Diagnosis of patent ductus arteriosus in the preterm newborn

A blinded comparison of clinical and echocardiographic evaluation of the preterm infant for patent ductus arteriosus

The accuracy of the characteristic physical signs of a patent ductus arteriosus (PDA), that is, a systolic murmur, increased volume of pulses and increased praecordial activity, in diagnosing a haemodynamically significant PDA in ventilated premature infants was prospectively evaluated. Fifty-five ventilated preterm infants (birthweight < 1500 g) had daily echocardiographic and clinical evaluation for a PDA for the first 7 days of life. The examiners were blinded to each other's findings. Probability analysis was performed for the accuracy of each clinical sign in detecting a haemodynamically significant PDA as defined by echocardiographic criteria. Clinical signs were poor at detecting a significant PDA in the first 4 days of life. On day 1, none of the 10 infants with a significant PDA had a murmur. By day 4, clinical signs were better at detecting a significant PDA, but specificity remained poor with many false positive signs. Six infants had murmurs with a closed duct. The development of echocardiographic haemodynamic significance preceded the development of physical signs by a mean of 1.8 days. Significant ductal shunts often occurred silently, but the development of a murmur often marked an increase in the velocity of the flow through the duct rather than an increase in the size of a shunt. This study confirms that echocardiography is required for the reliable early diagnosis of a PDA in ventilated preterm infants.

Effects of patent ductus arteriosus on left ventricular output and organ blood flows in preterm infants with respiratory distress syndrome treated with surfactant

Thirty preterm infants (birth weight < 1500 gm) treated with Surfactant TA for the respiratory distress syndrome, who had no complicating clinical problems other than ductal patency, were studied by serial Doppler flow examinations to determine the effects of early left-to-right shunt through the patent ductus arteriosus on the left ventricular output and organ blood flows. Doppler flow variables in 15 infants with a hemodynamically significant patent ductus arteriosus (hsPDA) were compared with those in 15 subjects without hsPDA matched for age, body weight, and gestational age. Infants with hsPDA had significantly higher left ventricular output and significantly lower blood flow volume in the abdominal aorta, and lower temporal mean blood flow velocities, with concomitant increases in the relative vascular resistance in the celiac artery, superior mesenteric artery, and renal artery. Pulsatility indexes of these vessels and the anterior cerebral artery were significantly higher in the hsPDA group, but the temporal mean blood flow velocities in the anterior cerebral artery and its vascular resistance were not significantly different between the two groups. After closure of the patent ductus arterious was achieved with mefenamic acid therapy, alterations in Doppler flow variables in the hsPDA group reverted to the levels seen in the group without hsPDA. These results suggest that despite large left-to-right ductal shunting, the heart of the preterm infant is capable of mounting a compensatory increase of cardiac output sufficient to maintain unchanged cerebral blood flow, but is unable to maintain postductal organ blood flows because of decreased perfusion pressure (ductal steal) and localized increase in vascular resistance.

Re-evaluation of the left atrial to aortic root ratio as a marker of patent ductus arteriosus

The aim of this study was to re-examine the accuracy of the left atrial aortic root ratio (LA:Ao) as a marker of significant patent ductus arteriosus (PDA) in the preterm infant by comparison with direct Doppler echocardiographic assessment. Fifty six infants (< 1500 g) had 463 serial echocardiograms. Firstly the LA:Ao was measured, then the duct was imaged and classified as wide open, restricting, or closed according to two dimensional and Doppler criteria. Probability analysis was performed to test the ability of the LA:Ao to discriminate between a wide open PDA and a restricting or closed duct. Mean LA:Ao was 1.17 and 1.21 when the duct was respectively closed or restricting compared with 1.61 when wide open. Using a LA:Ao of 1.5 as a cut off gives a sensitivity of 79% and specificity of 95% and increases the accuracy over the recommended levels of 1.3 and 1.4. With this cut off there were 20/94 false negatives, these were associated with scans on day 1 and large interatrial shunts. The sensitivity of the LA:Ao increased to 88% if only scans performed after day 1 were analysed. For diagnosing a PDA after day 1, the positive likelihood ratio of an LA:Ao of 1.5 or more was 17.5, and the negative likelihood ratio of an LA:Ao < 1.5 was 0.13. The LA:Ao is still a useful tool in the diagnosis of PDA. It is a simple method which needs less skill and resources than direct PDA imaging and is feasible on neonatal units without direct access to echocardiographic expertise. Its use on the first postnatal day is not recommended.