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ECG Interpretation Interactive Case Studies Sagar Kalahasti, M.D., F.A.C.C. Staff Cardiologist, Heart and Vascular Institute Cleveland Clinic No relationships to disclose What Should I Expect on the Boards? • ECG tracings with one or two major findings • Clinical vignette with each tracing • Questions that are focused as much on the clinical scenario as the ECG itself • No trickery • No coding of all of the abnormalities on the ECG ECG Interpretation: A Case-Based Review ECG Fundamentals • • • • • Rate: Fast or slow? Rhythm: Sinus or not? Narrow complexes or wide? Intervals: PR and QT normal or prolonged? P wave: Normal sinus axis? Atrial enlargement? QRS: Axis shift? Q waves? Ventricular hypertrophy? Bundle branch block? • The ST segment: Elevation or depression? • The T wave: Upright or inverted? Best approach is to apply the same systematic approach to each ECG ECG Interpretation: A Case-Based Review Heart Rate and Timing One small box = 0.04 sec = 40 ms One large box = 0.2 sec = 200 ms Paper speed 1500 mm/min One beat per 0.2 sec = 300 bpm Heart Rate = 1500/RR (mm) OR 300/ # large boxes between two R waves 300 150 100 75 3 seconds between hash marks ECG Interpretation: A Case-Based Review ECG Complexes and Intervals P wave: atrial depolarization (right-left) QRS: ventricular depolarization (septum-LV-RV) T wave: ventricular repolarization PR interval: efficiency of atrial and AV nodal conduction ST segment: “quiet time” between ventricular depolarization and repolarization QT interval: efficiency of ventricular depolarization and repolarization ECG Interpretation: A Case-Based Review Case 1 A 70 year-old man with a history of hypertension and paroxysmal atrial fibrillation presents to the emergency department complaining of episodic dizziness and palpitations. His medication list includes “a heart pill and a water pill.” ECG Interpretation: A Case-Based Review ECG Interpretation: A Case-Based Review Case 1 All of the following may account for this man’s presentation except… A. Hypocalcemia B. Hypomagnesemia C. Hyperkalemia D. An inherited ion channel disorder E. An adverse drug interaction ECG Interpretation: A Case-Based Review The QT Interval • • Normal QT is 0.35 – 0.43 seconds QTc = QT/√RR in seconds • Prolonged QTc if ≥ 0.44 sec • Entire T wave should fall in first half of the RR interval Normal QT Prolonged QT ECG Interpretation: A Case-Based Review Causes of QT Interval Prolongation • Medications – – – – Class Ia (quinidine, procainamide) and III (sotalol, amiodarone) antiarrhythmics Tricyclic antidepressants Non-sedating antihistamines Ranolazine • Electrolyte Deficiencies – Hypomagnesemia – Hypocalcemia – Hypokalemia • • • • Liquid Protein Diets Intracranial hemorrhage Inherited long QT syndromes Metabolic Derangement – Myxedema – Hypothermia (look for shivering artifact) ECG Interpretation: A Case-Based Review Case 2 A 44 year-old woman with a murmur since childhood presents with several months of progressive exertional dyspnea. Her physical examination is remarkable for a systolic ejection murmur along the left sternal border, a split S2 that does not change with respiration and pitting lower extremity edema. ECG Interpretation: A Case-Based Review ECG Interpretation: A Case-Based Review Case 2 Her subsequent echocardiogram is most likely to demonstrate which of the following? A. Flow across the interatrial septum detected by color Doppler B. A calcified aortic valve with a high transvalvular pressure gradient C. A large pericardial effusion D. Severe left ventricular hypertrophy with outflow tract obstruction in mid systole E. Normal left and right ventricular size and function ECG Interpretation: A Case-Based Review Right Axis Deviation • QRS axis between 100° and 270° • May be a