HEART PHYSIOLOGY

and HEART

DISORDERS

The Electrocardiogram

• The conduction of APs through the heart generates electrical currents that can be read through the skin• AP = Action Potential• Currents picked up by electrodes• The recording is called an ELECTROCARDIOGRAM (ECG or EKG)

The Electrocardiogram, cont.

• Each heartbeat produces three clearly recognizable waves.

•The P wave, the QRS Complex, and the T wave

The Electrocardiogram, cont.

P Wave• A small upward deflection• The P wave represents the AP as it

spreads throughout the Atria• A second after the P wave begins, the

atria contract

The Electrocardiogram, cont.

QRS Complex• QRS complex occurs as the AP

spreads through the ventricles• After the QRS complex begins,

the ventricles contract

The Electrocardiogram, cont.

T Wave• Upward deflection that occurs

just before the ventricles relax

The Cardiac CycleA single Cardiac Cycle includes all events associated with one heartbeat

The two atria contract while the two ventricles relax; ventricles contract while atria relax

The Cardiac Cycle, cont.Systole refers to the phase of contraction

Diastolerefers to the phase of relaxation

HEART DISORDERS

1. Pericarditis• Inflammation of the pericardium (the

membrane that surrounds and protects the heart)

• In one form of pericarditis, there is a build up of pericardial fluid (fluid that prevents friction between layers of the pericardium)

• Too much fluid build-up in the pericardium will compress the heart

• Symptoms of pericarditis include low blood pressure and difficulty breathing

1. Pericarditis

2. Heart Murmur• A heart murmur is an abnormal sound

consisting of a clicking, rushing, or gurgling noise that is heart before, between, or after the normal heart sounds

• A heart murmur could mask the normal heart sounds

• Heart murmurs are very common in children and are usually outgrown

• In adults, the heart disorders could indicate a valve disorder

Stenosis• Stenosis = Narrowing of a

heart valve opening that restricts blood flow

• The failure of a valve to close completely is termed insufficiency or incompetence

3. Mitral Stenosis

• Scar formation from an infection or a congenital defect causes narrowing of the mitral valve

4. Mitral Valve Prolapse

• In MVP, one or both cusps of the mitral (bicuspid) valve protrude into the left atrium during ventricular contraction

• Backflow of flood from the left ventricle into the left atrium

5. Aortic Stenosis

• The aortic valve is narrowed

• A backflow of blood from the aorta into the left ventricle

• Valves must be repaired or replaced by human or pig donors or by artificial valves

6. Artificial Pacemaker

• When the heart rate is too low, an artificial pacemaker can restore normal heart rhythm

• Sends out small electrical currents to stimulate the heart to contract

• Pacemaker wires are threaded through the superior vena cava and placed on the right atrium and right ventricle

• Pace makers are implanted beneath the skin inferior to the clavicle

7. Congestive Heart Failure• In congestive heart failure (CHF), the heart

begins to fail

• Pumps less and less effectively, leaving blood in the ventricles after every cycle

• PULMONARY EDEMA - If the left ventricle fails first, the heart cannot pump out all the blood it receives and blood backs up in the lungs. Can lead to suffocation.

• PERIPHERAL EDEMA – The right ventricle fails firsts, and blood backs up in systemic blood vessels. First noticeable as swelling in the feet and ankles.

8. Atherosclerosis• A progressive disease characterized by the

formation in the walls of large and medium of lesions called atherosclerotic plaques

• Two proteins are monitored in cholesterols for this disease are LDL and HDL

• LDL (low-density lipoprotein) and HDL (high-density lipoprotein)

• HDL removes cholesterols – is known as “good cholesterol”

• The HDL should be high and the LDL should be low

9. Myocardial Infarction• A complete obstruction to blood flow in a

coronary artery

• Myocardial Infarction (MI) = Heart Attack

10. Cardiac Arrest• A clinical term meaning cessation of an

effective heartbeat

• The heart may be completely stopped or in ventricular fibrillation (spontaneous contractions of individual muscle fibers)

11. Cardiomegaly

An enlarged heart

12. Tachycardia• Faster (than normal) heart rate at rest

13. Bradycardia• Slower (than normal) resting heart rate

14. Rheumatic Fever

• A streptococcal infection of the throat that affects the bicuspid (mitral) and aortic valves in the heart

• Bacterial infection triggers immune response that inflames damages the tissues – can weaken entire heart