Psychophysical measurements during lumbar discography: a heart rate response study.

STUDY DESIGN: Prospective clinical data analysis.

OBJECTIVE: To determine if heart rate (HR) response correlates with positive discography results.

SUMMARY OF BACKGROUND DATA: Lumbar discography is a controversial tool for the diagnosis of discogenic low back pain. The subjective nature of discography can make data interpretation difficult, leading to false-positive and false-negative results. HR changes have been found in numerous studies to be a reliable and valid indicator of acute pain. To date, there is no study analyzing the HR response to discography-induced pain.

METHODS: The HR measurements were recorded immediately preceding and after contrast injection into the each disc, and statistically correlated with the provocation of concordant pain, nonconcordant pain, and nonpainful discs.

RESULTS: Discography was performed in 26 subjects with low back pain. Among 75 discograms, 26 discs elicited concordant pain, 9 provoked nonconcordant pain, and 40 elicited no pain response. There was no significant change in HR during disc stimulation for negative [no pain response (P=0.19) and nonconcordant (P=0.26)] discograms, whereas positive discograms [concordant pain (numerical rating scale> or =6/10)] were associated with a statistically significant increase in HR (P=0.000002).

CONCLUSIONS: Lumbar discography induces positive HR response only in positive discograms. Although there is no immediate practical application of these results, 2 implications may deserve future research: (a) correlation of HR response with surgical and intradiscal electrotherapy treatment outcomes; (b) evaluation of HR measurement in cases of false-positive results (concordant pain on discography but no HR response).