Self Study ECG Made Easy Mary Dunlap Spring 2015

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.

Electrocardiography

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

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)

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

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.

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

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.

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.

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

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.

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)

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

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.

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

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

Cardiac Conduction System

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.

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

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.

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.

Cardiac Conduction System http://www.youtube.com/watch?v=qiIUrCe2Sxs http://www.youtube.com/watch?v=te_SY3MeWys

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

Basic ECG Complex

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

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

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 0.04-0.10 sec. J point the junction where the QRS complex ends and the ST segment begins

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

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

ECG Complex Video http://www.youtube.com/watch?v=4vkbywows-o

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

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

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

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

ECG Rhythm Analysis Measure the PR interval Are they identifiable? Are they within normal limits (0.12-0.20 sec)? Are they constant across the tracing?

ECG Rhythm Analysis Measure the QRS duration Are they within normal limits (0.04-0.10sec) ? Are the complexes of equal duration ? Do thy all look alike ?

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

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

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

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

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