normal variant in children and young adults • Causes – Pulmonary embolism – Obstructive pulmonary disease – Right ventricular hypertrophy left posterior fascicular block – Lateral wall myocardial infarction – Ostium secundum ASD ECG Interpretation: A Case-Based Review QRS Axis Determination QRS (+) in I and aVF? QRS (+) in I and (-) in AVF? RExtreme Axis Extreme Axis Look at II… xxiiss A A t LLeefft L If (+) in II + If (-) in II QRS (-) in I and (+) in aVF? QRS (-) in I and (-) in aVF? Lead I (0°) Normal Normal Axis Axis Right Right Axis Axis Normal Normal Axis Axis III + + Lead II (60°) Lead aVF (90°) ECG Interpretation: A Case-Based Review Right Atrial Enlargement • Causes of Right Atrial Enlargement – COPD – Pulmonary Hypertension – Congenital Heart Disease – ASD – Pulmonic stenosis – Eisenmenger’s – Normal variant in thin patients ECG Interpretation: A Case-Based Review P Wave Morphology Left Atrial Enlargement P wave duration > 0.12 sec in II, III, aVF P wave notched in II, III, aVF V1 terminal P deflection > 1mm V1 terminal P deflection > 0.04 sec Right Atrial Enlargement P wave amplitude > 2.5 mm in II, III, aVF P wave peaked in II, III, aVF P wave axis ≥ 70° V1 initial P deflection > 1.5 mm ECG Interpretation: A Case-Based Review Right Ventricular Hypertrophy • Diagnostic Criteria – Right axis deviation – R/S ratio in V1 > 1 or R/S ratio in V5 or V6 ≤ 1 – R wave in V 1 ≥ 7 mm – R wave in V1 + S wave in V5 or V6 ≥ 10.5 mm – qR complex in V1 – ST depression or T wave inversion in right precordial leads – Onset of intrinsicoid deflection in V1 < 0.05 sec • Common Causes – Pulmonary Hypertension – Pulmonic Stenosis – COPD ECG Interpretation: A Case-Based Review Case 3 An 83 year-old man with paroxysmal atrial fibrillation, diabetes and stage II chronic kidney disease presents to your office complaining of lethargy for one week. Two weeks ago he twisted his left ankle while walking his dog. He developed subsequent left ankle pain and swelling that improved with an over-the counter oral analgesic. Examination reveals a well appearing man in no distress. Blood pressure is 110/65 mmHg. His cardiovascular exam is remarkable for a regular bradycardia and occasional prominent jugular venous a waves. ECG Interpretation: A Case-Based Review ECG Interpretation: A Case-Based Review Case 3 The most likely culprit for this man’s presentation is which of the following? A. B. C. D. E. Advanced age. Coronary artery disease. Digoxin. A tick bite. Dental therapy without amoxicillin prophylaxis. ECG Interpretation: A Case-Based Review Complete (3rd degree) AV Block • Criteria – Atrial and ventricular impulses occur independent of each other – Atrial rate is usually faster than ventricular rate – PR interval varies – PP and RR interval are constant • Causes – Digitalis toxicity – Myocardial infarction – Inferior – better prognosis – Anterior – usually requires permanent pacing – Degeneration of the conduction system – Endocarditis – Lyme Disease ECG Interpretation: A Case-Based Review AV Conduction Delays • Second Degree AV Block – Mobitz Type 1 – Progressive PR prolongation until P does not conduct – RR containing the dropped P is < 2 x PP interval – Normal QRS duration (usually) – Consider myocardial infarction (inferior in particular) – Mobitz Type 2 – Intermittent non-conduction of P wave – PR interval constant – RR containing the dropped P is = 2 x PP interval – Widened QRS ECG Interpretation: A Case-Based Review 2:1 AV Block * Regular atrial rhythm with two P waves for each QRS * Can be Mobitz I or Mobitz II • Favors Mobitz I • Narrow QRS • Block improves with atropine • Block worsens with vagal maneuvers • Inferior MI setting • Favors Mobitz 2 • Widened QRS • Block worsens with atropine • Block improves with vagal maneuvers • Anterior MI setting ECG Interpretation: A Case-Based Review Digitalis and the ECG • Digitalis can cause practically any ECG abnormality • Digitalis Effect – PR prolongation and QT shortening – Sagging “hockey stick” ST segments – Flat, biphasic or inverted T waves • Digitalis Toxicity – Second or third degree AV block – Atrial fibrillation or atrial tachycardia with third degree AV block – Bidirectional ventricular tachycardia ECG Interpretation: A Case-Based Review Case 4 A 64 year-old woman presents to an urgent care center complaining of nausea, vomiting and diaphoresis that began two hours ago. She was previously well and does not see a doctor on a regular basis. Her vital signs include a blood pressure of 110/70 mmHg and heart rate of 75 bpm. Examination reveals a pale, diaphoretic woman who looks uncomfortable and in mild respiratory distress. Cardiopulmonary auscultation is unremarkable. ECG Interpretation: A Case-Based Review ECG Interpretation: A Case-Based Review Case 4 Which of the following will not provide a long term survival benefit for this patient? A. Aspirin B. Atorvastatin C. Isosorbide Dinitrate D. Ramipril E. Metoprolol ECG Interpretation: A Case-Based Review Coronary Disease and the ECG • Myocardial Ischemia – Horizontal or downsloping ST segment depression – Symmetric T wave inversion • Myocardial Infarction – ST elevation often preceded by increased T wave amplitude – Horizontal or upwardly convex ST segment elevation of ≥ 1 mm in two contiguous limb leads – Horizontal or upwardly convex ST segment elevation of ≥ 2 mm in two contiguous precordial leads – Associated ST depression in non-infarct leads – Q waves, indicative of completed infarction – Q ≥ 0.03 sec and > 1 mm deep in I, II, avL, aVF, V4-6 – Q of any size in V1-3 ECG Interpretation: A Case-Based Review Infarct Localization • Left Anterior Descending (LAD) – Septum: V1 and V2 – Anterior: V3 and V4 – Anterolateral (diagonal branches): 1, aVL, V3-6 – Apical: V1-4 and II, III, aVL • Circumflex – High Lateral: I, aVL – Lateral: V4-6 – Anterolateral: I, aVL, V3-6 • Right Coronary Artery (RCA) – Inferior: II, III, aVF – Posterior: tall R or ST depression in V1 and V2 – RV: V4R – V6R ECG Interpretation: A Case-Based Review Case 5 A 53 year-old man with a history of hypertension, COPD and remote myocardial infarction presents to the emergency department complaining of intermittent palpitations for the past few days. He denies any recent chest pain, dizziness or syncope. He appears well and is in no obvious distress. The intake nurse measures his blood pressure with an automated cuff and gets a reading of 116/65 mmHg but states that the pulse reading “can’t be right”. You come over to investigate and perform an ECG. ECG Interpretation: A Case-Based Review ECG Interpretation: A Case-Based Review Case 5 The most appropriate next step would be to… A. Give adenosine 6 mg IV push. B. Give diltiazem 20 mg IV bolus followed by a drip at 5 mg/hour. C. Give digoxin 0.5 mg IV push. D. Deliver a 360 Joule unsynchronized shock immediately. E. Give amiodarone 150 mg IV bolus followed by a drip at 1.0 mg/min. ECG Interpretation: A Case-Based Review Wide Complex Tachycardia • Favors VT • • • • • • AV dissociation Fusion beats Very wide QRS (>0.14 s) Precordial concordance Extreme or left axis Absence of RS complex in all precordial leads • Any precordial RS interval > 0.1 sec • Favors Aberrant SVT • • • • • • • No AV dissociation No fusion beats QRS < 0.14 s Precordial discordance Relatively normal axis Any precordial RS complex All precordial RS intervals < 0.1 sec ECG Interpretation: A Case-Based Review Case 6 A 23 year-old woman with no significant medical history presents to your office complaining of chest pain for the past three days preceded by malaise and a cough productive of yellow sputum. The chest pain has been constant