1. Regulation of the Heartbeat
Pacemaker
A specific region of your heart muscle
sets the rate at which your heart contracts.

2. The pacemaker
located in the wall of the right atrium. (SA Node)
generates electrical impulses that spread rapidly over the walls of both atria, making them contract.
impulses spread to a region of the heart called the AV node (atrioventricular node).

3. From there, the electrical impulses spread to the ventricles, causing them to contract.
The contracting ventricles propel blood to the rest of the body.

4. Pacemaker ensures that the heart beats in a rhythmic cycle.
The relaxation phase, called diastole, the atria and ventricles are relaxed, allowing blood from veins to enter the heart.
The contraction phase is called systole.

5. The pacemaker is controlled by
the nervous system and the endocrine system.
two sets of opposing nerves by speeding it up and by slowing it down.
Hormones secreted into the blood.

6. EX: The hormone epinephrine, also called adrenaline, increases heart rate when the body is under stress

7. How is the Heart Wired?
The impluse travels from the SA node to the AV node (atrioventricular node)
A structure called the bundle of His emerges from the AV node and divides into thin, wire-like structures called bundle branches that extend into the right and left ventricles.

8. How is the Heart Wired?
The electrical signal travels down the bundle branches to thin filaments known as Purkinje fibers.
These fibers distribute the electrical impulse to the muscles of the ventricles, causing them to contract and pump blood into the arteries.

10. Voltage is measured along the vertical axis.
How to Read an EKG Strip
Voltage is measured along the vertical axis.
10 mm is equal to 1mV in voltage.
The diagram on the next slide illustrates the configuration of EKG graph paper and where to measure the components of the EKG wave form

12. Heart rate can be easily calculated from the EKG strip:
When the rhythm is regular, the heart rate is 300 divided by the number of large squares between the QRS complexes.
For example, if there are 4 large squares between regular QRS complexes, the heart rate is 75 (300/4=75).

13. Heart rate can be easily calculated from the EKG strip:
The second method can be used with an irregular rhythm to estimate the rate. Count the number of R waves in a 6 second strip and multiply by 10.
For example, if there are 7 R waves in a 6 second strip, the heart rate is 70 (7x10=70).

14. P wave
* Indicates atrial depolarization, or contraction of the atrium. * Location: precedes the QRS complex * Amplitude (height) is no more than 3 mm * Duration: 0.06 to 0.12 seconds * Usually rounded and smooth

15. PR Interval
Tracks the atrial impulse from the atria through the AV node, bundle of His and right and left bundle branches.
Location: from the beginning of the P wave to the beginning of the QRS complex.
Duration 0.12 seconds to 0.20 seconds
Short intervals indicate that the impulse originated somewhere other than the SA node.

16. Location: follows the PR interval
QRS complex
Indicates ventricular depolarization, or contraction of the ventricles.
Location: follows the PR interval
Amplitude: 5 to 30 mm high, but differs with each lead used.
Duration: 0.06 to 0.10 seconds or half of the PR interval measured from the beginning of the Q wave to the end of the S wave
R waves are deflected positively and the Q and S waves are negative

17. Indicates ventricular repolarization
T wave
Indicates ventricular repolarization
Location: follows the QRS wave (complex)
Amplitude: 0.5 mm in standard leads and 10 mm in precordial leads
Rounded and smooth

18. Indicates repolarization time
QT interval
Indicates repolarization time
Location: extends from the beginning of the QRS complex to the end of the T wave
General rule: duration is less than half the preceding R-R interval.
Duration varies according to age, gender and heart rate. From 0.36 to 0.44 seconds

19. Paper and Pencil method of measuring Rhythm
Place the ECG strip on a flat surface.
Position the straight edge of a piece of paper along the strip’s baseline.
Move the paper up slightly so that the straight edge is near the peak of the R wave.
Mark the paper at the R waves of 2 consecutive QRS complexes. This distance is the R-R interval.

20. Move the paper across the strip lining up the two marks with succeeding R-R intervals. If the distance for each R-R interval is the same, the ventricular rhythm is REGULAR.
If the distances varies the RHYTHIM ins irregular.
The same can be done using the distance between the P waves to determine atrial rhythm

21. Measuring Blood Pressure
When the ventricles contract, they increase pressure on the blood.
The resulting force that blood exerts against the artery walls is called blood pressure.

22. Measuring Blood Pressure
This force drives blood through the arteries and into the capillaries.
Artery walls are elastic, which enables them to stretch in response to this force.

23. Blood pressure
represented by two numbers separated by a slash, such as 120/80.
measured in millimeters of mercury (mm Hg), a standard unit of liquid pressure.
The first number is referred to as systolic pressure, the highest recorded pressure in an artery when the ventricles contract (systole).
Diastolic pressure, the second number, is the lowest recorded pressure in an artery during the relaxation phase of the heartbeat (diastole).

24. A blood pressure of about 120/80 is the average for a healthy young adult.
As a person ages, blood pressure may increase. Smoking or a fatty diet can contribute to this increase by causing arteries to become less elastic.
A blood pressure above 140/90 is considered high and may lead to other cardiovascular diseases.

25. The Electrical System

26. The pumping of the heart muscle generates a pulse, or heartbeat.
The Electrical System
The pumping of the heart muscle generates a pulse, or heartbeat.
The normal pattern of muscle contraction begins in the upper chambers (atria), which pump blood into the lower chambers (ventricles).

