Complications of aortic valve stenosis
Heart failure is the most common and potentially the most life-threatening complication of aortic valve stenosis. Despite what the name implies, heart failure does not mean that your heart stops beating. Heart failure occurs after your heart has spent months or more—often many years—compensating for the problem of aortic valve stenosis. Just like a runner struggling up an endless hill, eventually your heart begins to tire out and lose its ability to pump a sufficient amount of blood to your body at a sufficient rate.
Initially, stenosis causes a buildup of pressure inside the left ventricle (pressure overload). The ventricle compensates for the pressure by thickening (hypertrophy) and pumping harder to force a sufficient amount of blood through the narrowed valve. As the ventricle gets thicker, it becomes stiff and can't fill with blood as effectively (diastolic dysfunction).
Heart failure begins when the pressure in the left ventricle is transmitted back into the left atrium and lungs, causing shortness of breath, usually with exertion. As stenosis becomes worse, the left ventricle can no longer compensate and the pressure begins to stretch (dilate) the heart muscle. Eventually the heart loses its ability to pump enough blood to meet the body's needs (systolic dysfunction).
Contributing to the onset of heart failure is your heart's inability to supply itself with enough oxygen, a condition called myocardial ischemia.
Complications of advancing heart failure
If aortic valve stenosis is left untreated, a person whose heart begins to fail may not live long enough to develop the more advanced complications of heart failure, which include pulmonary hypertension (high pressure in the blood vessels that carry blood from the lungs to the heart) and pulmonary edema (buildup of excess congestive fluid in the lungs).
As the left ventricle begins to fail, blood will begin to back up into the left atrium. As the left atrium becomes overloaded with blood, it will begin to stretch out of shape (dilate), just as the left ventricle does as it begins to fail. When your left atrium dilates, it can disrupt the web of nerves that deliver the electrical signal from the sinoatrial (SA) node (which generates heart contractions) to the rest of the heart. Instead of the normal, perfectly coordinated contraction, the different parts of the atrium essentially start to contract at random. This is called atrial fibrillation.
Because atrial fibrillation is often a complication of heart failure, it tends to occur when aortic stenosis and the resulting heart failure have become extremely serious and potentially life-threatening. In fact, atrial fibrillation is not common in people who have aortic stenosis, likely because most people either have valve replacement surgery (which resolves the problem) or they do not live long enough to develop this complication. Atrial fibrillation is also more likely to occur if you also have a leaky mitral valve (mitral regurgitation) that is allowing blood to flow back into the left atrium.
An infection of the heart can be life-threatening and needs immediate treatment.
An infection in the heart is caused by bacteria that have attached to the wall of the heart or valve. Normally, the heart and blood vessels are structured so that bacteria have a difficult time attaching and causing an infection. The surfaces of both the insides of the heart and blood vessels are smooth and uniform, giving bacteria little chance to gain a foothold. But when the structure of the aortic valve is altered from stenosis, the smooth lining is also altered, giving bacteria a place to move in, attach, and grow.
The bacteria have access to all the food they need from the sugar (glucose) in your blood, so they will likely grow rapidly, often so fast that your body's immune system cannot keep them in check. When this happens, the bacteria expand rapidly to make room for all the new bacteria by clumping together and becoming a larger mass attached to the heart muscle or valve. These clumps are called vegetations, and as they become larger, pieces are likely to break off. The broken-off pieces act much like a blood clot and can block your arteries, causing heart attacks and stroke. They can also spread the infection throughout your body by traveling through your bloodstream. In addition, if your heart has already been weakened by valve problems, the vegetations can make it function even more poorly.
Sudden cardiac death occurs when the heart abruptly ceases to function from one or more existing problems. Before the advent of successful aortic valve replacement surgery, aortic stenosis was a common cause of sudden cardiac death, but surgery has significantly reduced the likelihood that someone will die suddenly from aortic stenosis. It should be emphasized that sudden death almost never occurs in people who do not yet have symptoms of aortic valve stenosis.
Although sudden death is impossible to predict, people who experience low blood pressure (hypotension) when they exercise, have developed serious problems with their left ventricle as a result of aortic valve stenosis, or have severe stenosis (a very narrow valve) are at much higher risk of sudden death. In general, sudden death in people who have aortic valve stenosis is closely associated with heart failure. Additionally, sudden death can occur when severe stenosis and advancing heart failure cause an irregular heartbeat or blocked vessels.