Textbook: Zelman, M. (2015). Human Disease – A Systematic Approach (8th Edition). Publisher: Pearson Inc.  

Chapter 6: Diseases of the Cardiovascular System – Heart Disease

Objectives

By the end of this lesson you should be able to

  1. Define coronary heart disease
  2. Identify risk factors for coronary heart disease
  3. Define heart attack
  4. Explain how a heart attack occurs and signs of a heart attack
  5. Explain what to do in the event of someone having a heart attack
  6. Define stroke
  7. Differentiate between an ischemic and a hemorrhage stroke
  8. Define transient ischemic stroke
  9. Explain how a stroke occurs and signs of a stroke
  10. Explain what to do in the event of someone having a stroke 
  11. Identify risks factors for heart attack and stroke

Heart disease is the leading cause of death in the US. According to the Center for Disease Control and Prevention (CDC) 1 in 4 deaths in the US is due to heart disease and one person die from a heart disease in the US every 36 seconds. The term heart disease includes many diseases affecting the function of the heart. The most common one in the US is coronary artery disease (CAD). Remember that the coronary artery is the artery that supplies blood to the heart muscles to make sure it has the oxygen and nutrients it needs to have energy for proper functioning. Over time these arteries may become blocked due to buildup of fat, cholesterol and other substances restricting blood flow.

Figure 1. Normal coronary artery (left) and narrowing artery (right). Source: Wiki Commons.

Risk Factors for CAD Include:

  1. High blood pressure (hypertension): This puts excess strain on arteries causing them to lose elasticity and build up cholesterol and fat deposits  
  2. High cholesterol: Excess in the blood results in buildup in the arteries
  3. Smoking: Chemicals in cigarette smoke such as nicotine and carbon monoxide stresses the heart to work harder, increasing blood pressure, promoting blood clotting, and hardens the arteries
  4. Diabetes: High sugar in the blood sticks to walls of the arteries, contributing to hardening 
  5. Overweight and obesity: Increases blood lipids and cholesterol levels
  6. Unhealthy diet: Increases blood lipids and cholesterol levels 
  7. Lack of exercise: Increases blood lipids and cholesterol levels  
  8. Excessive Alcohol: May result in high blood sugar, excess blood lipids and high blood pressure  

A word on cholesterol if that term is new to you or you have heard it but don’t know what it means. Cholesterol is a fat-like substance that the body makes to carry out very essential functions. For example, it is used to make vitamin D, some hormones, and bile which is used in fat digestion. We are able to make all the cholesterol we need so we really don’t need to consume any. When we do, and get too much of it, it can cause health problems. The two types of cholesterol that you may hear about is good and bad cholesterol. The good cholesterol is called high density lipoproteins (HDL) and the bad one is called low density lipoproteins (LDL). HDL cholesterol removes unwanted buildup of cholesterol in the blood vessels while LDL cholesterol deposits cholesterol in blood vessels. Therefore, when you do your routine cholesterol check, you want to hear that your good cholesterol is high and the bad ones are low. Here are desirable cholesterol levels according to the CDC:

  • Total cholesterol: Less than 200 mg/dL
  • LDL cholesterol: Less than 100 mg/dL
  • HDL cholesterol: Greater than or equal to 60 mg/dL

Heart Attack

Now let’s get back to CAD. The most common outcome of CAD’s myocardial infarction or heart attack. This happens when the blockage to the coronary artery is so severe that a part of the heart is no longer getting enough blood. That will cause cells in that area to begin to die. A heart attack may happen suddenly or you may see signs and symptoms ahead. There are 5 of these to look out for i.e.

  1. Chest pain
  2. Weakness or light-headedness
  3. Pain in jaw, neck or back
  4. Pain in one or both arms or shoulders, and
  5. Shortness of breath. 

If you notice someone experiencing symptoms of a heart attack you must call 911 immediately. The faster they can get to an emergency room the higher the chance they will survive it. Emergency response may include cardiopulmonary respiration (CPR) to make sure that vital organs are oxygenated, or defibrillation (electric shock) to get the heart working again. Defibrillators are often located in workplaces, public buildings and schools so one may not be too far from you. 

Make sure to avoid using a defibrillator if the victim is lying in water or covered with sweat or water. Do not put the defibrillator over a medical path or pacemaker (hard lump under chest skin). If the victim is an infant (<12 months) do not use a defibrillator on them unless you are trained to do so. Also remember to stay clear when applying the electrical shock to the victim. Otherwise, you will get a nasty shock as well. Recovering from a heart attack may likely involve lifestyle changes such as more physical exercise, eating more healthy, quitting smoking and managing stress.  

Stroke

Stroke is a cardiovascular medical emergency affecting brain function. It happens to be very common, being the fifth leading cause of death in the US. A stroke happens when the brain cannot get enough oxygen due to a blood clot in the brain (ischemic stroke) or when a blood vessel in the brain burst (hemorrhage stroke), causing damage to brain tissue. If brain tissue cannot get oxygen or if they are damaged, it will not be able to properly carry out the function that it should. The loss of function will depend on which part of the brain is damaged. Depending on the affected part of the brain, the person may experience loss in vision, or speech, confusion, or loss of function in one side or both side of the body.

Ischemic stroke (left) and hemorrhage stroke (right). Source. Wiki Commons.

