Cardiac Markers

What are four types of Cardiovascular disease?

1. Coronary Heart Disease (heart attack)

1. Cerebrovascular Disease (stroke)

2. Peripheral Artery Disease (localized pain in extremities)

3. Aortic atherosclerotic disease (aneurysms)

What is CRP, where is it synthesized, and what is it an indicator of?

1. Acute Phase Reactant

2. Liver

3. Inflammatory state

Is CRP used to assess CVD risk?

No

What is the normal CVD level?

< 10 mg/L

What form of CRP is used to evaluate CVD risk? What does it measure?

1. High sensitivity CRP (hs-CRP)

2. CRP levels at lower analytical sensitivity level

What level of hs-CRP is considered low risk? What is moderate risk? What is high risk?

1. Low: < 1 mg/L

2. Moderate: 1-3 mg/L

3. High: > 3 mg/L

What is regular CRP used to detect?

Sepsis

What is the main cause of hospitalization for elderly patients?

Congestive Heart Failure

What is congestive heart failure?

Decreased cardiac output and excess fluid retention in lungs

What are risk factors for Congestive Heart Failure?

1. Prior MI

2. Hypertension

How easy is it to diagnose congestive heart failure? What are two methods used to diagnose it?

1. Difficult

2. Echocardiogram & physical symptoms

Two signs and symptoms of Congestive Heart Failure?

1. Dyspnea

2. Edema

What is B-Type Natriuretic Peptide?

A cardiac hormone secreted by the ventricles when the heart wall stretches

In what conditions is B-Type Natriuretic Peptide increased in?

1. CHF: Cardiac volume and pressure increases

2. Myocardial ischemia w/o necrosis

3. Heart valve disease, atrial fibrillation, and renal failure.

How is B-Type Natriuretic Peptide used in CHF diagnosis?

It’s used to confirm diagnosis but is not appropriate for routine screening for ambulatory patients

What is NT-proBNP?

The N-terminus of the prohormone

In what kind of tube should BNP be collected and why?

Plastic, because BNP loses immunoreactivity in glass tubes.

What is Coronary Heart Disease?

Progressive, chronic inflammatory disorder of the coronary arteries

What causes the inflammation in Coronary Heart Disease?

1. Endothelial Damage

2. Development of plaque

3. Destabilization of protective plaque cap

What is Acute Coronary Syndrome?

A spectrum of conditions and acute symptoms resulting from decreased blood to the heart (CVD)

What is unstable angina?

Unstable plaque rupture, thromboses, and arterial occlusion

Three steps involved in myocardial infarction

1. Occlusion decreases blood flow

2. Tissue necrosis

3. Myocardial infarction

Physical Symptoms of ACS

1. Angina (chest pain upon exertion)

2. Myocardial infarction

Symptoms of myocardial infarction

1. Painful pressure in chest often radiating to arms, throat, and back

2. Perspiration

3. Indigestion

4. Weakness, numbness in arms or legs

What is the WHO criteria for diagnosing AMI?

Patient must exhibit two out of three:

1. Clinical symptomology

2. Characteristic ECG changes

3. Risk of cardiac markers

What is the most common cause of malpractice lawsuits against ED physicians?

Inappropriate discharge from ED of patients with AMI

How does AMI influence ECG?

Damage creates an area which is electrically inert

How many patients get diagnosed with AMI due to an initial ECG?

50%

What causes the ECG to change?

Ischemia, injury, or death of myocardial cells.

What cardiac markers are increased during MI?

1. Myoglobin

2. CK-MB

3. Troponin I and T

4. Myeloperoxidase

5. CK, AST, LDH

Which of the increased cardiac markers lacks specificity?

Total CK, AST, LDH

Why is Myeloperoxidase increased during AMI?

Inflammation causes WBC to release this

What are the most popular Cardiac Markers?

1. CK-MB

2. Troponin T and I

What are six characteristics of an ideal cardiac marker?

1. Cardiac specific

2. Rises soon after MI

3. Stays increased for several days

4. Easy to assay, stat capacity

5. Is correlated with patient outcomes

6. Testing available 24 hours/day

How would a cardiac marker influence patient outcomes?

1. Risk assessment

2. Detects reinfarction

3. Assesses success of reperfusion treatment

What is myoglobin?

An oxygen binding protein in cardiac and skeletal muscle

How soon after an MI will myoglobin increase?

Within an hour

When will myoglobin return to normal?

12-24 hours

How can myoglobin be useful?

Useful as a marker for reinfarction early after initial event.

What does CK-MB do and how soon does it rise after reinfarction?

1. It catalyzes reaction for energy storage in the muscle

2. Rises 3-4 hours post MI

When does CK-MB return to normal?

Falls to normal 48-72 hours

How is CK-MB affected if there is a delay in medical treatment?

It will be normal

What is the magnitude of CK-MB increase related to?

The infarction size

How is CK-MB tested?

Mass immunoassay

What is a pro and con of CK-MB?

1. Pro: Sensitive

2. Con: Not specific

What other medical condition can cause an increase in CK-MB?

Muscle trauma

What is troponin, where is it found, and what does it do?

1. Complex of three structural proteins

2. Cardiac and skeletal muscle

3. Transmits calcium signal that triggers contractions

What causes an increased concentration of troponin?

Recurrent ischemic events

What condition that causes an increased troponin concentration has a poorer outcome?

Angioplasty

What is associated with an increased troponin concentration?

An increased risk of death

Is troponin better or worse than CK-MB?

Better, because it’s less influenced by skeletal muscle trauma and is more cardiac specific

How soon does troponin increase after MI, when does it peak, and how long does it remain elevated?

1. 3-12 hours after injury

2. Peak 12-24 hours

3. Remain elevated for over 1 week

How long will Troponin T remain elevated?

8-21 days

How long will Troponin I remain elevated?

7-14 days

What is the sensitivity of troponin?

2.5 ng/L

What is the procedure for serial troponin sampling?

1. See trend go up or down in Tn to differentiate between acute and chronic heart disease

2. At least one value > 99th percentile of normal reference value

3. 0, 3, 6, 9 hours after sampling

4. Run along with ECG

5. Evaluate symptoms

What are three limitations of troponin?

1. Not as clinically sensitive as CK-MB in early detection of MI

2. Can’t detect reinfarction because it’s elevated for so long

3. Hemolysis can yield false decrease or increase depending upon assay.

What is the turn-around time of Cardiac biomarkers?

< 60 minutes

Is the TAT achieved by most hospital labs? What should be considered?

1. No

2. POC devices

The CV at elevated concentrations should be what?

< 10%

What is a pulmonary embolism?

A circulating mass that lodges in pulmonary arteries and blocks pulmonary circulation

Where does 95% of pulmonary emoblisms come from?

Lower extremities

Symptoms of pulmonary embolism?

1. Chest pain

2. Dyspnea

3. Tachycardia

4. Tachypnea

5. Coughing

What condition is hard to distinguish from a Pulmonary Embolism? What test is used to differentiate between the two?

1. ACS

2. D-dimer by latex agglutination

What is the D-dimer used for, and what is a pro and con of it?

1. Used to rule out PE vs. diagnosing

2. High sensitivity, low specificity

What other conditions can cause an increased D-dimer?

1. Cancer

2. Recent surgery

3. Kidney disease