SupplementFunctional Echocardiography in Assessment of the Cardiovascular System in Asphyxiated Neonates
Section snippets
Assessment of the Cardiovascular System
Transient myocardial ischemia is a recognized association of perinatal asphyxia, with an incidence from 30% to 82% of severely asphyxiated neonates.2, 9, 10 The incidence of myocardial dysfunction may be higher in preterm neonates who already have risk factors for myocardial impairment because of immaturity of the myocardium.11 Transient myocardial ischemia is often associated with evidence of myocardial damage, such as a rise in cardiac troponin levels.12 Diagnosis of myocardial involvement
Clinical Assessment
The mainstays of clinical assessment of asphyxiated neonates have been capillary refill time, acidosis, and blood pressure, which are all limited in both accuracy of assessment and the information obtained. Capillary refill time is used in adult and pediatric intensive care settings as an indicator of poor perfusion with some correlation;14, 15 however, accuracy in predicting low cardiac output is limited. Similarly, acidosis, as indicated by lactate level or base deficit, probably reflects
Qualitative Assessment of Cardiac Function
A simple visual assessment with echocardiography in either the parasternal long axis or a short-axis parasternal view can provide significant information about the function of the myocardium. Visual assessment of contractility is assessed with the movement of the septum and posterior myocardial wall and is reasonably accurate for clinicians experienced in echocardiography.19 Similarly, the filling of the heart can be assessed by observing the residual volume in diastole—the LV end diastolic
M Mode Measurements
M Mode imaging allows measurement of fractional shortening (FS) and ejection fraction (EF), which are more quantitative measures of the contractility of the ventricles. The reference range for FS in term neonates is 25% to 40%. EF is similar to FS, but each of the measures is cubed to allow assessment of volume changes; this also multiples any measurement error, particularly because in the neonate the RV dominance alters the shape of the ventricles. Other measures of EF, such as the modified
Systolic/Diastolic Time Intervals
Other measures of cardiac function can be determined by measuring peak velocity, mean acceleration, acceleration time, and LV ejection time. The systolic time interval ratio (acceleration time/LV ejection time) was not predictive of asphyxia.20 Use of more sophisticated measures of contractility that are independent of preload/afterload, such as the velocity of circumferential shortening or the ratio of velocity of circumferential shortening to end systolic wall stress, an afterload adjusted
Myocardial Performance Index
The myocardial performance index (MPI) combines a measure of both the systolic and diastolic intervals to characterize global myocardial performance.24 The MPI is a Doppler ultrasound scanning-derived index of myocardial performance, combining the isovolumetric contraction and relaxation time intervals, used to assess ventricular function. The index is independent of heart rate and blood pressure and does not rely on geometric assumptions. Preterm neonates with evidence of mild perinatal
Cardiac Output with Doppler Ultrasound Scanning
A more global assessment of cardiac function can be achieved by measuring cardiac output non-invasively by using Doppler ultrasound scanning techniques.3, 26, 27, 28, 29 Ventricular outputs are measured with two-dimensional echocardiography to measure outflow tract diameter and the velocity time integral.3 The cardiac index is derived by correcting for birth weight. This Doppler ultrasound scanning-derived non-invasive measure of cardiac output has been well validated against invasive measures
Superior Venal Caval Flow
Measurement of superior venal cava (SVC) flow has been used primarily in premature neonates to assess cardiac output independent of the transitional circulation shunts that result in the actual measured LV and RV output being higher than the true systemic blood flow. The LV output is increased by the left-to-right shunt through a patent ductus arteriosus, and the RV output is increased by the shunt through the patent foramen ovale.11, 31 SVC flow is potentially a proxy measure for cerebral
Right Ventricular Function
Assessment of the RV function can be achieved with a visual qualitative assessment of the contractility and filling in a long-axis view. Paradoxical movement of the septum or bowing to the left with increased RV pressure can be assessed in a short-axis view. The pattern of the velocity time ratio in the RV outflow tract (systolic interval) may also provide information about RV function and increased pulmonary pressure, with a reduction in the time to peak velocity as a proportion of total
Assessment of Volume Status/Fluid Responsiveness
