Low Birth Weight Infants Do Not Have Capillary Rarefaction at Birth

Abstract

Abstract-Low birth weight predicts adult essential hypertension and is linked to increased cardiovascular mortality in adult life. A reduction in capillary density (ie, rarefaction) is a hallmark of essential hypertension, and evidence suggests that rarefaction precedes the onset of the rise in blood pressure, because it is found in normotensive individuals at high risk of developing hypertension, suggesting that rarefaction is likely to be a primary structural abnormality. We hypothesized that low birth weight infants would have significant capillary rarefaction at birth. We studied 44 low birth weight infants born to normotensive mothers (33 were born preterm, birth weight: 1823Ϯ446 g; and 11 were born at term, birth weight: 2339Ϯ177 g) and compared them with 71 infants born at term with normal weight (birth weight: 3333Ϯ519 g). We used orthogonal polarized spectroscopy to measure basal (ie, functional) and maximal (ie, structural) skin capillary densities. Low birth weight infants, whether born preterm or at term, had significantly higher functional capillary density (mean difference of 10.5 capillaries per millimeter squared; 95% CI: 6.6 -14.4 capillaries per millimeter squared; PϽ0.0001) and higher structural capillary density (mean difference of 11.1 capillaries per millimeter squared; 95% CI: 7.6 -14.5 capillaries per millimeter squared; PϽ0.0001) when compared with normal weight term infants. We conclude that low birth weight infants born to normotensive mothers do not have capillary rarefaction at birth. These results contradict what might have been predicted from the concept of the intrauterine origins of adult disease and suggest that microcirculatory abnormalities observed in individuals of low birth weight occur in postnatal life rather than during their intrauterine existence. (Hypertension. 2011;58:847-851.)Key Words: capillary rarefaction Ⅲ microcirculation Ⅲ hypertension Ⅲ low birth weight M icrocirculatory abnormalities and impaired tissue perfusion have been implicated in the pathogenesis of essential hypertension, obesity, diabetes mellitus, and insulin resistance. 1 In essential hypertension in particular, a reduction in the spatial density of arterioles and capillaries (ie, rarefaction) appears to play a central role. 2 We have shown previously that much of the capillary rarefaction in essential hypertension is attributed to the structural (ie, anatomic) absence of capillaries. 3 We have also shown significant capillary rarefaction in patients with borderline intermittent essential hypertension and in normotensive offspring of hypertensive parents, suggesting a familial predisposition in which capillary rarefaction represents a primary vascular abnormality that antedates the onset of sustained elevation of blood pressure (BP). 4,5 There is now a strong body of evidence showing that low birth weight (LBW), that is, birth weight of Ͻ2.5 kg regardless of gestation or causation, 6 is associated with structural and functional vascular abnormalities, 7 the development of essential hypertension, 8...

Early Life Microcirculatory Plasticity and Blood Pressure Changes in Low Birth Weight Infants Born to Normotensive Mothers: A Cohort Study

“…We have previously reported that LBW infants born at term or preterm to mothers with normotension do not have CR: instead, these infants have a significantly higher CD at birth compared with their normal birth weight (NBW) counterparts. 10 Our findings appeared to contrast with reports that functional and structural microcirculatory abnormalities, including CR, are already present in childhood and young adulthood, respectively, in individuals born with LBW. 11–16 We, therefore, conducted a longitudinal study of a large cohort of infants from birth over a 1-year period.…”

“…Basal CD (BCD), which represents functional CD, was calculated as the mean of these 4 microscopic fields. We then used venous congestion to maximize the number of visualized perfused skin capillaries 10,17,18 by applying a size-appropriate neonatal blood pressure (BP) cuff around the calf muscle. The cuff was then inflated and maintained at 30 mm Hg for 2 minutes to determine the maximal CD (MCD), which represents the structural (anatomical) CD.…”

Elevated Blood Pressure in Preterm-Born Offspring Associates With a Distinct Antiangiogenic State and Microvascular Abnormalities in Adult Life

“…Whereas reduced capillary number has been identified as a specific vascular abnormality in young adults with a family predisposition, 30 individuals born with low birthweight do not consistently demonstrate changes in capillary density. 31 We also observed a lack of association between birthweight and capillary density in our preterm study. The finding of reduced capillary density relating to preterm birth per se is more established, even when blood pressure differences are still relatively modest.…”

Phenotyping the Microcirculation

“…[54][55][56][57] Surprisingly, low birth weight infants do not have capillary rarefaction at birth. 58 In low birth weight infants, capillary density may be even higher because of the relative systemic hypoxia that these infants experienced in utero. 56 Basal capillary density decreases progressively after the first week of life because of a process of pruning.…”

“…Alternatively, a "catch-up" process with abundant availability of nutrients may cause capillary hyperpruning. 59 Follow-up studies on the neonatal cohort described by D'Souza et al 58 have to be awaited to decide on this hypothesis.…”