Objective: Heart rate has been shown to predict cardiovascular morbidity and mortality in a very reliable and easily accessible manner. The exact definition of the conditions under which heart rate is measured appears to be as crucial as the determinations of blood pressure or plasma catecholamines. It was investigated how accurately heart rate measurements were performed, and conditions were described in 56 studies identified from prominent journals within the Medline database: (a) search phrases were "heart rate" and "rest" or "resting"; (b) publication date was from 1996 to 2001; and (c) publication type was "clinical trial".
Methods: Five conditions were considered as most influential: (a) resting period before measurement; (b) posture of the patient; (c) environmental conditions such as temperature or visual and acoustic stimuli; (d) method used to record heart rate; and (e) data analysis, i.e., derivation from raw data. An average of only 1.7 of those 5 criteria for the determination of heart rate were met in the studies included. Information on conditions of, for example, resting period, or environmental conditions is almost completely lacking.
Results and conclusion: The data show that a very important risk predictor and treatment target heart rate-is not reported in a scientifically sufficient manner, even in large trials. Valuable information is lost despite the fact that the investment of adequately defining, controlling, and performing this determination is modest in comparison to the potential gain. It is recommended to standardize heart rate measurements in analogy to that of blood pressure determinations.