Cardiovascular-Specific Labs

Question 1

Troponin I (cTnI) and T (cTnT)

Answer 1

two biomarkers that are sensitive, specific indicators to the myocardium of the heart

released when cardiac injury occurs (6 hours after insult to 3 days)

greatest use for diagnosing a myocardial infarction (> 0.10 ng/mL)

Newer highly-sensitive assays can detecting circulating troponin in healthy “normal” individuals at levels as low as (N < 0.03 ng/mL) in their blood

Question 2

troponin may also be elevated in other situations in which there is stress to the heart but not in the setting of myocardial infarction:

Answer 2

rhabdomyolysis with cardiac damage

renal failure

inflammatory disease (myocarditis or endocarditis)

hypertrophic cardiomyopathy
drug toxicity
critical illness
congestive heart failure
cardiac surgery (ablation, defibrillation, and cardioversion)

large body-surface-area burns aortic valve disease

aortic dissection
pulmonary embolism
pulmonary hypertension
COPD
blunt thoracic damage

acute neurologic disease (stroke or subarachnoid hemorrhage)

Question 3

B-Type Natriuretic Peptide (BNP)

Answer 3

strongest independent predictor of congestive heart failure (CHF), with an odds ratio of 29.60

Question 4

BNP <100 pg/mL

Answer 4

Indicates no heart failure

Question 5

BNP 100–300 pg/mL

Answer 5

Class I – Cardiac disease, but no symptoms and no limitation in ordinary physical activity (i.e. no shortness of breath when walking, climbing stairs, etc.).

Symptoms-based approach when determining appropriateness for activity.

Question 6

BNP > 300 pg/mL

Answer 6

Class II – Mild symptoms (mild shortness of breath and/or angina) and slight limitation during ordinary activity.

Symptoms-based approach when determining appropriateness for activity

Question 7

BNP > 600 pg/mL

Answer 7

Class III – Marked limitation in activity due to symptoms, even during less-than-ordinary activity (i.e. walking short distances [20–100 m]). Comfortable only at rest.

Symptoms-based approach when determining appropriateness for activity

Question 8

BNP > 900 pg/m

Answer 8

Class IV – Severe limitations. Experiences symptoms even while at rest.

Symptoms-based approach when determining appropriateness for activity

Question 9

The following confounding factors can contribute to an elevated BNP:

Answer 9

gender (females have higher levels)

race (African-American and Hispanic subjects have higher levels than Caucasians)

anemia

atrial fibrillation

Obesity is associated with lower BNP levels

Question 10

Creatinine Kinase (CK) =

Answer 10

is an isoenzyme that is released into the blood when skeletal, brain, or cardiac muscle is injured

Question 11

Creatinine Kinase (CK) norms =

Answer 11

Normal = 30-170 U/L Adult

Males: 52-336 U/L Adult

Females: 38-176 U/L

Question 12

CK1-BB brain tissue

Answer 12

Rarely present, but described as a marker for adenocarcinoma of the prostate, breast, ovary, colon, gastrointestinal tract, and for small-cell anaplastic carcinoma of lung

BB has been reported with severe shock and/or hypothermia, infarction of bowel, brain injury, and stroke

Question 13

CK2-MB cardiac muscle

Answer 13

Commonly elevated in myocardial infarction within 3-6 hours of cardiac injury and then returns to normal within 2-3 days (peaks 18-24 hours).

Useful for diagnosing re-infarction.

Might be elevated in cases of carbon monoxide poisoning, pulmonary embolism, hypothyroidism, crush injuries, and muscular dystrophy.

Sensitivity and specificity are not as high as troponin levels.

Question 14

CK3-MM skeletal muscle

Answer 14

Can have an increase following strenuous exercise, but not considered rhabdomyolysis.

Intramuscular injection can increase