Transient tachypnoea of the newborn: two distinct clinical entities?

Twenty-five infants with transient tachypnoea of the newborn (TTN) were examined by serial echocardiography during the first 4 days of life. The infants could be divided clinically into two groups: group 1 (n = 19) babies with mild classical TTN requiring less than 40% oxygen, and group 2 (n = 6) babies with severe TTN needing greater than 60% oxygen. Apart from amount of oxygen these two groups differed in that those with severe TTN had lower Apgar scores and arterial pH soon after birth. Echocardiography showed that the babies with classical TTN had increased left ventricular pre-ejection period to ejection times (LPEP/LVET) during the first day of life. Initial LPEP/LVET ratio correlated with duration of treatment with oxygen. The babies with severe TTN increased LPEP/LVET and right ventricular pre-ejection period to ejection times ratios (RPEP/ RVET) during the first 3 days of life. There was no correlation between systolic time intervals and duration of oxygen treatment. These findings suggest that there may be two distinct types of TTN: mild or classical type resulting from mild left ventricular failure, and a severe type associated with generalised myocardial failure, pulmonary hypertension, and right-to-left shunting.