Structural Heart Disease

The heart is a muscular pump located between the lungs in the chest. As the hub of the circulatory system, it is one of the body’s most vital organs and beats to pump blood around the body. This blood delivers oxygen and nutrients and removes waste from the tissues such as carbon dioxide, practically every moment that most of us are alive. 

The heart has four chambers. The right atrium and ventricle receive deoxygenated blood from the body and pump it to the lungs for oxygenation, while the left atrium and ventricle receive oxygenated blood from the lungs and pump it around the body to the tissues.

These chambers are separated by walls of muscle (the cardiac septa), and are connected to each other via valves, which are tissues that prevent blood from flowing backwards when the heart beats. Two important valves are the tricuspid valve between the right atrium and ventricle, and the mitral valve, between the left atrium and left ventricle.  

As the left side of the heart relaxes, oxygenated blood is drawn into the left atrium and then through the mitral valve into the left ventricle. Lastly, as the heart contracts, the powerful muscles around the left ventricle force the oxygen-rich blood through the aortic valve and the aorta (a large artery) to reach the rest of the body.

For the blood to be pumped effectively, the various valves must open and close at the right time, and the different parts of the heart must be properly synchronised (Yale Medicine). This double cycle gives rise to the characteristic double “thump” of the heartbeat.

When most people think about heart disease, they think of coronary heart disease. This is distinct from structural heart disease. Coronary heart disease, or coronary artery disease, is caused by plaques of fatty material building up in the blood vessels (arteries) supplying oxygen to the heart muscle.

This buildup restricts the local oxygen supply and causes the muscle tissue to die, leading to a heart attack. This is often the result of an unhealthy lifestyle or a disease like diabetes. Structural heart diseases, on the other hand, are caused by defects in the structure or function of the heart itself, such as the tissues and valves. Similarly, structural heart disease is distinct from arrhythmias (irregular heartbeat) such as atrial fibrillation.

Many structural heart problems cause no obvious symptoms, and are usually found when investigating other problems.

Risk factors for structural heart disease vary from condition to condition, but include:

• Older age
• Certain infections that affect the heart e.g. rheumatic fever
• Heart attack, heart failure, and some types of heart disease
• High blood pressure (hypertension)
• Use of certain drugs
• Heart condition present at birth (congenital heart defect)
• Radiation to the chest
• Obesity
• Diabetes
• People assigned female at birth (AFAB)

Types, Causes and Symptoms of Structural Heart Disease

Mitral Valve Disease

There are two main types:

1. Mitral valve prolapse and regurgitation: Blood “leaks” backward through a faulty mitral valve into the left atrium.
2. Mitral valve stenosis: Blood flow is restricted through a stiffened and partly fused mitral valve.

• Causes include: congenital heart defects, rheumatic fever (a complication of strep throat which causes scarring of the heart), other heart conditions, infections, autoimmune conditions
• Symptoms include: Fatigue, irregular heart sound (heart murmur), irregular heartbeat, and shortness of breath
• Complications include: irregular and often rapid heart rate (atrial fibrillation), high blood pressure in the blood vessels in the lungs (pulmonary hypertension), blood clots, congestive heart failure, and stroke
• Diagnosis is by imaging techniques including echocardiography, 3D echocardiography, and transesophageal echocardiography
• Treatment is by surgical valve repair or replacement

Aortic Valve Stenosis

Blood flow from the left ventricle into the aorta is restricted.

• Causes include: congenital heart defects (such as bicuspid rather than tricuspid aortic valve), calcium buildup on the valve structure, and rheumatic fever
• Symptoms include: abnormal heart sound (heart murmur), chest pain (angina), tightness, feeling faint or dizzy with activity, shortness of breath, fatigue, fluttering heartbeat (palpitations). In children, it may present as undereating or failure to gain weight
• Causes include: a congenital defect, calcification of the valve and rheumatic fever
• Complications include: heart failure, stroke, blood clots, bleeding, heart rhythm problems (arrhythmias), infections that affect the heart, such as endocarditis, death.
• Diagnosis is by echocardiogram, electrocardiogram (ECG), chest X-ray, exercise stress tests, cardiac CT, cardiac MRI
• Mild symptoms require regular monitoring but more severe cases may require surgical valve repair, replacement, or balloon valvuloplasty

Hypertrophic Cardiomyopathy (HCM)

Often caused by a genetic defect that causes the heart muscle to grow abnormally thick and impair the outflow of blood from the heart chambers.

• Symptoms include: chest pain, fainting and shortness of breath (especially during exercise), heart murmur, heart palpitations
• Causes include:  genetic abnormality. The septum between the ventricles typically becomes thickened or stiffened, which may obstruct blood flow out of the heart
• Complications include: atrial fibrillation, blocked blood flow, mitral valve problems, dilated cardiomyopathy, heart failure, sudden cardiac death
• Diagnosis is by echocardiogram, ECG or cardiac MRI
• Treatment is by beta blockers such as metoprolol or atenolol; calcium channel blockers such as verapamil or diltiazem; heart rhythm drugs such as amiodarone or disopyramide. Blood thinners such as warfarin, or rivaroxaban are given to prevent blood clots if you have atrial fibrillation. Surgically, procedures include septal ablation (destruction of the excess heart muscle with alcohol), septal myectomy, or an implantable cardioverter-defibrillator (ICD).

Holes in the Heart

Holes in the heart is usually used to refer to diseases such as: atrial septal defect (ASD) and patent foramen ovale (PFO). PFO is a normal feature of the foetal and newborn heart but usually closes during infancy.  If it remains open, some of the blood will bypass the lungs, resulting in low blood oxygen levels.

