12 lead ecg
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12 lead ecg






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12 lead ecg 12 lead ecg Presentation Transcript

  • 12 Lead ECG Heidi Whitman, ICP Paramedic
  • Role of the 12 Lead
  • Role of the 12 Lead
    • 12 Lead ecgs are a diagnostic test that help to identify pathologic conditions, particularly in acute coronary syndrome (ACS) and acute myocardial infarction (AMI)
    • Indicated in: arrhythmias, ACS symptoms, overdoses, strokes, pulmonary emboli
    • How many times have we seen an AMI where SOB is the only presenting symptom?!
  • Early and Often
    • Cardiac events are a changing process
    • Obtaining capture of ST segment elevation is important because it will speed time to thrombolysis once patient is in the ER
    • GTN treatment can mask the signs of infarction by reducing elevation
    • Our goal in EMS is to ensure the best outcome for our patients
    • This means becoming quick and proficient at performing 12 leads so that on-scene times still remain minimal
  • How it works
    • The leads record electrical activity and depolarization
    • The waveforms obtained from each lead vary depending on the location of the lead in relation to the wave of depolarization passing through the myocardium
    • As electricity passes through the heart, it creates small electrical forces called vectors. The mean of all these vectors is called the axis.
  • A picture of the heart
  • How it works
    • Limb leads measure along the frontal plane of the heart
    • Precordial leads, V1-V6, measure around the horizontal plane of the heart
  • Lead Placement
  • Lead Placement
    • Angle of Louis is where the second rib connects to the sternum
    • V1 and V2 are 4 th intercostal space, on the sternal border
    • V4 is midclavicular 5 th intercostal
    • V3 split the difference
    • V6 is midaxillary 5 th intercostal
    • V5 split the difference
    • V4R is midclavicular on the other side, remember to mark it on the ecg!
    • V7-V9 continue around the chest on the left side, mark it on the ecg!
  • Lead Placement
    • Do a right sided 12 lead when there are inferior changes and especially when lead 3 changes are greater than lead 2
    • Do a posterior 12 lead when there is ST depression in leads V1 and V2… (more on reciprocal changes later)
  • Let’s Practice!
  • Axis
    • The axis of the heart is the average direction of the heart’s electrical activity during ventricular depolarization
    • Myopathies can affect the axis and should increase the medic’s index of suspicion that something bad is happening
    • Causes of left axis deviation (LAD): AMI, LAHB (fascicle block), LBBB, LVH, WPW, ageing, mechanical shifts (pregnancy, ascites)
    • Causes of right axis deviation (RAD): AMI, RBBB, emphysema or other respiratory disorders
  • Axis
    • How to determine axis deviation: Look at leads 1 and aVf..
    • Are they positive or negative?
  • Waveforms The PR interval should be no longer than 0.20s, or 5 little squares. The length of the QRS should be shorter than 0.12s, or 3 little squares.
  • Q waves
    • Deep or long q waves are abnormal and bad
    • Abn q waves indicate that an AMI has happened in the past or is happening right now, but we can’t tell
    • Longer than 0.03s =Bad, or deeper than 1/3 the height of the R wave =Bad
  • R wave progression
    • R waves start in V1 as negative and gradually progress to positive deflection in V6, with the change happening in V3-V4
    • If R wave progression isn’t smooth, or doesn’t progress at all, then increase your index of suspicion that something is Bad!
  • ST segment
    • ST changes from baseline can indicate bad things for the heart
    • ST depression indicates ischemia
    • ST elevation indicates injury or infarct
    • Also beware the sloping ST segment
  • ST segment Gross elevation is often described as tombstoning, or a fireman’s hat
  • T waves
    • T waves should be rounded and upright, not tall, peaked or inverted
    • Inverted T waves don’t always mean something is wrong, but they shoud increase your index of suspicion of ischemia
  • Blocks
    • The heart contains conduction pathways of specialized cells, called fascicles, which transmit electrical impulses throughout the heart and depolarize the ventricles.
    • Fascicular blocks are different than those found in dysrhythmias, as those are blocks at or around the AV node
    • Bundle branch blocks (BBB’s) are not diagnoseable on a 3-lead rhythm strip
  • BBB
    • Bundle branches are bundles of fascicles
    • If cardiomyopathy occurs in the BB’s then these specialized cells are unable to quickly conduct impulses
    • Depolarization then occurs through regular ventricular cells which are much slower to conduct and stimulate the ventricles =wide QRS
  • BBB
    • If the QRS is 0.12s (3 little boxes) or longer =BBB
    • 0.11s does not equal a block!
