Pulmonary hypertension is a condition that makes the heart work harder than usual, due to increased blood pressure in the lungs, forcing the heart to work harder to pump blood into the lungs. This severe condition can damage the heart and even lead to heart failure. 

An enlarged heart is medically known as cardiomegaly, which simply means an enlarged heart muscle. It indicates that another condition is putting extra strain on the heart. 

Pulmonary hypertension causes the blood vessels in the lungs to narrow, creating an increased workload for the heart as it tries to pump blood into the lungs. This increased workload can cause the heart to become enlarged. 

The article will continue to discuss both pulmonary hypertension and enlarged heart in-depth, focusing on each condition's causes, symptoms and diagnosis. 

Pulmonary hypertension 

Pulmonary hypertension develops when the blood pressure in the lungs is consistently higher than usual, and affects about 1% of the worldwide population, with over 50% of cases having no known cause.¹ The other 50% is caused by an underlying disease or a condition. The increased workload on the heart to pump blood into the lungs can damage the heart and cause symptoms such as shortness of breath, chest pain, dizziness, or light-headedness. 

Pulmonary hypertension can be categorised into five different groups:

• Pulmonary arterial hypertension (PAH) 
• Pulmonary hypertension due to left-sided heart disease
• Pulmonary hypertension due to lung disease and or hypoxia
• Pulmonary hypertension due to pulmonary artery obstructions, including chronic thromboembolic pulmonary hypertension (CTEPH)
• Pulmonary hypertension with unknown or multiple causes²

What causes pulmonary hypertension?

There is not always a known cause of pulmonary hypertension. It is known that some medical conditions can cause a change in the blood vessels in the lungs, resulting in damage or a block of these vessels, which can lead to pulmonary hypertension.⁹ 

Some of the known medical conditions that can cause pulmonary hypertension are:

• Heart disease affecting the left side of the heart, such as left heart disease
• Other heart and blood vessel diseases, including congenital heart diseases
• Chronic obstructive pulmonary disease (COPD)
• Interstitial lung disease
• Emphysema
• Sleep apnea
• Other conditions may include liver disease and sickle cell disease

Symptoms and diagnosis of pulmonary hypertension

Common symptoms

The main symptom of pulmonary hypertension is breathlessness. Other symptoms may include:

• Feeling tired
• Feeling dizzy or faint, often when exercising
• Fast heartbeat
• Swelling of the leg, ankle and/or tummy area
• Chest pain, which is often felt after exercise

Strenuous movement like walking up stairs or exercise may worsen symptoms.

Diagnostics tests

Pulmonary hypertension is difficult to diagnose because the symptoms are often the same as those of many other heart and lung conditions. Your GP must refer you to a hospital or appropriate clinic for various tests to ensure an accurate diagnosis. These tests may include:

Echocardiogram

An echocardiogram is a scan used to see how the heart works. A small probe sends out high-frequency sound waves, which bounce off the heart and create echoes, which are then picked up by the probe and turned into a moving image. The echo can estimate the pressure in the blood vessels and how well the heart's chambers are working or if there are any congenital defects, as these can cause pulmonary hypertension.

Right heart catheterisation

The right heart catheterisation test, or cardiac catheterisation, is the primary test to diagnose pulmonary hypertension.⁴ It provides accurate information on the blood pressure in the right side of the heart and the pulmonary artery. This is important as pulmonary hypertension typically affects the right side of the heart. It is usually performed by a cardiologist or a respiratory physician. It involves the passing of a small tube (catheter) into your vein, which is then guided around the body to take measurements in the heart and lungs. The procedure is carried out under local anaesthetic, so the insertion of the catheter will not be felt, and you won't usually be required to stay in hospital overnight for this test, as it can typically be done as a day visit test.

Other possible tests

These are other tests which your physician may want to perform:

• ECG (electrocardiogram).This test records the electrical signals of your heart. It is carried out by attaching sticky patches (electrodes) to your body, which will record your heart's electrical signals and can show possible problems with heart rhythm
• Blood tests
• Breathing/lung function tests
• Sleep studies may be required to record oxygen levels and breathing patterns when you're asleep
• CT scans can be used to take pictures of the inside of specific areas of your body; these can be used to look at your lungs for signs of lung disease
• VQ scans are used to see if the lungs are working correctly and to look for blood clots⁵ 
• An ultrasound may be required to look at your liver
• An MRI scan (Magnetic resonance imaging) uses magnetic fields and radio waves to create images of the inside the body, including the heart
• CPET test, also known as cardiopulmonary exercise testing, or sometimes called a VO2 (oxygen consumption) test, is used to measure your exercise ability and if your heart and lungs response to exercise is normal or not. This test is also useful in helping assess the cause of breathlessness

Understanding heart enlargement

The medical term for an enlarged heart is cardiomegaly. The condition can be visualised on an X-ray, as the heart will look notably bigger than it should be.⁶ The result of this could mean that the heart is not pumping effectively. Without seeing the heart on imagery, the condition can be difficult to spot. Medical professionals look at a list of symptoms when imagery is not available, to decide if further testing is required. 

