Assessment of abdominal aortic intima media thickness in late pre-term appropriate for gestational age and growth restricted fetuses : a comparative cross-sectional study
Date of Award
2017
Document Type
Thesis
Degree Name
Master of Science in Epidemiology & Biostatistics (MSc Epidemiology & Biostats)
Department
Community Health Sciences
Abstract
Cardiovascular diseases share the topmost burden of mortality worldwide. According to fetal origin of adult atherosclerotic disease hypothesis, the cardiovascular derangement appears to originate in-utero in undernourished fetuses secondary to the cardio-metabolic stress they experience. This study investigates the abdominal aorta intima media thickness (aIMT) and aortic diameter (AD) in growth restricted fetuses (GRF) and appropriate for gestational age (AGA) fetuses as a non-invasive marker of future cardiovascular disease risk. Methodology: We conducted a cross-sectional study from February to August 2017 on 29 GRF and 85 AGA singleton fetuses enrolled in the late third trimester at the Aga Khan University, Karachi. The study was approved by the University Ethics Committee. Fetuses with structural and chromosomal abnormalities were excluded. Growth restricted fetuses were defined as those whose estimated fetal weight and birth weight were below the 10th centile for that particular gestational age .Abdominal aIMT and AD were obtained in a coronal view between the renal and the iliac arteries using high-end resolution Medison Accuvix 20 ultrasound machine with a 3.5 to 5-MHz linear array transducer. Measurement of aIMT was performed offline using digital software by manual placement of calipers on the intima-media surface by two observers separately. aIMT was measured as the distance between the leading edge of the blood intima interface and the leading edge of the media adventitia interface on the far wall of the vessel. AD was measured at the same level of aIMT, between blood intima interfaces at both ends of the vessel. All images were taken at end-diastole of the cardiac cycle. The reading was obtained three times and the mean measurement was analyzed. Inter-rater agreement was calculated by Bland-Altman technique Results: Mean (SD) maternal age (years) of AGA and (30.3±5.2) and GRF (31.4±5.5) did not differ significantly (p value 0.65). Similarly, gestational age at ultrasound and delivery (weeks) respectively, for AGA {(35.7 ±1.2) and (37.1 ±1.6)} and GRF {(35.6 ±1.4) vs. (36.5±1.7)} did not differ. However, as expected GRF weighed (in grams) less at birth in comparison to AGA fetuses (2082.4±400.7 vs. 2871.5±457.2). Mean abdominal aIMT on far wall examination was found to be significantly greater among GRF compared to AGA fetuses {(0.498 mm ± 0.09) vs. (0.417 mm ± 0.07); p-value<0.003)}. Inter-rater agreement calculated by Bland-Altman technique constituted maximum observations within 95% confidence intervals as excellent measure of agreement (mean difference = 0.007 mm; 95% CI: -0.77, 0.791). Multivariable model revealed significant association of GRF with aIMT (adj.13=0.07, 95% CI: 0.033, 0.109) after adjustment of birth weight, induced conception and male gender of the fetus. Conclusion: GRF demonstrate thicker aIMT in the late third trimester as compared to AGA fetuses. This adaptive mechanism appears to depict vascular remodeling of aortic intima and could likely predispose to ischemic vascular disease later in life. Long-term longitudinal studies are required to understand underlying mechanism of in-utero initiation of vascular changes and its association with cardiovascular disease in adult age.
Recommended Citation
Akhter, Z. (2017). Assessment of abdominal aortic intima media thickness in late pre-term appropriate for gestational age and growth restricted fetuses : a comparative cross-sectional study (Unpublished doctoral thesis). Aga Khan University, Karachi, Pakistan.