Which rhythm has a firing rate below 60 bpm?

The rhythm characterized by a firing rate below 60 beats per minute (bpm) is known as Sinus Bradycardia. This condition occurs when the heart's natural pacemaker, the sinoatrial (SA) node, generates impulses at a slower rate than normal. Sinus Bradycardia is typically classified as a heart rate of less than 60 bpm while maintaining a normal sinus rhythm with a uniform P wave preceding each QRS complex.

In a clinical context, Sinus Bradycardia can be a normal finding in well-conditioned athletes or during sleep, reflecting increased vagal tone. However, it can also indicate underlying issues such as medication effects, hypothyroidism, or other cardiac conditions. The distinguishing feature of this rhythm is the slower heart rate coupled with a consistent and regular rhythm pattern.

The other options refer to rhythms with different characteristics: Stellar Rhythm is not a recognized term in cardiac physiology, Sinus Rhythm typically refers to a normal rate between 60-100 bpm, and Sinus Tachycardia is when the heart rate exceeds 100 bpm. Understanding these definitions can help in recognizing and diagnosing different cardiac rhythms effectively.