Heart Valve Disease

By Britney Watermolen

Background Information

Chambers

  • Two upper chambers are the atria
  • Two lower chambers are the ventricles.
  • The right atrium receives blood from the cranial vena cava, caudal vena cava and coronary sinus. The right atrium also houses the sinoatrial node. Blood flows from the right atrium to the right ventricle through the tricuspid valve.
  • The right ventricle forms most of the anterior surface of the heart. The right ventricle is separated from the left by a partition called the interventricular septum.
  • Deoxygenated blood passes from the right ventricle through the pulmonary semi-lunar valve to the pulmonary trunk, which conveys the blood to the lungs.
  • The left atrium forms the dorsocaudal section of the base of the heart and is similar to the right atrium in structure and shape. It receives oxygenated blood from the lungs from the pulmonary veins.
  • Blood passes from the left atrium to the left ventricle through the bicuspid or left atrioventricular valve. The left atrium lies under the tracheal bifurcation and enlargement of this area of the heart can cause breathing difficulties. The left ventricle forms the apex of the heart and is conical in shape. Blood passes from the left ventricle to the ascending aorta through the aortic semi-lunar valve. From here some of the blood flows into the coronary arteries, which branch from the ascending aorta and carry blood to the heart wall. The remainder of the blood travels throughout the body.

The pericardium

  • Membrane that surrounds and protects the heart. It is composed of two layers separated by a narrow cavity. The inner layer is firmly attached to the heart wall and is known as the visceral layer or epicardium. The outer layer is composed of relatively inelastic connective tissue and is termed the parietal layer. This fibrous layer prevents distension of the heart, thus preventing excessive stretching of the heart muscle fibres. The cavity between the two layers contains a small volume of fluid which serves as a lubricant, facilitating the movement of the heart by minimising friction. The sternopericardiac ligament connects the parietal layer to the sternum and the phrenopericardiac ligament joins the parietal layer to the diaphragm. The latter is present only in the canine.

Blood Flow

Starting with the superior and inferior venae cavae (deoxygenated blood)


  • Blood flows to the Right Atrium
  • Tricuspid valve
  • Right ventricle
  • Pulmonary valve
  • Pulmonary trunk
  • Left and right pulmonary arteries


Left and right lungs (oxygenate blood)


  • Four pulmonary veins carry to
  • Left atrium
  • Mitral valve
  • Left ventricle
  • Aortic valve
  • Ascending and descending aortae


Heart Valves

There is a valve through which blood passes before leaving each chamber of the heart. The valves prevent the backward flow of blood. These valves are actual flaps that are located on each end of the two ventricles (lower chambers of the heart). They act as one-way inlets of blood on one side of a ventricle and one-way outlets of blood on the other side of a ventricle. Normal valves have three flaps, except the mitral valve, which has two flaps. The four heart valves include the following:

  • tricuspid valve - located between the right atrium and the right ventricle
  • pulmonary valve - located between the right ventricle and the pulmonary artery
  • mitral valve - located between the left atrium and the left ventricle
  • aortic valve - located between the left ventricle and the aorta

Major Blood Vessels

  • Superior vena cava- carries deoxygenated blood from the upper body to the right atrium of the heart (vein).
  • Inferior vena cava - carries deoxygenated blood from the lower body to the right atrium of the heart (vein).
  • Pulmonary arteries - carry deoxygenated blood from the right ventricle to the lungs
  • Pulmonary veins - carry oxygenated blood from the right ventricle to the lungs
  • Aortic artery - carries oxygenated blood from the lungs to the left atrium
  • Carotid arteries- carry oxygenated blood from the aorta to the brain
  • Pulmonary trunk - carry oxygenated blood from the right side of the heart to the lungs.
Conducting System Of The Heart

Pulmonary and Systemic Circulation

Pulmonary circulation

  • From the right atrium, the deoxygenated blood drains into the right ventricle through the rightatrioventricular (AV) valve. This valve is also referred to as the tricuspid valve because it has three flaps in its structure. When the ventricles contract, the AV valve closes off the opening between the ventricle and the atrium so that blood does not flow back up into the atrium.
  • As the right ventricle contracts, it forces the deoxygenated blood through the pulmonary semilunar valve and into the pulmonary artery. Note that this is the only artery in the body that contains deoxygenated blood; all other arteries contain oxygenated blood. The semilunar valve keeps blood from flowing back into the right ventricle once it is in the pulmonary artery.

