A conceptual chapter - no rhythm strips of its own. It establishes where rhythms come from and the supraventricular/ventricular divide that drives the systematic read.
Chapter 3 is conceptual: it maps WHERE each rhythm originates rather than showing strips. The supraventricular-vs-ventricular divide is the first split - anything above the ventricles gives a narrow QRS; the ventricles give a wide QRS. Each origin becomes a later chapter.
| Origin (the hideout) | Rhythm family | QRS | Chapter |
|---|---|---|---|
| SA node | Sinus rhythms | Narrow | 4 |
| Atria (ectopic) | Atrial rhythms (PAC, AT, flutter, AF, WAP/MAT) | Narrow | 5 |
| AV junction | Junctional rhythms | Narrow | 6 |
| Ventricles | Ventricular rhythms (PVC, VT, VF, etc.) | Wide | 7 |
| Conduction block | AV blocks | Narrow or wide | 8 |
| Device | Pacemaker rhythms | Paced | 9 |
| Reentry circuit | AVNRT / AVRT / WPW | Narrow (or wide) | 10 |
The five-step read connects to origin: QRS width first splits supraventricular (narrow) from ventricular (wide); the P wave and its relationship to the QRS then pinpoint which room above the ventricles the rhythm came from; rate/regularity and clinical context finish the call. Practice strips for each origin live in Chapters 4-12.