The effect of sex and prematurity on the cardiovascular baroreflex response in sheep

Abstract

Very preterm infants have an increased risk of cardiovascular disease, however the effects of a late preterm birth on future cardiovascular function are not known. We hypothesized that well describes impairments in heart rate variability and baroreflex sensitivity would persist into adulthood following a late preterm birth. To test this hypothesis sheep born preterm (0.9 gestation: 9M, 7F) or term (11M, 6F) underwent surgery at 14 months of age for insertion of femoral arterial and venous catheters and femoral flow probe. Following recovery, heart rate variability (HRV) was assessed followed by a baroreflex challenge (using vasoactive agents; phenylephrine and sodium nitroprusside) in conscious adult lambs. Our data demonstrate decreased low frequency (LFnu) and LF/high frequency (HF) ratio in female but not male ex-preterm sheep at rest. When challenged, mature male ex-preterm sheep have an increased blood pressure response but dampened heart rate baroreflex response. We show that even a late preterm birth leads to cardiovascular dysfunction in adulthood. These early signs of cardiovascular dysfunction may underpin the later hypertension and increased risk of heart disease observed in adults born preterm. These findings are particularly important as late preterm infants are often assumed to escape the long-term morbidities known to impact on very and extremely preterm offspring.

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