The heart is a very tough organ; it beats about two or three billion times in an average lifetime and will do so until the very last minute that you live.
At the same time, the heart is a very fragile organ in that it is susceptible to numerous diseases.
The heart has four chambers four valves and a right and left side. The right side of the heart pumps low-pressure volume blood into the lungs, while the left side of the heart pumps high-pressure volume into the body. This pressure difference is called a gradient and is responsible for keeping the blood circulating through the body. Fluids travel from a high-pressure environment to a low-pressure environment, and the cycle begins again.
Any time that there is a disruption between the delicate balance of right and left sided volumes or pressures, then congestive heart failure can occur. In adults for example, CHF may occur as a result long-standing hypertension, severe LVH and renal failure, diseases of the myocardium, ischemic heart disease, and arrhythmias such as atrial fibrillation.
In a pediatrics setting, there is often a communication between the right and left heart that causes a volume or pressure overload on one side of the heart or the other. This includes most congenital heart defects.
Afterload: is the amount of pressure that must be exerted by the myocardium to push blood out of the heart during systole.
Preload: the volume of blood that the ventricle is capable of holding during end diastole, or the ability of the ventricles to stretch just prior to systole.
These two concepts are very important in that congestive heart failure can occur as a result of both systolic and diastolic dysfunction. Systolic dysfunction can occur as a result of any obstruction of the left ventricle such as aortic stenosis or coarctation of the aorta, while diastolic dysfunction may occur as a result of mitral and aortic regurgitation. These are just two examples.
In the end, blood flow tends to congest in the lungs causing a syndrome known as â€œwet lungsâ€, causing the pulmonary capillaries to reduce their ability to transfer oxygen. The lungs respond by increasing their vascular resistance in order to protect the rights heart. This results in pulmonary hypertension, and eventually right ventricular hypertrophy, and eventual failure of the right ventricle.
Meanwhile, decreased left ventricular output causes metabolic acidosis, which affects all organs of the body, especially the kidneys, resulting in renal failure. Metabolic acidosis also affects the myocardium and causes it to be less responsive, which causes the cascade of heart failure to get worse.
Without intervention, eventually the entire heart fails, cardiovascular collapse occurs and then death.
Once the right heart begins to fail, this is a very dire situation. If the right heart cannot adequately pump blood through the lungs and into the left heart, then the left heart cannot adequately fulfill systemic needs. This results are anÂ ever worsening condition that is essentially a downward spiral that eventually results in death.
Ken Heiden RDCS