How Does Aortic Stenosis Lead To An Enlarged Heart?

Aortic stenosis refers to a narrowing of the aortic valve, a valve in the heart that prevents oxygenated blood flowing from the left ventricle (chamber) to the aorta (the body’s main vessel) from flowing the wrong way back into the heart. 

When this valve does not function as it should, it becomes harder for the heart to pump blood out. This can lead to complications such as an enlarged heart and can be potentially dangerous. 

Here we will know more about aortic stenosis, how it leads to enlargement of the heart, what the risks are associated with aortic stenosis, and how to diagnose and treat aortic stenosis. 

What is aortic stenosis? 

The aortic valve

The heart is responsible for circulating blood around the body. The deoxygenated (containing no oxygen) blood enters the heart, passes through the lungs to become oxygenated, and then leaves the heart to be circulated throughout the entire body. 

During circulation, the heart valves particularly help the blood flow only in one direction. A heart valve comprises cusps (flaps) that stop the blood from flowing backwards.

The aortic valve is the last valve where the oxygenated blood passes through before leaving the heart. It is found between the aorta – the body’s main blood vessel – and the left ventricle (chamber) of the heart.¹

The purpose of the aortic valve is to make sure that when the blood is flowing into the aorta, it does not flow back into the left ventricle. 

Stenosis of the aortic valve

When the heart’s valves are not functioning, this may be referred as a valvular disorder. One of the most common types of valvular disorders is aortic stenosis.²

Aortic stenosis is a condition when the aortic valve and/or surrounding area becomes narrower and/or stiffer, and the valve is unable to open. Consequently leading to a reduced flow of oxygenated blood traveling from the heart into the aorta.

What causes aortic stenosis? 

There are various causes of aortic stenosis. 

Calcium build-up

The most common cause of aortic stenosis in older patients (over 70s) is a build-up of calcium in the wall of the aortic valve, which causes it to become stiffer, diminishing its ability to open properly (NHS). 

This process gradually progresses as one gets older. Calcium is naturally found in the blood, and over time, as the blood flows through the aortic valve, calcium deposits can build up there. 

Rheumatic fever

One or more episodes of rheumatic fever (a rare inflammatory disease that can be a complication of a bacterial throat infection) can cause the aortic valve to become rigid and can even distort the valve’s cusps (flaps), which are the mechanism for ensuring the blood flows in one direction.

However, another heart valve – the mitral valve –is more commonly affected by rheumatic fever than the aortic valve.³

Bicuspid aortic valve

Aortic stenosis can also be caused by a congenital heart defect – an abnormality of the heart present at birth. 

This means that instead of being made up of three cusps (flaps), the aortic valve only has two cusps. It is the most common congenital defect and affects 1% to 2% of the population.⁴

This defect can result in a degeneration of the valve and ultimately lead to it becoming narrower or obstructed.⁵

Symptoms of aortic stenosis 

In the early stages of aortic stenosis, a patient can be asymptomatic – meaning they do not present with any symptoms. 

However, as it worsens and the heart has to work harder to compensate, symptoms may include: 

• A pain in the chest 
• Tightness in the chest, which may extend to the tummy/neck/arms/shoulders
• Fatigue
• Coughing 
• Difficulty breathing and/or dizziness when exercising 
• Temporary loss of consciousness after exertion 

What is an enlarged heart?

When the heart becomes enlarged, it is referred to as cardiomegaly, and it can occur for various reasons.

To be classed as cardiomegaly, the cardiac silhouette (outline of the heart on radiographic scans in a certain position) must have a transverse diameter which is at least half of the transverse diameter of the entire chest. The transverse diameter is the measurement between the two widest points.⁶

Often, an enlarged heart, or cardiomegaly, is a symptom of another problem within the heart.

How does aortic stenosis cause an enlarged heart?

As mentioned, oxygenated blood leaves the heart by passing through the aortic valve from the left ventricle (chamber) and into the aorta. However, in a patient with aortic stenosis, the aortic valve will not function normally, and it will be harder to open and let the blood flow through. 

