Cardiovascular Laboratory Medicine

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Cardiovascular Laboratory Medicine

• Brenda Beckett, PA-C

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Specimen Collection

• Fasting
• nothing to eat or drink for 10-12 hours
• can have H2O and medication

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Specific Tests to System

• - Screening tests Lipids, CRP, Homocysteine
• - Identifying disease BNP, cardiac enzymes

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CV Screening Tests-Lipids

• FASTING SPECIMEN
• Total Cholesterol
• HDL
• Triglycerides
• LDL - calculated or direct

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Newest Guidelines

• Third Report of the National Cholesterol
  Education Program (NCEP) Expert Panel on
  Detection, Evaluation, and Treatment of High
  Blood Cholesterol in Adults (Adult Treatment
  Panel III), or ATP III

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Screening

• Can screen with Total Cholesterol, if gt200,
  perform complete lipid profile
• Screening should be performed on adults every 5
  years
• Normal Ranges are not determined as other lab
  tests - national standard

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Total Cholesterol Levels

• lt 200 mg/dl
• 200-239 mg/dl
• gt 240 mg/dl

• Desirable, low risk for heart disease
• Borderline high
• High Cholesterol. In this range, a person has
  twice the risk of heart disease as person with
  lt200 mg/dl

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HDL-Cholesterol Levels

• lt 40 mg/dl
• 40-59 mg/dl
• gt60 mg/dl

• A major risk factor for heart disease
• The higher the HDL, the better
• Considered protective against heart disease

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LDL-Cholesterol Levels

• lt 100 mg/dl
• 100-129 mg/dl
• 130-159 mg/dl
• 160-189 mg/dl
• gt190 mg/dl

• Optimal
• Near Optimal/ Above Optimal
• Borderline High
• High
• Very High

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LDL-Cholesterol Levels

• Target levels of LDL are adjusted if someone has
  existing risk factors for cardiovascular disease.
• Tables, p 118 Wallach

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Triglyceride Levels

• lt 150 mg/dl
• 150-199 mg/dl
• 200-499 mg/dl
• gt500 mg/dl

• Normal
• Borderline High
• High
• Very high

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Determining CV Risk

• Identify presence of clinical atherosclerotic
  disease that confers high risk for coronary heart
  disease (CHD) events (CHD risk equivalent)
• Clinical CHD
• Symptomatic carotid artery disease
• Peripheral arterial disease
• Abdominal aortic aneurysm
• Note Diabetes is regarded as a CHD risk
  equivalent.

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Determining CV Risk, cont

• Determine presence of major risk factors (other
  than LDL)
• Cigarette smoking
• Hypertension (BP 140/90 mmHg or on
  antihypertensive medication)
• Low HDL cholesterol (lt40 mg/dl) HDL gt60 counts
  as a "negative" risk factor and removes one risk
  factor from count.
• Family history of premature CHD (CHD in male
  first degree relative lt55 years CHD in female
  first degree relative lt65 years)
• Age (men 45 years women 55 years)

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Determining CV Risk, cont

• Determine risk category
• Establish LDL goal of therapy
• Determine need for therapeutic lifestyle changes
  (TLC)
• Determine level for drug consideration

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Determining CV Risk, cont

• LDL Cholesterol Goals for TLC and Drug Therapy in
  Risk Categories
• CHD risk equivalent lt100 mg/dl
• 2 risks lt130 mg/dl
• 0-1 risk lt160 mg/dl

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Determining CV Risk, cont

• Initiate therapeutic lifestyle changes (TLC) if
  LDL is above goal.
• Diet, weight management, physical activity.
• Consider adding drug therapy if LDL continues to
  exceed goal.
• http//www.nhlbi.nih.gov/guidelines/cholesterol/at
  glance.htm

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Other Screening Tests

• Homocysteine
• Amino acid in the blood.
• Increased homocysteine related to increased risk
  of coronary heart disease, stroke and peripheral
  vascular disease.
• Strongly influenced by diet - folic acid and
  vitamins B6 and B12 as well as by genetic factors

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Other Screening Tests

• CRP (Cardio or ultrasensitive)
• Traditionally used to diagnose and monitor acute
  inflammatory states
• Mild CRP elevation (within the normal,
  non-acute-phase range) has recently emerged as a
  valuable marker of cardiovascular risk.
• Measured twice, 2 weeks apart.

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Diagnosis of AMI

• A number of laboratory tests are available.
• None is completely sensitive and specific for
  MI, particularly in the hours following onset of
  symptoms.
• Timing is important, as are correlation with
  patient symptoms, ECGs, and angiographic studies.

