Introduction to cardiovascular Diagnostic Testing Flashcards
Why do we order diagnostics?
- To establish the presence or absence of illness, disease, condition, injury or other pathological state.
- Rule in primary diagnosis
- Rule out differential diagnoses
- Risk stratification
- Assess for comorbidities
- Assess for response to therapeutic intervention
- Assess for adverse reaction to therapeutic intervention
- Screening purposes
Categories / types of cardiovascular diagnostic studies
- Laboratory
- Radiology
- Electrocardiography / Electrophysiology
What do you have to consider when determining what type of lab testing should be done?
- Outpatient / emergency / inpatient
- Time frames for receiving testing results
- i-Stat(2-10 minutes)
- Seconds to 10+ days
Outpatient lab stat request consideration
CBC w/ diff, CMP, Lipid Panel w/ reflex LDL direct, cTnI, CK w/ reflex to isoenzymes
Critical values
Sample availability
Describe the pre-test and post-test probability in relation to the Prevalence of CVD (Cardiovascular Disease) and the factor of age
Ex: There is a low probability that someone in the age range of 20-39 would have hyperlipidemia so they would have a low pre-test probability. If this person is older, they would have a high post test probability.
What is the most prevalent tupe of Cardiovascular Disease?
Coronary Heart Disease (48%)
Coronary Heart Disease
- Primary cause of death and disability in the US
- 1 out of 5 deaths in US
- Every 25 seconds someone will have a myocardial infarction
- Every minute someone will die from a myocardial infarction
Non-modifiable risk factors for CVD
- Age
- Gender
- Family History
Modifiable risk factors for CVD
- High Blood cholesterol
- High Blood Pressure
- Physical inactivity
- Obesity and Overweight
- Smoking
- Diabetes
Cholesterol
Essential substance required for synthesis of:
- Cell membranes
- Steroid hormones
- Multiple other compounds utilized in daily physiological processes
Triglycerides
- Glycerol + three fatty acids = 1 triglyceride
- Energy source (primarily aerobic exercise)
- Energy storage
- Transported through blood within lipoproteins
- Chylomicrons and VLDL have greatest concentration
- Stored in skeletal muscle and adipose tissue
- Elevated in a non-fasting state → nothing to eat or drink other than water for 8 to 10 hours
- No coffee
- No chewing gum
Lipoproteins (VLDL, IDL, LDL, HDL)
- Lipid and protein structures
- Transport cholesterol and triglycerides
Chylomicrons
-Transport dietary exogenous triglycerides (TG) and cholesterol from the intestines to the liver
VLDL
- very low density lipoprotein
- Transport TG & cholesterol from liver into circulation
- Pre-cursor of IDL and LDL
- Contain
- Triglycerides
- Cholesterol
- Apolipoprotein B (Apo B 100)
- Atherogenic particle (B for BAD)
- Linked to pathologic affects of hyperlipidemia
IDL
- intermediate density lipoprotein
- Transport TG & cholesterol within circulation
LDL
- low density lipoprotein
- Transport TG & cholesterol within circulation
- Enriched with cholesterol
- Small enough to enter cells
HDL
- high density lipoprotein
- Transport endogenous cholesterol from the tissues to the liver
- Densest and smallest of lipoproteins
- Contains Apolipoprotein A-1 (ApoA-1)
- A is better than B
- Responsible for reverse cholesterol transport
- Anti-atherogenic
- Termed “good / healthy cholesterol”
Total Cholesterol
HDL + VLDL + LDL
Atherogenesis
- Fatty material and plaque are deposited in the wall of an artery
- Narrowing of lumen
- Eventual impairment of blood flow
- Excess cholesterol (VLDL and LDL) starts process
- Abnormal cholesterol metabolism
- Genetic
- Insulin resistance
- Dietary intake
- Saturated fats/ trans-fats
- Dietary cholesterol
- Obesity
Hyperlipidemia - Laboratory Evaluation
- In fasting serum, cholesterol is carried within:
- VLDL, LDL, and HDL molecules
- Total cholesterol equals the sum of these three components:
- Total Cholesterol = HDL + VLDL + LDL
- Most clinical laboratories measure total cholesterol, triglycerides, and HDL
- LDL and VLDL are more difficult to measure and are thus commonly calculated as an estimate
Friedewald equation
Total Cholesterol = HDL + VLDL + LDL
[LDL-chol] = [Total chol] - [HDL-chol] - ([TG]/5)
- The Friedewald equation should not be used under the following circumstances:
- When chylomicrons are present which means that the patient should be fasting for 8 to 10 hours
- When plasma triglyceride concentration exceeds 400 mg/dL
- Specialized lab test must be utilized to determine LDL
- Fasting lipid panel vs.
- Fasting lipid panel w/ reflex to LDL direct
Hyperlipidemia: Normal ranges for adults
- Total cholesterol < 200 mg/dl
- LDL cholesterol < 130 mg/dl
- HDL cholesterol > 40 mg/dl
- VLDL cholesterol < 30 mg/dl
- Triglycerides < 150 mg/dl
Creatine Kinase (CK or CPK)
- Enzyme contained in the heart muscle, skeletal muscle and brain
- CK – MM (skeletal muscle)
- CK – MB (heart muscle)
- Rise 4-6 hours , peak 18-24 hours, normalizes 48-72 hours
- CK – BB (brain)
CK – MM 94-100%
CK – MB 0-6%
CK – BB 0%
Creatine kinase (CK) aka (CPK) is an isoenzyme found in skeletal and cardiac muscle, brain and lung. The isoenzymes are defined as follows:
- CK-MM is skeletal muscle
- CK-MB is cardiac muscle
- CK-BB is brain and lung tissue
In a “normal” healthy individual there is always remodeling of skeletal muscle so that is why the normal value is 94-100%, at times there can be some breakdown of cardiac muscle which is why the CK-MB can range from 0-6%, rarely if ever is there enough breakdown of brain or lung tissue to cause elevation of the CK-BB so it almost always 0%
In the setting of an MI the increased breakdown of cardiac tissue results in elevation of the CK-MB levels which causes it to become more detectable in the blood so the percentage level increases. If all of the numbers need to add up to 100% it should make sense that the skeletal muscle percentage drops down to 85% due to the CK-MB rising to 15%.
