Genetic Influences on Baroreflex Function in Normal Twins

Blood pressure and heart rate are strongly influenced by genetic factors; however, despite the pivotal role of genetics in short-term cardiovascular regulation, little is known about the genetic contribution to baroreflex function. We assessed genetic influence on baroreflex sensitivity (BRS) in 149 twin pairs (88 monozygotic of age 33±13 years and BMI 23±4 kg/m 2 and 61 dizygotic of age 33±11 years and BMI 24±4 kg/m 2 ). ECG and finger arterial blood pressures were measured continuously under resting conditions. BRS values were calculated by use of cross-spectral analysis (baroreflex slope calculated as mean value of transfer function between systolic blood pressure and the R-R interval in the low-frequency band [BRSLF] and baroreflex slope calculated as the mean value of transfer function between systolic blood pressure and R-R interval in the respiratory frequency band [BRSHF]) and the sequence technique (BRS+, BRS-). Heritability ( h 2 ) was estimated with a path-modeling approach. BRS values did not differ significantly between groups (monozygotic, BRSLF, 17±13; BRSHF, 21±18; BRS+, 19±16; and BRS-, 21±15, and dizygotic, BRSLF, 16±9; BRSHF, 20±14; BRS+, 18±10; and BRS-, 20±11 ms/mm Hg), and were significantly correlated ( P <0.001). When variances and covariances for monozygotic and dizygotic twins were compared, significant correlations were found for BRS in monozygotic (range, r =0.38 to 0.48) but not in dizygotic twin pairs ( r =-0.03 to 0.09). Thus, BRS is heritable; the variability can be explained by genetic influences ( P <0.01; h 2 range, 0.36 to 0.44). The genetic influence on BRS remained strong after correction for BMI and blood pressure. Therefore, BRS is strongly genetically determined, probably by different genes than are resting blood pressure and BMI.