Cardiac troponin T and cardiac dysfunction in extremely low-birth-weight infants.

Extremely low-birth-weight (ELBW) infants frequently manifest signs of cardiac dysfunction requiring inotropic support. It is not clear if this is due to cardiac injury, which can be monitored by measuring cardiac troponin T (cTnT). We performed a nested prospective cohort study at a university level III neonatal intensive care unit. The study included 27 infants weighing between 500 and 999 g. Exclusion criteria included evidence of sepsis, use of postnatal steroids, and cardiac anomalies. Measurements included serum cTnT and echocardiogram in the first 48 hours of life. The mean serum cTnT level of the study population was 0.52 +/- 0.38 ng/ml. It was higher in those with lower Apgar scores (0.89 +/- 0.37 if 5-minute Apgar < 4 vs 0.36 +/- 0.26 ng/ml, p < 0.001) and correlated to initial base deficit (r = -0.37, p < 0.05). Infants who required inotropic support had higher cTnT levels than those who did not (0.73 +/- 0.43 vs 0.39 +/- 0.29 ng/ml, p < 0.03). cTnT concentrations did not relate to simultaneous echocardiographic measures of cardiac function. In ELBW infants, serum cTnT levels are higher than normally seen in term infants and adults, and they are higher in infants with greater perinatal stress as well as those who show evidence of cardiac dysfunction requiring pressor support.

Fetal presentation of congenital long QT syndrome.

Thirty-two-week prenatal ultrasound revealed a fetal heart rate of 100 bpm with decreased variability on the heart rate tracing. Echocardiogram documented normal anatomy and sinus bradycardia. Newborn electrocardiogram revealed sinus rhythm at 100 bpm with a QTc of 0.657. Follow-up electrocardiogram revealed a QTc interval of 0.568, 2:1 atrioventricular block with a ventricular rate of 60 bpm, and ventricular ectopy. The infant received a pacemaker and beta-blocker therapy. Long QT syndrome should be in the differential diagnosis of the fetus with bradycardia and decreased heart rate variability in the absence of distress. Early diagnosis allowed for preventative care in the infant and identification of family members at risk.

Doppler echocardiographic analysis of flow in the ductus arteriosus of infants with hypoplastic left heart syndrome: relationship of flow patterns to systemic oxygenation and size of interatrial communication.

Excessive pulmonary overcirculation related to imbalance in the pulmonary/systemic vascular resistance ratio contributes to hemodynamic instability in infants with the hypoplastic left heart syndrome. Because the ductus arteriosus bridges the two vascular circuits in this lesion, we studied the Doppler echocardiographic flow patterns in the ductus arteriosus of 50 infants with hypoplastic left heart syndrome to investigate their relationship to the degree of pulmonary blood flow as measured by simultaneously obtained levels of partial pressure of oxygen in arterial blood. The degree of restriction to pulmonary venous egress as determined by size of the interatrial communication was also correlated with ductal flow patterns and partial pressure of oxygen in arterial blood. Biphasic flow was noted in all infants. Mean peak velocity of antegrade flow (pulmonary artery to aorta) was greater than that of retrograde flow (aorta to pulmonary artery) (131 +/- 45 cm/sec versus 54 +/- 15 cm/sec; p < 0.001), mean time of retrograde flow was greater than that of antegrade flow (246 +/- 60 msec versus 174 +/- 28 msec; p < 0.001), and mean velocity-time integral of antegrade flow was greater than that of retrograde flow (13.3 +/- 4.8 cm versus 6.3 +/- 3.4 cm; p < 0.001). The ratio of velocity-time integral of retrograde flow/antegrade flow (a volumetric estimate of diastolic reversal into the pulmonary vascular bed indexed to systemic output) correlated extremely well with partial pressure of oxygen in arterial blood (r = 0.91; p < 0.0001). Categoric size of the interatrial communication (none, n = 2; small [<2 mm], n = 9; moderate [3 to 4 mm], n = 23; and large [>4 mm], n = 16) correlated with partial pressure of oxygen in arterial blood (r = 0.82; p < 0.001); the smaller the interatrial communication the lower the partial pressure of oxygen in arterial blood and velocity-time integral ratio of retrograde/antegrade flow. Doppler flow patterns in the ductus arteriosus of infants with hypoplastic left heart syndrome are reflective of the resistance ratio between the pulmonary and systemic vascular circuits and may be helpful in monitoring the hemodynamics of these infants.