Approaching the ECG: Read Right In A Minute

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Approaching the ECG: Read Right In A Minute. BGSMC Cardiology Study Group Nick Sparicino, DO Mohamad Lazkani, MD Tomas Rivera-Bonilla, MD. February 3, 2011. History of the ECG/EKG. - PowerPoint PPT Presentation


  • Approaching the ECG:Read Right In A MinuteBGSMC Cardiology Study GroupNick Sparicino, DOMohamad Lazkani, MDTomas Rivera-Bonilla, MDFebruary 3, 2011

  • History of the ECG/EKGDuring the late 1800s and early 1900s, Dutch physiologist Willem Einthoven developed the early electrocardiogram He won the Nobel prize.

    Hubert Mann first uses the electrocardiogram to describe electrographic changes associated with a heart attack in 1920

    Electrocardiograms must be viewed in the context of demographics, health history, and other clinical test correlates. They are especially useful when compared across time to see how electrical activity of the heart has changed (perhaps as the result of some pathology). Why PQRST and not ABCDE? The choice of P is a mathematical convention dating from Descartes by using letters from the second half of the alphabet. N has other meanings in mathematics and O is used for the origin of the Cartesian coordinates. P is simply the next letter. (For more on Descartes see Henson JR. Descartes and the ECG lettering series. J Hist Med Allied Sci. April 1971;181186)

  • Electrocardiography A recording of the electrical activity of the heart over time Gold standard for diagnosis of cardiac arrhythmiasHelps detect electrolyte disturbances (hyper- & hypokalemia), arrhythmias, myocardial ischemia and infarction, pericarditis, chamber hypertrophy, drug toxicity (i.e. digoxin and drugs which prolong the QT interval) Allows for detection of conduction abnormalities Screening tool for ischemic heart disease during stress tests Helpful with non-cardiac diseases (e.g. pulmonary embolism or hypothermia)

  • Electrocardiogram (ECG/EKG)Is a recording of electrical activity of heart conducted through ions in body to surface

  • ECG RulesWave of depolarization traveling towards a positive electrode causes an upward deflection on the ECG.

    Wave of depolarization traveling away from a positive electrode causes a downward deflection on the ECG.

  • Vectors: directions and amplitudeVector 1 depolarization of atrium(corresponds to P wave)

    Vector 2 Ventricular Septum (1st deflection of QRS)

    Vector 3 Bulk of ventricular muscle

    Vector 4 Repolarization of ventricular muscle

  • Approach to the ECGSystematic Approach rhythm, rate, intervals, axis, morphology RRIAM: Read Right In A Minute

  • RHYTHMLocate the P wave Establish the relationship between P waves and QRS complexIf no P wave analyze the QRS morphologySearch for other cluesInterpret the rhythm in the clinical setting

  • Determining rate:Regular rhythm:Big box: 300, 150, 100, 75, 60, 50Irregular rhythm:# cycles in a 6 second strip x10# cycles in a 12 second strip x5 remember to use halves if half a cycle is present in the strip

    RATE10mm = 1mV1mm = 0.1mV

  • SA node 60-100 BPMAtrial cells 55-60 BPMAV node 45-50 BPMHis bundle 40-45 BPMBundle branch 40-45 BPMPurjkinje cells 35-40 BPMMyocardial cells 30-35 BPMRATE: Intrinsic rates of pacing cells(transmits the impulses through the inter-atrial septum)

  • ATRIAL COMPONENTSP wave atrial depolarization Duration 0.08 to 0.12 sec

    PR interval - impulse initiation, atrial depol, atrial repol, AV/His/BB/Purkinje stimulation0.12 to 0.20 seconds (>0.20 seconds = PR prolongation; Heart Block discussed later)

  • VENTRICULAR COMPONENTSQRS complex - ventricular depolarization0.06 to 0.12 seconds

    Q wave Significancepathological/MI >0.03s or >1/3 height of R wave

  • QT Interval - all the events of ventricular systoleBeginning of QRS to end of T waveDuration varies with heart rate, age, sex but should be less than half the RR intervalCorrection formulas exist to balance HR, a major variable (as HR decreases, QT interval increases) Fridericia Correction (QTf):QTf = QT interval / cubed root of the RR interval (in sec)Bazetts formula (QTc):QTc = QT interval / square root of the RR interval (in sec) VENTRICULAR COMPONENTS

  • ST segment - electrically neutral period between ventricular depol and repol (time myocardium is maintaining contraction in order to push the blood out of the ventricles)

    T wave - ventricular repolarizationShould be asymmetrical with a slow upstroke and a fast downstroke


  • AXIS - Quadrant Graphing Method

    I (+) aVF (+)=normalI (+)aVF (-)=LADI (-)aVF (+)=RADI (-)aVF (-)=extreme LAD or RAD

  • AXIS - Isoelectric MethodFind isoelectric leadFind perpendicular leadIf QRS positive, vector towards lead, if negative, away12

  • MORPHOLOGYHypertrophy (atrial & ventricular)Bundle branch blocks and hemiblocksSegment depressions & elevationsPR segment, ST segmentU wavesT wave morphologiesDelta waveOsborne waveST T changes

