Providing medical care to a newborn with known or suspected cardiovascular disease can be daunting. An understanding of the pathophysiology of these conditions and the application of a few general principles will promote effective care and minimize the chance of iatrogenic misadventures. It is imperative that a concerted team of specialists with expertise in advanced pediatric cardiac care be assembled, including physicians from several specialties (neonatology, cardiology, critical care, cardiac surgery, and anesthesiology), nurses (neonatal, pediatric cardiac intensive care, and pediatric cardiac acute care), and other health care professionals (respiratory therapists, physical therapists, dieticians, pharmacists, social workers, etc.). Effective and ongoing communication is essential for optimizing care and providing a uniform approach to the management of these complex medical patients.
Heart failure in infancy is a syndrome that occurs as a consequence of the inability of the cardiovascular system to meet the metabolic and growth demands of the infant. It is a common feature of congenital cardiovascular disease presenting symptomatically in neonates. Heart failure in neonates and infants is most commonly caused by structural defects that result in decreased systemic output. In contrast to adults, most infants with heart failure have preserved cardiac contractile function but have increased demands on the cardiovascular system with increased myocardial oxygen requirements. The most common conditions associated with heart failure in infants are those in which there is a dominant left-to-right shunt with excessive pulmonary blood flow and increased oxygen demand. Heart failure in neonates can also result from any structural defect that results in decreased systemic blood flow (eg, severe aortic stenosis) or from myocardial dysfunction regardless of the etiology. Occasionally, heart failure occurs in situations in which the heart is structurally normal, but systemic output is very high and is associated with abnormal distribution of flow (eg, a large arteriovenous malformation), severe anemia, or excessive metabolic demands (eg, neonatal thyrotoxicosis).
The development and progression of heart failure results from a complex interplay of hemodynamic and neurohormonal factors. As illustrated in Figure 11-1, heart failure is viewed as a clinical syndrome that incorporates hemodynamics and compensatory neurohormonal responses in the overall conceptual framework. It should be noted that the roles of compensatory mechanisms that regulate cardiovascular function have been studied largely in chronic compensated states in adult patients and mature animal models. Although it is likely that developmental differences impact the compensatory physiological responses and the responses to therapy that have been designed for adult patients, the general concepts are likely applicable to infants. Additional clinical and experimental studies are necessary to define the spectrum of pathophysiology of heart failure in preterm and term newborn infants.
Interrelationships of various influences on the heart failure syndrome. Much of the theoretical and experimental framework for understanding the pathophysiology of heart failure has been developed in ...