Cardiovascular and Endocrine Diseases

Introduction

The cardiovascular system is made up of the heart, arteries, veins, and the lymphatic system. It's the body's transport system. The body needs the cardiovascular system to bring oxygen and nutrients to cells, remove metabolic waste products, and carry hormones. This system is also called the circulatory system because the blood circulates through the arteries, veins, and capillaries.

The endocrine system consists of organs and glands that secrete chemical messengers called hormones into the bloodstream. Hormones regulate metabolic activities and maintain internal homeostasis.

 

The Cardiovascular System

The cardiovascular system begins to develop when the fetus is barely four weeks old and is the last body system to cease activity at death. This system helps define the presence of life.

The heart has a big job to do all day, every day. The heart pumps blood to the lungs, where it picks up oxygen and eliminates the carbon dioxide that it picked up as it flowed through the body. This is called pulmonary circulation. The circulation of blood throughout the rest of the body is called systemic circulation. During systemic circulation, the blood carries oxygen and nutrients to active cells and transports waste away for excretion.

 

Acute Coronary Syndrome

Acute coronary syndrome (ACS) is a general term for situations where the blood supplied to the heart muscle is suddenly blocked. Myocardial infarction (heart attack) and angina (chest pain and pressure) are part of the ACS group.

Key Facts

Usually, a rupture or erosion of plaque in an artery is the initiating event. This rupture results in platelet adhesions, fibrin clot formation, and activation of thrombin. The thrombus grows and eventually occludes blood flow. The degree of blockage, the time elapsed, and the blood vessel affected will determine the type of infarct (cell death) that occurs. Because not enough oxygen is able to reach that area of the heart, an imbalance of oxygen supply and demand occurs. Death commonly results when an ACS event isn't treated immediately.

Etiology

Several risk factors can lead to ACS:

• Family history
• Obesity
• Smoking
• Diet high in fat and carbohydrates
• Sedentary lifestyle

 

Angina

Key Facts

Angina pectoris, commonly known as angina, is the sensation of chest pain, pressure, or squeezing, often due to ischemia (restriction in blood supply) of the heart muscle due to obstruction or spasm of the coronary arteries.

There are four major forms of angina:

1. Stable (chronic) angina is the most common form of angina. Symptoms arise with effort and subside with rest.

2. Unstable angina is either a new onset of angina or a change in the patient's usual pattern of chest discomfort. Angina at rest is also considered unstable angina. This is a warning sign of a heart attack.

3. Microvascular angina, or cardiac syndrome X, affects the heart's smallest blood vessels. Spams occur in the walls of the vessels and result in decreased blood flow to the heart. Chest pain with this type of angina can last longer than 30 minutes.

4. Variant angina is an extremely rare form of angina caused by spasms of a coronary artery that tend to come in cycles. It may occur with or without a diagnosis of heart disease.

Etiology, Signs, and Symptoms

Angina is caused by reduced blood flow to the heart muscle. The muscle cells need a steady supply of oxygen delivered by the blood to be able to perform the work needed to keep the heart pumping. When the muscle cells aren't getting the oxygen that they need, chest pain occurs. Ischemia means that cells aren't getting enough oxygen. Necrosis occurs when the lack of oxygen causes the cells to die. During angina, cell ischemia occurs, but not cell necrosis.

Many patients experience angina with symptoms of burning, squeezing, and tightness in the chest. Angina often follows physical exertion, emotional excitement, exposure to cold, or a large meal.

 

The physician may order several different tests to help diagnose angina:

Electrocardiogram (ECG or EKG)

An electrocardiogram traces the heart's electrical signals with each heartbeat.

Stress Test

The patient exercises on a treadmill or pedals a stationary bike. During this exercise, the patient's blood pressure and an electrocardiogram are continuously monitored.

Echocardiogram

An echocardiogram uses sound waves to see the heart.

Nuclear Stress Test

A radioactive substance is injected into the bloodstream. A scanner detects the radioactive substance and creates images of the heart. If an area of the heart isn't getting enough oxygen, it will show up as a light spot on the images.

 

Treatments for angina are as follows:

Nitrates relax and widen the blood vessels, allowing more blood and oxygen to reach the heart. Nitroglycerin SL is commonly used for immediate relief of angina symptoms. This form of nitroglycerin is placed under the tongue (sublingual) and allowed to dissolve.

