Evaluation of a brief cardiovascular autonomic screen

To test the validity and practicality of a simple, rapid autonomic cardiovascular evaluation (RACE).

Assessment of the autonomic nervous system is costly and time consuming. Consequently, briefer measures are often utilized as evaluations of autonomic function. We therefore set out to assess the validity and practicality of a simple, rapid autonomic cardiovascular evaluation protocol which mimicked the bedside evaluations used in many healthcare centers.

Every eligible patient undergoing full autonomic testing (FAT) in our laboratory was enrolled. The protocol, performed blinded to FAT results, consisted of one breath in the supine position, and supine and standing (1 and 3 min) pressures and pulse. Results were scored for cardiac variation during the breath, a drop in pressure during the stand. Pulse increase was also scored. Aggregate RACE score was regressed against a similarly scored FAT.

The single breath response correlated poorly with the standard response to deep breathing with convergent results in only 26/37 patients, with a specificity of 30%, and sensitivity of 85%. HR and BP changes standing showed little regression against matching values during FAT. Only 5/11 patients who met the criteria for postural tachycardia syndrome by FAT demonstrated a >20 bpm increase in HR by 3 min standing. Finally, aggregate scores for FAT and RACE correlated poorly.

The RACE does not satisfy the criteria to serve as a robust dysautonomia screen. Full autonomic testing provides more complete and accurate information than simple bedside assessment.