Sinus Bradycardia

Sinus Bradycardia is defined as any heart beat that originates in the sino-atrial node and causes a ventricular beat of less than 60 per minute. Sinus bradycardia is generally benign and most patients are asymptomatic.

Sinus Bradycardia ECG

Heart Rate: Less than 60/min
Rhythm: Regular
Pacemaker Site: SA node.
PR Interval: Normal
QRS Complex: Normal.

Sinus Bradycardia Signs and Symptoms

In general patients who show a sinus bradycardia on their ECG will show little other signs and symptoms depending on the rate of their rhythm and any co-factors such as an acute coronary syndrome, pain, injuries, etc. Most patients will appear well perfused with good skin colour, warmth and no diaphoresis. If patients are on common blood pressure medications such as Beta Blockers it is likely that these will have artificially lowered the person’s heart rate and that their normal resting heart rhythm is a sinus bradycardia.

In general, patients who have a sinus bradycardia are not hypotensive. This is because as we learned in Starling’s Law, the slower the heart rate the greater time allowed for ventricular filling (which is passive), ventricular stretching (pre-load) and subsequent cardiac output.