Plasma biomarkers and echocardiographic indices of left ventricular function in very low birth weight infants.

OBJECTIVE: Evaluate plasma markers of myocardial function and ischemia [B-type natriuretic peptide] (BNP) and cardiac troponin T (cTnT)] in relationship to echocardiographic indices of left ventricular (LV) function and severity of illness score (SNAPPE-II) in Very-Low-Birth-Weight-Infants (VLBWIs) prospectively.

STUDY DESIGN: Serial echocardiography studies, clinical data, BNP and cTnT were obtained in thirty VLBWIs on postnatal days 1, 2, 3 and 7.

RESULTS: BNP increased and cTnT decreased significantly day 1 through 3. BNP was significantly associated with patent ductus arteriosus (PDA), but did not correlate with LV function or cTnT and did not reflect use of inotropic medication. Cardiac troponin T increased with severity of illness, SNAPPE-II, score and was highest in babies receiving inotropic medication; Low cardiac output (CO) was common in the first seventy two hours and correlated negatively with cTnT (p < 0.01). A contractility index, the corrected LV mean velocity of circumferential fiber shortening, (mVcfc) was not related to cTnT. The LV mVcfc was inversely related to LV end systolic wall stress (p < 0.001) in all subgroups, and this index of contractility (mvcfc-ess) did not differ with large caliber PDA or use of inotropic medication.

CONCLUSION: Cardiac troponin T exclusively rather than a combined biomarker approach may be useful in assessing myocardial injury. Cardiac output was low in sick VLBWIs with myocardial ischemia. Left ventricular contractile state was apparently preserved in significantly ill babies with elevated cTnT. Further research is needed to define the complex relationship between biomarkers and echocardiographic indices.