The “aperiodic” ballistocardiogram as a function of age

Abstract

1. 1. A modification of the Wittern “aperiodic” ballistocardiograph, capable of quantitative registration of force in 2 degrees of freedom is described in detail. 2. 2. The records of seventy-three normal subjects ranging in age from 2 1 2 to 87 years comprise the material for this report. 2.1. A. The wave form of the “aperiodic” ballistocardiogram varies with age and force direction, though the shape of the record for any single individual is a unique and highly reproducible characteristic. 2.2. B. Progressive shift of the frontal plane vector toward the transverse axis of the body begins at approximately age 40. Bidirectional recordings are therefore essential in the age group of primary clinical interest. 2.3. C. Respiratory variation cannot be explained on the basis of change in force direction. Though reversed respiratory variation is highly significant in subjects under 40, it may be entirely normal beyond age 50. 3. 3. The most important fact elucidated by this study is that reaction force remains constant throughout adult life. The hemodynanic alterations responsible for constant force output despite progressive decrease in stroke volume and contractility are discussed. 4. 4. Though the “aperiodic” ballistocardiogram has proved to be a valuable clinical and investigative technique, the complexity of instrumentation and interpretation precludes its use as a “service” diagnostic procedure in its present state of development.