    • Examine lead V1 and V6 to determine whether it is the right or left side; RBBB vs LBBB
  • RBBB
    • RBBB causes: MI, CAD, or lung disorders stressing the heart such as corpulmonale or PE, also rate-related RBBB
    • V1 changes: rabbit ears, tall R
    • V6 changes: slurred s wave
  • LBBB
    • LBBB causes: AMI, CHF, CAD
    • New LBBB=STEMI
    • Frequently will require a pacemaker
    • V1 changes: big broad complex with negative deflection
    • V6 changes: big broad complex like a PVC
  • BBB
    • The turn signal technique for figuring out if its RBBB or LBBB:
    Flick the lever to go Right, it pops up, like the tall R wave in an RBBB in V1 Flick the lever to go Left, it pops down, like the deep complex in LBBB in V1
  • AMI in BBB’s
    • Any new onset LBBB, call a STEMI
    • ST elevation in LBBB is normal, however ST elevation of 5mm or more in an old LBBB =STEMI
    • Be suspicious of new RBBB
    • There are no ST changes normally associated with RBBB so any elevation =STEMI
  • AMI
  • AMI
    • Initial goals of EMS: limit the size of infarction by decreasing cardiac workload and increasing oxygen supply to the myocardium
    • Rest, O2 as needed, ASA, GTN, iv fluid and pain relief prn
    • Long term goals for EMS: definitive care including expediting transport to hospital and decreasing amount of time to needle (thrombolysis), such as starting an IV, doing a 12 lead
  • SALLI S =septal, A =anterior, L =(low) lateral, L =(high) lateral, I =inferior Memorize this as an aid to locating AMI’s on the heart!
  • Coronary Arteries
    • The different areas of the heart are fed from certain arteries
    • The left ventricle is the main pump for the body, which is why an occlusion in the LAD is called the widowmaker
    • Because one artery can feed many areas, we rarely get an AMI isolated to one area. i.e. an anteroseptal MI with lateral extension
  • Reciprocal changes
    • Damage to the myocardium represented by ST elevation will be reflected as ST depression on the anatomically opposite side
    • Inferior leads are reciprocal to high laterals and anterior leads
    • Anterior leads are reciprocal to posterior leads
    • Look at reciprocal leads to help you confirm elevation
  • Septal MI Which leads are the septal leads?
  • Anterior MI What kind of block is this? LBBB or RBBB?
  • Lateral MI Where else is there involvement? Are there reciprocal changes?
  • Lateral MI Reciprocal changes? Is this high lateral or low lateral?
  • Inferior MI Do you think the depression in the precordial leads is reciprocal or ischemic? Which coronary artery can cause this much damage?
  • Right sided MI This good medic marked V4R on her 12 lead  What made this medic suspect right sided involvement?
  • Posterior MI What made this medic suspect posterior MI?
  • Ya, I feel that way too… don’t worry, we’re almost done!
  • Imposters: Pericarditis
    • Pericarditis can cause global ST elevation and PR interval depression.
    • S/S: sharp pn that hurts more leaning forward, hx of infection
  • Impostors: Early Repolarization
    • Early Repolarization is usually benign and symptomless
    • It is found in young skinny men
    • Note the distinctive notched J-point
  • Impostors: Hypothermia
    • Hypothermia will also cause a notched J-point
    • Careful moving the hypothermic patient as they can easily turn into VF from movement
  • Impostors: LVH
    • Left Ventricular Hypertrophy is usually caused by a lifetime of hypertension, so suspect cardiac problems
    • LVH can cause ST elevation and depression as a normal variant. Use the same criteria as LBBB for diagnosing an AMI, 5mm or more of elevation.
  • Impostors: Hyperkalemia
    • S/S: vague complaints, syncope, weakness
    • Suspect in kidney disorder pts, esp dialysis, also in adrenal disorders, or secondary to diuretics
    • The p-wave will flatten out and the t-waves will become tall and peaked. Eventually VT/VF likely.
  • Impostors: Digoxin toxicity
    • Digoxin is a drug commonly used to treat advanced CHF
    • It has a small therapeutic index meaning it is easy to OD
    • It can cause a depressed scooping ST segment, in addition to other cardiotoxic changes.
    • Patients with dig tox will describe seeing a “yellow haze”
  • All Done!! Time to do Bad things To our Arteries!!