3 ECGElectrocardiogram, 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.
5 ECG PaperECG paper is a grid where time is measured along the horizontal axis moving from left to rightEach small square is 1mm in length and represents 0.04 secondsEach larger square is 5mm in length and represents 0.20 seconds
6 ECG Paper ContinueHash 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 squares3 sec = 15 large squares6 sec = 30 large squares
8 Cells of the HeartMyocardial cells contract to propel the blood out of the her chambersPacemaker 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 cellsContractility 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 solutionNa+, 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
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 heartbeator 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.
27 Basic ECG ComplexP wave indicates SA node function and atrial depolarization and preparation for contraction. First positive upward defection,Normal length 0.06 to 0.10 secAmplitude 0.5 to 2.5 mmPR 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 ComplexPR 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 secQ wave is the first negative (downward) deflection
29 Basic ECG ComplexQRS 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 ComplexST segment early ventricular repolarization and measured from end of S to beginning f T wave can flat(normal), elevated, or depressedT 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 ComplexU wave (not always present)late ventricular repolarization, may indicate hypokalemiaQT interval total time required for ventricular depolarization & repolarization. Measured from QRS complex to end of T wave
33 ECG Rhythm AnalysisThe 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 6sec period and then multiply by 10 todetermine the number of beats per minNormal rate is 60 to 100 beats/minQuick assessment- look at space between QRX complexesMore space slower HR- Less space faster heart rateHeart rate that is faster or slower may indicate problems that requirePrompt interventionMethods to calculate HR6 second interval X 10 methodMultiply by 10 the number of QRS complexes found in a 6Second portion of the ECG tracingExamples8 QRS complexes in 6 sec block = 80 HR12 QRS complexes in 6 sec block = 120 HR5 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 consecutiveP waves & QRS complexes?The cycles should repeat themselves over and over againYou can measure them using a calipers or the paper methodPaper & Pen MethodPlace the tracing on a flat surfacePlace the straight edge of a piece of paper aboveor over the ECG tracing so the intervals are visible3. Choose a starting point the peak of an R wave or P waveplace a mark on the paper above to correspond with the wave4. Find the peak of the next R or P wave and mark the paper inthe corresponding position5. Move the paper across the ECG tracing, aligning the 2 markswith succeeding R-R or P-P intervalsIf the two marks line up with subsequent consequent P or R waves,the rhythm is regularIf 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 mmDuration 0.06 to o.10 secIs 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 arosefrom SA node & if it is traveling through the atria & AV junction in normal fashionAmplitude 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 lessIs it a flat, elevated or depressed line?Elevated segment of 1 mm or more above thebaseline may indicate myocardial injuryElevation can also be related to BB block, pericarditis, ventricular hypertrophy,hyperkalemia, hypothermia
40 ECG Rhythm AnalysisAsses T waves; is it upright and normal height, inverted, peaked or flattened?Should follow ST segmentConfiguration uprightAmplitude no higher than 5mmDeflection same direction as the precedingQRS complex5mm (5 small boxes)Tall or peaked T waves are seen in myocardial ischemia or hyperkalemia
41 ECG Rhythm AnalysisAssess QT intervals; normal duration 0.36 to 0.44 sec.U waves; are they present?U wave considered normal in younger peopleIt is thought to represent repolarization of the papillary muscles or Purkinje fibers
42 ECG Rhythm Analysis ECG ANALYSIS you tube VIDEO Basic ECG interpretationUnderstanding an ECGMechele Kuntz basic overview
43 Power Point Recourses Fast & Easy ECG’s (2e) Bruce Shade Medical Surgical Nursing 6th edIgnatavicius & WorkmanMedical Surgical Nursing 5th ed LeMone, Burke, & BauldoffLinda Ball, RN, BSN, CCRN, CENEducator for Central Florida Health Alliance
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