Introduction To 12 Leads Flashcards
Time is critical, the sooner the patient gets to the catch lab, the higher their chances of survival. After what period of time does the benefit of the cath lab intervention diminishes signifanctly
10 hours however after 3 hours the chances of benefit significantly decreases
What is the difference between the 3 lead and 12 lead
3 lead primarily monitors the patients rate and rhythm but lacks precision to accurately capture electrical activity especially in the ST segment and T waves
12 lead uses a diagnostic mode which provides a more detailed picture of the hearts electrical activity
What is the frequency range of the 12 leads diagnostic quality?
0.5 - 150 hz
Why are 3 lead ECG only good for monitoring rate and rhythm and reduce the range of cardiac electrical activity displayed?
Because its set in monitoring mode, it filtered out artifact to give a clearer picture but this reduces the range of cardiac electrical activity displayed
What is frequency response?
This is the diagnostic modes ability to filter artifact and provide a clearer view of the QRS,ST, and T waveforms. This is the broader spectrum of cardiac electrical activity
What is the timing intervals for a 12 lead ECG?
The ECG captures 2.5 Seconds of data for each set of 3 leads totalling 10 seconds
What is the frequency range of monitoring quality ECGs?
0.5 to 20-50 Hz
What does the PR interval/segment represent?
The time from atrial depolarization to ventricular depolarization
What does the q wave represent?
- it represents ventricular septal depolarization
The Q wave travels in what direction electrically?
Left to right, posterior to anterior
What are the characteristics of physiological Q waves?
- less than 0.3 in duration
- less than 30% of the height of the following R wave
What are the characteristics of a pathological Q wave
- greater than 0.3 seconds in duration
- greater than 30% in length of the following r wave
What does the R wave represent?
- depolarization of the ventricles from right to left
From what plane does the Standard Limb leads and Augmented Limb leads view?
They view the electrical activity in the frontal/vertical plane
From what plane does the precordial leads (chest leads) view the heart?
The horizontal plane
What is the purpose of the right leg electrode/lead?
This lead is a grounding electrode. It does not measure any electrode activity but helps to reduce artifact
The limb leads are meant to be placed on the limbs, however you may place them on the torso as long as to space them out. How should they be placed on the torso?
10cm apart
What part of the heart does lead 1 view?
The high lateral surface of the left ventricle
What part of the heart does the lead 2 look at?
The inferior surface of the left ventricle
What portion of the heart does lead 3 look at?
It also looks at the inferior surface of the left ventricle but from a different angle than lead 2
What portion of the heart does aVR view
The atria and great vessels
What portion of the heart does aVL view?
The lateral wall of the heart
What portion of the heart does aVF view?
The inferior wall of the heart
What is the normal range for QRS electrical axis
-30 to +90 degrees
When does axis deviation occur?
It occurs when the hearts electrical current takes an abnormal path
What is left axis deviation? What is the range of QRS axis? And what does it indicate?
- hearts electrical current moves to the left
- <-30 degrees
- left ventricular hypertrophy
What is right axis deviation? What is the range for the QRS axis. And what does it indicate?
- electrical current shifts towards the right
- QRS axis is >+90 degrees
- right ventricular hypertrophy
What is extreme axis deviation (northwest axis)? What is the range of the QRS axis in this case?
- hearts energy flows in an opposite abnormal direction
- between -90 degrees and 180 degrees
Which leads must you look at for axis determination?
Lead 1 and aVF
What conditions are associated with right axis deviation (early rising creates wonderful productivity)
- emphysema
- right ventricular hypertrophy
- COPD
- WPW syndrome
- pulmonary embolism
What conditions are associated with left axis deviation (healthy actions lead to daily excellence)
- Hyperkalemia
- Acites
- Left atrial hypertrophy and left anterior fascicular block
- tumour (abdominal)
- diaphragmatic displacement and dextrocardia
- emphysema
What is dextrocardia
A condition where the heart is positioned on the right side of the chest rather than the left
