12 Leads Flashcards
Define J point
- junction between the end of the QRS complex and the beginning of the ST segment
- The point where the QRS stops and makes a sudden sharp change in direction
Define Ischemia and what it causes on the ECG
- lack of oxygen
- ST segment depression or T wave inversion
Define Injury in the context of a 12 lead
Prolonged Ischemia
ST segment elevation
Define Infarct in the context of a 12 lead
Prolonged injury results in death of tissue
May or may not see Q wave
What is the purpose of a 4 lead?
desgined to provide information needed to determine rate and underlying rhythm
designed to filter out artifact
What is the purpose of the 12 lead?
Designed to reproduce QRS, ST and T waveforms accurately
Designed to look more broadly at electrical activity
May result in greater artifact
Define Frequency Response
Term used to describe the breadth if the electrical spectrum viewed by the ECG monitor
What is the frequency response of a diagnostic quality ECG?
0.05 Hz to 150 Hz
What is the frequency response of a monitor quality ECG
0.5 Hz - 20-50 Hz
4 things that can influence the accuracy of an ECG
- lead placement
- frequency response
- calibration
- paper speed
Where do you place leads V1-V6
V1 - 4th ICS right of the sternum
V2 - 4th ICS, left of the sternum
V3 - Directly between leads V2 and V4
V4 - 5th ICS, left mid clavicular line
V5 - Level with V4 left axillary line
V6 - level with V5 at the left mid-axillary line
If the AVR lead is upright, what might be the cause?
Limbs leads are reversed
How many mm of elevation do you need in leads V1-V3 for it be classified as a STEMI?
2mm
How many mm of elevation does it need to be a STEMI in all leads except V1-V3?
1mm (one small box)
In order to qualify as an OMI there needs to ST elevation in how many leads?
2 anatomically continous
Define consectuive leads
- leads that look at the same portion of the heart (2, 3, aVF)
- Number continuously (V1,V2,V3,V4,V5.V6)
What does the right coronary artery supply?
- right ventricle
- inferior wall of LV
- SA and AV node
Posterior Descending Artery supplies
Posterior wall of left ventricle
Inferior wall of Right Ventricle
What does the left main coronary artery supply?
Extensive anterior
What does the left circumflex artery supply?
Lateral
Inferior (20%)
What does the left anterior descending artery supply?
Aneroseptal
What type of MI is known as a widowmaker?
Anterior MI
What leads would you see elevation in in a widow maker MI?
Septal, Anterior, and lateral leads
What are some common complications of a widowmaker MI?
Left Ventricular failure, CHF/Pulmonary edema, cardiogenic shock
Earliest sign of OMI?
Hyperacute T waves
- Tall and peaked within minutes of blood flow interruption
Does a normal 12 lead rule out an OMI?
No, the pt may be having an N-STEMI and requires blood work
What is happening in the ventricles during a bundle branch block?
The ventricles are out of sync
What are some causes of a BBB?
acute ischemia, or secondary to HTN or heart disease
Key identifiers of BBB
Wide QRS (greater than 120ms)
Pitching
Must have a P wave
Key identifiers of a LBBB
Long QRSn (greater than 120ms)
Dominant S wave in V1
Broad Monophasic R wave in lateral leads
Absence of q waves in lateral leads
What are causes of LVH?
HTN - most common
mitral or aortic stenosis
Hypertropic cardiomyopathy
What is the biggest sign of LVH on a 12 lead?
There will be massive increase in voltages
Diagnostic Criteria for LVH (Sokolov-Lyon Criteria)
S wave depth in V1+tallest R wave height in V5-V6 is greater than 35mm
Signs and Symptoms of Pericarditis
Chest pain, dyspnea, tachycardia, fever, weakness, chills,
Made worse by lying flat, twisting
Made better by leaning forward
Worse on inhalation
Pain can last for hours-days
What would a 12 lead look like from someone who has pericarditis
Widespread ST elevation
Sinus Tachycardia as well
Would someone who has pericarditis respond to NTG administration?
No
In what population does BER usually occur?
Young, healthy peaople under 50 years old
In a patient who has BER what would you see on the 12 lead?
- Widespread concave ST elevation, most prominent inferior and precordial leads
- notching or slurring at the J point
- St elevation is usually greater than 2mm in the precordial leads
- No reciprocal ST depression to suggest STEMI
If you see ST elevation in leads 2, 3, aVF? what vessel is likely occluded?
Right Coronary Artery
If you see ST elevation in leads 1 and AVL, what vessel is likely occluded
Left Circumflex and possibly right coronary artery
What vessels are likely occluded if there is ST elevation in leads V1-V4
Left anterior descending
What vessel is likely occluded if you see elevation in leads V5 and V6
Left Circumflex Artery
What are tombstone characteristics?
- absent R wave or less than 0.04sec on duration
- ST segment convx upward merging with ascending (upward limb of QRS
- Peak of ST higher than the R wave
- ST segment merging with ascending limb of T wave
What does PAILS mean in the context of reciprocal changes in STEMIs.
- If you see elevation in POSTERIOR leads you may see depression Anterior
- If you see elevation in ANTERIOR leads you may see depression Inferior
- If you see elevation in INFERIOR leads you may see depression lateral
- If you see elevation in LATERAL leads you may see depression septal
- If you see elevation in SEPTAL leads you may see depression Posterior
When would do a modified 15 lead be warranted?
- when a pt has an inferior STEMI
- or Reciprocal changes with ST depression in V1-V4
Why would you do a 15 lead?
Can confirm a posterior MI (usually associated with an Inferior MI)
Can confirm RVI which is a larger and more complicated Inferior MI
What vessel is likely occluded in a RVI?
RCA and left circumflex
Does the presence of a inferior wall MI mean that there is right ventricular involvement or vice versa?
No, but approximately half of inferior wall MI have RVI
What is the RVI Triad?
- Jugular Vein Distension
- Hypotension
- Clear lung sounds
