ABC | Volume 112, Nº5, May 2019

Guideline Brazilian Fetal Cardiology Guidelines – 2019 Arq Bras Cardiol. 2019; 112(5):600-648 Table 6.1 – Diagnostic criteria and classification according to the severity of ductal constriction Criteria 1 point each 2 points each 3 points each Systolic velocity, m/s 1.40–1.69 1.70–1.99 ≥ 2.00 Diastolic velocity, m/s 0.30–0.34 0.35–0.39 ≥ 0.40 Pulsatility index 2.2–2.1 2.0–1.9 ≤ 1.8 RV:LV ratio 1.30–1.59 1.60–1.79 ≥ 1.80 PA:Ao ratio 1.30–1.59 1.60–1.79 ≥ 1.80 Septal bulging to the left 0 – +/4 ++/4 +++/4 – ++++/4 Tricuspid regurgitation 0 – +/4 ++/4 +++/4 – ++++/4 Ao: aorta; LV: left ventricle; PA: pulmonary artery; RV: right ventricle. 6.1. Prevalence, Diagnosis, Clinical Consequences, and Prognosis of Fetal Ductus Arteriosus Constriction The prevalence of ductal constriction detected in a convenience sample of 16,079 records of fetal echocardiograms performed during the third trimester of gestation, over a period of 11 years, excluding all other concomitant anomalies, in Porto Alegre, Rio Grande do Sul, Brazil was 2.7% (435 cases). During this period, there were 207,323 live births; the sample thus represented 7.75% of births. 79 Experimental studies have shown that fetal ductal constriction results in an increase in the medial layer of the pulmonary artery, which leads to a secondary increase in pulmonary vascular resistance in utero. 80 Thus, the majority of studies on persistent pulmonary hypertension are based on the experimental model of fetal ductal constriction induced by the administration of indomethacin. 81 Moderate or chronic ductal constrictions lead to pulmonary hypertension due to the increase in the medial layer and consequent increase in pulmonary artery constriction. This sustained increase in right ventricular afterload may lead to morphological, functional, and histological modifications in the right ventricular myocardium. 82 Ventricular dysfunction in cases related to maternal medication ingestion may be completely reverted following its interruption. The persistence of the dysfunction, however, may even lead to myocardial ischemia with papillary dysfunction. 80,83,84 Fetal cardiac dysfunction is described as one of the characteristics of fetal ductal closure and, in severe cases, the possibility of anticipation the childbirth should be considered, once fetal pulmonary maturity is reached. 85 Postnatal clinical outcome depends on the severity of in utero right ventricular failure and response to the increased pulmonary vascular resistance. 86 Long-term prognosis is uncertain; however, in cases with favorable initial outcome, there usually are no chronic complications. Nevertheless, after fetal heart failure, functional modifications may persist during the neonatal period, even in those with benign outcome. Echocardiographic diagnosis of fetal ductal constriction is based on the presence of turbulent flow in the ductus, with an increase in systolic velocity (> 1.4 m/s), increase in diastolic velocity (> 0.3 m/s), and decrease in pulsatility index (PI) (< 2.2). In the first publication, the cutoff point for PI was 1.9. 87 Recent studies, however, have considered a higher threshold. 78,88 With the increased afterload secondary to ductal constriction, the heart shows symptoms of growth in earlier stages, hypertrophic response, with hyperplasia (substituted by apoptosis), increased right chamber proportions, increased pulmonary artery to aorta ratio, and interventricular septum bulging into the left ventricle. 89,90 It is important to highlight that the diagnosis of ductal constriction and the evaluation of its severity cannot be established solely in terms of categorical variables of the “yes/no” sort, but are based rather on continuous variables, with a spectrum of circulation compromise (mild, moderate, or severe) which has been summarized in Table 6.1. The scores are classified as followed: Mild constriction: 3–7 points, the first 3 criteria being required Moderate constriction: 8–14 points, the first 3 criteria being required Severe constriction: > 15 points, the first 3 criteria being required. As the vasoconstrictor effect in the ductus arteriosus is dose-dependent, 91 the disappearance of hemodynamic abnormalities and non-development of fetal/neonatal cardiac dysfunction are common after the use interruption of constrictor substances. 89,92-95 Even in severe cases of ductal constriction following use of substances that 620