Broadly, arrhythmias are classified into:
1: Tachyarrhythmias
2: Bradyarrhythmias
Let’s individually discuss our diagnostic approach.
Diagnostic Approach to Tachyarrhythmias
Obtain an ECG:
– Is the QRS complex less than 3 small boxes?
Yes: Narrow complex tachycardia
No: Normal sinus tachycardia
Differential Diagnoses (D/D) in Normal QRS Tachycardia:
1: Sinus tachycardia
2: Paroxysmal supraventricular tachycardia
3: Atrial flutter
D/D in Narrow and Irregular QRS Tachycardia:
Atrial fibrillation (AFib) – Variable RR interval
Multifocal atrial tachycardia – More than 3 morphologically distinct P
waves
D/D in Wide Regular QRS Tachycardia:
Ventricular tachycardia
D/D in Wide and Irregular QRS:
Ventricular fibrillation
Torsades de pointes – Prolonged QT interval with sudden polymorphic
ventricular tachycardia (VT) presentation, resembling a “ribbon” on
the ECG
Diagnostic Approach to Bradyarrhythmias
Obtain an ECG:
– Check for:
1: Sinus rhythm
2: Dropped QRS complexes
3: Normal PR interval (less than one big box)
– If all three are normal, it is sinus bradycardia.
– Consider an AV block if there is an abnormal PR interval or dropped
QRS.
AV Blocks:
1: First degree: Increased PR interval
2: Second degree (Type 1): Progressively longer PR interval with dropped
3: QRS
4: Second degree (Type 2): Constant PR interval with dropped QRS
Third degree: Complete AV dissociation
