial necrosis occurs within 3-6 hours
What is the preferred marker for myocardial injury because it is highly sensitive and specific for even small amounts of cardiac damage?
Troponin
How do troponin levels change over time during an MI?
- increase within 3-6 hours
- peak at 24-48 hours
- return to baseline over 5-14 days
When should troponin levels be measured?
- At presentation
- Again in 90 minutes
- Every 6-8 hours after symptom onset x 3 or until trending down
What are other potential causes for elevated troponin other than MI?
Troponin shows presence of myocardial injury
- CHF
- Sepsis
- PE
- CKD
- Myocarditis
- ESRD
- Aortic dissection
- Cardiotoxic chemo
- Cardiac contusion
- RF ablation
- Post-PCI
- Post CABG
What is the normal value for troponin?
essentially 0 (0.0-0.04)
When looking at troponin, what has more weight than a single reading
trends
This cardiac biomarker is less sensitive and specific than troponins
creatine kinase (CK-MB)
How do creatine kinase levels change over time?
- Increase 4-8 hours after injury
- Peak around 24 hours
- Return to normal by 48-72 hours
When would CK-MB be positive?
If CK-MB >5% of total CK
What can cause false positive CK-MB?
- Exercise
- Trauma
- Muscle disease
- DM
- PE
What are the isoenzymes of creatine kinase?
- CK-BB (brain and lungs)
- CK-MB (heart)
- CK-MM (skeletal muscle)
This is a cardiac biomarker found in cardiac and skeletal muscle that is released more rapidly from infarcted myocardium than troponin and CK-MB
Myoglobin
Is myoglobin sensitive or specific?
High sensitivity, poor specificity
This is the most sensitive early marker for myocardial infarction with the only real use in very early detection of an MI
Myoglobin
Why is lactate dehydrogenase not used frequently?
Not specific: found in many tissues (kidney, skeletal muscle, brain, blood cells, lungs, liver)
What is the timeline of lactate dehydrogenase after an MI?
- Rises within 24-72 hours after MI
- Peaks in 3-4 days
- Returns to normal in 14 days
In addition to cardiac biomarkers, what are other possible lab findings in an MI?
- Leukocytosis within several hours after AMI (peaks in 2-4 days and returns to normal levels within 1 week)
- Patients without biochemical evidence of myocardial necrosis but with elevated CRP are at increased risk of subsequent ischemic event
- ESR rises above reference range within 3 days and may remain elevated for weeks
What is the most commonly used and recommended noninvasive procedure for evaluating inducible ischemia in the patient with angina?
Stress testing
What are the 2 ways the stress component can be added to test for ischemia?
- Exercise
- Pharmacologic
When would exercise stress testing be used over pharmacologic?
For patients who can attain an adequate level of exercise
What are indications for exercise (only) stress testing?
- To confirm diagnosis of angina
- Determine severity of limitation due to angina
- To assess prognosis in patients with known CAD, including patients recovering from an MI
- To evaluate response to therapy
What are limitations of exercise stress testing?
- More false-positives than true-positives
- Not a screening tool in asymptomatic patients
- Most useful in patients with low pretest likelihood and normal baseline EKG
- Typically used in young, females with atypical symptoms
What is done in exercise stress testing?
- Incline adjusted via Bruce TM protocol (MC) to achieve 85% HR
- Hemodynamic monitoring of 12 lead EKG, HR, BP
- Intensity of exercise periodically increased until patient reaches maximum HR, changes in heart function detected on EKG, or patient is symptomatic
What is considered a positive exercise stress test?
ST segment depression of 1 mm
How is the Haskell and Fox HR max calculated?
220-age
What are absolute indications for termination of exercise testing?
- Drop in SBP of >10 mmHg from baseline BP despite increased workload when accompanied by other evidence of ischemia or hypoperfusion
- Moderate to severe angina
- Increasing nervous system symptoms
- Signs of poor perfusion
- Subject’s desire to stop
- Technical difficulties in monitoring
- Sustained VTach
- ST elevation in leads without diagnostic Q waves
What are relative indications for terminating exercise testing?
