Inheritance of heart rate variability: the kibbutzim family study

Heart rate variability (HRV) measures are associated with coronary heart di sease incidence and mortality. Therefore insight into the genetic and envir onmental determinants of these measures may have clinical relevance. We ass essed the role of genetic and environmental factors of time domain and freq uency domain HRV indices. Participants were 451 kibbutz members, aged 15 an d up, belonging to 80 families. HRV indices were calculated from Holter rec ordings measured over 5 min. Our data indicate that for the two time- and f our frequency domain indices, a mixture of two normal distributions fit the data significantly better than a single normal distribution (P<0.05). We u sed complex segregation analysis to infer the modes of inheritance of these HRV measures. We found evidence for possible involvement of a recessive ma jor gene in the inheritance of the root mean square of successive differenc es in RR intervals (RMSSD), which is predominantly vagally mediated. A puta tive major gene explains 28%-34% of the adjusted inter-individual variabili ty. The SD, determined by a mixture of mechanisms, is influenced by environ mental and polygenic effects, but: not by a major gene. The findings regard ing the heritability of the frequency domain indices were not conclusive. H owever, the involvement of genetic factors was not rejected. Additional stu dies in extended families are needed to confirm the involvement of major ge nes in the determination of the autonomic activity.