Cardiac diseases are also known as heart diseases. Cardiac diseases are a very broad term for a number of conditions that affect the heart and as of 2007, it is the leading cause of death in England, Wales, and the United States.

The leading cause of cardiac disease is a narrowing of the lumen of arteries that supply blood to the heart, commonly called coronary artery disease (CAD).

There are various other heart conditions that come under the umbrella of cardiac diseases.

Types of Cardiac Disease

Cardiovascular diseases

A number of conditions that affect the heart itself or any of the arteries or veins leading to and from the heart are called cardiovascular diseases. Long studies have suggested that women are more prone to conditions that affect the blood vessels themselves while men are more prone to conditions that affect the heart muscles. The most common conditions that cause cardiovascular diseases are:

• High blood pressure
• Diabetes
• Increased fats (lipids) in blood
• Hyperhomocysteinemia

The most common type of cardiovascular disease is atherosclerosis.

Coronary heart disease

A disease of the heart itself where the arteries supplying the heart muscles are clogged by atheromatous plaques. An atheroma is a collection or a swelling on the vessel wall composed of fats, cell debris, calcium, connective fibrous tissues, etc.

Symptoms:

Angina - chest pain due to the insufficient blood supply to the heart

'Ischemic heart disease', is another term used to denote a condition where the blood supply to the heart is reduced.

Congenital heart disease

Structural problems of the heart present right from birth are known as congenital heart disease. Genetic defects are to blame for this condition.

The heart cannot function properly because it is incompletely or improperly developed. There is an abnormal flow of blood through the heart. There occur abnormal heartbeats (arrhythmias), structural abnormalities, and cardiomyopathies (abnormalities of the heart muscles). Abnormal connections between two arteries occurring outside the heart, valvular defects, or the presence of holes within the muscular walls of the heart are some of the conditions frequently found. Common conditions are:

• Atrial septal defect (ASD): A hole in the septa (membrane) dividing the atria (the upper chambers of the heart) allows oxygen-rich blood from the left atrium to flow into the right atrium instead of flowing to the left ventricle as it should. Many children with this defect show few symptoms if any.
  Most ASDs are small and need no treatment. Occasionally, medium-sized ASDs require surgical correction with a catheter procedure.
• Ventricular septal defects (VSD): A hole in the membrane dividing the ventricles (lower chambers of the heart) oxygen-rich blood to flow from the left ventricle into the right ventricle instead of flowing into the aorta and out to the body as it should. VSDs can be large or small.
  Large VSDs overload the left side of the heart and increase the pressures within the right side of the heart and within the lungs. There is more than the usual volume of blood flowing into the lungs and within the right atrium. As the load on the heart increases, the patient can develop heart failure (also called congestive heart failure). Increased back pressure on the lung can damage delicate arteries in the lungs. Hence, large VSDs need to be surgically repaired (open heart surgery) as soon as possible.

Valvular heart disease:

Valves are flap-like structures present at the openings of the atria into the ventricles, and at the openings into the large blood vessels arising from the heart. They prevent the back-flow of the blood as it passes (or is pumped) through the heart chambers. Any structural abnormalities of these valves bring about multifold changes in the dynamics of blood flow.

Common terms for valvular defects seen are:

• Stenosis: or narrowing of the lumen because the valves do not open properly. This means that the heart has to pump with added force to make the blood pass through the lumen.
• Atresia: this defect means that the valves do not develop correctly. They are ill-formed and mostly the lumen appears completely closed. So there is no opening from which the blood can pass through.
• Regurgitation: here the valves do not close properly. Hence, there is regurgitation or back-flow of the blood pumped, into the cambers.

The most common valvular defect encountered is Pulmonary valve stenosis.

Through this valve, the blood flows from the right ventricle to the lungs where it picks up oxygen. When the valve is stenosed, the severity ranges from mild to severe. Mild forms require no treatment. Just occasionally, an abnormal heart sound (murmur) can be heard. Correction of the condition when necessary, it was done by a catheter procedure.

Complex congenital heart defect:

The commonest complex congenital heart defect seen worldwide is known as 'the Fallot's tetralogy'. This defect has a combination of the following:

• A large VSD
• Right ventricular hypertrophy - the muscles of the right ventricle enlarge due to the excess stress of pumping more than usual blood volumes.
• Overriding of the Aorta - the aorta is a large vessel carrying blood from the left ventricle to various body parts. Normally, its origin is in the left ventricle only. In Fallot's tetralogy, the aorta is placed above the left as well as the right ventricle as opposed to normal. Thus, impure blood from the right ventricle gets mixed with the pure (oxygenated) blood from the left ventricle.
• Pulmonary valve stenosis - this occasionally causes the presence of a murmur.

Cardiomyopathy:

Cardiomyopathy means any disease of the heart muscles themselves. The heart muscle is referred to as the 'myocardium'. Any condition that causes impaired functioning of this muscle is considered cardiomyopathy. The heart muscles become inflamed and don't work as they should.

Common structural changes seen in the heart are:

Dilatation of heart muscles

Restricted contractility of the heart muscles

Increased (hypertrophy) size of the heart muscles.

Previous heart attacks, viral and bacterial infections, and many other conditions cause cardiomyopathies.

Types of Cardiomyopathy

Cardiomyopathies caused by outside factors

• Ischemic cardiomyopathy: this means there is a deficiency of blood (oxygen) supply to the heart muscles themselves. This is the leading cause of cardiomyopathy caused by coronary artery disease (CAD).
• Alcoholic cardiomyopathy: This is a form of dilated cardiomyopathy. Toxins from alcohol directly attack the heart muscle cells. Eventually, the heart is unable to pump properly and there is heart failure.
• Hypertensive (high blood pressure) cardiomyopathy: this is the most common cause of death in Western Societies.
• Congenital heart diseases
• Valvular cardiomyopathies
• Coronary artery disease
• Nutritional deficiencies causing cardiomyopathies.
• Metabolic diseases causing cardiomyopathies

Cardiomyopathies caused by intrinsic factors:

Weakness of the heart occurring from no identifiable external cause. The major types are:

• Restrictive: least common cardiomyopathy. Ventricular walls are stiff and occasionally thickened. Since, for optimal filling of ventricles, they need to be relaxed, this condition impairs normal filling.
• Dilated: this is the most common form. The left ventricles are commonly affected and they cannot pump blood received with adequate force.
• Hypertrophic: the walls of the heart appear thicker, and they obstruct the normal flow of blood. This is mostly due to a genetic defect. It is a genetic disorder
• Arrhythmogenic right ventricular cardiomyopathy (ARVC): scar tissues replace normal tissues due to improper electrical circuits.

Hypertensive (high blood pressure) cardiomyopathy

Is heart disease caused by high blood pressure? High blood pressures increase the load acting on the heart. Over a period of time, the left ventricle thickens and cannot pump sufficient blood. Factors that cause this condition are

1. Coronary heart disease
2. Left ventricular hypertrophy
3. Arrhythmias (irregular heartbeats)
4. Congestive heart failure
5. Hypertensive cardiomyopathy

Inflammatory heart disease

Inflammation of the heart and the tissues surrounding it.

Any viral or bacterial infections can set off inflammatory heart disease in a susceptible person. This inflammation can be either in the inner layer of the heart (the endocardium) or in the muscular part of the walls (myocardium). The conditions are then called endocarditis or myocarditis respectively.

Valvular heart disease:

Any disease that affects the valves can over a prolonged period of time cause impaired functioning of the heart.