arrhythmia

What Is an Arrhythmia?

An arrhythmia is any deviation from the normal rhythm of the heartbeat. This can include a heart that beats too fast (tachycardia), too slowly (bradycardia), irregularly, or with extra beats (extrasystolic beats / premature ventricular contractions). In polygraph testing, arrhythmias are important because they can produce artefacts in the cardiovascular channel that may be confused with question-related responses or may degrade the quality of cardiovascular data below the threshold needed for reliable scoring.

Impact on Polygraph Data

The polygraph cardiograph records a continuous pulse waveform based on the regular, rhythmic expansion and contraction of the arterial wall with each heartbeat. When an arrhythmia occurs, this regularity is disrupted. Premature beats produce early, often smaller-amplitude pulses followed by a compensatory pause and a subsequent larger-than-normal beat. Atrial fibrillation creates an irregularly irregular pattern with variable pulse amplitudes. These disruptions can make it difficult to evaluate the cardiovascular scoring features that depend on consistent beat-to-beat waveform characteristics.

Distinguishing Arrhythmia from Deception Responses

Trained examiners learn to distinguish between cardiovascular changes caused by arrhythmias and those caused by autonomic arousal in response to test questions. Key differences include: arrhythmias typically produce abrupt, isolated disruptions in the waveform pattern, while deception-related cardiovascular responses involve gradual, sustained changes in blood pressure baseline, heart rate, and pulse amplitude that develop over several seconds and correlate with question presentation.

Examiner Protocol

When arrhythmias are identified during the pre-test interview (through medical history) or observed during testing (in the cardiovascular tracing), the examiner should document the condition using chart markings, assess whether the arrhythmia is frequent enough to compromise cardiovascular data quality, and determine whether the other channels (electrodermal and respiratory) provide sufficient data for a reliable diagnostic opinion. If arrhythmias are severe or frequent enough to invalidate the cardiovascular channel, the examiner may rely on the remaining channels or determine that the examinee is unsuitable for testing at that time.

Common Medications

Many examinees with arrhythmias take antiarrhythmic medications, beta blockers, or calcium channel blockers. These medications can affect overall physiological reactivity and should be documented during the suitability screening. However, as with other medication effects, the differential responsivity framework means that reduced overall cardiovascular reactivity does not necessarily invalidate the examination — the within-subject comparison pattern may still be interpretable.