Introduction to cardiovascular Diagnostic Testing

Question 1

Why do we order diagnostics?

Answer 1

• 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

Question 2

Categories / types of cardiovascular diagnostic studies

Answer 2

• Laboratory
• Radiology
• Electrocardiography / Electrophysiology

Question 3

What do you have to consider when determining what type of lab testing should be done?

Answer 3

• 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

Question 4

Describe the pre-test and post-test probability in relation to the Prevalence of CVD (Cardiovascular Disease) and the factor of age

Answer 4

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.

Question 5

What is the most prevalent tupe of Cardiovascular Disease?

Answer 5

Coronary Heart Disease (48%)

Question 6

Coronary Heart Disease

Answer 6

• 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

Question 7

Non-modifiable risk factors for CVD

Answer 7

• Age
• Gender
• Family History

Question 8

Modifiable risk factors for CVD

Answer 8

• High Blood cholesterol
• High Blood Pressure
• Physical inactivity
• Obesity and Overweight
• Smoking
• Diabetes

Question 9

Cholesterol

Answer 9

Essential substance required for synthesis of:

• Cell membranes
• Steroid hormones
• Multiple other compounds utilized in daily physiological processes

Question 10

Triglycerides

Answer 10

• 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

Question 11

Lipoproteins (VLDL, IDL, LDL, HDL)

Answer 11

• Lipid and protein structures
• Transport cholesterol and triglycerides

Question 12

Chylomicrons

Answer 12

-Transport dietary exogenous triglycerides (TG) and cholesterol from the intestines to the liver

Question 13

VLDL

Answer 13

• 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

Question 14

IDL

Answer 14

• intermediate density lipoprotein
• Transport TG & cholesterol within circulation

Question 15

LDL

Answer 15

• low density lipoprotein
• Transport TG & cholesterol within circulation
• Enriched with cholesterol
• Small enough to enter cells

Question 16

HDL

Answer 16

• 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”

Question 17

Total Cholesterol

Answer 17

HDL + VLDL + LDL

Question 18

Atherogenesis

Answer 18

• 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

Question 19

Hyperlipidemia - Laboratory Evaluation

Answer 19

• 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

Question 20

Friedewald equation

Answer 20

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

Question 21

Hyperlipidemia: Normal ranges for adults

Answer 21

• Total cholesterol < 200 mg/dl
• LDL cholesterol < 130 mg/dl
• HDL cholesterol > 40 mg/dl
• VLDL cholesterol < 30 mg/dl
• Triglycerides < 150 mg/dl

Question 22

Creatine Kinase (CK or CPK)

Answer 22

• 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%

Question 23

Myoglobin (MB)

Answer 23

• 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%

Question 24

cTroponin I & T

Answer 24

• 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

Question 25

B-type Natriuretic Peptide (BNP)

Answer 25

* 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

Question 26

High Sensitivity C-Reactive Protein | (hs-CRP)

Answer 26

* 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

Question 27

PT/INR

Answer 27

* 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.

Question 28

D-Dimer

Answer 28

* 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

Question 29

Electrocardiography (ECG)

Answer 29

* Disorders of rate and rhythm * Myocardial ischemia / injury * Electrolyte imbalances * Structural changes * Conduction disturbances

Question 30

Ambulatory Monitoring

Answer 30

* 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

Question 31

Exercise Stress Test

Answer 31

* Measures heart's response to exercise while a patient exercises following a specific protocol * ECG * Myocardial perfusion imaging (“nuclear stress test”) * Echo

Question 32

Chemical Stress Test

Answer 32

* Indications * Unable to exercise * Poor motivation * Stimulates physiological state * Medication supplied until 85% of age predicted max * Dobutamine * Adenosine

Question 33

Intracardiac Electrophysiology Study (EPS)

Answer 33

* Internal ECG * Detection and recording of timing and conduction of electrical impulses * Induce arrhythmias and see where they originate

Question 34

Myocardial Perfusion Imaging

Answer 34

•Scintigraphic studies (administration of a radionuclide tracer and imaging with a gamma camera)

Question 35

Echocardiography

Answer 35

* 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

Question 36

Transesophageal Echocardiography

Answer 36

* Utilized to evaluate posterior structures * Atria * AV valves * Portions of aorta

Question 37

Computed Tomography (CT)

Answer 37

* 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

Question 38

Cardiac MRI

Answer 38

* 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

Question 39

Cardiac Catheterization & Angiography

Answer 39

* 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.