Causes of an enlarged heart

Having an enlarged heart is not a condition in itself, but indicates the presence of another condition, which puts extra strain on the heart muscle and causes it to become enlarged, for example, due to pregnancy. There are many possible causes of an enlarged heart, which include:

• Coronary artery disease -Occurs when fatty deposits known as plaques build up in the main arteries of the heart, resulting in the narrowing of the arteries and causing the heart to work harder than normal
• High blood pressure (hypertension)- When blood is pumped with more force than normal, putting strain on the heart 
• Pulmonary hypertension (high blood pressure in the arteries of the lungs) - When the heart has to work harder to move blood between the lungs and the heart, often causing the right side of the heart to become enlarged
• Idiopathic dilated cardiomyopathy - A disease of the heart muscle with an unknown cause
• Myocarditis - inflammation of the heart usually caused by a virus 
• Heart valve disease - When there is a problem with one of the valves of the heart, it causes a change in the blood flow and puts more pressure on the heart as it tries to rectify this.
• Cardiac ischemia - A reduced blood flow to the heart and can be the cause of angina
• History of heart attack -Following a heart attack the heart muscle is weakened, and it may enlarge to maintain adequate pumping of the blood around the body
• Anaemia (low red blood cell count) - This means there is a lack of red blood cells to sufficiently carry oxygen around the body, causing the heart to work harder to pump the blood to provide enough oxygen to vital organs
• Thyroid disease - Untreated thyroid conditions can lead to high blood pressure, high cholesterol levels and an irregular heartbeat, as well as an enlarged heart. This is because the thyroid gland is not functioning properly, so it cannot regulate all the chemical processes needed for the body to function correctly
• Obesity - Being overweight can lead to high blood pressure, which can, in turn, lead to an enlarged heart
• Lack of exercise increases the risk of coronary heart disease and high blood pressure
• Age - The likelihood of high blood pressure increases with age as our arteries lose their elasticity⁶ 

Symptoms of an enlarged heart

Oedema

This is the medical term used to describe swollen limbs caused by a buildup of fluid and can be a sign of a problem with a person's circulation. The swelling can also occur on the face, hands or abdomen. In the case of an enlarged heart, the ineffective pumping of the blood by the heart allows blood to flow backwards and collect in areas, causing swelling.

Unusual fatigue

Unusual fatigue also includes tiredness, lightheadedness, especially after exercise or exertion, shortness of breath, vertigo and fainting. This happens because the enlarged heart cannot efficiently pump the blood around the body, resulting in the body's vital organs being unable to receive the nutrients and oxygen they depend upon to function well from the blood. 

Irregular heart rhythms (arrhythmias) 

This includes a heartbeat that is too fast or too slow or varies in speed. This occurs because an enlarged heart can't beat evenly or as effectively as an average sized heart. 

Aches and pains 

An enlarged heart is known to cause pain, starting with mild to severe chest pain and aches, which can extend to other parts of the body such as the arms, back, neck, and jaw. These symptoms should be taken very seriously, and medical attention should be sought immediately.

Diagnosis of an enlarged heart

After discussing symptoms with your medical practitioner, they may want to perform a few common tests to make a diagnosis. 

ECG (electrocardiogram) 

This test records your heart's electrical signals. It is carried out by attaching sticky patches (electrodes)to your body, which record your heart's electrical signals and can show possible problems with heart rhythm. 

Chest x-ray

This can show an enlarged heart as more prominent in the image. However, other tests will usually be required to verify that the enlargement is genuine and to find the cause. 

Blood tests

Blood tests are used to rule out conditions that could be causing heart enlargement. They can also be helpful in checking for substances in the blood caused by heart muscle damage. 

CT scan

This can be used to take pictures of the inside of specific areas of your body and can be used to look at your heart for enlargement.

MRI scan

An MRI scan (Magnetic resonance imaging) uses magnetic fields and radio waves to create images of the inside of the body, including the heart. 

CPET test

The CPET test, also known as cardiopulmonary exercise testing or sometimes called a VO2 (oxygen consumption) test, measures your exercise ability and determines whether your heart and lungs respond to exercise normally or not. This test is also useful in helping assess the cause of breathlessness. 

Echocardiogram 

This test uses sound waves to create images of the heart. It shows blood flow through the heart chambers to see how well the heart functions.⁶

The relationship between pulmonary hypertension and heart enlargement

The normal anatomy of the heart consists of a right side and a left side. The role of the right side is to pump blood to your lungs to pick up oxygen. The left side then pumps the oxygen-rich blood around the body to deliver oxygen to the vital organs. Pulmonary hypertension causes a condition called right ventricular hypertrophy.⁷ This condition is called cor pulmonale and happens due to the heart's right side thickening and enlarging. This happens as the lower right chamber has to work harder to pump the blood through narrowed or blocked lung arteries. Eventually, the heart walls thicken, and the lower right chamber (ventricle) stretches to hold more blood. These changes increase strain on the heart and can eventually lead to the heart's lower right chamber failing. 

Right-sided heart failure disrupts the normal workings of many organs and systems throughout the whole body, thus making diagnosis and rapid treatment of extreme importance, and if left untreated, pulmonary hypertension is life-threatening.⁸

Treatment 

The treatment course is based on what is causing pulmonary hypertension and any other medical conditions you may have. Currently, only two types of pulmonary hypertension can be directly treated:

• Pulmonary artery hypertension 
• Chronic thromboembolic pulmonary hypertension

Treatment for other types of pulmonary hypertension involves the management of underlying medical conditions.

Summary 

• Pulmonary hypertension is a condition that makes the heart work harder than usual
• An enlarged heart is medically known as cardiomegaly, which simply means an enlarged heart muscle
• Cardiomegaly indicates that another underlying condition is putting extra strain on the heart
• Pulmonary hypertension develops when blood pressure in the lungs is higher than usual and affects about 1% of the worldwide population
• The main symptom of pulmonary hypertension is breathlessness
• Having an enlarged heart is not a condition in itself but indicates the presence of another condition
• Pulmonary hypertension can cause a condition called right ventricular hypertrophy