Cardiovascular Disease

According to a recent study by the World Health Organization, cardiovascular disease is the Number One cause of death world-wide, claiming the lives of over 12 million people around the world each year. More than 3 million Canadians have heart and/or blood vessel diseases. In North America, cardiovascular disease kills almost as many people as all other causes of death combined. Often there is a genetic cause for the disease. In Quebec, for example, there is a very high incidence of heart attack due to inherited diseases.

Illustration of the direction of blood flow in the human artery

Cardiovascular disease is a general term describing afflictions of the heart and blood vessels. One of the major causes of cardiovascular disease is atherosclerosis, or hardening of the arteries, which contributes to nearly a million stroke and heart attack deaths each year.

Another cause of cardiovascular disease is hypertension, or high blood pressure, which afflicts nearly 2 million Canadians. Like atherosclerosis, hypertension is an important risk factor for heart attack, stroke and kidney disease.

Because the causes of hypertension are not entirely known, research using animal models is essential to unlock the mysteries of this condition.

A certain strain of laboratory rat that was found to spontaneously develop hypertension has served researchers well in developing an understanding of this disease. The rat model has provided an understanding of the effect of salt on blood pressure and the mechanism of hormone action in hypertension, to name a few examples. These rats also have a major role in the testing of anti-hypertensive medications.

Research in mice is providing a deeper understanding of cardiac cell growth. After the fetal stage of life, the human heart cannot grow new cells and is unable to repair itself, in the way that other mature muscles and organs can, by replacing damaged cells with healthy new ones. Instead, the heart responds to a heart attack by forming scar tissue in place of injured cells and is permanently weakened as a result. This same mechanism that keeps cells in the heart from growing and reproducing has also made it impossible to grow heart cells in culture.  Transgenic, or genetically altered, mice are helping researchers to study cardiac cell growth where cell culture techniques have so far failed. This area of research is expected to make it possible one day to implant synthetically- produced heart cells into patients who have lost cardiac tissue in heart attacks.

New surgical techniques are constantly under development in cardiology, using animals as models. For instance, roughly one thousand children are born each year with only one of the heart's two main pumping chambers fully developed. In a normal heart, the right ventricle supplies blood to the lungs, but if this chamber is absent or malformed, surgeons can now bypass it completely and channel blood from the veins directly to the lungs. As a result of this procedure, called the Fontan operation, many children with underdeveloped right hearts are now able to live normal lives.

The use of animals, among them rodents, rabbits and dogs, is essential to all cardiovascular research. Cell culture techniques are useful adjuncts to this research, as is computer and mathematical modeling, but research in this area would essentially be halted without animal models. A combination of adjunct methodologies and laboratory animal models will keep cardiac research on the path to finding cures and treatments for the cardiovascular diseases which will afflict most of us at some point in our lifetime.