Aspirin reduces the ability of the blood to clot. Patients may be ordered to take 81 mg of aspirin daily as a preventive measure.

Beta blockers block the effects of epinephrine, resulting in the heart beating more slowly and with less force, reducing the heart's workload. Beta blockers also help the blood vessels to relax and widen, which increases the blood flow to the heart.

Ranexa (ranolazine) is an antiangina medication that may be prescribed with other angina medications. It reduces oxygen requirements for the heart muscle.

Balloon angioplasty is an endovascular procedure used to open up and widen obstructed arteries. A deflated balloon catheter is inserted and passed to where the obstruction is located. Then the balloon is inflated to a specified size. This stretches the vessels. A stent may be placed during the procedure. The stent ensures that the vessel stays open.

 

Myocardial Infarction

Key Facts

A myocardial infarction occurs when the myocardial cells are deprived of oxygen due to a blockage in the artery that supplies the area of the heart. A myocardial infarction results from the death of myocardial cells. Myocardial cells don't regenerate, so the heart damage is permanent.

There are different names given to myocardial infarctions, depending on the area of the heart that's involved:

• Inferior
• Anterior
• Septal
• Lateral
• Anterolateral
• Posterior
• Right ventricular

Etiology, Signs, and Symptoms

Many of the signs and symptoms are very similar to angina symptoms:

• Chest pain
• Burning, squeezing, and pressure in the chest
• Diaphoresis (excessive sweating)
• Jaw pain
• Indigestion or heartburn
• Back pain

 

Myocardial infarction is diagnosed by a physical exam, obtaining a 12-lead EKG, and blood test for the following:

• Troponin levels
• Creatine kinase levels
• Cardiac enzymes
• Myoglobin levels

Emergency care focuses on assessing and recording the severity of the pain, location, type, and duration. Treatment attempts to save as much viable heart muscle as possible and to prevent further complications.

Therapies include the following:

• Nitroglycerin
• Percutaneous transluminal coronary angioplasty (PTCA)
• IV beta-adrenergic blocker (followed by oral therapy)
• ACE inhibitors
• Stent placement
• Lipid-lowering drugs
• Trans-myocardial revascularization (laser surgery)
• Epinephrine
• Defibrillation
• Thrombolytic therapy, which should be initiated within three hours of the onset of the symptoms if the patient is a candidate
• Oxygen supplementation (with respiratory distress only)

*Potential complications include the following:

• Heart failure
• Cardiogenic shock
• Heart arrhythmias 
• Pericarditis
• Multisystem organ failure
• Death

 

Congestive Heart Failure

Congestive heart failure (CHF) is also known simply as "heart failure." This condition occurs when the heart muscle doesn't pump blood as well as it should. Treatments can improve the signs and symptoms of heart failure and increase the quality of life for the patient.

Heart failure can be chronic or it can be an acute condition. Heart failure can involve the left ventricle, right ventricle, or both ventricles. The left ventricle is the heart's main pumping chamber and this side is usually affected first. The condition is termed "congestive heart failure" because the blood backs up into and congests the liver, abdomen, and lower extremities. 

 

The main chambers of the heart don't fill properly between beats. When the heart becomes weakened, the ventricles stretch to the point that the heart can no longer keep up with the demands placed upon it. The heart isn't able to pump the blood to the rest of the body effectively.

Coronary artery disease, high blood pressure, uncontrolled diabetes, or obesity can, over time, leave the heart too weak or stiff to pump efficiently. Patients who have leaky heart valves or myocarditis can also develop heart failure

The ejection fraction is an important measurement of how well the heart is pumping. It's used to help classify the type of heart failure. In a healthy heart, the ejection fraction is 50 percent or higher. This means that more than half of the blood that fills the ventricle is pumped out with each beat. There are cases where a patient has hypertension and the heart becomes stiff over time, yet the ejection fraction remains in a normal range.

