bradycardia

What Is Bradycardia?

Bradycardia is a condition in which the heart rate falls below the normal resting range, typically defined as fewer than 60 beats per minute in adults. In polygraph testing, bradycardia is relevant because it can reflect either a normal physiological variant (common in athletes and individuals with high cardiovascular fitness) or a response to medication, medical conditions, or parasympathetic nervous system dominance that may affect cardiovascular data interpretation.

Causes Relevant to Polygraph Testing

Bradycardia may be observed during polygraph testing for several reasons: the examinee may be a trained athlete with a naturally low resting heart rate; they may be taking beta blockers or other heart rate-reducing medications; they may have a medical condition affecting the cardiac conduction system; or they may be experiencing a strong vagal response. In rare cases, bradycardia could result from deliberate relaxation techniques used as countermeasures, such as autogenic training or controlled breathing.

Impact on Cardiovascular Scoring

A slow baseline heart rate does not necessarily invalidate a polygraph examination. The CQT scoring framework evaluates changes in cardiovascular parameters relative to the examinee's own baseline, not absolute values. An examinee with a resting rate of 50 bpm who shows a heart rate increase to 58 bpm at a relevant question is demonstrating the same type of sympathetic activation as an examinee whose rate increases from 70 to 78 bpm. The differential response pattern between relevant and comparison questions remains interpretable regardless of the baseline rate.

However, very slow heart rates produce fewer pulse cycles within the standard scoring window for each question, potentially providing less cardiovascular data per question presentation. In extreme cases, this reduction in data density could affect the precision of cardiovascular feature measurements.

Examiner Protocol

When bradycardia is identified during the pre-test interview or observed in the cardiovascular tracing, the examiner should document the finding, record any relevant medications or medical conditions, and assess whether the cardiovascular data quality is sufficient for reliable scoring. The examiner should ensure the cuff inflation level is optimised for the examinee's blood pressure range and that the gain settings produce readable tracings despite the slower rate.

Bradycardia contrasts with tachycardia (abnormally fast heart rate), which presents different but analogous challenges for cardiovascular data interpretation.