The Cardiovascular System

Polycythemia

Heart Structure

The human heart has four cavities that fill with blood. The chambers in the heart include the right atria, left atria, right ventricle, and left ventricle. The septum separates the right and lefts sides of the heart. A valve prevents blood vessels from going the wrong way, and connects each atrium to the ventricle below it. The mitral valve connects the left atrium with the left ventricle, and the tricuspid valve connects the right atrium with the right ventricle.

Pericardium

This cavity is filled with pericardial fluid which serves as a shock absorber by reducing friction between the pericardial membranes.

1) Keeps the heart contained in the chest cavity

2)Prevents heart from over expanding when blood volume increases

3)Limits heart motion

Major Blood Vessles

Blood Flow & Conduction System of the Heart

Electrocardiogram (EKG) Test

An electrocardiogram is a test that checks for problems with the electrical activity of your heart. An EKG translates the heart's electrical activity into line tracings on paper. The spikes and dips in the line tracings are called waves.


  • Check the heart's electrical activity.
  • Find the cause of unexplained chest pain.
  • Find the cause of symptoms of heart disease, such as shortness of breath, dizziness, fainting, or rapid, irregular heartbeats.
  • Find out if the walls of the heart chambers are too thick (hypertrophied).
  • Check how well medicines are working and whether they are causing side effects that affect the heart.
  • Check how well mechanical devices that are implanted in the heart are working to control a normal heartbeat.
  • Check the health of the heart when other diseases or conditions are present, such as high blood pressure, high cholesterol, cigarette smoking, diabetes, or a family history of early heart disease.

Influences in Blood Pressure

1) Blood Volume- The less blood there is in the arteries, the lower the blood pressure.

2) Strength of Heart Contractions- The stronger the heart beat, the increase in blood pressure. The weaker the heart beat, the decrease in blood pressure.

3) Heart Rate- When the heart beats faster, more blood enters the aorta, and therefore the arterial blood volume and blood pressure would increase.

4) Blood Viscosity- If blood is less viscous than normal, blood pressure will decrease.

5) Resistance to Blood Flow- Peripheral resistance describes any force that acts against the flow of blood in a blood vessel. When vessel wall muscles are contracted, resistance increase and therefore so does the blood pressure.

Tests

Cardiac Cycle

Measure of how much blood your heart pumps in one minute.

Stroke Volume

Measurement of how much blood the heart pumps in one beat.

Pulse

Number of heart beats per minute.

Normal Heart Sounds

The patient should be examined in the supine position, and while sitting and leaning forward. The doctor will use a stethoscope on the surface of the chest to listen for heart sounds. Each area should be systematically auscultated for S1, S2, physiologic splitting, and respiratory variations. Murmurs are blowing, whooshing, or rasping sounds heard during a heartbeat. The sound is caused by turbulent blood flow through the heart valves or near the heart.Murmurs occur when a valve does not close tightly and blood leaks backward.

Blood Tests

Blood tests help doctors check for certain diseases and conditions. They also help check the function of your organs and show how well treatments are working.

  • Evaluate how well organs are workings—such as the kidneys, liver, thyroid, and heart
  • Diagnose diseases and conditions such as cancer, HIV/AIDS, diabetes, anemia, and coronary heart disease
  • Find out whether you have risk factors for heart disease
  • Check whether medicines you're taking are working
  • Assess how well your blood is clotting

Polycythemia

High Red Blood Cells Count

Polycythemia is genetic. Genetic mutations of the JAK2 gene were found to be responsible for most cases of polycythemia vera. These mutations are thought to possibly increase the sensitivity of the red blood cell precursors to erythropoietin, therefore, increasing red blood cell production.

• Gender -- Men may be slightly more likely than women to develop the condition.
• Age -- People older than 60 are most likely to develop the condition, though it may occur at any age.
• Environment – Exposure to intense radiation may increase the risk for the condition.

If you have polycythemia, the thickness of your blood and the slowed blood flow can cause serious health problems.


Blood clots are the most serious complication of polycythemia.


  • They also can cause your liver and spleen to enlarge. Blood clots in the liver and spleen can cause intense pain.
  • Slowed blood flow also prevents enough oxygen-rich blood from reaching your organs. This can lead to chest pain or discomfort and heart failure. The high levels of red blood cells that PV causes can lead to stomach ulcers, gout, or kidney stones.
  • Some people who have PV may develop myelofibrosis, which is a condition in which your bone marrow is replaced with scar tissue. Abnormal bone marrow cells may begin to grow out of control.
  • This abnormal growth can lead to acute myelogenous leukemia, a cancer of the blood and bone marrow. This disease can worsen very quickly.



Electrocardiogram

All patients had a standard surface 12-lead electrocardiogram recorded with a 50 mm/s paper speed at 10 mm/1mV amplitude.

Pulse

Polycythemia can cause a rapid increase in the pulse rate.

Blood Pressure

The increase in the viscosity of the blood which makes the heart pump thicker blood through the circulatory system, can cause high blood pressure. Also, polycythemia can also cause clogging of the vessels that feed the kidneys which can trigger the release of renin. Increased secretion of renin increases the secretion of angiotensin, which raises blood pressure.

Stroke Volume

Sometimes in the early stages of polycythemia, a symptom could be a blot clot forming in the brain, which can result in a stroke.

Cardiac Output

Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. While the influence of acute changes in blood volume and hematocrit upon cardiac output have been well-documented, the cardiac output in polycythemia vera has been reported variously as increased, unchanged, and decreased. In this study an effort was made to clarify the effects of chronic change in blood volume and hct on cardiac output by studying 32 subjects, 25 with polycythemia vera and 7 who were normal.

Heart Sounds

There shouldn't be a change in the heart sounds of a patient. They should continue to be normal.

Blood Tests

Polycythemia may result in the overproduction of white blood cells and platelets. Most of the health concerns associated with polycythemia vera are caused by the blood being thicker as a result of the increased red blood cells.

Polycythemia Treatments

Polycythemia vera does not have a cure. However, treatments can help control the disease and its complications. PV is treated with procedures, medicines, and other methods. Some treatments to lower the red blood cell count are, phlebotomy, medicines, and radiation treatments.

Sources

"Cardiac Output." SBCC Biological Sciences Department. N.p., n.d. Web. 13 Mar. 2013. <http://www.biosbcc.net/doohan/sample/htm/COandMAPhtm.htm>. (tags: none | edit tags)

"How Is Polycythemia Vera Treated? - NHLBI, NIH." NIH Heart, Lung and Blood Institute. N.p., n.d. Web. 13 Mar. 2013. <http://www.nhlbi.nih.gov/health/health-topics/topics/poly/treatment.html>. (tags: none | edit tags)

"Polycythemia vera - MayoClinic.com." Mayo Clinic. N.p., n.d. Web. 13 Mar. 2013. <http://www.mayoclinic.com/health/polycythemia-vera/DS00919>. (tags: none | edit tags)

"Understanding Blood Pressure Readings." www.heart.org. N.p., n.d. Web. 13 Mar. 2013. <http://www.heart.org/HEARTORG/Conditions/HighBloodPressure/AboutHighBloodPressure/Understanding-Blood-Pressure-Readings_UCM_301764_Article.jsp>.