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Mary Dunlap Spring 2015.   Electrocardiogram, which can be referred to as an ECG or EKG, is a graphic representation of the hearts electrical activity.

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Presentation on theme: "Mary Dunlap Spring 2015.   Electrocardiogram, which can be referred to as an ECG or EKG, is a graphic representation of the hearts electrical activity."— Presentation transcript:

1 Mary Dunlap Spring 2015

2

3   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. ECG

4  Electrocardiography

5   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 ECG Paper

6   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) ECG Paper Continue

7  ECG Paper

8   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. Cells of the Heart

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

10   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. Cardiac Electrophysiology

11   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. Cardiac Electrophysiology

12   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 Nerve Impulse and Muscle Contraction

13   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. Nerve Impulse and Muscle Contraction

14   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) Nerve Impulse and Muscle Contraction

15   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 Nerve Impulse and Muscle Contraction

16   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. Nerve Impulse and Muscle Contraction

17   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 1 st 3 rd of the T wave Nerve Impulse and Muscle Contraction

18   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 Nerve Impulse and Muscle Contraction

19  Cardiac Conduction System

20   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. Cardiac Conduction System

21   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 Cardiac Conduction System

22   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. Cardiac Conduction System

23   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. Cardiac Conduction System

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   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 Basic ECG Complex

28   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 Basic ECG Complex

29   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 Basic ECG Complex

30   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 Basic ECG Complex

31   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 Basic ECG Complex

32   ECG Complex Video

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

34   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 ECG Rhythm Analysis

35   Determine the heart rhythm Is it regular or irregular? Is the distance the same between consecutive P waves & QRS complexes? ECG Rhythm Analysis

36   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? ECG Rhythm Analysis

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

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

39   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 ECG Rhythm Analysis

40   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 ECG Rhythm Analysis

41   Assess QT intervals; normal duration 0.36 to 0.44 sec.  U waves; are they present? ECG Rhythm Analysis

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

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


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