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I’ve said it before, and I’ll say it again, your heart is a remarkable biological machine that has been tweaked to work with maximum efficiency over eons of evolution. We’ve already talked about the heart’s electrical system here (in the context of atrial fibrillation) and here (in the context of Wolff-Parkinson-White Syndrome). Now, we will discuss the heart’s mechanics and its function as a pump.
The heart as a pump
What is a pump? For our purposes, a pump is something that moves fluids from one place to another using force. The heart is a pump that moves blood by physical action against the resistant force of the diameter of the blood vessels (or, systemic vascular resistance).
All pumps should be equipped with a system that prevents backflow. After all, you don’t want all the energy expended by the pump negated by having the fluid flow back in again. This prevention of backflow would be the function of a valve that opens to allow the pump to move the fluid through, then closes to guard against backflow. Your heart has four valves that do just this.
The heart valves
Your heart has four chambers—the right atrium, the left atrium, the right ventricle, and the left ventricle. It also has four valves, two between the upper and lower chambers and two that that connect the heart to the exterior vessels. Between the right atrium and the right ventricle, we have the tricuspid valve. Between the left atrium and the left ventricle, we have the mitral valve. The valve that keeps blood from flowing back into the lungs from the right ventricle is the pulmonic valve. And, finally, the valve that keeps the blood from flowing back into the heart from the aorta (which leads to the systemic circulation) is the aortic valve.
Ideally, each of these valves opens smoothly to let blood flow through and then closes tightly to prevent backflow. However, sometimes the valves malfunction.
Malfunctioning heart valves
Your heart valves are made out of flexible leaflets that open to accommodate the forward flow of blood and close to prevent against backflow. There are two common ways heart valves can malfunction: stenosis or regurgitation. Let’s take them one at a time.
Valve stenosis is a stiffening of those formerly flexible leaflets. This stiffening can lead to outflow obstruction, or a narrowing of the pathway through which the blood is pumped. Stenosis can be caused by a congenital heart defect, called a bicuspid valve, in which the valve has two leaflets instead of three. It can also be the result of scarring from a bout of rheumatic fever. It can be caused by the build-up of calcium deposits that come with age. Or, it can be caused by any combination of the three. The stiffening prevents the leaflets from opening and closing effectively. Your doctor may say that she hears an opening snap followed by a murmur when she listens to your heart through her stethoscope.
Valve regurgitation occurs when the leaflets of the valve don’t close properly. In valve regurgitation, some of the blood leaks backward through the valve. This also causes a heart murmur that your doctor can hear through a stethoscope. Some of the same causes of stenosis can also apply to regurgitation.
The aortic valve
The aortic valve is located at the intersection of the heart’s left ventricle and the aorta, the largest artery in the body. Blood that flows through the aorta is destined to travel throughout the rest of your body. This blood has already traveled through your lungs and is fully oxygenated, ready to bring that oxygen to your muscles so your body can get on with the business of being alive.
Aortic stenosis is the condition in which the aortic valve opening is constricted due to the causes of stenosis mentioned above (bicuspid valve, scarring from rheumatic fever, calcification due to age). In order for the left ventricle to pump the blood through a stenotic aortic valve it is forced to work harder. As with any muscle, if it works harder, it gets bigger. We call this hypertrophy. While hypertrophy may be stellar for your biceps, it’s not so good when it comes to cardiac muscle. You really want to keep your heart muscle lean and mean so it can function properly.
Aortic regurgitation, on the other hand, is the condition in which the leaflets of the aortic valve do not close properly to prevent backflow. This condition can be caused by the same conditions as above and can also interfere with the function of your heart.
Management in pregnancy
If you have aortic valve dysfunction, it’s best to schedule a visit with your doctor prior to conceiving so you can discuss your treatment options. It is critical that your heart function optimally so as not to compromise your blood supply. Furthermore, some medications that may be used to manage aortic valvular disease in a non-pregnant patient have been deemed harmful in pregnancy. It’s vital that your medications be adjusted accordingly. You and your doctor may even want to consider surgically repairing the valve.
Management in labor and delivery
Ideally, you want labor to be as short, stress-free, and pain-free as possible. Your doctor will carefully monitor both you and your baby for any signs of hemodynamic instability. A vaginal delivery is preferred as it places less overall hemodynamic stress on your body.
You can find more information about aortic valve disease in pregnancy and during breastfeeding here.