7.6.1 Normal sinus rhythm
The normal resting heart rhythm is called sinus rhythm because the sinoatrial node acts as the pacemaker governing rhythm (see section 1.5.3). The pulse rhythm is regular and pulse quality is consistent. On auscultation, clear A, S1, S2 and S3 sounds may be heard, with a regular rhythm. The ECG will show that each QRS complex is preceded by a P wave, and that a QRS complex follows each P wave. The R-R and P-P intervals are consistent (Figure 4.2).
Fig 4.2 A typical normal ECG recorded with a base-apex lead.