BASIC ECG :
BASIC ECG By: Ashish Jai Kishan Moderator: Dr Anil SaxenaHistory :
History 1842- Carlo Matteucci -electricity is a/w hrt beat 1876- Marey - electric pattern of frog’s heart 1895 - William Einthoven - invention of EKG 1906- Einthoven diagnoses some heart problems 1924 - Noble prize - Einthoven for EKGHistory :
History 1938 -AHA & Cardiac society of great Britain defined position of chest leads 1942- Goldberger increased Wilson’s Unipolar lead voltage by 50% & made Augmented leadsECG interpretation - step-by-step :
ECG interpretation - step-by-step Rate Rhythm Cardiac Axis P – wave PR - interval QRS Complex ST Segment QT interval (T & U wave) Other ECG signsELEMENTS OF ECG:
ELEMENTS OF ECGCardiac Electrophysiology:
Cardiac Electrophysiology Electrical activity is governed by multiple transmembrane ion conductance changes 3 types of cardiac cells 1. Pacemaker cells - SA node, AV node 2. Specialised conducting tissue - Purkinje fibres 3. Cardiac myocytesPacemakers of Heart:
Pacemakers of Heart SA Node - Dominant pacemaker -intrinsic rate of 60 - 100 beats/minute . AV Node - 40 - 60 beats/minute. Ventricular cells - 20 - 45 beats/minute .PowerPoint Presentation:
S Allen 2003 Electrocardiogram:
Electrocardiogram Is a recording of electrical activity of heart conducted thru ions in body to surface 13-60Waveforms & Intervals:
Waveforms & IntervalsSegments and Intervals:
Segments and Intervals Segment – Straight line b/w waves Interval – wave + segment ST segment – end of ventricular depolarization to start of vent. repolarization QT interval – ventricular cycle, 40% of each cardiac cycleECG Graph Paper :
ECG Graph Paper Runs at a paper speed of 25 mm/sec Each small block of ECG paper is 1 mm 2 At speed of 25 mm/s, 1 small block = 0.04 s 5 small blocks make up 1 large block = 0.20 s Hence, there are 5 large blocks/sec Voltage: 1 mm = 0.1 mV between each individual block verticallyPowerPoint Presentation:
Depolarization of both atria Relationship b/w P & QRS - distinguish various arrhythmias Shape & duration of P - indicate atrial enlargement P WavePowerPoint Presentation:
Always +ve in lead I & II Always -ve in lead aVR <3 small sqs - duration <2.5 small sqs - amplitude Biphasic in lead V1 Best seen in lead II P WaveP Pulmonale:
P Pulmonale P MITRALEPowerPoint Presentation:
Onset of P wave to onset of QRS Normal = 0.12 - 2.0 sec Represents A to V conduction time (via His bundle) Prolonged PR interval indicate AV block PR INTERVALShort PR Interval:
Short PR Interval WPW Sx Accessory pathway (Bundle of Kent) - early activation of the ventricle (delta wave & short PR interval)Short PR Interval:
Short PR Interval WPW Sx Accessory pathway (Bundle of Kent) - early activation of the ventricle (delta wave & short PR interval)Long PR Interval:
Long PR Interval 1 st degree Heart BlockVentricular Depolarization:
Ventricular Depolarization Includes Bundle of His Bundle Branches Right Left Septal Anterior Posterior Terminal Purkinjie fibersVentricular Depolarization:
Ventricular Depolarization Ventricular Waves Q wave – 1 st downward deflection after P wave Rwave – 1 st upward deflection after Q wave R` wave – any second upward deflection S wave – 1 st downward deflection after R wavePowerPoint Presentation:
Ventricular depolarization Is > P wave d/t > Ventricular mass Normal duration = 0.08 - 0.12 secs Q wave >1/3 the height of R wave, >0.04 sec –abnormal; may represent MI QRS COMPLEXPowerPoint Presentation:
Connects QRS complex & T wave Duration = 0.08 - 0.12 sec ST SegmentPowerPoint Presentation:
“small to moderate” size +ve deflection wave after QRS complex, Ht is 1/3 rd - 2/3 rd that of corresponding R wave Septal repolarization (not always seen on ECG) T Wave U WavePowerPoint Presentation:
Beginning of QRS to end of T wave Normal QT is usually about 0.40 sec QT varies based on HR- faster HR ,shorter QT . Hence QTc . Bazett’s formula: QT C = QT / √ RR Fredericia’s formula: QT C = QT / RR 1/3 Framingham formula: QT C = QT + 0.154 (1 – RR) Hodges formula: QT C = QT + 1.75 (HR– 60) QT IntervalPowerPoint Presentation:
Bazett’s formula -most commonly used d/t its simplicity. H/E over-corrects at HR> 100 bpm & under-corrects at HR < 60 bpm , but adequate for HR 60 – 100 bpm . HR >100 bpm range- Fredericia / Framingham If ECG is fortuitously captured while patient’s HR= 60 bpm , absolute QT interval should be used QT IntervalPowerPoint Presentation:
Maximum slope intercept method - end of T wave as the intercept b/w isoelectric line with tangent drawn through maximum down slope of the T wave When notched T waves are present- tangent drawn from maximum down slope of the 2 nd notch, T2Some causes of prolonged QT :
