Objective: To present a 3-dimensional approach to displaying and interpreting processes of cardiovascular adaptation.
Design: Laboratory study of blood pressure changes in response to a protocol set in advance. The authors plotted the coordinates of 3711 cardiovascular change events (CVCEs) in 3-dimensional space defined by changes in systolic blood pressure, diastolic blood pressure and heart rate. This was followed by cluster analyses and preliminary estimates of reliability and construct validity.
Setting: The teaching hospitals of a large southwestern US medical centre.
Participants: Approximately 100 female nursing personnel aged 25 to 50 years.
Interventions: Medical history, self-administered questionnaires, laboratory protocol of pressor challenges, rest periods.
Results: Nine distinct clusters ("species of response") were identified and replicated in randomly chosen halves of the sample. Postural, isomorphic and psychologic challenges generated several distinctive profiles of "rising" responses, and were also followed by distinctive "declining" responses. The frequencies of various cardiovascular reactions ("clusters") to the same protocol were correlated with psychosocial characteristics and hypertension risk indicators.
Conclusions: The 3-dimensional approach reveals many features of cardiovascular adaptation not discernible from traditional univariate displays and analyses. This paradigm might prove useful for matching patients with hypertension by their cluster patterns to their most suitable medication, but it requires further validation by direct hemodynamic measurements.