1. Self Study ECG Made Easy
Mary Dunlap
Spring 2015

3. ECG
Electrocardiogram, which can be referred to as an ECG or EKG, is a graphic representation of the hearts electrical activity over time.
Electrocardiography records the electrical current activity in the heart by electrodes that are placed on the patients skin.

4. Electrocardiography

5. ECG Paper
ECG paper is a grid where time is measured along the horizontal axis moving from left to right
Each small square is 1mm in length and represents 0.04 seconds
Each larger square is 5mm in length and represents 0.20 seconds

6. ECG Paper Continue
Hash marks that are located on the top of the paper mark time.
From one hash mark to the next is 5 large squares which is 1 second.
Voltage is measured along the vertical axis(top to bottom) and each small square represents 1mm or 0.1 millivolt(mV)

7. ECG Paper Hash marks will be at the top of the paper above the graph
1 sec = 5 large squares
3 sec = 15 large squares
6 sec = 30 large squares

8. Cells of the Heart
Myocardial cells contract to propel the blood out of the her chambers
Pacemaker cells and electrical conducting cells are responsible for generating and carrying impulses throughout the heart.

9. Cardiac Electrophysiology
Automaticity, excitability, conductivity, and contractility are the four characteristics of the cardiac cells.

10. Cardiac Electrophysiology
Automaticity is the ability of cardiac pacemaker cells to generate an electrical impulse spontaneously and repetitively. Other muscles in the body require stimulation from the nervous system.
Excitability the ability of non-pacemaker cells to respond to an electrical stimulus.

11. Cardiac Electrophysiology
Conductivity the ability of cardiac cells to receive an electrical stimulus and then conduct it to other cardiac cells
Contractility the ability of myocardial cells to shorten, causing myocardial contraction in response to an electrical stimulus.

12. Nerve Impulse and Muscle Contraction
A muscle must be electrically stimulated to contract.
Myocardial cells are bathed in electrolyte solution
Na+, K+ and Ca++ are the primary electrolytes responsible for initiating this process

13. Nerve Impulse and Muscle Contraction
Polarized or Ready State- Muscle is relaxed and ready to receive electrical impulse. The cell has a high concentration of negatively charged ions inside the cell and positively charged ions outside the cell. The difference in the ions inside and outside the cell is know as a resting membrane potential (RMP). K+ is inside the cell & Na+ and Ca++ are found outside the cell.

14. Nerve Impulse and Muscle Contraction
Depolarization (P wave)- electrical stimulus causes the cell membrane to become permeable allowing the Na+ & Ca++ to inter the cell while K+ flows into the cell. This causes shorting of the muscle fibers leading to myocardial contraction.
The change in electrical charge is referred to as action potential and is measured in millivolts (mV)

15. Nerve Impulse and Muscle Contraction
Repolarization (The recovery phase)- process of restoring the cell to it’s polarized state. As the K+ flows out of the cell this process is initiated. The sodium-potassium pumps move the Na+ & Ca++ out of the cell. The cell returns to its’ original negative state

16. Nerve Impulse and Muscle Contraction
Refractory Period- the time between the end of the contraction and the return to ready state. This period is divided into two phases Absolute Refractory Period and Relative Refractor Period.

17. Nerve Impulse and Muscle Contraction
Absolute Refractory- cells are not repolarized and can not be stimulated to conduct an electrical impulse and contract again. This prevents spasm producing (tetanic) contractions. This period is measured from QRS through the 1st 3rd of the T wave

18. Nerve Impulse and Muscle Contraction
Relative Refractor Period- cells have repolarized to a point that some cells can again be stimulated to depolarize if the stimuli is strong enough. The impulse may be slow and an abnormal pattern may be noted. This period starts at the end of the Absolute Refractory Period to the end of the T wave and is a vulnerable period

19. Cardiac Conduction System

20. Cardiac Conduction System
SA node (pacemaker cells) is the hearts primary pacemaker and generates 60 to 100 impulses per min. It is located high on the posterior wall of the right atrium, just below the opening of the superior vena cava under the epicardium. It initiates the electrical impulse that travels downward throughout both the R & L atrium causing depolarization. The impulse is then transmitted to the AV node.

21. Cardiac Conduction System
Atrioventricular (AV) node lies on the floor of the R atrium above the ventricle. This is the only pathway for the impulse, generated from the SA node, to travel from the atrium to the Bundle of His in the ventricles.
AV node if needed can act as the secondary pacemaker generating 40 to 60 impulses per minute

22. Cardiac Conduction System
Bundle of His is located below the AV node and continues transmitting the impulse to the bundle branches.
The bundle passes through an opening in the fibrous skeleton to the interventricular septum where it divides into the L & R bundle branches (BB). The R branch goes to the R ventricle, while the L branch goes to the L ventricle.

23. Cardiac Conduction System
Purkinje fibers is where the R & L bundle branches transmit their impulses to as well as terminate. The countless number of Purkinje Fibers extend into the muscle walls of the ventricles, where they transmit the impulses.
Purkinje fibers and BB can initiate an impulse at a rate of 20 to 40 beats per min.
If SA node or AV junction (AV node it's pathway & Bundle of His) fail to initiate a heartbeat
or there is a blockage 0f conduction through the AV node or bundle of His,
the Purkinje fibers will produce an impulse as a last resort.

