The cardiovascular system and you

AORTIC STENOSIS is one of the most common and serious valve disease problems. Aortic stenosis is a narrowing of the aortic valve opening and can sometimes be referred to as a failing heart valve. Aortic stenosis restricts the blood flow from the left ventricle to the aorta and may also affect the pressure in the left atrium.

Although some people have aortic stenosis because of a congenital heart defect called a bicuspid aortic valve, this condition more commonly develops during ageing, as calcium or scarring damages the valve and restricts the amount of blood flowing through.

According to Ajani Ausaru, assistant lecturer, Department of Mathematics in the Faculty of Science and Technology at The University of the West Indies, Mona, the cardiovascular system comprises the heart, the distributary system (arteries and arterioles), the diffusing system (fine capillaries), and the collecting system of veins.

“The heart acts like a pump and its elastic walls rhythmically contract, enabling the pulsatile flow of blood throughout the vascular system. Other organs supplementing the function of the cardiovascular system are the lungs, which allows the transfer of oxygen to the blood and the removal of carbon dioxide from it; the kidney, liver, and spleen, which aid in preserving the chemical quality of blood under normal conditions and under conditions of extreme stress,” Ausaru said.

The cardiovascular system, also termed the circulatory system, is a vast network of organs and vessels responsible for the transporting of oxygen, nutrients, hormones, and gases to and from cells. This system is an indispensable part of the human make-up, without which the body would be incapable of fighting disease and maintaining proper balance.

A primary cause of blood vessels becoming narrow or partially blocked is the deposits of fats, cholesterol, and accumulation of fibrous tissue on the interior wall of the blood vessel.

“Stenosis is the localised narrowing occurring in the lumen of an arterial segment. This can mean hardening of the arteries, with arterial wall thickening and loss of elasticity. Types of stenosis of the heart are aortic stenosis, mitral stenosis, pulmonary stenosis, and tricuspid stenosis,” Ausaru said.

Blood flow reduced

The presence of stenosis, he said, means there is a level of constriction in the diseased artery, resistance is increased, and this constriction influences the blood flow pattern. Blood flow in the artery is reduced; there is a notable change in the pressure distribution and forces acting on the wall of the vessel.

“The dispersion process is subjected to the continuous injection of a solute concentration at the inlet of the artery. The effects of parameters impacting the mean concentration and the local concentration are studied. It is attested that the smaller the value of the yield stress, the more stretched and extended the dispersion trajectory,” Ausaru said.

“This means that the solute is able to travel much further axially for lesser values of the yield stress. Analysis of the mean concentration reveals a buildup of solute as the stenotic region is encountered. For a smaller yield stress value, the fluid velocity is greater, permitting the solute to disperse a much greater distance axially. We see that a larger catheter radius entails a later start in the quantity of solute being transported in the stenosed vessel,” he added.

Symptoms of aortic stenosis may not appear for 10–20 years after the condition has started to cause changes in the heart. However, if symptoms do appear, they may include chest pain, rapid heartbeat, a fluttering sensation in the chest, difficulty breathing, shortness of breath, dizziness or fainting, difficulty walking short distances, swelling in the ankles or feet, difficulty sleeping or preferring to sleep sitting up.

Symptoms of aortic stenosis may make it difficult for a person to carry out daily tasks. Because symptoms develop gradually, a person may not initially be vocal about them. Instead, other people may first notice a decrease in the person’s physical ability.

Ageing is one of the biggest risk factors for stenosis of the heart. This is because as a person ages, calcium or scarring can damage the valve and restrict its opening. Other risk factors also include congenital heart defects, high blood pressure, elevated cholesterol, smoking, diabetes, and radiation therapy.

Risk of complications

If a person does not receive treatment for stenosis of the heart, it can lead to heart failure, angina, or irregular heart rhythms, and it can be fatal.

To reduce the risk of complications from stenosis of the heart, people should follow a doctor’s instructions closely and be honest about any new or worsening symptoms they experience.

If a person has mild or no symptoms, maintaining a healthy lifestyle as much as possible will help reduce the risk of complications. Doctors will monitor a person regularly with testing.

“The gold-standard diagnosis for cardiac stenosis is an echocardiogram. It can also help doctors determine whether a person is a suitable candidate for surgery. Doctors may suggest exercise testing in people who are not experiencing symptoms. If a person has calcific aortic valve disease, doctors may send them for a CT scan or a left-heart catheterisation if other tests have not been conclusive,” Ausaru said.

MRI scans can also help assess ventricle function and mass when the echocardiography has not been definitive.

keisha.hill@gleanerjm.comSOURCE: Faculty of Science and Technology, University of the West Indies, Mona