Blood Testing

PCL 2 TASK – Blood Tests & Relevant components
"Nondetectable TN levels in asymptomatic patients at admission and within the first 6 hours after admission can rule out relevant myocardial injury.”
When a patient presents to Emergency with chest pain, generally the first test ordered is a blood test. This is because it is
- Relatively affordable
- Easy to administer
- Convenient
- Results are readily available
Importantly, treatment should commence before results are available.
Components obtained should include –
- Full blood count
- Serum electrolytes
- Glucose
- Lipid profile
Certain components identified in a blood test can indicate the source of a patients chest pain –
- Cardiac Troponin
o Serum troponin level testing is routine in those presenting with cardiopulmonary complaints
o Results within 24 hours
o A marker of cardiac damage from any cause
o Elevated Troponin levels are typically related to cardiac damge –
 defining in the diagnosis of acute myocardial infarction
 However, it is not pathognomonic for acute coronary syndrome
o Cardiac Troponin is a regulatory protein and is found in striated (skeletal and cardiac) muscle
o It has 3 subunits
 TN-T
 TN-I
 TN-C
TN-C is found in smooth muscle and as such is the least cardiac-specific. Because of this, it is TN-T and TN-I that are tested for in suspected cardiac episodes.
TN-I is the most cardiac-specific as it has not been found in skeletal muscle
TN-T may be indicative of renal damage
DISEASE TROPONIN LEVELS
ACS TN increase
- Indicative of adverse cardiac events
- Should prompt more aggressive treatment
Congestive Heart Failure TN elevations
- High risk patients with poor short term prognosis
- Also associated with increased risk of ventricular dysrhythmias
Myocarditis and Pericarditis TN elevations
- Useful in identifying myocyte necrosis (myocytisis)
- May also be present in pericarditis
While TN levels do not correlate with patient prognosis, there is some correlation between elevated TN and 1-month duration of heart failure symptoms
Cardiac Trauma - Patients with TN elevations have a higher risk of cardiac dysrhythmias and LV dysfunction
- Interestingly, TN level is not related to a patients prognosis
Cardiotoxins - Snakebite can cause acute MI or vasospasm  elevated TN levels
- This is as the venom has a direct myocardial effect
Tachycardia - Severe tachycardia can induce TN elevations
- This is due to increased myocardial oxygen demand and decreased supply
Chronic Obstructive Pulmonary Disease - Severe exacerbations are associated with right ventricular strain  thus produce TN (as below)
- Another option is that patients may have concurrent acute MI or PE, and thus have elevated TN
- TN elevations correlate with severity of COPD
Pulmonary embolism - TN elevations predict complications and mortality
- The proposed reason for TN release is  large PEs induce acute right ventricular pressure overload  causes increased wall tension  regional wall ischemia

- CKMB
o Results in 2 hours
o
- Haemoglobin
o Results in 2 hours
http://www.medscape.com/viewarticle/582721
Kumar & Clarke
http://www.sydpath.stvincents.com.au/spec_db/

Gah it looked much prettier in word!
Will try and improve this this afternoon
thanks everyone, and apologies for the lateness!

georgia