To investigate the early diagnosis of myocardial injury after neonatal asphyxia based on the clinical manifestations of myocardial injury, electrocardiogram (ECG), cardiac enzymes and tissue Doppler echocardiography.

From January 1, 2013 to June 30, 2014, 101 cases of neonatal asphyxia in the neonatal intensive care unit of the First Hospital of Tsinghua University, with gestational age >37 weeks and birth weight>2 500 g, were enrolled. Apgar scores were used to diagnose neonatal asphyxia. Myocardial damage after neonatal asphyxia was diagnosed according to the hypoxia history, clinical presentation, ECG and cardiac enzymes. According to the umbilical arterial blood gas analysis, severe asphyxia was divided into two groups: the severe asphyxia with severe acidosis group and the severe asphyxia without acidosis group. The incidence of myocardial damage, clinical manifestations associated with myocardial damage, ECG and myocardial enzymes [creatine kinase isoenzyme MB (CK-MB) and cardiac troponin T (TnT); control group involved 50 cases for the same period of admission with newborn jaundice] and echocardiography (control group involved 30 cases for the same period with normal term delivery) were compared among the three groups [mild asphyxia (n=72), severe asphyxia with severe acidosis (n=18) and severe asphyxia without severe acidosis (n=11)]. One-way ANOVA, the LSD test, Kruskal-Wallis test for independent samples, Chi–square test and Fisher's exact test were used for statistical analysis.

(1) The incidence of myocardial damage after asphyxia was 34.6% (35/101). It was higher in the severe asphyxia group than in the mild asphyxia group [62.1% (18/29) vs 23.6% (17/72), χ²=7.549, P=0.006]; and it was higher in the severe asphyxia with severe acidosis group than in the severe asphyxia without severe acidosis group (14/18 vs 4/11, Fisher's exact test, P=0.048). (2) Clinical manifestations: The proportion of bradycardia was greater in the severe asphyxia with severe acidosis group (13/14) than in the severe asphyxia without severe acidosis group (1/4) and the mild asphyxia group (7/17); the differences were statistically significant (Fisher's exact test, P=0.019 and 0.007). (3) ECG: Eighteen cases (51.4%, 18/35) showed ECG abnormalities. (4) Cardiac enzymes: CK-MB 48 h after birth in the severe asphyxia with severe acidosis group, severe asphyxia without severe acidosis group, mild asphyxia group and the control group were 78.72 (34.63-122.01), 31.71 (21.33-37.12), 23.11 (14.61-36.02) and 11.82 (8.64-18.93) μg/L, respectively. CK-MB in the severe asphyxia with severe acidosis group was higher than in the severe asphyxia without severe acidosis group, mild asphyxia group and the control group (H=48.425, 90.040 and 96.045, respectively, all P<0.01). After treatment for 5-7 days, there was no statistically significant difference in these four groups (H=7.165, P=0.416). TnT 48 h after birth in the four groups was 0.19 (0.12-0.39), 0.11 (0.06-0.34), 0.07 (0.05-0.13) and 0.06 (0.04-0.08) μg/L, respectively. TnT in the severe asphyxia with severe acidosis group was higher than in the other three groups (H=45.753, 44.665 and 61.215, respectively, all P<0.01). Despite the reduced TnT level after treatment for 5-7 days, TnT in the severe asphyxia with severe acidosis group was higher than that in the other three groups (H=17.520, 21.122 and 43.286, respectively, all P<0.01). (5) Echocardiography: Twenty cases (57.1%, 20/35) showed abnormalities. The values of mitral systolic peak velocity and late diastolic peak velocity in the severe asphyxia with severe acidosis group were lower than those in the control group found by tissue Doppler echocardiography [(3.4±0.3) vs (4.8±0.3) cm/s, (4.1±0.2) vs (6.0±1.1) cm/s, respectively, t=3.293 and 2.542, both P<0.05].

Myocardial damage can occur after neonatal asphyxia. Cord blood pH value should be combined to determine the severity of asphyxia. Myocardial damage is more serious in the severe asphyxia with severe acidosis group. Clinical manifestations should be taken seriously, and laboratory examinations should be improved for early diagnosis and treatment.

Asphyxia neonatorum; Cardiomyopathies; Echocardiography, Doppler; Creatine kinase, MB form; Troponin T