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Electrocardiogram Interpretation Andrew P. Wilper, MD Disclosures Disclaimer • Brief review presented here today, not comprehensive Thanks • C. Scott Smith, MD • William Weppner, MD, MPH • Blaze Sekovski, MD A bit of history Nobel Prize • Willem Einthoven awarded Nobel prize in 1924 for his development of the ECG Definition • Electrocardiogram-recording electrical activity of the heart via electrodes placed on patient body. Detect heart muscle depolarizations during each cardiac cycle. Lead Placement Leads • Each lead detects different portions of the heart anatomy ECG • Immeasurably useful for detecting primary diseases of the heart or cardiac manifestations of systemic disease Structure • Basics of ECG review • Cases A Primer • • • • • • • Have an approach to ECG interpretation! Rate Rhythm Axis Intervals Chambers Ischemia Rate • The rate can be estimated by counting the number of big boxes between QRS complexes • Rate = 300 / number of large boxes • You can remember 300…150…100…75…60…50… • Bradycardia is defined as a HR < 60 • Tachycardia is defined as a HR >100 What is the rate? What is the rate? What is the rate? Number of big boxes=4 300/4=75 What is the rate? What is the rate? What is the rate? 300/~8 Rate=37 A Primer • • • • • • • Have an approach to ECG interpretation! Rate Rhythm Axis Intervals Chambers Ischemia Rhythm • Look for p waves before each QRS complex • Sinus rhythm has a P wave before every QRS, and a QRS after every P wave • Are QRS complexes regular or irregular? What is the rhythm? What is the rhythm? What is the rhythm? What is the rhythm? What is the rhythm? What is the rhythm? Extra Credit A Primer • • • • • • • Have an approach to ECG interpretation! Rate Rhythm Axis Intervals Chambers Ischemia Axis • The axis refers to the direction of depolarization that spreads throughout the heart • It can be determined by summating the vectors in the frontal plane •A normal axis is between 0 and +90 degrees. Left Axis= zero to -90 degrees Right Axis= +90 to +150 degrees Normal Axis= zero to +90 degrees Axis • A quick and easy way to determine axis is to look at leads I and aVF: • • • • • I + + - aVF + + - Axis Normal Left axis deviation Right axis deviation Extreme Right axis deviation What is the axis? What is the axis? Up in I and aVF Normal Axis What is the axis? What is the axis? Up in I and down in aVF Left Axis What is the axis? Down in I and up in aVF Right axis deviation Left Axis Deviation • Left ventricular hypertrophy • Left bundle branch block • Left anterior fascicular block Right Axis Deviation • Spurious (arm electrode reversal) • Dextrocardia • Right ventricular overload – Acute-PE, severe asthma attack – Chronic-COPD, pulmonic stenosis, pulmonary htn • Lateral wall AMI • Left posterior fascicular block • RBBB A Primer • • • • • • • Have an approach to ECG interpretation! Rate Rhythm Axis Intervals Chambers Ischemia Intervals • The Atria – P wave: Represents the contracting atria – PR interval: Beginning of the P wave to the beginning of the QRS complex – Normal duration .12-.20 seconds or 3-5 small boxes – Prolonged PR interval: Heart block – Shortened PR: Accessory pathways Intervals • The Ventricle • QRS complex: Represents the contracting ventricle • QRS duration: Is measured from start of QRS to end of QRS • Normal is <.12 seconds or 3 small boxes • Prolonged QRS seen in ventricular conduction abnormalities such as LBBB or RBBB Intervals • T wave represents repolarization of the ventricle • QT interval: Measured from the beginning of the QRS complex to the end of the T wave • The QT interval is inversely proportional to the heart rate • A rule of thumb the QT interval should be ½ the RR interval for HR’s from 60-80. A Primer • • • • • • • Have an approach to ECG interpretation! Rate Rhythm Axis Intervals Chambers Ischemia RIGHT VENTRICULAR HYPERTROPHY (RVH) • Right axis deviation without other cause (RBBB, ALMI) • R wave in V1 > 7mm • S waves in V5 and V6 RIGHT ATRIAL ENLARGEMENT (RAE)-Tall narrow P waves • P wave > 2.5 small boxes high best seen in inferior leads RVH ECG R wave in v1 >7mm Down in I and up in aVF-Right axis S waves in V5 and V6 RAE ECG P wave > 2.5 small boxes high LEFT ATRIAL ENLARGEMENT (LAE) • P wave > 2.5 small wide (especially in inferior leads) • Notched P wave in II • Negative terminal deflection in P wave in lead V1 LAE ECG Sinusoidal p wave in V1 Broad P wave in inferior leads LEFT VENTRICULAR HYPERTROPHY (LVH) The Cornell criteria for LVH S in V3 + R in aVL > 28 mm (men) S in V3 + R in aVL > 20 mm (women) Most accurate Sensitivity ~ 50% Specificity ~ 95-100% Inspiration Normal Paradoxical Expiration LVH ECG Measure S in V3 and R in aVL A Primer • • • • • • • Have an approach to ECG interpretation! Rate Rhythm Axis Intervals Chambers Ischemia Infarction • Q wave: represents infarction if >1 box by 1 box and in contiguous leads • ST segment: Elevation during infarction with typical convex pattern • Depressed with ischemia • T wave: May become inverted during ischemia and/or infarction ISCHEMIA • ST elevation (transmural ischemia) In setting of MI, data suggests that an invasive approach has better outcomes (may have Printzmetal’s) Beware of pericarditis, early repolarization, LVH • ST depression (subendocardial ischemia) In the setting of MI, this can be treated with anticoagulants unless hypotensive or not resolving with treatment Beware hyperventilation, digoxin, CNS disease • T wave inversion Beware BBB, LVH w/strain, digoxin, CNS (NL in aVR) • Q wave Old transmural scar OR beware accessory pathway What is the abnormality? Q waves in antero-lateral leads suggesting prior transmural infarction You are seeing a 61-year-old man in urgent care. He complains of vague chest pain and dyspnea. Both are worse when lying. He had a flu like illness earlier in the week. Pericarditis – Don’t cath ACUTE PERICARDITIS History: Pain is better sitting forward Physical exam: Friction rub, CO, pulses paradoxus Findings: Diffuse ST elevation and PR depression (except aVR and V1) Elevated ESR, CRP Causes: Infection (viral, bacterial, TB) Inflammatory (SLE, other) Traumatic Treatment: NSAID’s, colchicine. Avoid steroids in recurrent pericarditis You are seeing a 61-year-old man in urgent care. He complains of vague chest pain and dyspnea. EMS says he resisted leaving his house and he feels he might die. Panic attack with RBBB – Don’t cath You are seeing a 61-year-old man in urgent care. He complains of vague chest pain and dyspnea. The pain is squeezing and radiates into his jaw and L shoulder. Anterior STEMI complicated by RBBB and LAFB – CATH! You are seeing a 61-year-old man in urgent care. He complains of vague chest pain and dyspnea. The pain is squeezing and radiates into his jaw and L shoulder. Inferior-lateral NSTEMI – Cath optional Break