The heart rhythm can be defined as the succession of heartbeats. On the electrocardiogram, we talk about the succession of QRS complexes for the duration of that one.
Usually, the heart rate is regular with a normal heart rate (between 60 bpm and 100 bpm) although some diseases may cause it to be irregular, too fast or too slow.
The first step in heart rate analysis is to determine if it is regular or irregular. For this, one must measure the distance between two consecutive R waves (RR interval). If the rhythm is regular, this distance is identical from one beat to another.
Sinus rhythm is the standard rhythm of the heart. It is produced by the sinus node, which stimulates both atria, passes through the AV node and leads to the ventricles through the His bundle.
The second step is to measure the frequency (the heartbeat). In tachycardia, the electrocardiogram displays a frequency greater than 100 bpm.
In sinus tachycardia, the electrocardiogram fulfills all the characteristics corresponding to the sinus rhythm, but the frequency it displays is greater than 100 bpm.
