Month: December 2016

Concepts that interfere with understanding gyroscopes

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1. A force in the y-direction cannot change any motion in the x-direction or z-direction. (SHOOTING MONKEY EXPERIMENT AND DROPPING BULLET)

2. Common explanations with torque, angular momenta. These explanations use more abstract concepts than force, velocity and momentum.

3. The difference of order of magnitude of the angular momenta.

How to identify Hemi-blocks..

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Correct! The mainly negative QRS in lead II should clue you in to a left axis deviation which is the main ECG abnormality produced by LAFB.

Some other findings are:
1) rS complexes in leads II, III, and aVF
2) tiny q waves in I and/or aVL
3) poor R wave progression in V1-V3 (not seen in this ECG)
4) narrow (normal) QRS

LAFB is the most common IV conduction defect.

 

Correct! This is the most common of the bifascicular blocks. RBBB is most easily recognized in the precordial leads by the rSR’ in V1 and the wide S wave in V6 (i.e., terminal QRS forces oriented rightwards and anterior).

LAFB is best seen in the frontal plane leads as evidenced by left axis deviation (-50 degrees), rS complexes in II, III, aVF, and the small q in leads I and/or aVL.

Recognizing hypertrophy on ECG

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Note that hypertrophy signs on ECG are specific, but not very sensitive. In other words, if criteria are met it is highly likely that the patient has hypertrophy. But if the criteria are NOT met, patient can still have hypertrophy! You can’t exclude hypertrophy with a ECG, (you need a echo for that)

  • LAE: Left atrial enlargement
  • RAE: Right atrial enlargement
  • LVH: Left ventricular enlargement
  • RVH: Right ventricular enlargement or ‘pseudoinfarct’.

For atrial enlargement check II and V1

For ventricular enlargement check the precordial leads.

LAE: LAE causes a P wave duration > 0.12s in the frontal plane. The P wave is also notched.
Also, in LAE Lead V1 shows terminal P negativity.

RAE: RAE is recognized by the tall (> 2.5mm) P waves in leads II, III, aVF.

LVH: The combination of voltage criteria (S-V2 + R-V6 >35mm) and ST-T abnormalities in V5-V6 are definitive for LVH. S wave depth in V1 + tallest R wave height in V5-V6 > 35 mm).

RVH: The prominent anterior forces seen in RVH are also seen in a number of other conditions including a true posterior MI. Thus, RVH is sometimes referred to as a pseudoinfarct. RVH is likely because of right axis deviation (+100 degrees) and the Qr (or rSR’) complexes in V1 and V2.

RVH+strain: ST depression and T-wave inversion in V1-4 (plus lead III), in this case due to right ventricular hypertrophy.

LVH+strain: T wave inversion in the lateral leads V5-6, I and aVL

Any ECG-abnormality is in the following categories

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  1. Rhythm disorder
    1. Tachy-arrhytmia
      1. SVT (Afib,Aflut,AVNRT, o/a-AVRT)
      2. VT (monomorphic, polymorphic (TdP), Vfib)
    2. Brady-arrhytmia
      1. Sinus Bradycardia
      2. Sinus arrhytmia
      3. Sinus arrest
      4. Sinuatrial block
      5. AV-block
    3. Ectopic rhythms
      1. PAC-atrial rhythm
      2. PJC-junctional rhythm
      3. PVC-idioventricular rhytm
  2. Signs of ischemia
    1. Wellen’s warning (negative T’s)
    2. ST-depression (anterior, inferior, lateral)
    3. ST-elevation (anterior, inferior, lateral)
    4. Hyperacute T’s
    5. Pathological Q-waves
  3. Signs of hypertrophy
    1. Atrial hypertrophy
    2. Left ventricular hypertrophy
    3. Right ventricular hypertrophy
  4. Pacemaker ECG
  5. Conduction abnormalities
    1. WPW
    2. AV-block
    3. Bundle branch block
    4. Prolonged QT
  6. Electrolyte disorders
    1. Hyperkalemia
    2. Hypokalemia
    3. Hypercalcemia
    4. Hypocalcemia

How to differentiate wide-complex tachycardia

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NOTE: 80% of wide-complex tachycardia are VT!

Clinical history:

  • Cardial infarct or Heart failure makes it very likely that it is VT
  • An age higher than 40 is also very specific for VT.

ECG Signs:

  • Brugada Criteria
  • AV-dissociation – Capture beats – Fusion beats make VT more likely
  • A BBB morphology makes SVT with BBB more likely
  • Negative concordance, or all QRS-complexes are negative makes VT more likely.
  • The more broad the QRS-complex, the higher the chance of VT

Brady-arrhythmia

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Sinus bradycardia

(Sinus bradycardia + prolonged QT = Torsades des Pointes)

AV-block

  • First degree
  • Second degree
    • Mobitz I (Wenkebach Warning)
    • Mobitz II
  • 2:1 Block
  • High grade AV-block
  • Third degree

Pacemaker criteria

  • Escape frequency of lower than 40
  • Symptomatic
  • Unstable

Trans cutaneous Pacing

Temporary Pacing

Medication:

Isoproteronol (Beta-agonist)

STOP OR REVERSE BLOCKADE (BB/CCB or Amiodarone, no adenosine)

STOP OR REVERSE LONG QT.