• There are usually no discernible symptoms of PFO or ASD
• The underlying causes of PFO are unclear but may be genetic, at least in part.
• Complications include: low blood oxygen and stroke
• Diagnosis is by transthoracic echocardiogram, transesophageal echocardiogram, colour flow doppler or saline contrast study, also known as a bubble study
• Treatment is usually not necessary. However, in cases of low blood oxygen or stroke, surgical closure may be required

Left Ventricular Hypertrophy

Thickening of the wall of the left ventricle raises pressure and impairs pumping action.

• Signs and symptoms gradually increase as the hypertrophy progresses, and include shortness of breath, fatigue, chest pain after exercise, palpitations, and dizziness or fainting
• Causes include enlarged heart muscle cells and abnormal tissue around the muscle. This often happens if the heart is forced to work harder, for example by high blood pressure (hypertension, a heart condition such as aortic valve stenosis, or prolonged, intense athletic training. There may also be a genetic cause, and other factors are amyloidosis and hypertrophic cardiomyopathy
• Complications include: reduced blood supply to the heart, heart failure, arrhythmias, irregular, often rapid heartbeat that increases the risk of stroke, ischemic heart disease, stroke, and sudden cardiac arrest
• Diagnosis is by ECG, echocardiogram or cardiac MRI
• Treatment usually involves one or more of the following medications to manage high blood pressure: Angiotensin-converting enzyme (ACE) inhibitors such as enalapril, angiotensin receptor blockers (ARB) such as losartan, calcium channel blockers like diltiazem, diuretics like chlorthalidone or beta blockers like propranolol. Surgical treatment includes aortic valve repair or replacement, and other underlying conditions like amyloidosis might be treated with medications, or even a stem cell transplant.  Leading a healthy lifestyle and eating healthily, giving up smoking, and moderating alcohol intake are all recommended.

Myocarditis

Myocarditis is inflammation of the heart muscle tissue (myocardium), which impairs muscle contraction and thus pumping action. It usually resolves without major complications.

• Symptoms include: chest pain, shortness of breath at rest or after exercise, arrhythmias, lower limb swelling (oedema), fatigue, virus-like symptoms such as headaches or joint pain. In children, these signs also include fainting and rapid breathing or breathing difficulties
• Causes include: viral infections such as COVID-19, hepatitis B and C or herpes simplex, and bacterial infections such as staphylococcus or streptococcus. Parasitic infections such as toxoplasmosis and Chagas disease (a tick-borne parasite), or fungi such as candida and aspergillus might also play a role. Medication or illegal drug toxicity, radiation, and diseases like lupus can cause myocarditis.
• Complications are relatively rare but include heart failure, heart attack, stroke, sudden cardiac death, and arrhythmias
• Diagnosis is by ECG, echocardiogram, cardiac MRI, chest X-ray and blood tests including a complete blood count and a test to check the levels of certain proteins (enzymes) that signal heart muscle damage. Cardiac catheterization and a heart muscle biopsy might also be done to check for tissue abnormalities or inflammation
• Treatment is primarily by medications, including corticosteroids to treat inflammation, blood pressure medications like beta blockers, diuretics, ARBs or ACE inhibitors, and drugs to treat underlying conditions like lupus. Surgical options include an intra-aortic balloon pump implant, ventricular assist devices, extracorporeal membrane oxygenation, and heart transplant

Tricuspid Valve Regurgitation

Backflow of blood from the right ventricle to the right atrium through a faulty tricuspid valve.

• Symptoms include: fatigue, arrhythmias, pulsing in the neck, shortness of breath after activity, swelling in the belly area, legs, or neck veins
• Causes include: congenital heart defects, genetic disorders like Marfan syndrome, rheumatic fever, infective endocarditis (an infection of the heart lining), carcinoid syndrome, chest trauma, pacemaker wire placement or removal, heart muscle (endomyocardial) biopsy, radiation therapy
• Complications include: atrial fibrillation and heart failure, meaning the heart is unable to pump blood around the body properly
• If your doctor thinks you might have tricuspid valve regurgitation, there are several tests that might be ordered to determine severity and cause. These include an echocardiogram, cardiac MRI, cardiac catheterisation, ECG, chest X-ray, and an exercise stress test.
• Treatment is by medications and/or surgery. If the condition is mild, no treatment may be needed. Medications include diuretics, antiarrhythmic drugs, and drugs to treat heart failure, such as ACE-inhibitors and beta blockers. Surgical interventions would involve valve repair or replacement

When to See a Doctor

You should go and see your doctor if you experience chest pains, palpitations, shortness of breath (particularly with activity), or a rapid or irregular heartbeat. If you experience unexplained chest pain or shortness of breath for more than a few minutes, call an ambulance, as this might be a heart attack. If your doctor has detected a heart murmur or other symptoms of heart disease, you may be referred to a  specialist healthcare professional.

Take Good Care of your Heart

While lifestyle changes such as healthy diet and exercise are of great value in preventing and managing coronary artery disease, they probably aren’t going to help much if you have a structural heart condition, although they certainly won’t do any harm. Some conditions which are linked to high blood pressure, such as left ventricular hypertrophy, may be an exception to this rule. Early detection and regular monitoring appear to be the key to managing most structural heart conditions, as well as avoiding infections, getting vaccinated, and minimising exposure to ticks in the case of myocarditis and other conditions linked to infection.