Ischemic strokes are more common than hemorrhage strokes occurring 87% of the time among stroke victims.

Another type of stroke called a transient ischemic stroke (TIA) or mini stroke may occur. This type of stroke lasts for about 5 minutes before symptoms go away. This should not be ignored. It should be treated with the same urgency as having a full stroke. TIAs are usually a big warning sign that a major stroke is coming unless action is taken immediately. If you see any of the following signs and symptoms of a stroke, you must call 911 right away.

  1. Sudden numbness in one side of the body e.g. numbness on one side of the face, one arm or leg
  2. Sudden trouble speaking or understanding 
  3. Sudden loss of vision in one or both eyes
  4. Sudden dizziness, lack of balance or coordination
  5. Sudden trouble walking
  6. Sudden massive headache

Use the F.A.S.T. test to determine if someone might be having a stroke. (1) F – See if the person’s face is drooping on one side. (2) – Ask the person to raise both arms, and see if one drifts downward or cannot be moved at all. (3) S – Ask the person to repeat a simple phrase like “How are you today?”. Listen to his speech to hear if it sounds slurred. (4) T – If you see any of these signs then it’s time to call 911. Do not attempt to drive yourself, and if at all possible, do not have someone drive you to the hospital. Wait for the ambulance. That is the best way to get fast treatment than going to wait in an emergency room. When it comes to stroke, time is of the essence since brain cells begin to die within minutes of oxygen deprivation. Getting to the hospital quickly will help prevent long term disability which may include paralysis, permanent vision loss, or loss of speech, or difficulty reasoning, remembering or understanding.

When the victim of a stroke gets to the hospital he may likely get a thrombolytic drug e.g. tissue plasminogen activator (tPA) to break up the clot. This will greatly reduce the likelihood of permanent damage; assuming they are taken to the hospital early (within 3 hours of first sign of stroke). If the stroke is caused by a hemorrhage, an endovascular procedure may be done to insert a coil to block off the bleeding. In some cases, a stent (blood vessel scaffold) is put in before the coil is inserted. If you have a stroke or even a TIA, the chance of future strokes is significantly higher unless steps are taken to lower your risks. Risk for stroke include the following factors. 

  1. Genetics: Genes passed on from one generation to the next can affect conditions that may increase your risk for a stroke e.g. obesity, hypertension, diabetes and sickle cell disease. Sickle cell is a genetic disease that causes blood cells to have an abnormal shape resulting in increased risk of blood vessel blockage. 
  2. Age: According to the CDC, the chances of you getting a stroke doubles every 10 years after you are 65
  3. Gender: Stroke is more common in women. The CDC reports that 1 in every 5 women in the US will have a stroke. One big contributor for this is the use of oral contraceptives.
  4. High blood pressure: Puts too much pressure and strain on the blood vessels until they are no longer able to hold up. Therefore, blood vessels bulge (aneurysm) and eventually burst (hemorrhage)  
  5. High cholesterol: Increases plaque buildup, blocking blood vessels 
  6. Coronary heart disease: Prevents the heart from pumping efficiently, sending less oxygen to the brain 
  7. Unhealthy diet: High saturated and trans fats, and overeating can increase plaque buildup in the arteries. High salt content increases blood pressure  
  8. Lack of exercise: Prevents you from controlling blood sugar and blood lipid (fat) levels. This can cause plaque accumulation
  9. Obesity: Associated with high blood lipids, high blood pressure and diabetes which leads to plaque formation  
  10. Too much alcohol: Increases blood pressure and blood lipids. Higher lipid accumulation will lead to plaque formation
  11. Smoking: Increase blood pressure leading to plaque accumulation of hemorrhage, and prevents adequate oxygen from reaching brain cells   

So how do you prevent a stroke? Based on the risk factors outlined above, stroke is for the most part preventable. Keys steps you will need to take will include quitting smoking if you have that habit, stop drinking or drink no more than the recommended 1 drink per day for women and 2 for men, exercise consistently and eat a healthy diet. Healthy diet includes eating more fruits, vegetables, nuts, legumes and grains, eating less meat, and avoiding fatty meat cuts. You will also need to follow your doctor’s orders in managing any health condition that you may already have that may increase your risk of stroke such as your obesity, high blood pressure, high cholesterol and diabetes. 

Definitions

Thrombosis: Condition in which blood clots the veins or arteries

Heart Attack: Sudden thrombosis of the coronary arteries resulting in loss of blood supply and function of heart muscles

Ischemic Stroke: Stroke resulting from a blood clot in the brain

Hemorrhage Stroke: Stroke resulting from a burst vessel in the brain  

Transient Ischemic Stroke: A brief stroke-like attack that last momentarily (minutes to hours)

LDL Cholesterol: Low density lipoprotein or “bad” cholesterol

HDL Cholesterol: High density lipoprotein or “good” cholesterol

Cardiopulmonary Resuscitation (CPR): A life saving emergency technique involving chest compressions. It is used when someone’s breathing or heart has stopped 

Defibrillation: Administration of an electrical shock to the heart to restore normal rhythm  

Thrombolytic Drug: A blood clot-busting drug

Stent: A tubular support placed inside a blood vessel to relieve obstruction

Courtney Simons
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Courtney Simons is a food science professor. He holds a BS degree in food science and a Ph.D. in cereal science from North Dakota State University.
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