Assessment of myocardial function in preterm infants with chronic lung disease using tissue Doppler imaging.

OBJECTIVES: To assess myocardial function and presence of pulmonary hypertension (PH) using both tissue Doppler imaging (TDI) and conventional echocardiography in preterm infants of <32 weeks gestation with chronic lung disease (CLD). DESIGN: Prospective observational study. SETTING: Tertiary neonatal intensive care unit. PATIENTS: Three groups of preterm infants were recruited. Group 1-CLD receiving positive pressure airway support including high-flow humidified nasal cannula oxygen (n=25), group 2-CLD receiving low-flow nasal oxygen (n=25) and group 3-no CLD (n=22). METHODS: Echocardiography was performed around 36 weeks corrected gestational age. Myocardial function and PH were assessed using both conventional (left ventricular fractional shortening (LVFS) and left ventricular output (LVO), tricuspid regurgitation and ventricular septal flattening) and TDI techniques (myocardial velocities, myocardial performance index (MPI) and right ventricular isovolumetric relaxation time (RV-IVRT)). RESULTS: The MPI of right ventricle (RV) and left ventricle (LV) was significantly higher in CLD infants: mean RV MPI group 1-0.79, group 2-0.65 and group3-0.52. LV MPI: group 1-0.77, group 2-0.70 and group 3-0.45. There was a trend towards higher MPIs in group 1 compared with group 2. LVFS and LVO were similar across all three groups. RV-IVRT was also significantly higher in infants with CLD infants (group 1-64 milliseconds, group 2-62 milliseconds and group 3-52 milliseconds). PH was not detected by conventional echocardiography. CONCLUSIONS: Infants with CLD have evidence of relative biventricular dysfunction and higher pulmonary arterial blood pressure as demonstrated by TDI, which were not detected by conventional echocardiography.

Assessment of myocardial function in preterm infants with patent ductus arteriosus using tissue Doppler imaging.

OBJECTIVE: To assess myocardial function in preterm infants with different degrees of ductal patency in the first week of life using tissue Doppler imaging. STUDY DESIGN: Infants <30 weeks of gestation underwent echocardiography on day 3. A total of 72 infants were recruited into the study and categorised into three groups (i) haemodyamically significant ductus arteriosus, (ii) patent ductus arteriosus and (iii) no patent ductus arteriosus. Those with haemodynamically significant ductus arteriosus were treated with indometacin and echocardiography was repeated after 48-72 hours following treatment. Peak systolic and diastolic myocardial velocities were obtained using tissue Doppler imaging, and myocardial performance index was calculated. RESULTS: Initial myocardial velocities were significantly lower and myocardial performance index significantly higher in the haemodynamically significant ductus arteriosus group compared with other groups. For the haemodynamically significant ductus arteriosus group, post-treatment myocardial velocities were higher and myocardial performance index lower than pre-treatment. CONCLUSION: Preterm infants with haemodynamically significant ductus arteriosus had lower myocardial velocities and higher myocardial performance index, suggesting relative systolic and diastolic myocardial dysfunction. Babies whose patent ductus arteriosus remained open despite indometacin had lower pre-treatment myocardial velocities and higher myocardial performance index than those babies whose patent ductus arteriosus closed, suggesting worse myocardial function in this group. Measurement of myocardial function using tissue Doppler imaging in preterm infants is feasible and may prove to be helpful in the management of babies with patent ductus arteriosus.