Attenuated 24-h heart rate variability in apparently healthy subjects, subsequently suffering sudden cardiac death

Abstract

Attenuated cardiac parasympathetic activity appear to be an important risk factor contributing to sudden cardiac death in subjects with overt coronary disease but its predictive value in otherwise healthy normal subjects is not known. We have for 8 years followed 260 apparently healthy adult subjects who underwent Holter monitoring. Twelve died, 14 developed ischaemic heart disease and four suffered sudden cardiac death. A healthy control subject was matched, along with other risk factors, for each case. In each subject 24-h heart rate variability was calculated as the deviation of all normal R-R intervals from mean R-R (SD) and the percentage of successive R-R interval differences exceeding 6% (%DIF6%)--this was used as an index of cardiac parasympathetic activity. There were no significant differences in heart rate variability between the cases developing problems and controls. In the sudden cardiac death victims, however, there was a clear trend towards lower heart rate variability. In them waketime mean SD was 73 ms versus 85 ms for cases and controls respectively (p = 0.08), and for sleeptime 61 ms versus 76 ms (p = 0.07). Compared to normal limits for heart rate variability obtained in 140 subjects that remained healthy for 8 years, figures for both SD and %DIF6% in sudden cardiac death subjects were at or below 95% confidence limits. The results indicate that altered autonomic balance may contribute to sudden cardiac death even in apparently healthy subjects. Subjects with a low 24-h heart rate variability on Holter monitoring may be predicted at an early stage of being at greater risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Heart rate variability is related to training load variables in interval running exercises

“…Reduced 24-h HRV has been found as a risk factor for sudden cardiac death also in healthy individuals (Mølgaard et al 1991).…”

Exercise Training Fails to Modify Arterial Baroreflex Sensitivity in Ovariectomized Female Rats

“…It has been considered that increases in both tonic vagal activity and reflex vagal activity (BRSinc) play an important role in reducing susceptibility to ventricular fibrillation and sudden cardiac death (Moolgard et al 1991;Farrel et al 1992;Hull et al 1994;La Rovere et al 2001). Although epidemiological study has indicated that HRT protects women from sudden cardiac death (Sourander et al 1998), a combination of exercise training and HRT may be superior to each intervention alone in terms of preventing sudden cardiac death by maintaining both tonic and reflex vagal activity to favorable levels.…”

Average heart rate, atrial fibrillation and R-on-T ventricular ectopy in 24h Holter recordings predict all-cause mortality in healthy middle-aged men

“…Studies in random samples of the population, like those of Engström and colleagues [2], Mäkikallio and colleagues [3], cannot be used as comparative material, because such groups are not free of disease. Molgaard and colleagues [4,5] performed an 8-year follow-up study in 245 apparently healthy subjects (163/82 male/female, mean age 54 [40-79]), but did not present all-cause mortality statistics.…”