Systemic circulation

  • Freshly oxygenated blood returns to the heart via the pulmonary veins. Note that these are the only veins in the body that contain oxygenated blood; all other veins contain deoxygenated blood.
  • The pulmonary veins enter the left atrium. When the left atrium relaxes, the oxygenated blood drains into the left ventricle through the left AV valve. This valve is also called the bicuspid valve because it has only two flaps in its structure.
  • As the left ventricle contracts, the oxygenated blood is pumped into the main artery, the aorta. To get to the aorta, blood passes through the aortic semilunar valve, which serves to keep blood flowing from the aorta back into the left ventricle.

ECG (electrocardiogram)

ECG (electrocardiogram) is a test that measures the electrical activity of the heart. The heart is a muscular organ that beats in rhythm to pump the blood through the body. The signals that make the heart's muscle fibers contract come from the sinoatrial node, which is the natural pacemaker of the heart.

Wave


  • P wave - atrial depolarisation, < 120 ms
  • PR segment - end of P wave till beginning of QRS complex i.e. time taken between atrial and ventricular activation.
  • PR interval - onset of P wave till onset of QRS complex, 120-200 ms
  • QRS complex - ventricular depolarisation, <110 ms
  • T wave - ventricular repolarisation
  • U wave - repolarisation of Purkinje fibres
  • QT interval - beginning of QRS complex till end of T wave


Blood Pressure

Blood pressure is typically recorded as two numbers, written as a ratio like this:

Systolic

The top number, which is also the higher of the two numbers, measures the pressure in the arteries when the heart beats (when the heart muscle contracts).



Diastolic

The bottom number, which is also the lower of the two numbers, measures the pressure in the arteries between heartbeats (when the heart muscle is resting between beats and refilling with blood)


Five Factors


  • Blood Volume
-Direct cause of blood pressure is the volume of blood in the vessels. The larger the volume of blood in the arteries, the more pressure the blood exerts on the walls of the arteries, or the higher the blood pressure will be.
  • Strength of Heart Contractions
-The stronger the contraction is, the more blood it pumps into the aorta and arteries. The weaker contraction is, the less blood it pumps.
  • Heart Rate
-As heartbeats increase, more blood enters the aorta, and the arterial blood volume and blood pressure would increase.
  • Blood Viscosity
-if the viscosity or thickness of blood becomes less viscous than normal, blood pressure decreases.
  • Resistance to Blood Flow

-Peripheral resistance, describes any force that acts against the flow of blood in a blood vessel.


Cardiac cycle

  • each complete heartbeat, including contraction and relaxation of the atria and ventricles.
Stroke Volume

  • the amount of blood that is ejected from the ventricles of the heart with each beat.
Pulse

  • alternating expansion and recoil of the arterial walls produced by the alternate contraction and relaxation of the ventricles; travels as a wave away from the heart.
Normal heart sound

  • Isovolumetric contraction- closure of mitral and tricuspid valves
  • Isovolumetric relaxation- closure of aortic and pulmonic valves

Blood Tests

Hematocrit Test

  • Hematocrit is a blood test that measures the percentage of the volume of whole blood that is made up of red blood cells. This measurement depends on the number of red blood cells and the size of red blood cells.
White blood cell count

  • A WBC count is a blood test to measure the number of white blood cells (WBCs).

    White blood cells help fight infections. They are also called leukocytes.

Platelet count

  • Test to measure how many platelets you have in your blood. Platelets help the blood clot. They are smaller than red or white blood cells.