The most common symptoms of left-sided heart failure is fluid accumulating in the patient's lungs, which causes shortness of breath. The most common symptom of right-sided heart failure is fluid accumulating in the patient's abdomen and lower extremities, causing swelling. There are other common signs and symptoms of heart failure:

• Sudden weight gain
• Ascites (fluid buildup in the space between the lining of the abdomen and abdominal organs)
• Difficulty concentrating or decreased alertness
• Dyspnea
• Fatigue and weakness
• Edema in the lower extremities
• Rapid or irregular heartbeat
• Wheezing or a persistent cough (often expectorating white mucus)

 

In addition to physical examination, there are several different tests and procedures that may be performed to diagnose CHF:

• B-type natriuretic peptide (BNP) blood test (BNP is a substance secreted from the ventricles in response to changes in pressure that occur with heart failure.)
• Chest x-ray
• Echocardiogram
• Stress test

 

Treatments for congestive heart failure include the following:

• ACE inhibitors, such as enalapril (Vasotec), lisinopril (Zestril), or captopril (Capoten)
• Angiotensin II receptor blockers, such as losartan (Cozaar) or valsartan (Diovan), are good alternatives for patients who can't tolerate an ACE inhibitor.
• Beta blockers, such as carvedilol (Coreg), metoprolol (Lopressor), and bisoprolol (Zebeta)
• Diuretics, such as furosemide (Lasix)
• Digoxin (Lanoxin), also called digitalis, works to increase the strength of the patient's heart muscle contractions and slow the heart rate.
• Supplemental oxygen as needed

If other conditions are causing the heart failure, surgical intervention, such as heart valve replacement and coronary artery bypass surgery (CABG), may be appropriate.

*Potential complications include debilitation, arrhythmia, and eventually death.

 

The Endocrine System

The nervous system sends signals to the endocrine system, which secretes hormones in response. Hormones act on receptors in target tissues to deliver the chemical message and regulate tissue activity. This is called a feedback loop. Many endocrine organs are active all the time. The amount of hormone that they secrete varies depending on the time of day, activity level, or other factors.

Homeostasis is the state of equilibrium in the body, including acid-base balance, temperature, and metabolism.

Many of the body's chemical and physical characteristics have a set point, or standard level. For example, blood pressure, heart rate, temperature, blood oxygen, and blood sugar all have normal ranges for optimum health.

The nervous and endocrine systems work to keep these levels at or near the ideal range. The negative feedback loop is a physiological process that works to bring a level back to its set point.

 

If any of the body's levels stray too far from the ideal range, the nervous system will send a signal to the endocrine system, which will work to bring the level back to the set point and restore homeostasis in the body.

The body also has a positive feedback system, which increases a level away from a set point. During positive feedback, physiological processes send body chemistry or other attributes further and further away from the equilibrium (set point). The trend continues until something breaks the cycle. Sometimes positive feedback can be harmful, but sometimes the positive feedback is necessary for an important process to be completed.

An example is childbirth. When it's time for the baby to be born, the hypothalamus releases the hormone oxytocin from the posterior pituitary. The oxytocin increases the intensity of uterine contractions. As the baby moves down into the birth canal, the signal to the hypothalamus is to release more oxytocin and the contractions become more frequent and intense. This cycle of increasing uterine contractions and increasing oxytocin continues right up until the baby is born.

 

One of the major endocrine glands is the pancreas. The pancreas is mainly responsible for maintaining correct blood glucose (sugar) levels. The pancreas makes two hormones that control blood glucose.

Insulin promotes the absorption of glucose from the blood into the cells so it can be used for metabolism. It also directs the liver to store excess glucose as glycogen.

Glucagon does the opposite of insulin. Glucagon puts glucose into the bloodstream by directing the liver to release the stored glucose. Insulin and glucagon act as a feedback loop that keeps blood glucose levels stable. 

 

The thyroid gland is another part of the endocrine system. It's located in the anterior portion of the neck. This gland is responsible for secreting the hormones thyroxine (T4) and triiodothyronine (T3) when stimulated by the pituitary gland. T4 and T3 are essential for controlling cell metabolism and growth. Overproduction or underproduction of these hormones can cause a variety of clinical symptoms. The thyroid also secretes a third hormone called calcitonin.

Calcitonin is responsible for stimulating bone-building cells, thereby decreasing the amount of calcium in the blood. There are two small pairs of glands in the posterior portion of the thyroid called the parathyroid glands. They produce parathyroid hormone (PTH), which regulates the levels of calcium in the bloodstream. If the calcium in the blood gets too low then the parathyroid stimulates the release of PTH.

