.

    Approach to EKGs

    • Rate
      • 300/distance
    • Rhythm
      • Regular/Irregular
      • Sinus?
        • 1.  P before every QRSTriagnel.png
        • 2.  QRS before every P wave
        • 3.  P wave is positive in leads I and II
        • If not sinus rhythm find association btwn P and QRS
    • Axis

    Lead I

    Lead II

    Axis

    +

    +

    Normal

    +

    -

    Right Dev.

    -

    +

    Left Dev.

    -

    -

    Undefined

    •  
    • Intervals
      • PR --> big box (200ms)
      • QRS → 3 squares (120ms)
        • Wider = ventricular conduction not using conduction system (likely)
          • Check Right (v1/V2) and left (V5/V6) chest leads for block
          • zWideQRS.png
      • Q-wave (septal depolarization) must be <1mm (<0.4s, 1 small box) AND ≤1/3 of QRS amplitude.

     

    • QT --> less than 50% of the  RR
    • T amplitude --> less than 2/3 of R
    • HEMIBLOCKS (FASCIULAR BLOCK)
      • AV node and bundle of his àsupplied by R coronary
      • Anterior Fascicle -> LCA
      • Posterior Fascicle -> LCA or RCA twigs. (variable)
      • RBB -->L coronary
      • Occlusions:
        • LAD occlusion: RBBB + ant. Fascicular block
        • RCA occlusion: ant fascicular block
      • Anterior Hemiblock:
        • 1. LAD – usually MI or other heart disease.
          • R/O other LAD causes (LVH, horizontal heart, inferior MI)
        • 2. Normal or slightly widened QRS (0.10 - 0.12ms)
        • 3. Q1S3 (Q in lead I or a wide or deep S in III)
      • Posterior Hemiblock
        • Rare b/c posterior fascicle is short, thick and often has dual blood supply.
        • 1. Right-axis deviation (without another explanation  such as "vertical heart" in slim person, RVH, pulmonary HTN, etc..)
        • 2. Normal or slightly widened QRS (0.10 - 0.12ms)
        • 3. S1Q3
    • Ischemic ECG changes:
      • Inverted T wave (must be symmetrical)
        • Flat or minimal T-wave inversion can be normal in limb leads and V1.
        • ANY T wave inversion in V2-V6 is pathological
        • (T-wave inversion in leads V2-V3 is Wellens syndrome – stenosis of anterior descending coronary)
      • ST Elevation
        • Signifies ACUTE injury
        • ST elevation w/o Q wave0-->Non-Q-wave infarction. (may indicate impending infarction).
        • Other cases of ST elevation:
          • “Prinzmetal’s” angina -->ST elevation w/o infarction.
          • Brugada syndrome: RBBB + ST elevation in V1-V3 (sudden death w/o heart disease). (ST elevation peaked +downsloping).
            • Screen shot 2013-09-12 at 7.04.01 PM.png
            • Brugada: Na+ channel dysfunction, Half of young sudden deaths... Needs ICD. 
          • Pericarditis - ST segement may be flat or concave, and may even elevate T wave off of baseline (viral, bacterial, cancer, post-MI)
      • ST Depression:
        • Causes:
          • 1. Subendocarial Infarction (MI)
          • 2. Positive stress test
          • 3. Digitalis.
      • Q Wave (necrosis)
        • Insignificant Q wave: First downward inflexion after P wave.  Indicates septal depolarization from Pukinje filaments at mid-septum of LBB.  L-->R AWAY from I and AVL.
          • Must be TINY! Q < 0.04s (less than 1 milimiter, <1box)
            AND
          • Must be ≤1/3 of QRS amplitude.
          • (Ignore AVR)
        • Significant Q waves --> necrosis of a myocardial infarction.
    • Characterize vascular territory by Q waves
    • Q wave Leads Area Functional Vascular Territory Notes
      V1-V2 Anteroseptal   LAD  
      V3-V4 Anterolateral   LAD  
      V1-V4 Anterior   LCA (LAD)  
      II, III, aVF Inferior 1/3 involve RV RCA  
      I, aVL Lateral   LCA(Circumflex)  

      ST depression

      or

      Tall R wave:

      V1, V2

      Posterior   RCA

      - Get Posterior leads (V4R) V7 V8 V9 

       (15 lead EKG)

      - RCA supplies SA node, AV node, bundle of his

        often associated with arrhythmias

       

    •  

     

    Hypertrophy

    • RVH
      • R wave in V1 >7mm
      • R >S in V1
      • R axis deviation
      • R<S in V5, V6
    • LVH
      • R wave in aVL > 11mm
      • R wave in lead I + S wave lead III >25mm
      • R wave V5 or V6 >26mm
      • R wave in V5 or V6 + S wave V1 > 35mm
      • Largest R wave + largest S wave >45mm (precordial leads)
    • Infarct ST changes or Q wave
      • ST elevation (P-T = baseline)
        • More than 2 boxes in precordial and more than 1 box in limb leads
      • ST depression

    Supra-ventricular tachycardias:

    • AVNRT
      • Retrograde p-wave blends with tail of QRS in V1 giving Pseudo R
      • (Usually retrograde P wave burried in the QRS)
    • AVRT  (includes WPW)
      • P wave comes after QRS
      • WPW
        • Pre-exceitation delta-waves
        • AV node generally blocks Afib Aflutter signals.  
        • If additional pathway, conducts all, causes Vtach and Vfib
    • Tx:
      • Tachycardia termination: AVN blockers
        • Adenosine
        • B-blockers
        • CCB (all)
      • Tachycardia prevention
        • AVN blockers - BB, CCB
        • Antiarrhythmics - rarely needed
      • Pre-excited tachycardia
        • DO NOT USE AV BLOCKER - can incr conduction down accessroy pathway = death
        • use IV/oral antiarrhythmic or cardioversion.

    Metabolic Abnormalities in ECG

     

    Abnormalityq

    ECG

    Potassium

    Hyperkalemia

    • Wide QRS
      • Flat P wave
      • T wave peaks

    Hypokalemia

    • Flat T wave
    • U wave present

    Calcium

    Hypercalcemia

    • Wide QRS
    • Short QT

    Hypocalcemia

    • Long QT

    Temperature

    Hypothermia

    • ST elevation
    • Slow rhythm

    Digitalis

     

    • ST depression
    • Flat T wave (or invert)
    • Short QT

    BB

     

    • Low HR
    • Long PR

    Quinidine

     

    • Long QT
    • Flat T wave (or invert)
    • Long QRS

     

     

     

    Medications that prolong QT interval

    http://www.crediblemeds.org/everyone...t-all-qtdrugs/

    Tag page (Edit tags)
    • No tags
    Page statistics
    13142 view(s), 8 edit(s) and 9850 character(s)

    Comments

    You must login to post a comment.