chapter Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Electrolyte, Drug, and Other ECG Changes 13 Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ

Chapter 13 Objectives List the causes and clinical implications of various electrolyte abnormalities Describe ECG changes in potassium and calcium Explain how and why to measure QT interval Describe the ECG criteria for digitalis effect Describe ECG evidence of pericarditis and early repolarization 135

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Effects of Electrolytes Potassium (K+) Prevents shortened action potential Allows for organized fast heart rates Protects from excitability Slows heart in vagal responses 136

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Hypokalemia Serum level below 3.5–5.0 mEq/L Caused by vomiting, diarrhea, diuretics, gastric suctioning Hypomagnesemia Muscle weakness, polyuria Digitalis can take advantage and cause Torsades de pointes

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Hypokalemia ECG Changes ST segment depression T waves flatten or join U waves U waves get larger than Ts QT interval appears to lengthen PR interval increases

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Hypokalemia Potassium normal U waves overtake T 137

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Hyperkalemia Serum levels above normal range Most common cause is renal failure Sinus node can quit at 7.5 mEq/L VF or asystole at 10–12 mEq/L

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Hyperkalemia – ECG Tall T waves with a narrow base QRS widens Broad S waves in V leads Left axis deviation

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Hyperkalemia – ECG ST segment disappears “T wave grows, P wave goes” Sine waves in severe cases 138

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Calcium Hypercalcemia: Short QT interval Hypocalcemia: Prolonged QT interval

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ The QT Interval Measured from the start of the QRS complex to the end of the T wave Measures the total ventricular activity: “refractory time” QTc is corrected for rate

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ The QT/QTc Table 139

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ QT/QTc Table Quick reference Your measurement or the machine 460 ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ The Digitalis Effect 60% of those on “Dig” have it ST segment depression Scooped out appearance Best seen in inferior/lateral leads 140

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ 140 Pericarditis Inflammation of the pericardium Occurs in younger patients without history of CAD

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Pericarditis Signs and Symptoms Chest pain, dyspnea, tachycardia, fever, weakness, chills Chest pain sharp, radiating to back, neck, jaw Made worse by lying flat, twisting Made better by leaning forward

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Pericarditis Often pleuritic pain, worse on inhalation Pain can last for hours or days Pericardial friction rub Heard over left lower sternal border

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Pericarditis ECG Criteria ST segment elevation Concave in all leads T wave elevation PR depression

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Pericarditis

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Pericarditis: Diagnosis Physical Criteria (CP, relieving criteria, pleuritic) No response to NTG Pericardial rub ECG changes that do not localize 141

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Early Repolarization Occurs in young, healthy people African American males Notched J point Concave elevation Leads II, III, F, V4– V6 Lateral leads

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ Acute Pulmonary Embolism A diagnosis of exception History of recent surgery Anticoagulant use in A-fib ECG changes generally only show in a large embolism

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ ECG Criteria: APE Sinus tach (most common) Right atrial enlargement Right axis deviation Right bundle branch (possible) With so many rights, how could it be so wrong?

Page, 12-Lead ECG for Acute and Critical Care Providers © 2006 by Pearson Education, Inc. Upper Saddle River, NJ ECG Criteria: APE Deep S in Lead I Abnormal Q in Lead III Inverted T in Lead III