 

Diabetes

Diabetes mellitus is a disorder that occurs when the pancreas doesn't secrete enough (or any) insulin. Insulin is the hormone responsible for the proper utilization of blood sugar by cells in the body. Without insulin, the glucose in the blood doesn't get into cells, the blood glucose level rises, and eventually it spills over into the urine. Urinary detection of glucose is a positive diagnostic sign of diabetes. Diabetes mellitus is classified as either type 1 or type 2.

Type 1 diabetes as formerly called insulin-dependent diabetes mellitus (IDDM), or juvenile diabetes, because the age of onset was predominantly before adulthood. Patients with type 1 diabetes require insulin injections to sustain life.

Type 2 diabetes is usually diagnosed in adulthood.

 

Type 1 Diabetes

Key facts

Type 1 diabetes is usually diagnosed in children and young adults. Only 5 percent of people with diabetes have this form of the disease. 

In type 1 diabetes, the body doesn't produce insulin.

Etiology, Signs, and Symptoms

The exact cause is unknown. In most cases, the patient's own immune system destroys the islet cells in the pancreas, which produce insulin. Genetics may be a factor. It's also thought that exposure to certain environmental factors, such as viruses, may be a trigger.

Signs and symptoms include the following:

• Increased thirst
• Frequent urination
• Extreme hunger
• Bedwetting in children who previously didn't wet the bed during the night
• Fatigue and weakness
• Irritability and mood changes
• Vaginal yeast infections
• Unintended weight loss

 

As mentioned earlier, sugar in the urine is diagnostic for diabetes. Further diagnosis will be made using one or more of the following blood tests:

• Glycosylated hemoglobin (A1C) test indicates the average blood sugar for the past 2–3 months. A normal level is less than 5.7 percent.
• Random blood sugar test involves a blood sample taken at a random time without regard to when the last meal was consumed.
• Fasting blood sugar test involves a blood sample taken after fasting overnight. A fasting blood sugar of less than 100 mg/dl is normal.
• Oral glucose tolerance level involves multiple steps. The patient fasts overnight and the fasting blood sugar is measured. Then the patient drinks a sugary liquid and the blood sugar is measured periodically for the next two hours.

Treatment revolves around maintaining a consistent level of blood sugar:

• Take insulin as prescribed
• Monitor blood sugar regularly
• Count carbohydrates at meals and adjust insulin according to carbohydrates consumed
• Eat a healthy diet and exercise regularly

Potential complications, which are worse if blood sugars are uncontrolled, include the following:

• Heart and blood vessel disease
• Neuropathy (nerve damage)
• Nephropathy (kidney damage)
• Diabetic retinopathy (eye damage)
• Skin conditions such as slower wound healing
• Poor circulation in the lower extremities can result in foot ulcers, which may in some cases require amputation

 

 

Type 2 Diabetes

Key Facts

Type 2 diabetes was once known as adult onset or non-insulin dependent diabetes mellitus (NIDDM). Type 2 diabetes is a chronic condition that affects the way the body metabolizes glucose. The body may resist the effects of insulin or may not be producing enough insulin to meet its needs. Although type 2 is most common in adults, it's increasingly affecting children as childhood obesity increases.

There's no cure for type 2 diabetes, but there are ways to treat and manage the condition well.

Etiology, Signs, and Symptoms

The exact cause isn't known. However, genetics, environmental factors, excess weight, and a sedentary lifestyle are associated with the development of the disease. 

Symptoms can evolve slowly over a period of years:

• Increased thirst and frequent urination
• Increased hunger
• Weight loss
• Fatigue and irritability
• Frequent infections
• Blurred vision
• Slow-healing wounds
• Acanthosis nigricans (patches of darkened skin, most likely to occur in the axillary area and neck)

 

Diagnosis is made using the same tests as for type 1 diabetes:

• Glycosylated hemoglobin (A1C) test
• Random blood sugar test
• Fasting blood sugar
• Oral glucose tolerance level

Treatment is different from type 1 diabetes because of the difference in cause. Lifestyle changes including healthy eating, regular exercise, and maintaining a healthy weight are very important. Blood sugar monitoring is also important. Insulin may be prescribed, but not always.

