Sinus rhythm in ECG refers to the normal heart rhythm where the electrical impulses originate from the sinoatrial (SA) node, the heart's natural pacemaker, and follow the proper conduction pathway. This results in a characteristic pattern on an electrocardiogram (ECG).
Key Characteristics of Sinus Rhythm:
- Origin in the SA Node: The electrical impulse starts in the SA node, located in the right atrium.
- P Wave Present: A P wave precedes each QRS complex, indicating atrial depolarization (contraction). The P wave should be upright in leads II, aVF, and V4-V6, and inverted in aVR.
- Consistent PR Interval: The PR interval (the time from the beginning of the P wave to the beginning of the QRS complex) is consistent and typically between 0.12 and 0.20 seconds. This represents the time it takes for the impulse to travel from the atria to the ventricles.
- Normal QRS Complex: The QRS complex represents ventricular depolarization (contraction) and should have a normal duration (typically less than 0.12 seconds).
- Regular R-R Interval: The R-R interval (the time between successive R waves, representing ventricular contractions) is generally regular, although slight variations due to respiration (sinus arrhythmia) are normal.
- Heart Rate Within Normal Limits: The heart rate is typically between 60 and 100 beats per minute (bpm) in adults.
Why is Sinus Rhythm Important?
Sinus rhythm signifies that the heart's electrical system is functioning correctly. It ensures proper coordination of atrial and ventricular contractions, leading to efficient blood flow. Deviations from sinus rhythm, such as arrhythmias, can indicate underlying heart conditions.
Example of a Normal Sinus Rhythm ECG Strip:
Imagine an ECG strip where you see a clear P wave before every QRS complex. The PR interval is consistent, and the QRS complexes look normal and are evenly spaced. The heart rate falls within the range of 60-100 bpm. This would be a good example of sinus rhythm.
In Summary:
Sinus rhythm on an ECG signifies a healthy heart rhythm initiated by the SA node, resulting in specific and predictable electrical patterns. It is crucial for efficient cardiac function.
