Diabetes and Cardiovascular Disease

There are a number of complications associated with diabetes and coronary artery disease (CAD) is one of them. CAD is one disease among many included in the general category of cardiovascular disease. It may surprise you to learn that heart disease and stroke account for 65 percent of all deaths in people with diabetes. The risk of cardiovascular disease is significantly increased in men and women who have diabetes.[1]

The Physiology of the Heart

The heart is divided into four chambers. The 2 chambers on the right side of the heart receive venous blood. They send the blood to the lungs to remove the carbon dioxide and re-oxygenate it. The pair of chambers on the left side receives blood from the lungs. It then pumps it through the body by means of the aorta – a major artery.

The heart is a highly specialized muscle characterized by unique fibers or cells. They appear quite different from all the other types of muscle cells when viewed under the microscope. Nevertheless, the heart is a muscle. As such, it cannot function without an adequate supply of oxygen brought by blood to the cells.

The arteries and veins of the heart include:[2]

  • Coronary – These are the largest arteries that run from the root of the aorta and curl back over the surface of the heart spreading small branches inward. There are two main coronary arteries, left and right. Each supplies its own side of the heart, but individual variations do exist.

The coronaries are known also known as end arteries. There is no alternative route or option if an artery becomes blocked. When one is blocked, you have a heart attack (myocardial infarction) since the portion of the heart served by the coronary artery can no longer receive life giving oxygen.[3]

The blockage in the artery results when fatty (lipid) deposits accumulate slowly and over time decrease the size of the passageway. A piece may break free – an embolus. It is then carried by the bloodstream until it lodges where there is already a narrow passage. This may block the artery – partially or entirely.

  • Valves – Each of the heart’s chambers has its own valve. There are 4 valves situated at the outlets. The main function of the valve is to ensure blood moves forward and not backward.

Since type 1 diabetes patients live with diabetes the longest period of time, the rate of CAD is high. Also, men and women are affected in the same way by coronary artery disease. Patient’s with diabetes are very high risk for having coronary artery disease. In fact, a diabetic patient who has never had a heart attack has the same risk of having a heart attack as someone who has already had a heart attack.

Atherosclerosis

Lining your artery with lipids leads to atherosclerosis. This is not an inevitable consequence of having diabetes if you manager your diabetes and your general health. Unfortunately, based on research over the years and studies of many thousands of persons, the statisticians can tell you just how likely it is that it will develop CAD by considering the presence of certain “risk factors.”

The risk factors are divided in 2 groups – those you have control over and those you don’t.

Those over which you have no control include:

  • Ethnicity – some groups are more prone to atherosclerosis
  • Genetics – genes predispose you to developing CAD

There are also the risk factors over which you do have a certain amount of control. These consist of, among others, the following:

  • Smoking
  • Blood lipids levels (cholesterol)
  • Blood pressure
  • Weight
  • Diet  (sodium, fat and sugar intake)

For example, modestly reducing salt intake will cut down on the risk for cardiovascular disease.[4] Lowering your cholesterol can lower the risk of developing CAD, as can losing weight if you are overweight or obese. Quitting smoking would significantly reduce your chance of developing CAD more than any other change.

People with type 2 diabetes who are more likely to develop CAD include those who experience:

  • Obesity
  • Central adiposity in which fat is carried around the waist
  • High LDL cholesterol and triglycerides
  • High blood pressure

Symptoms

Atherosclerosis puts you at risk for developing coronary artery disease, which can progress to coronary artery disease. One form of CAD is angina pectoris. The primary symptom are chest pains that can become very intense. The pain is indicative of the fact that your heart muscle is continuing to work very hard but it lacks the necessary blood supply.[5] The pain may also occur in the left shoulder and down the arm or around the neck or jaw area.

Other symptoms include a feeling of pressure in the chest, perspiration, shortness of breath, and feeling nauseated.

If the blood to the heart is completely cut off, a heart attack will occur. The symptoms are virtually the same as angina pectoris and is usually very painful. However, some diabetics with autonomic neuropathy do not suffer from chest pain or angina because of the nerve damage. The first symptom of CAD in many of these cases is a “silent heart attack” that occurs once an artery becomes completely blocked.

Sometimes there might be a small warning that CAD exists if there is angina pectoris. Angina pectoris is the temporary pain or discomfort in your heart muscle that occurs when the blood circulation to the heart is poor.

How can the Heart be Assessed?

The best way to detect cardiovascular disease is through medical tests like the following:

  • Electrocardiogram: The painless and quick electrocardiogram (referred to as an ECG or EKG) is a very commonly performed test. It tells the doctor to a certain extent what has happened to your heart, and sometimes, what is happening at the current time. It is not, however, intended to be predicative of what might happen.
  • Stress test:  This involves exercise. The amount of stress your heart can handle is measured as you exercise enough to raising your heart rate. It provides some indication of the condition of your arteries and the flow of blood. This test may be combined with other tests such as an echocardiogram that provides a pictorial display of the functioning of the heart. [6]
  • Percutaneous Coronary Angiography (PCA): This test is done by a cardiologist invloves placing a catheter near the heart and injecting a dye into the coronary arteries. The cardiologist then takes pictures using a complex x-ray machine to establish whether there is any blockage or narrowing of the arteries and, if so, which arteries are affected. When the tests are completed both the patient and the referring physician receive a diagram of the heart and its arteries. Included are the estimates of the percentage of blockage of each of the vessels. It is then up to the medical team and the patient to decide what to do – balloon angioplasty, atherectomy, coronary bypass surgery and/or medications that can dissolve blood clots.

References

[1] Meltzer, SJ; and Belton, AB (2009). Diabetes in Adults. Toronto: Key Porter Books

[2] Marcovitch, H (2006). Black’s Medical Dictionary 41st edition. Lantham, Maryland: Scarecrow Press.

[3] Divya Gupta, Kathy K. Griendling and W. Robert Taylor (2010). “Oxidative Stress and Cardiovascular Disease in Diabetes Mellitus.” In Studies On Cardiovascular Disorders: Oxidative Stress in Applied Basic Research and Clinical Practice, H.Sauer, AM Shaw, and FRM Laurindo (eds).  New York: Springer: 263-281.

[4] Bibbins-Domingo, K; Chertow, GM. Coxson, P; Moran, A; Lightwood, JM; Pletcher, MJ; and Goldman, L (2010). “Projected Effect of Dietary Salt Reductions on Future Cardiovascular Disease.” New England J Medicine, 362 (February):590-599.

[5] American Diabetes Association (2009). Type 2 Diabetes. Your Healthy Living Guide. Alexandria, VA: ADA.

[6] NIH (2011). “Stress Testing.” Retrieved from http://www.nhlbi.nih.gov/health/health-topics/topics/stress/

[7] This article was originally published July 12, 2012 and last revision and update of it was 9/10/2015.