ECG R EVIEW : T HE B ASICS Megan Chan, PGY-1 UHCMC antipsychotics-by-elysha-elson-pharm-d-mph/

T HE B ASICS

T HE ECG U NIT

T HE S YSTEMATIC P ROCESS Rate 300/(# large boxes between R—R interval) Rhythm Regular vs irregular Sinus rhythm? P before every QRS (easiest to see in leads II and V1) Positive p wave in I & II; negative p in aVR Axis Normal axis? Positive QRS sum in I and II (or aVF ) Left deviation? Up in I, down in II Right deviation? Down in I, up/down in II

T HE S YSTEMATIC P ROCESS C ONT. Intervals PR interval: normal ms (3-5 small boxes) Short PR interval = WPW Long PR interval = heart block QRS complex: normal <120ms (≤ 3 small boxes) Long QRS: conduction delays, hyperkalemia, ventricular rhythm QT interval: normal ≤ 430 in men, ≤ 450 in females (less than R—R/2) Long QT: MI, myocarditis, hypocalcemia, hypothyroidism, subarachnoid hemorrhage, drugs—sotolol, amiodarone, hereditary

T HE S YSTEMATIC P ROCESS C ONT. Conduction Abnormalities AV blocks RBBB LBBB IVCD (interventricular conduction delay) Left Anterior Fascicular Block Left Posterior Fascicular Block

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H EMI B LOCKS = L EFT F ASCICULAR B LOCKS

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T HE S YSTEMATIC P ROCESS C ONT. Chamber size RAELAERVHLVH Tall P > 2.5 mm in lead II Large diphasic P with large initial phase in V1 P> 120ms Diphasic p with downward terminal phase > 1mm wide and 1mm deep in V1 M-shaped P in I, II, or aVL R in aVR > 5mm (or R>Q) R in V1 > 7mm qR in V1 R in V1 + S in V5/V6 > 10mm Deep S in V5/V6 > 7mm R in aVL > 11mm R in V5/V6 + S in V1/V2 > 35mm R in I + S in III > 25 mm R in aVF > 20mm S in aVR > 14mm

T HE S YSTEMATIC P ROCESS C ONT. Ischemia What ECG changes do you expect to see? Hyperacute T waves  Inverted T waves  ST segment elevation  Q waves ST depressions = ??? Subendocardial ischemia ST elevations = ??? Transmural ischemia What are Pathologic Q waves? 1 small box wide and/or >5mm or 1/3 of R wave deep Other changes: Old septal infarct: No R waves in V1-V3 Old lateral infarct: No R wave progression in V4-V6 RV infarct: ST elevation in V4 & V5 with right sided EKG

T HE S YSTEMATIC P ROCESS C ONT. Everything Else Pericardial Effusion Low voltage (R waves < 5mm in limb leads, <10mm in precordial leads) Pericarditis Diffuse ST elevations and PR depressions Pulmonary Embolism “S1Q3T3”:S wave in I, Q wave in III, T wave inversion in III

LocationLeadsOccluded Vessel AnteriorV2-V4LAD AnteroseptalV1-V4LAD AnterolateralV1-V6, I, aVLLAD, diagonal LateralV5-V6, I, aVLCircumflex, diagonal InferiorII, III, aVFRCA, circumflex PosteriorTall R in V1-V3, ST depression in V1-V2 RCA /photos_245a975b-66ad-4f7e-86d8- 82d3ca7d0120.jpg

THE DR. ORTIZ METHOD 4 step method to interpreting 80% of ECGs in 1 minute What are the most important ECG leads? II — best axis, dx inferior wall MI, most studied V1 —best p wave, dx anterior wall MI & RBBB V5 —dx lateral wall MI, LBBB, & LVH What 2 leads are best for determining axis? I & II 100% sensitive & specific w/ zero false + Normal axis is -30 to 90 aVF was used > 100 years ago Special thanks to Dr. Jose Ortiz!

THE DR. ORTIZ METHOD Step 1: Demographics Verifying pt name and calibration of ECG Step 2: Two second look at lead II Regularity of the tracing. Any funny beats? P waves Upright  sinus “M” shape  LAE Mountain peaks  RAE Axis: QRS positive  50% chance of normal axis Intervals Normal QRS <3 boxes >3 boxes BBB Q waves –75% risk for inferior MI

THE DR. ORTIZ METHOD Step 3: Study three things about the QRS Axis : normal vs L deviation vs R deviation Confirm suspected axis by looking at lead I Width : normal vs RBBB vs LBBB > 3 boxes wide = abnormal Look at V1  If RSR’ then RBBB; If large S then LBBB. Height : normal vs low voltage vs LVH Remember “ ” for LVH Lead I: R > 14 Lead aVL: R > 12 S in V1 + R in V5/V6 > 35

THE DR. ORTIZ METHOD Step 4: Rate, ST segments, T waves, Infarcts Anterior/Septal infarct: V1-V4 Inferior infarct: II, III, aVF Lateral infarct: aVL, I, V5, V6

D RAW A N ORMAL ECG

I II III aVR V1 V4 aVL V2 V5 aVF V3V6 Same as II Inverted II Same as aVR but T & P waves can be + or – Biphasic QRS Similar to V3 but less QRS voltage Similar to V3 with larger S, smaller R H OW T O D RAW A N ORMAL ECG Similar to V3 with smaller S, taller R Similar to V4 with smaller S, taller R (R wave progression)

REFERNCES Agabegi SS, Agabegi ED. Step up to Medicine, 3 rd ed Lippincott Williams & Wilkins. Philadelphia, PA. Gomella LG, Haist SA. Basic EKG reading. In: Clinician’s Pocket Reference. McGraw-Hill; Accessed Nov 18, Longo DL, Fauci AS, Kasper DL, et al. Electrocardiography. In: Harrison’s Principles of Internal Medicine, 18 th ed McGraw Hill. New York, NY. University of Illinois at Chicago. Online ICU Guidebook ver_442934/Image/1.1/residentguides/final/icuguidebo ok.pdf. Accessed December 1, ver_442934/Image/1.1/residentguides/final/icuguidebo ok.pdf