Converging methods in the assessment of sympathetic baroreflex sensitivity

AIMS: Abnormalities of the sympathetic baroreflex regulation are documented in various diseases. The recording of sympathetic nerve activity allows for the calculation of baroreflex gain but this is not available in practice. A non-invasive method based on blood pressure during the late phases of Valsalva manoeuvre (VM) was proposed. Sympathetic gain could be calculated from the pressure fluctuations following ventricular extrasystole or non-sustained ventricular tachycardia (NSVT). METHODS AND RESULTS: We assessed both indices in 25 subjects with no significant cardiovascular disease. VM was performed at 40 mmHg for 12 s. Paced NSVT consisted of five to six cycles. The sympathetic gains were determined based on the recovery of mean arterial pressure (MAP, mmHg/s). The maximum slope of five consecutive MAP elevations occurring within a 15-cycle period after NSVT was calculated. This MAP turbulence slope (MAP(TS)) was expressed in mmHg/cycle. Five patients were excluded because of unacceptable VM. VM-derived sympathetic gain (SBRS(vals)) and the NSVT-derived gain (SBRS(NSVT)) correlated closely (R = 0.86, P < 0.001). Their mean difference was 3.2 +/- 4.8 mmHg. Both SBRS(vals) and SBRS(NSVT) correlated closely with MAP(TS) (R = 0.77, P < 0.001 and R = 0.86, P < 0.001, respectively). CONCLUSION: The sympathetically mediated arterial pressure recovery is an analogous process following both VM and NSVT. SBRS(NSVT) or MAP(TS) may be useful in the assessment of patients with implanted antiarrhythmic devices.