Description
First-degree heart block involves a fixed prolonged PR interval (>200 ms). Second-degree AV block (type 1) is also known as Mobitz type 1 AV block or Wenckebach phenomenon. Typical ECG findings in Mobitz type 1 AV block include progressive prolongation of the PR interval until eventually the atrial impulse is not conducted and the QRS complex is dropped.
AV nodal conduction resumes with the next beat and the sequence of progressive PR interval prolongation and the eventual dropping of a QRS complex repeats itself.
Summary Listen
- The discussion centered around diagnosing various ECG rhythms, emphasizing the importance of a systematic approach. Key aspects included identifying P waves, assessing RR interval regularity, and determining QRS complex width. Correctly diagnosing sinus tachycardia requires verifying a one-to-one P wave to QRS ratio with a constant PR interval and a normal P wave axis.
- Atrial flutter was frequently highlighted, characterized by multiple P waves (flutter waves) compared to QRS complexes, especially visible in lead V1. Differentiating between typical and atypical flutter involved examining leads 2, 3, and AVF for "sawtooth" P wave patterns. Atrial fibrillation was identified by its irregular RR intervals and absence of defined P waves.
- Ventricular tachycardia (VT) diagnosis was explored in detail. AV dissociation (independent P waves and QRS complexes) and capture beats (occasional narrow QRS amidst broad complexes) were established as key indicators of VT. The ECGs were evaluated to distinguish monomorphic VT from polymorphic VT, associating monomorphic VT with scar-related re-entry post-MI and polymorphic VT with ongoing ischemia.
- Narrow complex tachycardias (SVT) were classified into AVNRT (AV nodal re-entrant tachycardia), AVRT (AV re-entrant tachycardia), and atrial tachycardia (AT). Differentiating these involved assessing the RP interval relative to the RR interval. A short RP interval favored AVNRT, while a long RP interval suggested AVRT or AT. Additionally, adenosine response was discussed as a diagnostic clue, with atrial tachycardias being less likely to terminate with adenosine administration.
- The session concluded with discussions on AV blocks, including first-degree AV block (prolonged PR interval), Mobitz type II (consistent PR interval with dropped QRS), and complete heart block (AV dissociation with independent P and QRS). Prompt temporary pacing was emphasized for unstable complete heart block presentations with broad QRS escape rhythms. Finally, the session reviewed the identification of Wellen's syndrome and the importance of identifying sinus pauses as indicators of Sick Sinus Syndrome.
Sample Certificate
About the Speakers
Dr Mohammed Sadiq Azam
MD (Med), DNB (Cardio),Interventional Cardiologist, KIMS Hospital
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