Echocardiographic Evaluation of Hemodynamics in Neonates and Children

Abstract

Hemodynamic instability and inadequate cardiac performance are common in critically ill children. The clinical assessment of hemodynamic status is reliant upon physical examination supported by the clinical signs such as heart rate, blood pressure, capillary refill time, and measurement of the urine output and serum lactate. Unfortunately, all of these parameters are surrogate markers of cardiovascular well-being and they provide limited direct information regarding the adequacy of blood flow and tissue perfusion. A bedside point-of-care echocardiography can provide real-time hemodynamic information by assessing cardiac function, loading conditions (preload and afterload) and cardiac output. The echocardiography has the ability to provide longitudinal functional assessment in real time, which makes it an ideal tool for monitoring hemodynamic assessment in neonates and children. It is indispensable in the management of patients with shock, pulmonary hypertension, and patent ductus arteriosus. The echocardiography is the gold standard diagnostic tool to assess hemodynamic stability in patients with pericardial effusion, cardiac tamponade, and cardiac abnormalities such as congenital heart defects or valvar disorders. The information from echocardiography can be used to provide targeted treatment in intensive care settings such as need of fluid resuscitation versus inotropic support, choosing appropriate inotrope or vasopressor, and in providing specific interventions such as selective pulmonary vasodilators in pulmonary hypertension. The physiological information gathered from echocardiography may help in making timely, accurate, and appropriate diagnosis and providing specific treatment in sick patients. There is no surprise that use of bedside point-of-care echocardiography is rapidly gaining interest among neonatologists and intensivists, and it is now being used in clinical decision making for patients with hemodynamic instability. Like any other investigation, it has certain limitations and the most important limitation is its intermittent nature. Sometimes acquiring high quality images for precise functional assessment in a ventilated child can be challenging. Therefore, it should be used in conjunction with the existing tools (physical examination and clinical parameters) for hemodynamic assessment while making clinical decisions.

Keywords: echocardiography in NICU; functional echocardiography; hemodynamic assessment in intensive care; hemodynamic evaluation; neonates and children.

Figure 1

Inferior vena cava (IVC) changes during the respiratory and cardiac cycles. Images a,b show normal physiological change in the IVC diameter during inspiration and expiration. Images c,d show no variation during the respiratory cycle in the presence of volume loading of the heart.

Figure 2

Left ventricle (LV) study in PLAX and PSAX views. FS and EF can be measured reliably on both views - image a shows FS measurement in PLAX and image b shows same measurement in PSAX view. However, EF probably best measured by Simpson’s method. PLAX, parasternal long axis view; PSAX, parasternal short axis view; LV, LV study; FS, fraction shortening; EF, ejection fraction.

Figure 3

Simpson’s biplane method for measurement of ejection fraction (EF). Image a shows left ventricular end-diastolic volume (LVEDV) and image b shows left ventricular end-systolic volume (LVESV) measurements in apical four-chamber view to calculate EF. Similar measurements are done in apical two-chamber view.

Figure 4

Tissue Doppler imaging on pulse-wave Doppler of interventricular septum (myocardium). Spectral above the baseline (s′) reflects the movement of myocardium toward apex in systole while below the baseline (e′ and a′) reflects the movement of myocardium away from apex in diastole.

Figure 5

Interdependency of right and left ventricular functions in the setting of pulmonary hypertension with increased PVR. LV, left ventricle; RV, right ventricle; PVR, pulmonary vascular resistance; IVS, interventricular septum; VQ, ventilation–perfusion.

Figure 6

Estimation of pulmonary artery systolic pressure (PASP). Image a shows tricuspid regurgitation (TR) jet in apical four-chamber view (A4C) and image b with Doppler assessment of TR—in this case a gradient of around 36 mmHg between right ventricle and right atrium (RA) suggests PASP between 40 and 45 mmHg (36 + RA pressure of 5–10 mmHg).

Figure 7

Interventricular septum (IVS) and left ventricle (LV) shapes in pulmonary hypertension. Image a shows normal IVS and LV shape with LV being a circular-shaped structure on sweep PSAX view. Images b–d show change in shapes with increasing flattening of IVS in presence of mild, moderate, and severe pulmonary hypertension, respectively.

Figure 8

Tricuspid annular plane systolic excursion (TAPSE) measurement on echocardiography. TAPSE reflects the longitudinal movement of the tricuspid annulus toward apex in systole measured on M-mode in apical four-chamber view.

Figure 9

Pulmonary artery acceleration time (PAAT) measurement. Image a shows normal ratio of PAAT and right ventricular ejection time (RVET) in a normal child. Image b shows significantly decreased PAAT and increased PAAT/RVET ratio suggestive of pulmonary hypertension. “Dicrotic notch” may be seen on pulse-wave Doppler spectral in the pulmonary artery.

Figure 10

Assessment of left ventricular output (LVO) on echocardiography. Image a shows LV outflow tract (red arrow) and AV annulus (red line), which has been zoomed in image b to measure diameter at the hinge point of AV valve. Image c shows LV outflow tract and the site for PW Doppler to measure VTI (red line showing PW sample gate). Image d shows LVO in milliliters per minute. AV, aortic valve; PW, pulse wave; LV, left ventricle; VTI, velocity time integral.

Figure 11

Assessment of right ventricular output (RVO) on echocardiography. Image a shows RV outflow tract (red arrow) and image b with measurement of PV annulus (red line) at the hinge point of PV valve. Image c shows RV outflow tract and the site for PW Doppler to measure VTI (red line showing PW sample gate). Image d shows RVO in milliliters per minute. PV, pulmonary valve; PW, pulse wave; RV, right ventricle; VTI, velocity time integral.

Figure 12

Measurement of superior vena cava (SVC) flow on echocardiography. Image a shows SVC in modified parasternal short axis view on 2D and image b with measurement of SVC diameter in M-mode. Image c shows acquisition of pulse-wave Doppler in the sub-costal view and SVC flow in milliliters per minute has been calculated in image d after measuring velocity time integral.