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Hello. My name is Dr. Christina VanderPluym, and I am the Director of the Ventricular Assist Device Program in the Heart Transplant and Heart Function Program at Boston Children's Hospital. And today, I'm going to discuss heart failure in children in this two-part part series. We're going to first start with the pathophysiology and diagnosis of heart failure in infants and children. We're going to start with the causes of heart failure in infants and children. We're going to follow with the classification and staging, then look at the clinical manifestations of heart failure in infants and children, and finally end with a diagnosis, which consists of the initial evaluation followed by further evaluation.
Causes of Heart Failure.
So there are three main causes of heart failure in infants and children, starting with ventricular pump dysfunction, otherwise known as systolic dysfunction. So when we consider the heart, with two ventricles, or even with some of the complex congenital anatomies with only single ventricles, the heart, functionally, is a pump. And if the pump has any dysfunction, then you're going to have a decrease in cardiac output, as well as sequelae of backup of all that pressure that results in pulmonary and systemic venous congestion.
Another cause of heart failure in infants and children is volume overload. And this can occur in the setting of both preserved ventricular function as well as in settings of ventricular dysfunction. This is otherwise known as increased preload, when there's just an additional amount of volume within the heart. And these have physiological consequences of backing up of this fluid into both the lungs as well as through systemic venous circulation as well. The last is pressure overload, and this can occur, once again, in the setting of preserved ventricular function or in the setting of ventricular dysfunction. This is otherwise known as increased afterload, or increased pressure that the heart must work against.
So starting with ventricular pump dysfunction, we categorize it into both structurally normal hearts and then congenital abnormality of hearts. So in considering structurally normal hearts, we have cardiomyopathies, of which there is dilated, hypertrophic, restrictive, non-compaction, and arrythmogenic right ventricular dysplasia. Now, these different types of cardiomyopathies just describe the appearance of the heart.
Dilated cardiomyopathies are those where the heart itself is dilated and enlarged. Generally, the wall of the ventricle is thinned out. And associated with the dilation of the ventricle, you get stretching of the annulus, resulting in either tricuspid or mitral regurgitation, which further exacerbates the dilation and the dysfunction.
In hypertrophic cardiomyopathy, you actually have preserved size of the ventricle, and if anything, the ventricle cavity becomes small because of hypertrophy or thickening of both the ventricular free walls and the septum. This hypertrophy is generally more pronounced in the left than the right. However, you can get cases of biventricular hypertrophy.
The most severe cases of hypertrophic cardiomyopathy result in significant left ventricular outflow track obstruction, which can have disastrous consequences of complete cessation of blood flow out of the heart, which can result in either syncope or ventricular arrhythmias.
Another cause of ventricular dysfunction is restrictive cardiomyopathies. This is a unique case of cardiomyopathy in which the systolic function-- i.e., the pumping of the heart-- is actually preserved. However, the relaxation of the heart is dramatically impaired.
This impairment in relaxation results in a buildup in pressure in the ventricle, which is then transduced into the atriums. If it's in the left ventricle, this pressure is then transduced into the pulmonary vasculature, which can result in pulmonary edema and pulmonary vascular congestion. And this presents clinically as significant tachypnea and inability to tolerate any dramatic changes in their volume status.