- CK – MB
- Rise 4-6 hours , peak 18-24 hours, normalizes 48-72 hours
- Sensitivity of 56% and specificity of 45%
Myoglobin (MB)
- Iron and oxygen binding protein found in muscle tissue
- When cardiac muscle cells are damage myoglobin is released into the blood stream
- Rise in 2-4, peak 6-12, normalize 24-36
- Sensitivity of 83% and specificity of 99%
cTroponin I & T
- Regulatory proteins found in skeletal and cardiac muscle
- Troponin I more specific for acute myocardial infarction (AMI) than Troponin T
- hs-cTnI sensitivity 99% / specificity 89%
- Increases within 2-6, peak 18-24 hours, hours and normalizes in 7-14 days
- ~80% w/ 2-3 hours ED arrival
- Recommend serial monitoring*
- Improved sensitivity and specificity compared to older biomarkers
cTroponin I & T
- <0.04 Normal
- 0.04 – 0.39 Elevated above the 99th percentile of a healthy population
- > 0.4 probable MI
B-type Natriuretic Peptide (BNP)
- Secreted primarily by the ventricular myocardium in response to wall stress
- Ventricular volume expansion
- Pressure overload
- Validated as a marker for CHF
- <100 pg/mL – CHF can be excluded
- 100 – 400 pg/mL – inconclusive
- >400 pg/mL – consistent with CHF
- Sensitivity 90% / specificity 73%
- Some studies have demonstrated that BNP may also be a useful prognostic indicator post MI
- Significant elevation of BNP post MI associated with decreased left ventricular ejection fraction
High Sensitivity C-Reactive Protein
(hs-CRP)
- Abnormal protein that appears in the blood in the acute stages of various inflammatory disorders
- Elevated hs-CRP is associated with an increased risk of CVD
PT/INR
- PT is a coagulation test that measures the time it takes to form a firm fibrin clot after thromboplastin (factor III) and calcium are added to the serum sample.
- The findings are expressed in terms of seconds or as a percentage of normal activity.
- Prothrombin time (PT) is also expressed in terms of the INR using standardized thromboplastin reagents.
D-Dimer
- Injury to a vein or artery activates the coagulation cascade, creating a blood clot.
- Fibrin threads are produced and cross-linked, forming a net to catch platelets
- Plasmin breaks down the clot for removal.
- Broken fibrin fragments are termed fibrin degradation products (FDP)
- One of the which is D-dimer
- High sensitivity but low specificity
Electrocardiography (ECG)
- Disorders of rate and rhythm
- Myocardial ischemia / injury
- Electrolyte imbalances
- Structural changes
- Conduction disturbances
Ambulatory Monitoring
- Assess for silent ischemia
- Asymptomatic patient with history of ischemia or MI
- Assess efficacy of antidysrhythmic medications or following the discontinuation of antidysrhythmic
- Palpitations*
- Unexplained weakness, fatigue, dyspnea, dizziness or syncope
- Pacemaker function
Exercise Stress Test
- Measures heart’s response to exercise while a patient exercises following a specific protocol
- ECG
- Myocardial perfusion imaging (“nuclear stress test”)
- Echo
Chemical Stress Test
- Indications
- Unable to exercise
- Poor motivation
- Stimulates physiological state
- Medication supplied until 85% of age predicted max
- Dobutamine
- Adenosine
Intracardiac Electrophysiology Study (EPS)
- Internal ECG
- Detection and recording of timing and conduction of electrical impulses
- Induce arrhythmias and see where they originate
Myocardial Perfusion Imaging
•Scintigraphic studies (administration of a radionuclide tracer and imaging with a gamma camera)
Echocardiography
- Ideal for assessing structure and function
- Chamber size
- Wall thickness
- Function
- Ejection fraction
- Direction and velocity of blood flow
- Wall motion
- Stress test
- Valvular abnormalities
- Congenital abnormalities
- Pericardial effusion
Transesophageal Echocardiography
- Utilized to evaluate posterior structures
- Atria
- AV valves
- Portions of aorta
Computed Tomography (CT)
- Not the best for cardiac structures
- Myocardium, chambers, valves
- Very good for vessel imaging (aorta)
- Newer uses
- Calcium score (CCT) – no contrast
- Angiography (CCTA) – contrast
Cardiac MRI
- Previous limitations are being overcome and now becoming utilized on a more frequent basis
- Follow up to echo (valvular, congenital, wall)
- Morphology, function, perfusion, viability, vascular anatomy (MRA)
- Primary limitation is availability and need for authorization
Cardiac Catheterization & Angiography
- Cardiac catheterization and angiography, although invasive procedures, remain invaluable in the management of most patients with congenital and valvular heart disease, as well as coronary artery disease.
- Right heart catheterization allows measurement of right atrial, right ventricular, pulmonary artery and pulmonary capillary wedge pressures, oxygen saturation, and cardiac output.
- Left heart catheterization is performed to assess the cardiac valves and left ventricular function.
