Heart Valve Disorders
There are four valves in the heart; two protect the main outflow tracts – the aortic and pulmonary and two lie between the atria and the ventricles – the mitral and tricuspid.
These valves are essential for the normal functioning of the heart as they only allow blood to flow in one direction only under normal circumstances.
However they may be narrowed and restricted in their opening which is called stenosis, or leak and become incompetent. If the valves do not work correctly then this causes either a pressure or a volume overload on the ventricles.
What is aortic stenosis and incompetence?
The aortic valve is the main outflow valve from the heart. Like all cardiac valves it is a one way valve – blood is ejected out of the heart into the aorta and the valve prevents it flowing back into the left ventricle. Aortic stenosis is the term used to describe narrowing of the valve so that its opening is restricted. This makes little impact upon cardiac function until the valve is quite severely narrowed.
When the aortic valve leaks this is called aortic incompetence or sometimes aortic regurgitation. If it is severe then blood pours into the left ventricle from the left atrium through the mitral valve, and also falls back into the ventricle through the incompetence aortic valve after it has been ejected. This results in a volume overload which also makes the left ventricle work harder and causes a compensatory increase in heart muscle size called hypertrophy.
What are the symptoms of aortic valve disease?
Symptoms generally do not develop until the valve disease is severe. These include breathlessness or chest pain on exercise and sometimes fainting on exercise. Both of these valve lesions produce characteristic murmurs which the doctor can hear with a stethoscope. In order to fully evaluate the severity of the leak or narrowing we use echocardiography which is a non-invasive ultrasound technique. It shows us the size of the cardiac chambers as well as the severity of the valve lesion.
What is mitral stenosis?
In this condition, the mitral valve (situated between the left atrium and left ventricle) is narrowed thus impeding forward flow from the left atrium into the left ventricle. To compensate for this reduced forward flow, the left atrium expands to accommodate more blood. Eventually the pressure in the left atrium rises and this impedes flow from the lungs. In effect the lungs become more congested. Eventually the blood pressure in the lungs rises and this is called pulmonary hypertension. With a higher pulmonary artery pressure, and increased pulmonary vascular resistance, the right ventricle has to work harder to continue to pump blood through the lungs. This causes the right ventricle to hypertrophy and higher right atrial pressure with right atrial enlargement.
What is mitral incompetence?
In this condition the mitral valve leaks. This makes it inefficient. As the left ventricle contracts then blood is ejected into the aorta but also backwards through the incompetent mitral valve.
This causes left atrial expansion and eventually left atrial hypertrophy. If the incompetence is severe this will cause high left atrial pressure which will be transmitted backwards into the pulmonary circulation causing pulmonary venous and then pulmonary arterial hypertension. This results then in right ventricular and right atrial hypertrophy. Severe metal incompetence also causes a volume overload on the left ventricle which results in left ventricular dilatation and hypertrophy.
What are the symptoms of mitral valve disease?
Both these valve problems result in lung congestion which causes breathlessness, initially on exercise. The lung congestion is worse when lying down so some people also report breathlessness in bed which may awaken them from sleep. When the left atrium stretches to accommodate more blood, it becomes more irritable which may result in a change in heart rhythm to atrial fibrillation which is a fast and irregular heart beat. This causes the symptom of palpitation.
What diagnostic tests are used for valve disease?
As with aortic valve diseases which cause both narrowing and leaking of the mitral valve result in murmurs which doctors can hear. Full evaluation requires echocardiography in the first place.
When the valve disease is severe causing real problems with cardiac function then the only realistic treatment option is valve replacement surgery.