  • Hypertrophy Criteria

    Left atrial enlargementTerminal negative P wave deflection in V1 > 0.04s and the amplitude of same P wave in V1 > 0.10mVP-mitrale in lead II (notched P wave) Duration b/w peaks of P wave notches >0.04sMax p wave duration >0.11sRatio of P wave duration to PR duration > 1:1.6

    Right atrial enlargementP wave amplitude >2.5 mm in II and/or >1.5 mm in V1 (these criteria are not very specific or sensitive) Better criteria can be derived from the QRS complex; these QRS changes are due to both the high incidence of RVH when RAE is present, and the RV displacement by an enlarged right atrium.QR, Qr, qR, or qRs morphology in lead V1 (in absence of coronary heart disease) QRS voltage in V1 is 6

    Biatrial enlargementFeatures of both RAE and LAE in same ECGP wave in lead II >2.5 mm tall and >0.12s in durationInitial positive component of P wave in V1 >1.5 mm tall and prominent P-terminal force

  • Hypertrophy Criteria

  • Hypertrophy CriteriaOther LVH Criteria

    Sokolow-Lyon CriteriaS wave in V1 + R in V5 or V6 >= 3.5mVOr R wave in V5 or V6 >2.60mV

    Cornell Voltage CriteriaFemale: R in aVL + S in V3 >2.0 mVMale: R in aVL + S in V3 > 2.8 mV

    Hypertrophic CardiomyopathyLVH (tall R in V2-V5)Deep narrow Q in aVL and V6LAE (increased negative terminal p wave in V1)

    Other Criteria (quick glance)I = R >14mmaVR = S >15 mmaVL = R > 12 mmaVF = R >21 mmV5 = R > 26 mmV6 = R >20 mm

  • Hypertrophy CriteriaRVH CriteriaRight ventricular hypertrophyAny one or more of the following (if QRS duration 90 degrees) in presence of disease capable of causing RVH R in aVR > 5 mm, or R in aVR > Q in aVRAny one of the following in lead V1:R/S ratio > 1 and negative T wave qR pattern R > 6 mm, or S < 2mm, or rSR' with R' >10 mmOther chest lead criteria:R in V1 + S in V5 (or V6) 10 mmR/S ratio in V5 or V6 < 1R in V5 or V6 < 5 mmS in V5 or V6 > 7 mmST segment depression and T wave inversion in right precordial leads is usually seen in severe RVH such as in pulmonary stenosis and pulmonary hypertension.

  • Hypertrophy CriteriaBiventricular Criteria1. High voltage, biphasic RS complex in midprecordial leads (also common in LV septal defect)2. LVH criteria in precordial leads with RAD in limb leads3. Low amplitude S in lead V1 combined with deep S wave in lead V24. LVH criteria in left precordial leads combined with prominent R waves in right precordial leads5. LAE as sole criteria for LVH combined with any criteria suggestive of RVH

    Left or right strain pattern CriteriaST-T wave changes associated with abnormal repolarisation secondary to increased ventricular tension have classically referred to as "strain" pattern.Left ventricular hypertrophy is often associated with ST depression and deep T wave inversion. These changes occur in the left precordial leads, V5 and V6. In the limb leads the ST-T changes occur opposite the main QRS forces. Therefore, if the axis is vertical, the ST-T changes are seen in II, III and aVF. If the axis is horizontal the ST-T changes are seen in I and aVL.Right ventricular hypertrophy can be associated with ST depression and T wave inversion in the right precordial leads, V1 - V3. Leads II, II and aVF may also show similar ST - T wave changes.

  • Put it all togetherTry to come up with a common theme to the differential diagnosis based on the list of abnormalities youve createdDo not overlook anythingPractice, Practice, Practice (look at many ECGs, especially normal ones in the beginning, developing good habits using RRIAM and calculate intervals committing normal values to memory)

    ** **Is a representation of the cardiac cycle and sections are electrical impulses/ represent three distinct waves*Rules of ECGWave of depolarization traveling towards a positive electrode causes an upward deflection on the ECGWvae of depolarization traveling away from a positive electrode causes a downward deflection on the ECG**Look at the ECG in a methodical fashion, starting with the rhythm strip at the bottom, keeping in mind that it correlates with the 3 second strips above it. Also note, in a normal EKG, the entire strip is 12 seconds (has 4 total, 3 second strips)

    RRIAM- Read right in a minute*P wave tells you if its sinus or not. Look at each lead as the p waves may not be obvious in some leads. Becareful as p waves may be burried in QRS complex as seen with junctional rhythm or AV nodal reentrant tachycardia. P waves can also be burried in the ST segment as seen with AV reentrant tachycardia or ventricular tachycardia.

    Are the p waves associated in a 1:1 fasion? If not, are there more or less p waves in QRS complexes, and what are the atrial/ventricular rates? More p waves than QRS then some form of AV block is present. Less p waves than QRS then the rhythm is an accelerated ventricular or junctional rhythm.