comprehensive Guide to ECG Abnormalities: A Summary Overview

1. Atrial Fibrillation (AFib)
● P wave: Absent; replaced by fibrillatory (f) waves.
● QRS complex: Normal (0.06–0.10 sec).
● T wave: Usually normal, may be distorted by f-waves.
● PR interval: Not measurable due to lack of distinct P waves.
● QT interval: Variable, depending on ventricular rate.
● Heart Rate: While often rapid, it can also be slow or normal.
● Rhythm: Irregularly irregular.

2. Atrial Flutter
● P wave: Replaced by sawtooth flutter waves
● QRS complex: Normal.
● T wave: Often obscured by flutter waves.
● PR interval: Not measurable due to continuous flutter waves.
● QT interval: Variable.
● Heart Rate: Atrial rate 250–350 bpm.
● Rhythm: It can be irregularly irregular if there is variable AV conduction.

3. Ventricular Tachycardia (VT)
● P wave: Absent or dissociated.
● QRS complex: Wide (>0.12 sec).
● T wave: Usually in the opposite direction of the QRS.
● PR interval:No PR interval
● QT interval: Prolonged due to wide QRS.
● Heart Rate: >100 bpm.
● Rhythm: It can be irregularly irregular in some cases.

4. Myocardial Infarction (MI)
● P wave: It can be abnormal in some cases, especially in the setting of acute MI.
● Q wave: Deep, pathologic Q waves (if present in later stages).
● T wave: Inverted in affected leads.
● PR interval: Normal.
● QT interval: May be prolonged.
● Other: ST-segment elevation or depression depending on the stage of MI.

5. First-Degree AV Block
● P wave: Normal.
● QRS complex: Normal.
● T wave: Normal.
● PR interval: Prolonged (>200 ms).
● QT interval: Normal.
● Other: Regular rhythm with delayed conduction between atria and ventricles.
● Heart Rate: Variable.
● Rhythm: Regular.

, 6. Second-Degree AV Block Type I (Mobitz I or Wenckebach)
● P wave:Normal but not all followed by QRS.
● QRS complex: Normal.
● T wave: Normal.
● PR interval: Progressively lengthens until a QRS is dropped.
● QT interval: Normal.
● Other: Grouped beating with a missing QRS complex after progressively increasing PR
intervals.
● Heart Rate: Variable.
● Rhythm: Irregular.

7. Second-Degree AV Block Type II (Mobitz II)
● P wave: Normal, consistent.
● QRS complex: It can be normal or wide, depending on the underlying conduction
abnormality.
● T wave: Normal.
● PR interval: Constant in conducted beats.
● QT interval: Normal.
● Other: Intermittent dropped QRS complexes without prior PR prolongation.
● Heart Rate: Often slow.
● Rhythm: Regular or irregular.

8. Third-Degree AV Block (Complete Heart Block)
● P wave: Normal but independent from QRS complexes.
● QRS complex: Normal or wide.
● T wave: Normal.
● PR interval: Not measurable due to AV dissociation.
● QT interval: Variable.
● Heart Rate: Ventricular rate <60 bpm.
● Rhythm: Regular, but P and QRS are independent.

9. Right Bundle Branch Block (RBBB)
● P wave: Normal.
● QRS complex: Wide with RSR' pattern in V1–V2.
● T wave: It can be normal or inverted, depending on the underlying cause of the RBBB.
● PR interval: Normal.
● QT interval: Prolonged due to wide QRS.
● Other: RSR' (rabbit ears) pattern in V1 and V2, with a slurred S wave in leads I and V6.
● Heart Rate: Variable.
● Rhythm: Regular.

10. Left Bundle Branch Block (LBBB)
● P wave: Normal.
● QRS complex: Wide (>0.12 sec).
● T wave: It can be normal or inverted, depending on the underlying cause of the LBBB.