Cardiac Assessment: Part 2

What examples of minor, historical, and POC markers?

• AST and 2-hydroxybutyrate dehydrogenase

• Marker history

• Triage cardiac panel

Describe AST and 2-hydroxybuyterate dehydrogenase.

• nonspecific and, with LD, are no longer recommended for routine MI diagnosis

What is the history of Markers?

• CK/LD isoenzymes (1975)

• automated CK-MD activity and LD-1 (1980)

• CK-MB isoforms (1985)

• CK-MB immunoassay (1989)

• troponin T (1991)

• Troponin I (1992)

What are Triage Cardiac Panel (biosite)?

• historical POC fluorescence immunoassay that measured myoglobin, CK-MB, and troponin I together in 15 min

• POC should give quantitative result and not all meet high sensitivity criteria

What is heart failure?

• clinical syndrome caused by a structural / functional cardiac abnormality that impairs ventricular filling, ejection, or both

• develops gradually

  • necrosis markers (CK-MB, troponin) are NOT useful tools

What can heart failure cause?

• shortness of breath

• fatigue

• exercise intolerance

• fluid retention

What markers are used for heart failure?

• BNP

• NT-proBNP

What are the different classes of heart failure by ejection fraction?

• HFrEF (reduced)

• HFmrEF (mildly reduced)

• HFpEF (preserved)

describe HFrEF

• reduced

• LVEF 40% or less

• impaired contraction reduces forward flow (systolic failure)

describe HFmrEF

• mildly reduced

• LVEF 41-49% with evidence of increased filling pressures

Describe HFpEF

• preserved

• LVEF 50% or greater with increased filling pressures

• impaired relaxation / stiffness limits filling

• (diastolic failure)

What is the function of Natiuretic peptides?

• polypeptide hormones that increase natriuresis and diuresis

• promote vasodilation

• suppress renin-angiotensin-aldosteronsystem

• reduce cardiac load

What are the forms of Natriuretic Peptides?

• ANP: mainly the atria

• BNP: mainly ventricles

  • in response to myocardial wall stress/ increased filling pressure

• CNP: mainly vascular endothelium / central nervous system

What is the structure of Natriuretic peptides?

• pro-BNP (108 amino acids) is cleaved into active 32-aa BNP and inactive 76-aa N terminal fragment (NT-proBNP)

What method is used for interpreting BNP / NT-proBNP?

• immunoassay

What unit is used for interpreting BNP / NT-proBNP?

• nanograms per litre (ng/L = pg/ml)

What BNP specimen is used for interpreting BNP?

• EDTA whole blood

• plasma in PLASTIC tubes

What NT-proBNP specimen is used for interpreting NT-proBNP?

• more robust

• heparinized (green top) plasma

What POC method is used for interpreting BNP / NT-proBNP?

• triage BNP: whole blood / EDTA plasma

• 15 min fluorescence immunoassay

What is a low value of BNP/ NT-proBNP mean?

• strongly argues against heart failure

What is a high value of BNP/ NT-proBNP mean?

• suggests heart failure BUT does not prove it

  • breathlessness has many causes

  • interpret with clinical exam and imaging

What can increase BNP/ NT-proBNP

• increased age

• kidney dystfunction

• atrial fibrilation

What can decrease BNP/ NT-proBNP

• obesity

If someone is < 75 years old, what is the normal What can increase NT-proBNP?

• approx 125 pg/mL

If someone is > 75 years old, what is the normal What can increase NT-proBNP?

• 450 pg/mL

What does it mean if triage BNP is below 100 pg/mL?

• acute heart failure is less likely in emergency situations

What analytes can measure longterm cardiovascular sisks?

• LDL / HDL cholesterol

• triglycerides

• Lp(a)

• hs-CRP

• homocysteine

What are C-reactice proteins (CRP/ hs-CRP)?

• acute phase protein made primarily by the liver that can increase with inflammation

  • atherosclerosis is an inflammatory process

what does it mean if CRP is < 1.0 mg/L?

• lower risk

what does it mean if CRP is 1.0 -3.0 mg/L?

• average risk

what does it mean if CRP is > 3.0 mg/L?

• higher risk

What does it mean if hs-CRP is 2.0 mg/L or greater

• means a risk enhancing factor in cholesterol management guidelines

What can increase CRP?

• infection

• injury

• surgery

What should happen if you see CRP is elevated?

• prompt evaluation for infection or inflammation and should not be used for risk classification until acute condition resolves

What is homocysteine?

• sulfur containing amino acid formed during methionine metabolism

What can cause an increase in homocysteine?

• folate, B12, or B6 deficiency

• kidney dysfunction

• hypothyroidism

• medications

• genetic variants

What diseases are associated with elevated homocysteine?

• cardiovascular and thrombotic disease

  • BUT a direct causal role has not been established

  • routine homocysteine screening is NOT recommended for general cardiovascular risk assessment

What drugs can treat cardiac disease?

• lidocaine

• quinidine

• proainamide

• digoxin

What drug has a very narrow therapeutic index?

• Digoxin

Describe Digoxin?

• very narrow therapeutic index

• blood concentration needs closet monitoring of the cardiac drugs

What marker is the most specific, and skeletal muscle does NOT raise it?

• Troponin I

What is the first choice marker that works any time 3h-9 days?

• Troponin I

What marker may be falsely raised in dystrophy, ESRD?

• Troponin T

What marker is the first choice from any time 3 h - 14 days?

• Troponin T

What marker is nonspecific and is raised by any muscle injury?

• myoglobin

What is a historical early marker (1-4 hr)

• myoglobin

What marker is total CK not specific, and skeletal muscle raises it?

• CK-MB

What marker is historical, and involved with early/re-infaction?

• CK-MB

What marker does hemolysis cause false elevation?

• LD-1

What marker is historical (late presenters)?

• LD-1

What marker has age-dependent cutoffs, and rule-out is its strength?

• BNP / NT-proBNP

What marker is associated with heart failure?

• BNP / NT-proBNP

What marker is not for diagnosis/prognosis of acute MI and is used for long-term risk estimentation?

• hs-CRP , homocysteine

What marker is IMA sensitive, not highly specific, and is best for when Ischemia before necrosis?

• Lactate, IMA (ACB test)

Injury vs. MI

• troponin rise = myocardial injury

• MI

  • needs rise/fall + clinical ischemia

Angina vs. MI

• angina

  • no necrosis

  • troponin normal

• MI

  • kills cell

  • troponin increases

cTnI vs. cTnT

• cTnI

  • more specific (never skeletal)

• CTnT

  • can be falsely raised in dystrophy and ESDR

BNP vs NT-proBNP

• BNP

  • acite 32-aa peptide

• NT-proBNP

  • inactive 76-aa N-terminal fragment

Total CK vs. CK-MB

• total CK

  • sensitive / not specific

• MB

  • fraction points to the heart

ECG

• specific but ONLY 50% sensitive

• the reason marker exist

Troponin timing specifics

• if any item pins an exact rise time, note that hs-assays detect within 1-3 hrs and exact times are assay specific