24. Cardiac Conduction System

25. Basic ECG Complex P wave PR segment PR interval Q wave QRS complex
J point
ST segment
T wave
U wave
QT interval

26. Basic ECG Complex

27. Basic ECG Complex
P wave indicates SA node function and atrial depolarization and preparation for contraction. First positive upward defection,
Normal length 0.06 to 0.10 sec
Amplitude 0.5 to 2.5 mm
PR segment time required for the impulse to travel through the AV node (where it is delayed), bundle of His, BB, & Purkinje fibers, just prior to ventricular depolarization

28. Basic ECG Complex
PR interval time it takes an impulse to be conducted through the Atria & AV node, until the impulse begins to cause ventricular depolarization. It is measured from the beginning of the P wave to the end of the PR segment. Normal length 0.12 to 0.20 sec
Q wave is the first negative (downward) deflection

29. Basic ECG Complex
QRS Complex ventricular depolarization and conduction of impulse from AV node through ventricular muscle. It is measured from the beginning of the Q wave to the J point. Normal length sec.
J point the junction where the QRS complex ends and the ST segment begins

30. Basic ECG Complex
ST segment early ventricular repolarization and measured from end of S to beginning f T wave can flat(normal), elevated, or depressed
T wave ventricular repolarization. The wave may be above or below the isoelectric line. T wave depressed frequently indication of previous cardiac ischemia. Wave greater than ½ the height of QRS complex

31. Basic ECG Complex
U wave (not always present)late ventricular repolarization, may indicate hypokalemia
QT interval total time required for ventricular depolarization & repolarization. Measured from QRS complex to end of T wave

32. ECG Complex Video

33. ECG Rhythm Analysis
The Nine Step Process assesses the main elements of an ECG tracing

34. ECG Rhythm Analysis Determine the heart rate
Is it normal, fast or slow?
Count the Number of R waves during a 6
sec period and then multiply by 10 to
determine the number of beats per min
Normal rate is 60 to 100 beats/min
Quick assessment- look at space between QRX complexes
More space slower HR- Less space faster heart rate
Heart rate that is faster or slower may indicate problems that require
Prompt intervention
Methods to calculate HR
6 second interval X 10 method
Multiply by 10 the number of QRS complexes found in a 6
Second portion of the ECG tracing
Examples
8 QRS complexes in 6 sec block = 80 HR
12 QRS complexes in 6 sec block = 120 HR
5 QRS complexes in 6 sec block = 50 HR

35. ECG Rhythm Analysis Determine the heart rhythm
Is it regular or irregular?
Is the distance the same between consecutive
P waves & QRS complexes?
The cycles should repeat themselves over and over again
You can measure them using a calipers or the paper method
Paper & Pen Method
Place the tracing on a flat surface
Place the straight edge of a piece of paper above
or over the ECG tracing so the intervals are visible
3. Choose a starting point the peak of an R wave or P wave
place a mark on the paper above to correspond with the wave
4. Find the peak of the next R or P wave and mark the paper in
the corresponding position
5. Move the paper across the ECG tracing, aligning the 2 marks
with succeeding R-R or P-P intervals
If the two marks line up with subsequent consequent P or R waves,
the rhythm is regular
If the distance differs, rhythm is irregular

36. ECG Rhythm Analysis Analyze the P wave Are they present?
Do they occur regularly?
Amplitude 0.5 to 2.5 mm
Duration 0.06 to o.10 sec
Is there a P wave for each QRS complex?
Are the P waves smooth, round, upright?
Do they all look similar?
The P wave can tell us if the impulse that initiated the heart beat arose
from SA node & if it is traveling through the atria & AV junction in normal fashion
Amplitude each small box from top to bottom is 1mm – 0.5 to 2.5 mm is ½ to 2 ½ boxes

37. ECG Rhythm Analysis Measure the PR interval Are they identifiable?
Are they within normal limits ( sec)?
Are they constant across the tracing?

38. ECG Rhythm Analysis Measure the QRS duration
Are they within normal limits ( sec) ?
Are the complexes of equal duration ?
Do thy all look alike ?

39. ECG Rhythm Analysis Assess ST segment;
Duration 0.08 to 0.12 sec. or less
Is it a flat, elevated or depressed line?
Elevated segment of 1 mm or more above the
baseline may indicate myocardial injury
Elevation can also be related to BB block, pericarditis, ventricular hypertrophy,
hyperkalemia, hypothermia

40. ECG Rhythm Analysis
Asses T waves; is it upright and normal height, inverted, peaked or flattened?
Should follow ST segment
Configuration upright
Amplitude no higher than 5mm
Deflection same direction as the preceding
QRS complex
5mm (5 small boxes)
Tall or peaked T waves are seen in myocardial ischemia or hyperkalemia

41. ECG Rhythm Analysis
Assess QT intervals; normal duration 0.36 to 0.44 sec.
U waves; are they present?
U wave considered normal in younger people
It is thought to represent repolarization of the papillary muscles or Purkinje fibers

42. ECG Rhythm Analysis ECG ANALYSIS you tube VIDEO
Basic ECG interpretation
Understanding an ECG
Mechele Kuntz basic overview

43. Power Point Recourses Fast & Easy ECG’s (2e) Bruce Shade
Medical Surgical Nursing 6th ed
Ignatavicius & Workman
Medical Surgical Nursing 5th ed LeMone, Burke, & Bauldoff
Linda Ball, RN, BSN, CCRN, CEN
Educator for Central Florida Health Alliance