27. The ventricles pump blood to the body and lungs.
The Electrical System
The ventricles pump blood to the body and lungs.
This coordinated action occurs because the heart is "wired" to send electrical signals that tell the chambers of the heart when to contract.

28. The Electrical System
Your heartbeat is able to speed up and slow down because it is wired with electrical tissue.
Your heart also has built-in "pacemakers" that are like electrical outlets.

29. The electrical system of the heart triggers the heartbeat.
The pacemakers and the wiring that run through your heart also coordinate contractions in the upper chambers and lower chambers, which makes the heartbeat more powerful so it can do its job effectively.

30. We normally have our own pacemakers that tell the heart when to beat.
How is the Heart Wired?
We normally have our own pacemakers that tell the heart when to beat.
The master pacemaker is located in the atrium (upper chamber).
It acts like a spark plug that fires in a regular, rhythmic pattern to regulate the heart's rhythm.

31. This "spark plug" is called the sinoatrial (SA), or sinus node.
How is the Heart Wired?
This "spark plug" is called the sinoatrial (SA), or sinus node.
It sends signals to the rest of the heart so the muscles will contract.
First, the atrium contracts.
The electrical signal from the sinus node spreads through the atria.

32. This electrical connection is critical.
How is the Heart Wired?
Next, the electrical signal travels to the area that connects the atria with the ventricles.
This electrical connection is critical.
Without it, the signal would never reach the ventricles, the major pumping chambers of the heart.

33. When Your Heart Doesn't Work as It Should
The S-A node doesn't produce the right number of signals.
Another part of the heart takes over as the natural pacemaker.
The electrical pathways are interrupted.

34. When Your Heart Doesn't Work as It Should
Slow Arrhythmias — When the heart beats too slowly it's called bradycardia (brady = slow, cardia = heart).
Slow arrhythmias can be a problem because they cause the oxygen- and nutrient-rich blood to travel more slowly to your organs and other tissues.
Your body may not receive enough oxygen and nutrients to function properly.

35. When Your Heart Doesn't Work as It Should
Fast Arrhythmias — When the heart beats too fast it's called tachycardia (tachy = fast, cardia = heart).
During tachycardia the heart isn't able to pump blood to the body as well as it should.
Fast rhythms in the upper chambers may not be life- threatening in themselves.
But they may contribute to other problems that are serious.
Fast arrhythmias in the lower chambers, the ventricles, can be dangerous and even fatal.

36. What Causes These Problems?
Heart disease causes changes in the heart tissue.
Aging of the heart muscle can also change the heart tissue.
Physical problems, such as diabetes, smoking, and excessive alcohol or drug use, can affect the heart tissue.
There could be an inherited heart problem.
There is evidence of heart failure or a heart attack.

37. Tests for the Conduction System
ECG or EKG (Electrocardiogram)
Measure heart rate
Look for arrhythmias
Identify enlargement of the heart's chambers
Help diagnose whether you've had a heart attack

38. The ECG or EKG, directly measures microvoltages in the heart muscle (myocardium) occurring over specific periods of time in a heartbeat, otherwise known as a cardiac impulse.
With each heartbeat, electrical currents called action potentials, measured in millivolts (mV), travel through a conducting system in the heart.

39. Cardiac Cycle
The events that occur from the beginning of one heartbeat to the beginning of the next.
Consists of ventricular diastole (relxation) and ventricular systole (contraction)

40. The aortic and pulmonic valves are closed.
Diastole
During diastole, blood flows from the atria through the open tricuspid and mitral valves into the relaxed ventricles.
The aortic and pulmonic valves are closed.
75% of blood flow is passive

41. Systole
During ventricular systole the mitral and tricuspid valves are closed.
The relaxed atria fill with blood. A ventricular pressure rises, the aortic and pulmonic valves open.
The ventricle contract, and blood is ejected into the pulmonic and systemic circulation.

42. Cardiac Output
Is the amount of blood the left ventricle pumps into the aorta per minute.
Is measured by multiplying heart rate times stroke volume.
Stroke volume refers to the amount of blood ejected with each ventricular contraction and is usually about 70 mls.

43. Cardiac Output
Normal CO is 4 to 8 L/min.
The heart pumps only as much blood as the body requires, based on metabolic requirements.

44. Three factors determines stroke volume: Preload Afterload
Cardiac Output
Three factors determines stroke volume:
Preload
Afterload
Myocardial contractility.

45. Preload
Is the degree of stretch or tension on the muscle fibers when they begin to contract..
Its usually considered to be the end-diastolic pressure when the ventricl has filled

46. Of the heart is represented on an ECG.
Electrical Activity
Of the heart is represented on an ECG.
ECG represent only electrical activity not the mechanical activity or actual pumping of the heart.

47. EKG paper is a grid where time is measured along the horizontal axis.
How to Read an EKG Strip
EKG paper is a grid where time is measured along the horizontal axis.
Each small square is 1 mm in length and represents 0.04 seconds.
Each larger square is 5 mm in length and represents 0.2 seconds.

48. Building 1 suite313
Dr. Sneider
Dec 2nd at 215

49. http://usasam.amedd.army.mil/_fm_course/Study/Understa ndingECG.pdf