213 Mechanism of Cardiovascular Dysfunction in Infants of Active Smokers

Abstract

Recently we showed that blood pressure and heart rate control is impaired in infants of mothers who smoke. This dysfunction resembles classic orthostatic intolerance and could indicate susceptibility to raised blood pressure later on. We analyzed whether this dysfunction reflects abnormal autonomic neural modulation of the heart, or the vasculature, or both. Methods: Subjects: term-born infants of mothers who smoked during pregnancy (15cigarettes/day; n=15) and infants of non-smokers (n=27). All were examined at least twice between 1 week and 18 months age. Supine blood pressure (BP; Finometer) and heart period (HP) were recorded for 4 min during quiet sleep. We used autoregressive cross-spectral analysis to compare age-related changes in low (LF; 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) power of HP and systolic BP (SBP). The gain of the heart-pressure relationship (α) was estimated by frequency domain analysis. We considered (i) LFHP and LFSAP power as markers of the sympathetic efferent modulation of the heart and blood vessels, respectively, and (ii) α as an index of baroreflex sensitivity. Results: Absolute values of, and variance in HP / BP of infants of smokers and non-smokers were comparable. In tobacco-exposed infants LFSAP (but not LFHP) decreased and α increased with age. Conclusions: Early-life tobacco exposure attenuates sympathetic drive to the blood vessels and augments baroreflex gain but leaves cardiac sympatho-vagal drive unchanged.