Normal Sinus Rhythm On ECG – What Does It Mean?

When a person is in normal sinus rhythm, the heartbeat originates from the sinoatrial (SA) node, which produces a P wave visible on the electrocardiogram (ECG). This P wave is typically upright in leads I, II, V2, and V4 through V6, and inverted in lead aVR. This pattern is known as sinus rhythm and represents the normal electrical activity of the heart.

Characteristics Of Normal Sinus Rhythm

In a healthy heart, nearly all electrical impulses originate from the SA node, which acts as the natural pacemaker. When this occurs, it is referred to as normal sinus rhythm. The presence of upright P waves in the specified leads confirms that the rhythm is controlled by the SA node, indicating a normal ECG reading.

Identifying Abnormal Rhythms

If the T wave appears inverted in leads I, II, and V4 to V6, it suggests that the heart rhythm is not under the control of the sinoatrial node. In such cases, the rhythm may originate from other areas of the heart, such as the atria, the junction between the atria and ventricles, or the ventricles themselves. These rhythms are commonly classified as atrial rhythm, junctional rhythm, or ventricular rhythm.

Types Of Atrial Rhythms

Atrial rhythms can be further categorized based on their origin within the atria. These include rhythms arising from the upper right atrium, lower right atrium, upper left atrium, and lower left atrium. Each type can have distinct characteristics on an ECG, helping healthcare providers identify the source of the rhythm disturbance.