Both hypotension and impaired cardiac output are common outcomes of asphyxial damage to the myocardium, and use of volume resuscitation in the setting of asphyxia is common. Volume is critical when there is evidence of hypovolemia or an acute change in the systemic vascular resistance resulting in vasodilation of the peripheral vasculature. Volume is also an important adjunct to the use of inotropes. Volume increases cardiac output in sick term neonates by increasing stroke volume rather than
Pulmonary Hypertension
Raised pulmonary pressures and PPHN are common complications of perinatal asphyxia, but the role of functional echocardiography in this area is also critically important. PPHN is a multifactorial dynamic process, and the treatment of asphyxiated neonates is assisted greatly by understanding the underlying physiology, particularly as the clinical situation changes.34, 42 The components of this include measures of myocardial and ventricular output (particularly right sided), various
Therapeutic Hypothermia and Cardiovascular Function
With the use of therapeutic hypothermia for the management of perinatal asphyxia, there is a lack of information on the effect of cooling on cardiac function and hemodynamics. This is likely to be particularly relevant during whole body cooling. Hypotension and sinus bradycardia are adverse effects of cooling that have been consistently noted.44 More recently, significantly decreased LV cardiac output (67% of post-hypothermic range) was demonstrated during therapeutic cooling, with a consistent
Training in Functional Echocardiography
The usefulness of bedside functional echocardiography is high in the setting of perinatal asphyxia. Bedside functional echocardiography has become an important tool in the treatment of critically ill intensive care patients in both adult and pediatric intensive care units,46 permitting rapid and precise diagnosis and longitudinal assessment of hemodynamic function. Increasingly the role of functional echocardiography in the neonatal unit has also been recognized.8, 47, 48 The expertise of a
Conclusion
Perinatal asphyxia commonly results in multiorgan damage and cardiovascular dysfunction. Myocardial damage, RV dysfunction, abnormal circulatory transition, and impaired autoregulation may all contribute to postnatal neurological damage. Adequate monitoring and appropriate targeted treatment are essential components of the intensive care of an asphyxial insult. Because standard methods of monitoring have limitations in assessing cardiovascular adequacy, functional echocardiography offers extra
Author Disclosures
Martin Kluckow, MBBS, FRACP, PhD, has no financial arrangement or affiliation with a corporate organization or a manufacturer of a product discussed in this supplement.
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Cited by (32)
Asphyxia, Therapeutic Hypothermia, and Pulmonary Hypertension
2024, Clinics in PerinatologyHypothermia and Cardiovascular Instability
2020, Clinics in PerinatologyCitation Excerpt :If they do, most organ dysfunction, except for the cerebral injury, usually is reversible. The heart dysfunction in the acute phase, however, further impairs blood supply to all organs and may hinder survival and exacerbate the permanent neurologic damage among survivors.2 Therapeutic cooling for 72 hours is now considered standard of care in asphyxiated infants with moderate or severe hypoxic ischemic encephalopathy.3
Updates on Management for Acute and Chronic Phenotypes of Neonatal Pulmonary Hypertension
2020, Clinics in PerinatologyCitation Excerpt :2) Hypoxia preventing the normal relaxation of the pulmonary vascular bed and increased PVR causing deoxygenated blood to be shunted to the systemic vasculature.77 As the aPH worsens (sometimes after initiation of therapeutic hypothermia),78 the impairment in oxygenation and pulmonary venous return further compounds the already reduced systemic blood flow from LV dysfunction.79 ( 3) Primary perturbation in RV performance with recent evidence showing RV systolic dysfunction with preserved LV function and normalization of pulmonary hemodynamics in infants with adverse neurologic outcomes following HIE.30
Comprehensive, real-time hemodynamic monitoring and data acquisition: An essential component of the development of individualized neonatal intensive care
2018, Hemodynamics and Cardiology: Neonatology Questions and ControversiesEvidence-based versus pathophysiology-based approach to diagnosis and treatment of neonatal cardiovascular compromise
2015, Seminars in Fetal and Neonatal MedicineCitation Excerpt :Therefore, the systemic cardiovascular and cerebral effects of asphyxia depend on multiple factors including the severity of the condition, the timing of the assessment relative to the insult and the methods used. This underscores the importance of the assessment of cardiac function and CBF in asphyxiated neonates as soon as possible after birth [48]. Another group of patients with myocardial dysfunction is the very preterm infant after PDA ligation.
Functional echocardiography in neonatal intensive care: 1 year experience in a unit in Spain
2014, Anales de Pediatria
Please see the Author Disclosures at the end of this article.