"Underlying sinus rhythm" refers to a normal heart rhythm that originates from the sinoatrial (SA) node, which is the natural pacemaker of the heart. This rhythm is characterized by regular heartbeats and typically has a rate of 60 to 100 beats per minute in adults.
When a medical report or ECG (electrocardiogram) mentions "underlying sinus rhythm," it often indicates that, although there may be other arrhythmias (irregular heartbeats) present, the heart is fundamentally operating under the normal sinus rhythm. This term is commonly used in contexts where arrhythmias or other cardiac issues are being assessed but the primary underlying electrical activity is still normal.
In clinical practice, it's reassuring because it suggests that under normal circumstances, the heart can maintain a proper rhythm.
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