定向新生儿超声心动图在新生儿重症监护病房中的应用：实践指南与培训建议：美国超声心动学会(ASE)、欧洲超声心动学会(EAE)及欧洲小儿心脏科医师协会(AEPC)联合撰写组

Background:

Neonatologists can assess the hemodynamic stability of infants using echochardiography. Once significant congenital heart disease (CHD) is ruled out, the clinician can perform more focused studies (targeted neonatal echocardiography [TNE]) for specific indications. With the increased availability of echocardiography and miniaturization of technology, neonatal intensive care units (NICUs) around the world are able to not just diagnose or monitor CHD and screen for patent ductus arteriosus (PDA) but also to monitor the process of therapy. The current indications for TNE, the recommendations for its performance, and training requirements for those performing and interpreting TNE were documented.

Indications:

TNE with standard imaging is indicated for clinically suspected PDA, especially in very low birth weight (VLBW) neonates at least 24 hours of age; to assess perinatal asyphyxia; for abnormal cardiovascular adaption manifest as hypotension, lactic acidosis, or oliguria during the first 24 postnatal hours or later in VLBW infants to diagnose low systemic blood flow; if persistent pulmonary hypertension is suspected in neonates; and for congenital diaphragmatic hernia (CDH). TNE with focused imaging is indicated if effusion (pericardial or pleural) is suspected; when a central line is placed; and for extracorporeal membrane oxygenation (ECMO) cannulation.

Recommendations:

If CHD or arrhythmia is strongly suspected clinically in a newborn, comprehensive echocardiography is done and interpreted by a pediatric cardiologist. Hemodynamically unstable newborns with no clinical suspicion of CHD undergo a comprehensive study done by a core TNE person and interpreted by an advanced TNE person, with interpretation by a pediatric cardiologist in a reasonable time. Children with no CHD are assessed by standard TNE as a targeted functional study.

Ultrasound systems used for TNE are optimized for imaging neonatal hearts, with special care when imaging a potentially unstable or VLBW infant to prevent infection, maintain body temperature, and monitor cardiorespiratory function. Quantitative assessment of left ventricular (LV) systolic function requires estimating LV dimensions from M-mode or two-dimensional (2D) measurements; measuring LV end-diastolic dimension and septal and posterior wall thickness; and determining shortening fraction (SF) if no regional wall motion or septal motion abnormalities occur. If either of these is abnormal, ejection fraction (EF) is calculated. Ideally the assessment of diastolic function and filling pressures are part of TNE, although no evidence supports the use of TNE data in the fluid management of neonates and infants. Assessing right ventricle (RV) size and function are also part of the TNE, with qualitative visual assessment the most commonly used technique. 2D measurements can aid quantitative serial follow-up. TNE should also include assessing the presence, size and direction of atrial-level shunting.

TNE can be used to determine the presence of a PDA, direction and characteristics of the shunt across the duct, and pressure gradient between the aorta and the pulmonary artery (PA).Hemodynamic significance is further evaluated using degree of volume overload by LV measurements.

TNE includes the estimation of RV systolic pressure (RVSp) and PA pressures and a measurement of cardiac index using the LV output method. Acquisition and analysis must be well standardized and optimized to guarantee maximal reproducibility. LV does not indicate systemic blood flow if a PDA is present. The superior vena cava (SVC) method can be used to follow changes in cardiac output with PDA, but interpretation must be done cautiously.

Pericardial effusion is measured from the epicardial surface of the heart to the maximal dimension on 2D imaging at end-diastole. Effusions should be measured by assessing maximal dimension at end-diastole and identifying the site.

All neonates clinically suspected to have PDA should undergo a comprehensive echocardiographic study before starting medical or surgical treatment to exclude ductal-dependent congenital heart defects and define arch sidedness. Standard TNE done subsequently defines the PDA's hemodynamic significance and documents spontaneous closure or treatment effects. TNE can also help identify the cause of hemodynamic instability in preterm infants after ductus ligation.

Comprehensive echocardiography is indicated for neonates with perinatal asphyxia and clinical or biochemical signs of cardiovascular compromise. Standard TNE helps optimize therapy, but its usefulness for monitoring cooling and rewarming phases of hypothermia care requires further study. TNE may also help define the underlying causes and medical management for hypotensive neonates who have no structural heart disease.

If pulmonary hypertension is suspected, comprehensive echocardiography can rule out structural heart disease. PA pressure, RV function, and shunt direction at the atrial and ductal levels can be determined using TNE in neonates with persistent pulmonary hypertension of the newborn (PPHN). In addition, all children with CDH should have comprehensive echocardiography to rule out CHD and assess PPHN severity. The effect of treatment on PA pressure, RV function, and shunt direction at atrial and ductal levels can be monitored, with focused TNE helping with line placement or ECMO use.

TNE with focused imaging can help diagnose pericardial and pleural effusions, assess their hemodynamic impact, and guide interventions. Comprehensive echocardiography is done after hemodynamic stabilization for infants with pericardial effusion. Focused TNE helps monitor treatment and can be used to identify catheter tip position after line placement or potential complications such as line thrombosis or infection. A pediatric cardiologist must perform or interpret echocardiographic procedures to rule out vegetations. Every child on ECMO must have comprehensive echocardiography. Focused TNE with focused imaging helps especially with assessing cannula position. The impact of venoarterial ECMO on ventricular filling must be considered when assessing PA pressure and ventricular performance.

Training Requirements:

The US and European training requirements for echocardiography are designed to cover individuals performing comprehensive pediatric and congenital echocardiography. The core or basic level includes the ability to perform comprehensive transthoracic echocardiography in neonates and children and the ability to distinguish normal from abnormal. Practitioners at the advanced or expert levels must be able to perform fetal echocardiography and transesophageal echocardiography (TEE) as well as diagnose complex disease and supervise and train core or basic practitioners. Specific cognitive and technical skills must be acquired during these training processes. Competence and quality assurance for TNE are maintained by having neonatal echocardiographers continue to perform a minimum of 100 echocardiographic studies per year and regularly participating in echocardiographic conferences or training courses.