Some causes of prolonged QT CAD Cardiomyopathy Severe Bradycardia, High-Grade AV Block Anti-Arrhythmics Psychotropic Drugs HypoCa, Autonomic dysfunction Hypothyroid Hypothermia Congenital Long QT SyndromeECG interpretation - step-by-step :
ECG interpretation - step-by-step Rate Rhythm Cardiac Axis P – wave PR - interval QRS Complex ST Segment QT interval (T & U wave) Other ECG signsECG interpretation - step-by-step :
ECG interpretation - step-by-step Rate Rhythm Cardiac AxisRATE:
RATEPowerPoint Presentation:
CALCULATING RATE 300 number of BIG SQUARE b/w R-R Rate = lead II - rhythm strip . Look at # of square b/w one R-R interval. 1500 number of SMALL SQUARE b/w R-R OR Rate =PowerPoint Presentation:
CALCULATING RATE 300 Rate = Eg 3 1500 15 Rate = or Rate = 100 beats/minutePowerPoint Presentation:
Rhythm irregular - # of beats in a 6-sec X by 10 CALCULATING RATE 1 2 3 4 5 6 7 8 = (Number of waves in 6-sec strips) x 10 = 8 x 10 = 80 bpm Rate There are 8 waves in this 6-seconds strip.Rhythm:
RhythmPowerPoint Presentation:
P -QRS relationships- Lead II is commonly used Regular or irregular? Ventricular rhythm –measured by R-R interval & Atrial rhythm - measured P-P interval. RHYTHMPowerPoint Presentation:
RHYTHM ECG rhythm -usual rate b/w 60-99 bpm, every P wave must be followed by a QRS & every QRS is preceded by P wave. P wave is upright in leads I and II Normal Sinus RhythmAxis :
AxisPowerPoint Presentation:
AXIS Axis refers to general direction of heart's depolarization wave front (or mean electrical vector) in the frontal plane. In healthy conducting system - axis is related to where the major muscle bulk of heart lies.PowerPoint Presentation:
William Einthoven developed a system capable of recording small signals & recorded 1 st ECG. Leads were based on Einthoven triangle a/w limb leads. Leads put heart in middle of a trianglePowerPoint Presentation:
Excitation begins at SA node atrial walls Cannot propagate across the boundary b/w atria & ventricle Resultant vector - in yellow Projections on Leads I, II and III are all +ve ECG Signal cPowerPoint Presentation:
ECG Signal AV node located on A-V boundary & provides conducting path Delay - allow ventricles to fill. Excitation begins with septumPowerPoint Presentation:
ECG Signal Depolarization Via bundle branches towards apex Overall electric vector points toward apex as both LV & RV depolarize & begin to contractPowerPoint Presentation:
ECG Signal Depolarization of RV reaches epicardium . LV wall is thicker & continues to depolarizePowerPoint Presentation:
ECG Signal As there is no compensating electric forces on Rt, electric vector reaches maximum size & points Lt Note: atria ‘ve repolarized, but signal is not seenPowerPoint Presentation:
ECG Signal Depolarization front continues to propagate to back of LV wall Electric vector < in size as there is less tissue depolarizingPowerPoint Presentation:
ECG Signal Depolarization of ventricles is complete & the electric vector has returned to zeroPowerPoint Presentation:
ECG Signal Ventricular REPOLARIZATION begins from epicardium with left being slightly dominantPowerPoint Presentation:
ECG Signal Note that this produces an electric vector that is directed as the depolarization traveling in opposite direction Repolarization is diffuse & generates a smaller and longer signal than depolarizationPowerPoint Presentation:
ECG Signal Upon complete repolarization, hrt is ready to go again & we record an ECG traceECG Information :
ECG Information 12 leads allow tracing of vector in all 3 planesAxis Determination & Deviation:
Axis Determination & Deviation Why Axis Determination? Definitions Axis Quadrants Axis Determination Axis DeviationAxis Determination & Deviation:
Axis Determination & Deviation What is Axis? “The general direction of electrical impulses as they travel through heart” “Sum total of all electrical currents generated by ventricular myocardium during depolarization” Normally from upper Rt to lower LtBasics of 12 Lead ECG Vector :
Basics of 12 Lead ECG Vector There are 3 basic "laws" of Electrocardiography. These "laws" ‘ ve to do with the direction of flow of electrical conduction in the heart or what we term as vector.Basics of 12 Lead ECG Vector :
Basics of 12 Lead ECG Vector 1. Movement of electrical impulse towards + ve electrode will result in a + ve deflection on ECG. - + =Basics of 12 Lead ECG Vector :
