One of the most important diagnostic tests in Cardiology to interpret is the EKG.

Here are my thoughts and notes. Will continue to this thread. Let me know what you think!

Thread #10: Fascicular Blocks

#arjuncardiology #medtwitter #CardioTwitter #MedEd #IMG
Fascicular Blocks:
- Left bundle branch system: sub-divided into an anterior & posterior fascicle.

- Hemi-block does not widen the QRS complex markedly (compared to a RBBB or LBBB)
Left Anterior Fascicular Block (LAFB):
- Diagnosed by finding of a left axis deviation (-45 degrees or more negative)
- Delayed activation of more superior & leftward position of the LV
- Isolated finding is non-specific; can be seen w/ HTN, AV disease, CAD, and aging
LAFB ECG:
- rS complexes in lead II, III, avF, and small R waves and deep S waves
- qR complexes in leads I, aVL, with small Q waves and tall R waves
- (+) deflection in I & avL and (-) deflection in II, III, aVF
Left Posterior Fascicular Block (LPFB):
- Right axis deviation (+ 120 degrees or more positive)
- Delayed activation of more inferior & rightward portion of LV
- Diagnosis of exclusion for right-axis deviation (other more common: RVH, emphysema, lateral wall infarction, PE)
LPFB ECG:
- rS complexes in leads I and avL, with small R waves and deep S waves
- qR complexes in leads II, III, avF with small Q waves and tall R waves
- Right axis deviation: (+) in II, III, aVF and (-) in I & aVL
Bi-fascicular Block
- Block in any of 2/3 fascicles
- RBBB + LAFB = RBBB with left-axis deviation
- RBBB + LPFB = RBBB with right-axis deviation
- Development of a new bi-fascicular block (usually RBBB with LAFB) during acute anterior MI may be warning for complete heart block
Tri-fascicular Block
- With 1:1 AV conduction is rarely present on ECG
- Patients can present with alternating LBBB & RBBB. In these patients, a permanent pacemaker is indicated because of high risk for abrupt complete heart block.
- Image: RBBB + LAFB + 3rd degree
Thanks to this amazing site for the graphics! Stay tuned for the next threads on myocardial ischemia!

litfl.com/left-anterior-…
litfl.com/left-posterior…
litfl.com/bifascicular-b…
litfl.com/trifascicular-…

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More from @akhadilkarMD

Mar 16
One of the most important diagnostic tests in Cardiology to interpret is the EKG.

Here are my thoughts and notes. Will continue to this thread. Let me know what you think!

Thread #9: Left Bundle Branch Block (LBBB)

#arjuncardiology #medtwitter #CardioTwitter #MedEd #IMG
LBBB:
- Similar to a RBBB, produces a wide QRS and affects the early phase of depolarization
- Septum will depolarize from (right to left; instead of normal left to right).
- Will see the loss of septal r-wave in V1 and septal q-wave in V6
LBBB:
- V1: Negative QRS complex b/c the LV is still electrically predominant (initial depolarization is negative and remains negative in the right-sided chest lead) (W-shape)
- V6: Entirely positive R-wave ('M'- Pattern)
Read 6 tweets
Mar 15
One of the most important diagnostic tests in Cardiology to interpret is the EKG.

Here are my thoughts and notes. Will continue to this thread. Let me know what you think!

Thread #8: Right Bundle Branch Block (RBBB)

#arjuncardiology #medtwitter #CardioTwitter #MedEd #IMG
Ventricular Conduction:
- Normal electrical stimulus reaches ventricles from the atria through the AV node & His-Purkinje systems
- First part of heart to be depolarized is the left-side of the septum; then spreads to RV and LV by right & left bundles
- Normal QRS < 0.10 sec
RBBB:
- 1st phase of depolarization: Left side of septum is stimulated first (branch of left bundle); on a normal ECG produces a septal r-wave in V1 and small septal q-wave in V6. No impact with RBBB.

- 2nd phase: Simultaneous depolarization of LV and RV. No impact with RBBB.
Read 7 tweets
Mar 3
One of the most important diagnostic tests in Cardiology to interpret is the EKG.

Here are my thoughts and notes. Will continue to this thread. Let me know what you think!

Thread #7: Ventricular Hypertrophy

#arjuncardiology #medtwitter #CardioTwitter #MedEd #IMG
Atrial and Ventricular Enlargement:
- Both dilation & hypertrophy usually result in chronic pressure and volume overload on the heart muscle

- Pathological hypertrophy & dilation are often accompanied by fibrosis (scarring); can lead to arrhythmias and heart failure.
Right Ventricular Hypertrophy:
- Right chest leads show tall R-waves
- R-wave > S-wave in V1 is suggestive; not diagnostic of RVH
- Can see right-axis deviation and T-wave inversions in the right & mid-precordial leads
- RV hypertrophy can lead to variations in repolarization
Read 9 tweets
Mar 2
One of the most important diagnostic tests in Cardiology to interpret is the EKG.

Here are my thoughts and notes. Will continue to this thread. Let me know what you think!

Thread #6: Atrial Abnormality

#arjuncardiology #medtwitter #CardioTwitter #MedEd #IMG
Atrial and Ventricular Enlargement:
- Both dilation & hypertrophy usually result in chronic pressure and volume overload on the heart muscle

- Pathological hypertrophy & dilation are often accompanied by fibrosis (scarring); can lead to arrhythmias and heart failure.
Right Atrial Abnormality (RAA):
- Overload of RA (dilation/ hypertrophy) may increase P-wave voltage

- Normal P-wave < 2.5 mm amplitude and < 0.12 seconds in width

- Tall, narrow P-waves: characteristic of RAA and can be best seen in II, III, aVF
Read 7 tweets
Feb 6
One of the most important diagnostic tests in Cardiology to interpret is the EKG.

Here are my thoughts and notes. Will continue to this thread. Let me know what you think!

Thread #5: Axis Deviation

#arjuncardiology #medtwitter #CardioTwitter #MedEd #IMG
QRS Axis:
- General direction in the frontal plane towards which the QRS complex is predominantly pointed

- General rule: Mean QRS points mid-way b/w any 2 leads that show tall R-wave of equal height

- If depolarization is perpendicular to any lead, will see biphasic complex
Axis Deviation:
- For most people, the axis lies between -30 and + 100 degrees

- Left axis: < -30 degrees, lead II rS pattern (S-wave deeper than R-wave is tall)

- Right axis: > +100 degrees (R-wave in III > II)
Read 6 tweets
Feb 6
One of the most important diagnostic tests in Cardiology to interpret is the EKG.

Here are my thoughts and notes. Will continue to this thread. Let me know what you think!

Thread #4: ECG Segments

#arjuncardiology #medtwitter #CardioTwitter #MedEd #IMG
General Principles:
- Positive deflection: wave of depolarization towards positive pole of that lead
- Negative deflection: wave of depolarization towards negative pole of that lead
- Biphasic deflection: wave of depolarization is perpendicular to a lead
Normal Sinus P-wave:
- Atrial depolarization that marks spontaneous depolarization of pacemakers cells in the right atrium
- Should be negative P-wave in aVR and upright in lead II
- Can communicate 'sinus rhythm with 1:1 AV conduction'
Read 7 tweets

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