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Diagnosis of AMI

• CK, Total (Creatine Kinase) Simple, quick test.
  Not specific for MI. Three fractions MM
  (skeletal muscle), MB (cardiac muscle), BB (brain
  tissue).
• CKMB Specific for cardiac injury. Rises 2-8 hrs
  after injury, returns to normal in 2-3 days.
  Serial testing every 4 hrs can provide a pattern.

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Diagnosis of AMI

• CKMB isoforms
• 1 and 2. Performed by electrophoresis.
• Ratio of 2 to 1 can determine early cardiac
  injury.
• Labor intensive and not routinely used.

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Diagnosis of AMI

• Troponins I and T Structural components of
  cardiac muscle. Released with injury. More
  specific than CKMB.
• Rise within 3-12 hours, remain elevated for up to
  2 weeks. Difficult to diagnose reinfarction,
  helpful with old MI.

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Diagnosis of AMI

• Myoglobin Protein in skeletal and cardiac
  muscle. Sensitive but not specific. Rises early
• LDH Not used routinely. Need to measure
  isoenzymes.

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On the horizon

• h-FABP Heart Fatty-Acid Binding Protein
• Early detection (as early as 20 min)
• Small cytosolic protein abundant in the heart
• Detects MI and reperfusion
• Renal clearance in few hours

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Diagnosis of AMI - ACC guidelines

• Typical rise and fall of biochemical markers
  (CKMB and Troponin) and at least one of the
  following
• Ischemic symptoms
• New pathological Q waves on ECG
• Ischemic ECG changes (ST elevation or depression)
• Coronary artery intervention

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Case Study 1

• 30 yo male, admitted with CC of severe squeezing
  pain, lasted 10 min. Began after dinner. Radiated
  to L shoulder and jaw, assoc with palpitations,
  SOB. Similar episode 1 mo ago. Smokes 2ppd
  cigarettes.
• FH grandfather, father, sister all died from
  heart attacks at early age.

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Case Study 1

• PE Pale, restless young man in severe distress
  due to 8/10 chest pain. Pain subsided after given
  nitro. BP 140/85, HR 90, RR 17, T 98F. Physical
  exam unremarkable.
• ECG Elevated ST segments in precordial leads.
• Differential Diagnosis?

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Case Study 1

• What labs to order to confirm diagnosis?

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Case Study 1

• What further testing do you want to order?

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Case Study 1

• Diagnosis?

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CHF

• BNP -B-type (brain) natriuretic peptide
• Useful for diagnosing CHF, predicting morbidity
  and mortality, and maximizing therapy in these
  patients
• First isolated from brain tissue, but is
  synthesized primarily in the ventricles of the
  heart.
• NT-proBNP (isomer of BNP) testing has the same
  clinical utility as BNP

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BNP

• Increases glomerular filtration rate
• Decreases sodium retention, and inhibits renin
  and aldosterone secretion.
• Marker of cardiac dysfunction that correlates
  with the severity of symptomatic and asymptomatic
  left ventricular hypertrophy and CHF

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CHF

• Other laboratory findings in CHF
• Anemia
• Renal function tests may have prerenal azotemia
• Lytes hypokalemia, hyperkalemia, hyponatremia

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Bacterial Endocarditis

• Blood culture Proper collection, multiple
  collections
• Pathogens Strep viridans, S. aureus, Strep
  pneumoniae, enterococcus.
• IV drug abusers S. aureus

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Hypertension

• In primary hypertension, lab results can be
  normal.
• Abnormalities may include
• UA hematuria, proteinuria, casts
• Lytes potassium abnormalities
• FBS screen for diabetes, metabolic syndrome.
• Lipids screen for atherosclerosis risk

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Other Lab tests

• PT - Prothrombin Time
• Includes INR - International Normalized Ratio
• Used to monitor Coumadin therapy
• PTT - Partial Thromboplastin Time
• Used to monitor Heparin therapy (not used with
  LMWH)

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Case Study 2

• 47yo female admitted with cc of increasing SOB
  and fatigue. Past medical hx cardiac
  arrhythmias, heavy alcohol consumption for many
  years and 40 pack year smoking history.

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Case Study 2

• PE AO, BP 100/65, HR 96, T 97.5F, RR 23.
• Exam of neck showed distended jugular veins.
  Abdomen protuberant abdomen with ascites. Liver
  and spleen not palpable. Pitting edema of LE.

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Case Study 2

• ECG Sinus tachycardia and non-specific S-T
  segment changes.
• CXR No pulmonary infiltrates, no masses.
  Enlarged heart.
• Labs?