Individual or Patient with Heart Valve Disease

Heart valves can have one or both of the two malfunctions:

  • regurgitation (or leakage of the valve)
    The valve(s) does not close completely, causing the blood to flow backward through the valve. The heart is forced to pump more blood on the next beat, making it work harder.
  • stenosis (or narrowing of the valve)
    The valve(s) opening becomes narrowed, limiting the flow of blood out of the ventricles or atria. The heart is forced to pump blood with increased force in order to move blood through the narrowed or stiff (stenotic) valve(s).

Heart valves can have both malfunctions at the same time (regurgitation and stenosis). Also, more than one heart valve can be affected at the same time. When heart valves fail to open and close properly, the implications for the heart can be serious, possibly hampering the heart's ability to pump blood adequately through the body. Heart valve problems are one cause of heart failure.

Causes

The causes of heart valve damage vary depending on the type of disease present, and may include the following:

  • a history of rheumatic fever (now a rare disease in north America due to effective antibiotic treatment) - a condition characterized by painful fever, inflammation, and swelling of the joints.
  • damage resulting from a heart attack
  • damage resulting from an infection
  • changes in the heart valve structure due to the aging process
  • congenital birth defect
  • syphilis (now a rare sexually transmitted disease in North American due to effective treatment) - a disease characterized by progressive symptoms if not treated. Symptoms may include small, painless sores that disappear, followed by a skin rash, enlarged lymph nodes, headache, aching bones, appetite loss, fever, and fatigue.
  • myxomatous degeneration - an inherited connective tissue disorder that weakens the heart valve tissue.

Treatment

In some cases, the only treatment for heart valve disease may be careful medical supervision. However, other treatment options may include medication, surgery to repair the valve, or surgery to replace the valve.

Medication

Medications are not a cure for heart valve disease but in many cases are successful in the treatment of symptoms caused by heart valve disease.

Surgery

Surgery may be necessary to repair or replace the malfunctioning valve(s). Surgery may include:

  • Heart valve repair: In some cases, surgery on the malfunctioning valve can help alleviate symptoms. Examples of heart valve repair surgery include cutting scarred flaps so they open more easily; remodeling valve tissue that has enlarged; or inserting prosthetic rings to help narrow a dilated valve. In many cases, heart valve repair is preferable, because a person's own tissues are used.
  • Heart valve replacement: When heart valves are severely malformed or destroyed, they may need to be replaced with a new mechanism. Replacement valve mechanisms fall into two categories: tissue (biologic) valves, which include animal valves and donated human aortic valves, and mechanical valves, which can be metal, plastic, or another artificial material.

Another treatment option that is less invasive than valve repair/replacement surgery is balloon valvuloplasty, a non-surgical procedure in which a special catheter (hollow tube) is threaded into a blood vessel in the groin and guided into the heart. The catheter, which contains a deflated balloon, is inserted into the narrowed heart valve and the inflated balloon is stretching the valve open. The balloon is then removed. This procedure is often used to treat pulmonary stenosis and, in some cases, aortic stenosis.

Variations in Results

EKG

  • This simple test detects and records the heart's electrical activity. An EKG can detect an irregular heartbeat and signs of a previous heart attack. It also can show whether certain chambers of your heart are enlarged.
Pulse

  • Those with aortic valve regurgitation may experience symptoms of a fluttering heart and rapid pulse, while those with a mitral valve prolapse (a chronic condition in which the mitral valve fails to close properly, allowing blood to leak backward into the left atrium) may develop a racing pulse or an arrhythmia, or irregular heart beat.

Blood Pressure

  • May cause hypertension (high blood pressure). Hypertension could be a cause of heart valve disease.

Stroke volume variations

  • With a leaky valve or a valve that has a smaller opening it may cause a differ in the amount of blood that is ejected from ventricles.

Cardiac output

  • Volume of blood that is pumped by ventricle may differ depending on the patients condition.

Heart sounds

  • Patients may develop a heart murmur (a swishing sound) detectable by doctors listening to the heart with a stethoscope.

Blood tests


  • Hematocrit test- patient will often have results of hematocrit being decreased.
  • WBC count- patient may tend to have a low WBC count.
  • Platelet count- may change depending on patient.


Sources