Relative Bradycardia: Clinical Significance and Assessment

Definition and Characteristics

• The American College of Cardiology and the American Heart Association define relative bradycardia as a heart rate that is inappropriately low for the clinical context, particularly during febrile illness, and it represents a pulse-temperature dissociation or pulse-temperature deficit 1, 2

Clinical Assessment

• The American College of Cardiology emphasizes that a slow heart rate may be physiologically normal for some patients, while a heart rate >50 beats per minute may be inadequate for others, and assessment should focus on whether the bradycardia is causing symptoms such as transient dizziness or lightheadedness, confusion resulting from cerebral hypoperfusion, heart failure symptoms, or exercise intolerance 1, 2, 3
• The American Heart Association suggests that intervention is warranted only when bradycardia is symptomatic or likely to progress to a life-threatening condition, and asymptomatic or minimally symptomatic patients with relative bradycardia do not necessarily require treatment 1

Clinical Implications

• The American College of Cardiology recommends that the presence of relative bradycardia should prompt consideration of specific infectious etiologies, particularly those caused by intracellular pathogens, and treatment should rarely be prescribed solely based on heart rate being lower than an arbitrary cutoff 1