**2. Functional echocardiography**

Bedside functional echocardiography provides physiological information and is a useful real-time noninvasive method among other monitoring tools for critically ill children. It is being increasingly used in making therapeutic clinical decisions and assessing response to treatment in unstable patients in the intensive and emergency units [7].

Functional echocardiography allows bedside use of cardiac ultrasound that brings fast and efficient investigation and recognition of the key hemodynamic changes, an assessment of cardiac function, pulmonary hypertension, pericardial effusion, and evaluation of the shunts. It provides insights into pathophysiology that leads to significant hemodynamic instability, and in addition, therapeutic interventions could be better planned and targeted. It also enables monitoring responses to treatment, which allows rapid therapeutic adjustments [7–10].

Functional echocardiography is also called targeted echocardiography, point-of-care cardiac ultrasound, or clinician performed ultrasound. It is being used to assess preload, afterload, and cardiac contractility while choosing inotropic or fluid therapy [4, 7].

Functional echocardiography performed in the newborn differs significantly from that performed in older children, because of the increased risk of critical or significant CHD. Therefore, the first echocardiography performed on a newborn should be accurate and structured with sequential segmental analysis of the heart. The subsequent scans can be functional, focused, or targeted to address specific clinical questions [7, 11–13].

**Table 1** summarizes the recommendations for the practice of functional echocardiography including neonatologist-performed echocardiography.

Clinical benefits of functional echocardiography are well seen in patients with hypotension and shock, which are common conditions in critically ill children, both likely to have high mortality. Furthermore, echocardiography is crucial in identifying


*DPAP, diastolic pulmonary artery pressure; FAC, fractional area change; LVEDD, left ventricular end-diastolic dimension; LVESD, left ventricular end-systolic dimension; MPAP, mean pulmonary artery pressure; PAP, pulmonary artery pressure; PDA, patent ductus arteriosus; PFO, patent foramen ovale; RVSP, right ventricular systolic pressure; SPAP, systolic pulmonary artery pressure; SVC, superior vena cava; TAPSE, tricuspid annular plane systolic excursion; TDI, tissue Doppler imaging; TVI, time velocity integral.*

#### **Table 1.**

*Recommendations for functional echocardiography.*

the underlying pathophysiology, evaluating hemodynamics, and managing the response to treatment in patients with shock [7, 14].

Information from functional echocardiography in conjunction with other clinical parameters and monitoring tools can be used in choosing fluid resuscitation therapy and appropriate inotropic, vasopressor, or vasodilator therapy [15–17]. Early recognition of increased pulmonary pressure may help in the early institution of pulmonary vasodilators, especially in neonates with pulmonary hypertension [7, 9, 11, 17].

Functional echocardiography offers the potential for novel insights into cardiovascular impairment. Specifically, whether the concern relates to preload, afterload, or myocardial contractility. Serial echocardiography evaluation to monitor treatment response may provide a better understanding of physiology and guide the duration of treatment, which minimizes drug exposure [11].

Assessment of volume status is usually made with inferior vena cava (IVC) size and collapsibility, which is also the method of choice to evaluate right heart filling pressure. This can be done easily in spontaneously breathing children, but some limitations exist in ventilated patients. In the presence of cardiogenic shock and increased right heart filling pressure, the IVC will appear dilated with no respiratory variation [15].

Qualitative estimation of the severity of pulmonary hypertension can be made by assessing the shape of the left ventricle and interventricular septum (IVS) motion, which is obtained from the parasternal short-axis view. With rising pulmonary artery pressure (PAP), the left ventricle begins to lose its circular shape and IVS starts to flatten, furthermore, paradoxical septal movement may occur in severe pulmonary hypertension [7, 9]. The shunt across the patent foramen ovale (PFO) is generally bidirectional in the presence of pulmonary hypertension but can sometimes be left-to-right even in the presence of severe pulmonary hypertension. An exclusively right-to-left shunt across the PFO is always abnormal and suggests elevated right heart filling pressure [6]. Direct assessment of the pulmonary artery pressures can be done by a peak velocity of the tricuspid insufficiency jet using the modified Bernoulli equation. The pulmonary artery systolic pressure (PASP) may be estimated by adding right atrial pressure to the peak systolic pressure gradient between the right ventricle and right atrium. The mean pulmonary artery pressure (MPAP) is assessed by using the peak diastolic velocity of the pulmonary regurgitation jet. The end-diastolic velocity of the pulmonary regurgitation jet is used to estimate diastolic pulmonary artery pressure (DPAP) [6, 7]. Functional echocardiography is useful in the initiation of vasodilator treatment (such as inhaled nitric oxide) and monitoring the response to treatment [6].

Pericardial effusion is a common condition in intensive care units; functional echocardiography allows easy diagnosis and timely echo-guided pericardiocentesis [18]. The hemodynamic effect of pericardial effusion does not depend solely on the amount of pericardial fluid. A large amount of pericardial fluid can be well tolerated when the fluid accumulates slowly. However, rapidly increasing pericardial effusion is more dangerous and may lead to cardiac tamponade. The main echocardiographic signs of cardiac tamponade are distended IVC with no respiratory variation, right atrial collapse at the end of diastole, right ventricular free wall collapse during diastole, and respiratory variation of Doppler mitral inflow for more than 10% and tricuspid inflow for more than 25% [7].

Patent ductus arteriosus (PDA) is an independent risk factor for intraventricular hemorrhage, necrotizing enterocolitis, bronchopulmonary dysplasia (BPD), and acute pulmonary hemorrhage [19, 20]. The hemodynamic significance of a PDA may not be directly related to the size of the PDA but depends upon the magnitude of the shunt and the ability of the myocardium to adapt to a left-to-right shunt [7, 20–22]. PDA causes pulmonary hyperperfusion and systemic hypoperfusion, which could be assessed with functional echocardiography. The duration of the shunt and the level of diastolic flow reversal in the descending aorta are good indicators of the significance of PDA and can be used for follow-up. An additional factor in assessing the PDA is pulmonary artery pressure, which can be monitored based on PDA Doppler velocity magnitudes. A low-pressure gradient between the aorta and pulmonary artery may be associated with pulmonary hypertension. Non-restrictive PDA has a low peak systolic velocity with a high systolic to diastolic velocity gradient, while restrictive shunt is

## *Clinical Benefits of New Echocardiographic Methods DOI: http://dx.doi.org/10.5772/intechopen.104808*

characterized by a high peak systolic velocity and a low systolic to diastolic velocity gradient [21]. Functional echocardiography has also been reported to improve the outcomes in infants being treated for PDA, the impact of this echocardiographic method is still the subject of ongoing research [23, 24]. Furthermore, it has been found that the performance of bedside echocardiography reduces the number of indomethacin doses used for treating PDA [25, 26]. The introduction of a functional echocardiography screening program for hemodynamically significant PDA on day 3 of life with the targeted intervention was associated with a reduction of severe intraventricular hemorrhage and ventilation duration [25, 27]. Serial echocardiography was associated with earlier identification and treatment of PDA, lower rates of severe intraventricular hemorrhage, and reduced ventilator days [11, 25].