Oral hypoglycemics are often used to treat this form of diabetes to stimulate the pancreas to secrete insulin. Some commonly prescribed oral hypoglycemics include the following:

• Januvia
• Micronase
• Glucotrol
• Glucophage
• Glynase
• Precose
• Amaryl
• Actose  

Gestational Diabetes

Key Facts

Gestational diabetes is a condition that develops during pregnancy and usually resolves after pregnancy. Like the other types of diabetes, gestational diabetes affects how the body's cells use glucose.

Etiology, Signs, and Symptoms

Women older than 25 are more likely to develop the condition, as are those who have a family history or personal history of diabetes or are overweight. For most pregnant women, gestational diabetes doesn't cause any noticeable signs or symptoms.

 

Diagnosis requires different tests than those used for the other forms of diabetes:

• Glucose challenge test—The patient drinks a sugary liquid, and one hour later the blood sugar is evaluated. A blood sugar of less than 130–140 mg/dl is usually normal.
• Follow-up glucose tolerance testing—The patient fasts overnight, then drinks a concentrated high-glucose liquid. The patient's blood sugar is checked every hour for three hours. If two out of the three readings are elevated, the patient is diagnosed with gestational diabetes.

Treatment hinges on monitoring blood sugar levels regularly and doing the following:

• Healthy diet
• Exercise
• Possible insulin therapy during pregnancy
• Close monitoring of the growth and development of the fetus

 

Hypoglycemia

Key Facts

Hypoglycemia is a condition caused by abnormally low blood sugar. Hypoglycemia isn't a disease by itself, but rather an indicator of an underlying health problem. Hypoglycemia is usually indicated by blood sugar lower than 70 mg/dl or when the patient feels symptomatic. 

Etiology, Signs, and Symptoms

Hypoglycemia is the most common side effect of hypoglycemic medications used for the treatment of diabetes. Signs and symptoms include the following:

• Heart palpitations
• Fatigue
• Pale skin
• Shakiness
• Anxiety
• Sweating
• Hunger
• Irritability 

As hypoglycemia progresses, symptoms worsen:

• Confusion and abnormal behavior
• Patient may slur words and appear intoxicated
• Visual disturbances, blurred vision
• Seizures and loss of consciousness

 

Diagnosis is made by the presence of symptoms and will be confirmed by documenting the blood sugar levels. Disappearance of the symptoms when the patient is treated for the condition is also diagnostic.

Treatment involves immediate glucose/carbohydrate intake to raise the blood sugar level. If the patient isn't alert enough to eat or drink, intramuscular or intravenous glucagon needs to be administered. Longer-term treatment requires treating the underlying condition that is causing the hypoglycemia.

 

Hyperglycemia

Key Facts

Hyperglycemia is a condition caused by abnormally elevated blood sugar. Hyperglycemia isn't a disease by itself, but rather an indicator of an underlying health problem. Hyperglycemia is usually indicated by blood sugar greater than 200 mg/dl or when the patient feels symptomatic.

Etiology, Signs, and Symptoms

Hyperglycemia is usually seen in diabetic patients who haven't yet been diagnosed or in known diabetic patients who are currently uncontrolled. The signs and symptoms of hyperglycemia are essentially the same as for diabetes:

• Frequent urination
• Increased thirst
• Blurred vision
• Fatigue
• Headache

 

Treatment for hyperglycemia and ketoacidosis focuses on bringing down the blood sugars and getting them back into a normal range.

Ketoacidosis occurs when the high blood sugars remain untreated and continue to rise. Ketones begin to build up in the patient's blood and urine to toxic levels. Signs and symptoms of ketoacidosis are as follows:

• Breath smells fruity
• Nausea and vomiting
• Shortness of breath
• Dry mouth
• Weakness
• Confusion
• Abdominal pain
• Coma

 

Hypothyroidism

Key Facts

Hypothyroidism is a condition in which thyroid hormone production by the thyroid gland is diminished.

Hypothyroidism most often affects the middle-aged population and is more predominant in older women. However, anyone can develop the condition, including infants and children.

Etiology, Signs, and Symptoms

Many causes can be attributed to the development of hypothyroidism:

• Congenital (present from birth)
• Autoimmune disorder
• Previous treatment for hyperthyroidism
• Total or partial removal of the thyroid gland through surgery can leave a patient with hypothyroidism.
• Previous radiation therapy
• Certain medications, such as lithium
• Pituitary disorders that diminish the production of TSH
• Hypothyroidism can develop during pregnancy or in the postpartum period.