- Drop in SBP of >10 mmHg from baseline BP despite an increase in workload in the absence of other evidence of ischemia
- ST or QRS changes such as excessive ST depression or marked axis shift
- Arrhythmias other than sustained VT, including multifocal PVCs, V triplets, SVT, heart block, or bradyarrhythmias
- Fatigue, SOB, wheezing, leg cramps, or claudication
- Development of BBB or IVCD that cannot be distinguished from VT
- Increased CP
- Hypertensive response
What are absolute contraindications to exercise testing?
- Acute MI (within 2 days)
- High-risk unstable angina
- Uncontrolled arrhythmia causing symptoms of hemodynamic compromise
- Severe symptomatic AS
- Uncontrolled symptomatic HF
- Acute PE or pulmonary infarction
- Acute myocarditis or pericarditis
- Acute aortic dissection
What are relative contraindications to exercise testing?
- Left main coronary stenosis
- Moderate stenotic valvular HD
- Electrolyte abnormalities
- Tachy or bradyarrhythmias
- Hypertrophic CM and other forms of outflow tract obstruction
- SBP >220 or DBP >110
- Mental or physical impairment leading to inability to exercise adequately
- High-degree AV block
What is an additional contraindication to exercise testing?
- EKG not interpretable due to baseline abnormalities: preexcitation syndrome (WPW), electronically paced ventricular rhythm, greater than 1 mm of resting ST depression, complete LBBB
What are indications for exercise stress testing with imaging component?
- Resting ECG makes an exercise ECG difficult to interpret
- Confirmation of the results of the exercise EKG when they are contrary to clinical impression
- To localize the region of ischemia
- To assess the completeness of revascularization following bypass surgery or coronary angioplasty
- As a prognostic indicator in patients with known coronary disease
What is used for exercise stress test with nuclear imaging?
Radiotracers of thallium or technetium
Why would exercise stress testing with nuclear imaging be used?
Provides relative perfusion data following injection of a radioactive material before and after a stress test
What is used for nuclear imaging with an exercise stress test?
SPECT (single photon emission computed tomography)
Why is SPECT helpful?
- Provides slices of the heart for imaging
- Enable imaging of wall motion and estimation of EF
Why would an exercise stress test be combined with echocardiography?
- Increases sensitivity and specificity and determines extent of myocardium at risk for ischemia
- Looks for regional wall motion abnormalities or LV dilation in response to exercise
Why would a pharmacologic stress test be performed?
- If a patient is not able to exercise to a sufficient cardiac workload or has a contraindication to or clinical reason not to perform an exercise stress test
What should you keep in mind with a pharmacologic stress test?
Sensitivity is very low so these tests are always combined with an imaging modality
What medication classes can be used as pharmacologic stress agents? Which one is preferred?
- Vasodilators
- Adrenergic Stimulating agents
- Preferred: vasodilators
What vasodilators can be used for a pharmacologic stress test?
- Adenosine
- Dipyridamole
- Regadenoson
What is the mechanism of action of vasodilators (adenosine, dipyridamole, and regadenoson) used in pharmacologic stress testing?
- Cause direct coronary artery vasodilation
- Attenuated in diseased coronary arteries which have reduced coronary flow reserve and cannot dilate further in response
What are symptoms of vasodilators used as stress agents?
- Shortness of breath
- Headache
- Flushing
- Chest discomfort or chest pain
- Dizziness
- Nausea
- Abdominal discomfort
- Metallic taste in mouth
- Feeling hot
What are contraindications to vasodilator stress agents?
- Bronchospasm
- SSS or >1 AVB (w/o a V demand PM)
- SBP <90
- Patients using dipyridamole or methyxanthines (ie caffeine and aminophylline)
- Unstable or complicated ACS
This medication class is 2nd line for patients who can’t exercise and have a contraindication to vasodilator stress
Adrenergic stimulating agents
What adrenergic stimulating agent is used as a stress agent?
dobutamine
Often used with atropine in patient who do not achieve target HR