What denotes unstable bradycardia according to the CPG?

Unstable bradycardia is defined primarily by the presence of inadequate perfusion, which indicates that the body's tissues and organs are not receiving sufficient blood flow. In this context, inadequate perfusion can manifest as symptoms such as hypotension, altered level of consciousness, or signs of shock. These evidence-based parameters guide the recognition of bradycardia as unstable, highlighting the need for immediate intervention to prevent further complications.

The other options may describe conditions or rates that are sometimes associated with bradycardia but do not signal instability on their own. For example, a heart rate above 100 BPM suggests tachycardia, which is not relevant to bradycardia classification. Similarly, a heart rate above 60 BPM could still fall within the normal range and does not necessarily imply instability. Lastly, a history of myocardial infarction may provide important context for a patient's cardiovascular health but does not directly indicate bradycardic instability in the present moment. Thus, the critical factor is the presence of inadequate perfusion to officially categorize the bradycardia as unstable.