The purpose of this study is to evaluate if a significant PDA increases O2 demand of myocardium as measured by serum BNP and CKMB.
Methods: We obtained consent from the parents of 37 infants weighing <1500 gms & performed an echocardiogram at 3-7 days of life. SPDA was defined as PDA diameter >1.5 mm on echocardiography. BNP, CKMB & Troponin I were measured in both infants with SPDA (Study group, n=7) and those without (Control group, n=30). Infants with SPDA were treated with 3 doses of indomethacin. We compared BNP, CKMB & Troponin I in SPDA & control groups prior to treatment. ANOVA and student t test were used for the statistical analysis (p <0.05, significant).
Results: The SPDA group had significantly lower gestation (25.8 vs 27.9 weeks), there was a higher prevalence of females in the SPDA group (85% vs 43%), and only 57% of SPDA infants were exposed to antenatal MgSO4 vs 100% of controls. Antenatal Indomethacin use, antenatal steroids exposure, and method of postnatal respiratory support were not significantly different between groups. Serum BNP levels in the SPDA group were significantly elevated (1195 ng/ml) compared to levels in the control group (29.8 ng/ml) as were CKMB levels (3.27 ng/ml vs 1.27 ng/ml). There were no significant differences between the groups in Troponin I levels. Multivariate ANOVA controlling for race, sex, Indomethacin exposure, MgSO4 exposure, and antenatal steroid exposure, continued to demonstrate a significant elevation in both BNP and CKMB levels in the SPDA group.
Conclusion: These data demonstrate significant elevations in BNP and CKMB among infants with SPDA and suggest by proxy an increased oxygen demand of the infant’s mycocardium.