This means that the heart is experiencing a constant increase in LV (left ventricle) afterload. 

Afterload refers to the pressure that the heart’s left ventricle needs to work against each time the heart contracts (beats), to pump the blood into the aorta.⁷

When the left ventricle is constantly working against this higher pressure, the muscle walls can become larger and thicker, just like when you consistently use another muscle in your body. This is referred to as Left Ventricular (LV) hypertrophy. 

However, whilst the heart is adapting to cope with the extra stress and pressure on the left ventricle, these changes to its structure can have dangerous repercussions for the patient’s health.

What are the dangers of an enlarged heart?

An enlarged heart can lead to serious complications such as: 

Blood clots, which can in turn cause:

• Pulmonary embolism: a blood clot that travels to a vessel in the lungs
• Heart attack: when the heart’s blood flow is obstructed 
• Stroke: when the brain’s blood flow is obstructed

Heart failure: when your heart can no longer pump blood around the body as it should, often due to the stiffening and weakening of the left ventricle in the case of aortic stenosis.

Heart murmur: an extra sound in your heartbeat that can sound like a ‘whoosh’ – this can be caused by the aortic valve not closing properly.

Sudden cardiac arrest: when the heart either stops beating and therefore stops pumping blood or beats too fast to pump blood – this can be fatal.

Diagnosing aortic stenosis 

Due to the complications that aortic stenosis and consequent enlargement of the heart can cause, aortic stenosis must be diagnosed as quickly as possible. There are various methods for diagnosing aortic stenosis. 

The preferred method for diagnosing aortic stenosis is an echocardiogram. This is a type of ultrasound scan that can examine certain aspects of the heart in better detail. It can also be used to assess the level of calcium build-up in the valve, so it helps to determine the severity of the aortic stenosis, too.⁸

A cardiac CT scan – CT scan of the heart – may also be used to help establish the severity of the disease and to form a prognosis.

In the rare event that the above methods still produce inconclusive findings in the diagnosis of aortic stenosis, cardiac catheterisation may be performed. This is a procedure whereby the patient is injected with a contrast medium (usually in the form of a liquid dye) before having X-ray images taken of the heart. 

Treating aortic stenosis 

Aortic stenosis cannot be treated with medication. 

In some cases, doctors may continue to monitor a patient who has aortic stenosis and not prescribe a treatment if they decide that the valve has not narrowed enough to need it. 

However, if a patient does require treatment, there are three options:

• Non-invasive valve replacement (Transcatheter Aortic Valve Implantation): a catheter is passed through a blood vessel in the leg or chest to the aortic valve, where it is used to place a replacement valve on top of the old one
• Aortic valve balloon valvuloplasty: a plastic tube is entered into the heart through a blood vessel where a balloon is then inserted and pumped up to open the aortic valve. This balloon remains in place, but the treatment is only effective for one year
• Sutureless aortic valve replacement: this is a modern alternative to open heart surgery whereby the valve is replaced without requiring sutures (stitches) to fix it

Summary

• Oxygenated blood leaves the heart’s left ventricle and flows into the aorta
• The aortic valve prevents blood from flowing back into the heart
• Aortic stenosis is when the aortic valve becomes narrow or stiffened and, therefore, cannot function properly
• Aortic stenosis can be caused by calcium buildup, rheumatic fever or a congenital defect
• If the aortic valve is not working properly, the left ventricle has to work against higher pressure to pump the blood out
•  High blood pressure can cause the left ventricle walls to become thicker and larger
• Once the left ventricle becomes thicker and larger, the heart becomes enlarged—sometimes referred to as cardiomegaly
• Heart enlargement can lead to complications such as heart failure, heart attacks, strokes, blood clots, etc.
• Aortic stenosis cannot be treated with medication, but there are different surgery options to either temporarily open the aortic valve or to replace it