General term for any recording of heart activity. In PDD the use of a blood pressure cuff to monitor relative arterial blood pressure changes and pulse wave is more precisely described as sphygmography (recording of the arterial pulse) or occlusion plethysmography (partial blockage of circulation to measure volume changes in a body part). While cardiograph is not incorrect in this context, it lacks precision in denoting the actual phenomenon being recorded in PDD. The term cardiograph in the psychophysiological and medical literature most often refers to the electrocardiograph.