Basics of 12 Lead ECG Vector 2. Movement of electrical impulse toward – ve electrode will result in a – ve deflection on the ECG. - + =Basics of 12 Lead ECG Vector :
Basics of 12 Lead ECG Vector 3. Movement of electrical impulse perpendicular to a line b/w + ve & - ve electrodes results in a bi- phasic (part upright & part downward) deflection on ECG. - + =PowerPoint Presentation:
AXISBasics of 12 Lead ECG's Determining AXIS :
Basics of 12 Lead ECG's Determining AXIS Technique #1: Two Lead Method or Quadrant Method Uses just 2 leads of the 6 limb leads Look at Lead I & aVFPowerPoint Presentation:
1. Lead I & aVF divide thorax into quadrants, (Lt, N , Rt, No Man's) 2. If Lead I & aVF are both upright- Axis is normal. 3. If lead I is upright & lead aVF is downward - Axis is Left. AXISPowerPoint Presentation:
4. If lead aVF is upright & lead I is downward - Axis is Rt 5. If both leads are downward - Axis is extreme Right Shoulder & most often is Vent. Tachy AXISAxis Determination:
Axis Determination Quick Axis Determination Determine net deflection in Leads I & aVF (+ve / -ve ) Lead I aVF N axis LAD RAD ERADThe Quadrant Approach:
The Quadrant ApproachQuadrant Approach: Example 1:
Quadrant Approach: Example 1 /Quadrant Approach: Example 2:
Quadrant Approach: Example 2 /Basics of 12 Lead ECG Vector :
Basics of 12 Lead ECG Vector Method 2 : Three Lead technique This method uses – 3 limb leads I, II, III to determine axis of the QRS.PowerPoint Presentation:
Axis Lead I Lead II Lead III Normal Positive Positive Positive/Negative Right axis deviation Negative Positive Positive Left axis deviation Positive Negative NegativeBasics of 12 Lead ECG Vector :
Basics of 12 Lead ECG Vector Method # 3: Using Hexaxial Diagram to find degree of Axis Deviation This technique - most accurate( + or – 10 0 to 15 0 )The Equiphasic Approach:
The Equiphasic Approach See which lead contains - most equiphasic QRS. Net vector is perpendicular this lead. Examine QRS in whichever lead lies 90° away from this lead. If QRS in this 2 nd lead is predominantly +ve, then axis of this lead is approx same as net QRS axis. If QRS is predominantly –ve , than net QRS- axis lies 180° from axis of this lead.Basics of 12 Lead ECG Vector :
Basics of 12 Lead ECG Vector Axis scaleHexaxial Array for Axis Determination :
Determination of angle of HEART AXIS in frontal plain Hexaxial Array for Axis DeterminationExample 1 :
Example 1 Lead I Lead aVF Lead aVLPowerPoint Presentation:
Lead I If lead I is mostly + ve , the axis must lie in Rt ½ of coordinate systemPowerPoint Presentation:
If lead AVF is mostly + ve , the axis must lie in the bottom ½ of coordinate system Lead AVFPowerPoint Presentation:
I AVF Combining the 2 plots, we see that axis must lie in bottom right hand quadrantPowerPoint Presentation:
I AVF AVLExample 2:
Example 2 Lead I Lead aVF Lead IIPowerPoint Presentation:
Example 2 Lead I Lead I is mostly - ve , the axis must lie in the Lt ½ of the coordinate.PowerPoint Presentation:
Lead AVF Lead aVF is mostly + ve , the axis must lie in the bottom ½ of the coordinatePowerPoint Presentation:
I AVF Combining the two plots- axis must lie in bottom Lt hand quadrant (RAD)PowerPoint Presentation:
I AVF IIPowerPoint Presentation:
Since Lead III is the most equiphasic lead and it is slightly more positive than negative, this axis could be estimated at about 40 o . Precise calculation of the axis can be done using the coordinate system to plot net voltages of perpendicular leads, drawing a resultant rectangle, then connecting the origin of the coordinate system with the opposite corner of the rectangle. A protractor can then be used to measure the deflection from 0. Net voltage = 12 Net voltage = 7 Precise Axis CalculationPowerPoint Presentation:
CARDIAC AXISPowerPoint Presentation:
Positive Positive Positive N Axis CARDIAC AXISPowerPoint Presentation:
CARDIAC AXISPowerPoint Presentation:
Positive Negative Negative LAD CARDIAC AXISPowerPoint Presentation:
CARDIAC AXISPowerPoint Presentation:
Negative Positive Positive RAD CARDIAC AXISPowerPoint Presentation:
Cardiac Axis Causes LAD Preg , obesity; Ascites , abdo distention, tumour ; LAHB, LVH, IWMI RAD N finding in children & tall thin adults, COPD, LPHB, Anterolateral MI. North West E mphysema , Hyperkalaemia , L ead transposition, Artificial cardiac pacing, VT CARDIAC AXISReferences :
References The EKG made easy-John R. Hampton An Introduction to Electrocardiography – Leo Schamroth Marriot’s Practical Electrocardiography. www.ambulancetechnicianstudy.co.uk www.learntheheart.comPowerPoint Presentation:
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