NEW YORK (Reuters Health), Jul 26 - Fetuses of mothers with diabetes are prone to cardiac hypertrophy, which is worsened by poor glycemic control and is probably related to fetal hyperinsulinemia, investigators in London report. However, the ventricular hypertrophy seems to represent functional adaptation.
It is well established that the prevalence of cardiac anomalies and fetal death is increased in the offspring of women with diabetes, even when maternal blood glucose control is good, Dr. Helena M. Gardiner and her associates note.
In a novel approach to investigate this relationship, the researchers used echocardiography to determine ventricular long axis function, which is a sensitive indicator of early ventricular dysfunction in adults.
They compared the findings in 41 fetuses of diabetic pregnancies and 159 normal control fetuses, assessed from 17 weeks until term. Ten mothers had type 1 diabetes and 31 had type 2 diabetes. All of the women used insulin throughout pregnancy.
Dr. Gardiner, from Queen Charlotte's and Chelsea Hospital, and her associates report their findings in the August issue of Heart.
Periconceptual diabetic control, indicated by glycosylated hemoglobin (HbA1c) levels, was assessed during early pregnancy.
Doppler flow and myocardial velocities were negatively associated with Hba1c, and fetal myocardial thickness was positively associated, although the latter relationship was not statistically significant.
The authors also report that fetuses of diabetic mothers generally had increased gestational-age-related values for Doppler velocimetry, myocardial velocities, amplitude of atrioventricular ring, and size of left free wall, septum, and right free wall when compared with control fetuses, "implying improved age-related cardiac performance."
Dr. Gardiner's team suggests that the increased amplitude of motion and myocardial velocities along with myocardial hypertrophy in fetuses of diabetic mothers indicates "an adaptive response to hypertrophy rather than a cardiomyopathic process."
The birth outcomes were good, with Apgar scores >8 and no cases of macrosomia, polycythemia or requirement for neonatal intensive care.
The investigators conclude: "We suggest the term 'fetal diabetic cardiomyopathy' should be more accurately referred to as 'adaptive hypertrophy,' and that altered autonomic control may be a more likely explanation for the increased rate of stillbirth in diabetic pregnancies rather than primary cardiac dysfunction."
In a related editorial, Dr. Lisa K. Hornberger from the University of California, San Francisco, points out that fetuses of diabetic mothers experience increased oxidative metabolism in response to hyperglycemia, and that cardiac hypertrophy may protect them from hypoxemia.
In most cases, she adds, the asymptomatic cardiac hypertrophy in these infants resolves within months of birth.
Nevertheless, the incidence of congenital anomalies, including heart defects, remains high in the presence of diabetes. Dr. Hornberger hopes that "flow and tissue Doppler investigations in the first trimester may ultimately elucidate the role of hemodynamic changes in the evolution of the fetal cardiac embryopathy of maternal diabetes."
Last Updated: 2006-07-25 14:50:58 -0400 (Reuters Health)
Heart 2006;92:1019-1021,1125-1130.
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