Blood pressure and carotid-femoral pulse wave velocity in twins. Effect of birth weight

Abstract

Disorders in the oxygen or nutrients supply during the so called critical periods of intrauterine growth (IUG) may cause permanent organ damage and result in higher blood pressure and cardiovascular risk. Viscoelastic properties of arteries depend on their amount of elastin and collagen fibres. Elastin synthesis only occurs during the critical period of blood vessel development, so that any disturb in this period can cause a lesser arterial compliance. Monozygotic twins with different birth weight (BW) are an ideal model to study the relation between arterial compliance and BW because differences cannot be from genetic load or maternal nutrition. We have studied whether low BW as an index of IUG affects blood pressure and arterial compliance in twins with different BW. 19 twin pairs (11 monozygotic) in which one of them had intrauterine growth retardation (IUGR; BW < percentile 5 for gestational age) were studied. Weigth, height and blood pressure were measured. Carotid-femoral pulse-wave velocity (PWV) was assessed with a Complior (Colson) ® device. Obstetric history and familial history of cardiovascular disease were registered. An uni- and multivariant analysis with PWV as dependent variable was performed. Values of ph0.05 were considered significant. Mean (SD) age, BW, birth lenght and gestational age were 5.63 (0.59) years, 2.21 (0.42) Kg, 46.75 (3.84) cm, 35.36 (3.38) weeks, respectively. Values of systolic (SBP) and diastolic blood pressure (DBP) were 86.68 (15.2) and 55.18 (12.2) mm Hg, and PWV was 6.16 (2.83) m/seg. Univariant analysis showed a negative relation between BW and PWV in monozygotics (r = -0.45 p=0.034). No significant relation was found in dizygotics (r = -0.2 p=0.45). In Multivariant Model (monozygotics and dizygotics) (R2 0.32 p=0,009) predicting variables of PWV were gestational age (= 0.43 p=0.014), SBP (= 7 p=0.016) and BW (= -4.21 p=..007). In monozygotics (R2 0.49) only BW was a predicting variable with a stronger negative relation (= -6.33 p=0.014). Our data support the hypothesis that a IUGR favours from early ages higher arterial stiffness and SBP. This relation is more evident when monozygotic twins are compared, although studies with a greater number of subjects as well as follow up to adult life are needed to confirm this hypothesis.