Generally, the condition develops slowly over a period of time. Signs and symptoms will vary but may include:

• Fatigue
• Dry skin
• Constipation
• Puffy face
• Hoarseness
• Muscle weakness
• High cholesterol
• Unexplained weight gain
• Increased sensitivity to the cold
• Muscle aches, tenderness, and stiffness
• Pain, stiffness, or swelling of joints

 

A blood test for TSH level is used to diagnose hypothyroidism. Treatment is lifelong replacement with levothyroxine (Levothroid or Synthroid). The oral medication is taken every morning on an empty stomach.

Myxedema, a swelling of the connective tissues, is a rare complication but can be life-threatening.

 

Hyperthyroidism

Key Facts

Hyperthyroidism is caused by an overactive thyroid. The thyroid gland produces too much thyroxine. This results in an overall increased metabolism.

Etiology, Signs, and Symptoms

There are several conditions that can cause the thyroid to become overactive:

• Graves' disease is an autoimmune disease that may have a genetic predisposition. It's more common in women.
• Toxic adenoma
• Plummer's disease is characterized by goiter, an enlarged thyroid.
• Thyroiditis (inflammation of the thyroid)

Hyperthyroidism can mimic other health problems and can be challenging to diagnose. Older adults are likely to have more subtle signs, like increased heart rate, heat intolerance, and fatigue. Other symptoms include the following:

• Sudden weight loss
• Increased appetite
• Tachycardia
• Anxiety, irritability, feeling nervous
• Tremor
• Sweating
• Menstrual pattern changes
• Increased sensitivity to heat
• Changes in bowel movement pattern, especially increased frequency
• Fatigue and muscle weakness
• Difficulty sleeping
• Thinning of the skin
• Fine, brittle hair
• Goiter

 

Diagnosis is usually made by obtaining a medical history and reviewing the patient's symptoms, doing a physical exam, and testing the TSH level.

Treatments include the following:

• Radioactive iodine
• Anti-thyroid medication—propylthiouracil and methimazole
• Thyroidectomy 

Potential complications include the following:

• Graves' ophthalmopathy is an autoimmune inflammatory disorder that affects the eye. The eye will protrude beyond the normal protective orbits, often quite noticeably. Patients may complain of dry, red, swollen eyes.
• Brittle bones result from untreated hyperthyroidism.
• Thyrotoxic crisis, or thyroid storm, is a sudden increase and intensification of symptoms, including high fever, rapid heartbeat, and vomiting. This condition requires immediate medical care.

 

Key Points

• Acute coronary syndrome (ACS) is a general term for situations in which the blood supplied to the heart muscle is suddenly blocked. Myocardial infarction (heart attack) and angina (chest pain and pressure) are part of the ACS group.
• Congestive heart failure (CHF) is also known simply as "heart failure." CHF occurs when the heart muscle doesn't pump blood as well as it should.
• The most common symptom of left-sided heart failure is fluid accumulating in the lungs, causing shortness of breath. The most common symptom of right-sided heart failure is fluid accumulating in the abdomen and lower extremities, causing swelling.
• Diabetes mellitus is a disorder that occurs when the pancreas doesn't secrete enough insulin, the hormone responsible for proper utilization of blood sugar by cells.
• Patients with type 1 diabetes require insulin injections to sustain life; this is usually diagnosed in children or young adults.
• Type 2 diabetes is a chronic condition that affects the way the body metabolizes glucose, either by resisting the effects of insulin or not producing enough insulin.
• Gestational diabetes occurs during pregnancy and usually resolves after pregnancy.
• Hypoglycemia is abnormally low blood sugar; hyperglycemia is abnormally high blood sugar. Both aren't diseases themselves, but an indicator of an underlying health problem.
• Hypothyroidism is when thyroid hormone production by the thyroid gland is diminished; it can cause fatigue, increased sensitivity to the cold, dry skin, constipation, and many other symptoms.
• Hyperthyroidism is caused by an overactive thyroid producing too much thyroxine, increasing metabolism. Hyperthyroidism can be caused by Graves' disease, toxic adenoma, Plummer's disease, and thyroiditis (inflammation of the thyroid).