Signal-averaged resting sympathetic transduction of blood pressure: is it time to account for prevailing muscle sympathetic burst frequency?

Calculating the blood pressure (BP) response to a burst of muscle sympathetic nerve activity (MSNA), termed sympathetic transduction, may be influenced by an individual's resting burst frequency. We examined the relationships between sympathetic transduction and MSNA in 107 healthy males and females and developed a normalized sympathetic transduction metric to incorporate resting MSNA. Burst-triggered signal averaging was used to calculate the peak diastolic BP response following each MSNA burst (sympathetic transduction of BP) and following incorporation of MSNA burst cluster patterns and amplitudes (sympathetic transduction slope). MSNA burst frequency was negatively correlated with sympathetic transduction of BP (r = -0.42; P < 0.01) and the sympathetic transduction slope (r = -0.66; P < 0.01), independent of sex. MSNA burst amplitude was unrelated to sympathetic transduction of BP in males (r = 0.04; P = 0.78), but positively correlated in females (r = 0.44; P < 0.01) and with the sympathetic transduction slope in all participants (r = 0.42; P < 0.01). To control for MSNA, the linear regression slope of the loglog relationship between sympathetic transduction and MSNA burst frequency was used as a correction exponent. In subanalysis of males (38 +/- 10 vs. 14 +/- 4 bursts/min) and females (28 +/- 5 vs. 12 +/- 4 bursts/min) with high versus low MSNA, sympathetic transduction of BP and sympathetic transduction slope were lower in participants with high MSNA (all P 0.05). In contrast, normalized sympathetic transduction of BP and normalized sympathetic transduction slope were similar in males and females with high versus low MSNA (all P 0.22). We propose that incorporating MSNA burst frequency into the calculation of sympathetic transduction will allow comparisons between participants with varying levels of resting MSNA.

Automated summary

The study examined the relationship between resting burst frequency and sympathetic transduction, finding negative correlations between burst frequency and sympathetic transduction of BP, as well as the sympathetic transduction slope. Meanwhile, burst amplitude showed different relationships with sympathetic transduction in males and females, with a positive correlation in females but no correlation in males. The researchers proposed that including burst frequency in the calculation of sympathetic transduction could facilitate comparisons between individuals with varying levels of resting MSNA.