since onset but waxes and wanes in intensity. She denies any dyspnea, palpitations or syncope. Vital signs include a pulse of 100 bpm, BP 138/80 mmHg and a temperature of 38.1° C. Exam reveals an uncomfortable young woman in no distress. Conjunctival injection is present but her cardiovascular exam is unremarkable except for regular tachycardia. Her lungs are clear. ECG Interpretation: A Case-Based Review ECG Interpretation: A Case-Based Review Case 6 All of the following are appropriate therapeutic agents for this patient except… A. Indomethacin B. Colchicine C. Aspirin D. Clopidogrel E. Ibuprofen ECG Interpretation: A Case-Based Review Acute Pericarditis • Stages – 1: concave up ST elevation in all leads (except aVR) – 2: ST point normalizes, T wave amplitude increases – 3: T wave inversion – 4: Normalization • Other Clues – Sinus tachycardia – PR depression – Low voltage or electrical alternans (if effusion) – Symptoms are important • Differential diagnosis – Myocardial Infarction – usually focal, look for reciprocal changes – Early repolarization – normal variant, young, asymptomatic patients ECG Interpretation: A Case-Based Review Case 7 A 58 year-old woman comes to you for preoperative risk assessment prior to an elective abdominal hysterectomy. Her medical history is significant only for bleeding uterine fibroids. She denies any concerning symptoms and exercises regularly without limitations or symptoms. Her physical examination is completely within normal limits and her ECG is shown. ECG Interpretation: A Case-Based Review ECG Interpretation: A Case-Based Review Case 7 Which of the following statements regarding this patient is false? A. She will likely remain asymptomatic. B. Radiofrequency ablation is appropriate therapy if she develops palpitations. C. Procainamide is appropriate therapy if she develops rapid atrial fibrillation. D. Verapamil is appropriate therapy if she develops rapid atrial fibrillation. E. Cardioversion is appropriate therapy if she develops rapid atrial fibrillation ECG Interpretation: A Case-Based Review Wolff-Parkinson White (WPW) • Criteria – PR interval < 0.12 seconds – QRS widening with ventricular pre-excitation “delta” wave • Presentation – Narrow complex tachycardia – Wide complex tachycardia – Atrial fibrillation – AVOID AV nodal blocking drugs • Management – Antiarrhythmic therapy – Cardioversion – Radiofrequency Ablation ECG Interpretation: A Case-Based Review Case 8 A 62 year-old man with a history of diabetes and hypertension presents to the emergency department with two days of lethargy and malaise. He was seen in the emergency department four days ago for left flank pain and hematuria. A contrast enhanced CT scan was negative for kidney stones or other abdominal or pelvic pathology. His pain resolved with IV morphine and toradol and he was sent home with oral percocet and instructions to strain his urine. His flank pain and hematuria have since resolved. His physical examination is unremarkable. ECG Interpretation: A Case-Based Review ECG Interpretation: A Case-Based Review Case 8 All of the following interventions are appropriate at this time except… A. intravenous calcium chloride B. intravenous glucose and regular insulin C. nebulized albuterol D. oral polystyrene sulfonate E. intravenous magnesium sulfate ECG Interpretation: A Case-Based Review Potassium and the ECG • Hyperkalemia • Mild (K 5.5-6.5 mEq/L) – Peaked T waves – > 10 mm in precordial leads – > 6 mm in limb leads – Shortened QT • Moderate (K 6.6-7.5 mEq/L) – – – First degree AV block Wide P with low amplitude QRS prolongation • Severe (K > 7.5 mEq/L) – – – – – • Hypokalemia • Prominent U waves • ST depression, flattened T waves (K usually < 2.5 mEq/L) • • • • Increased P amplitude Prolonged QT All degrees of AVB Ventricular arrhythmias Sinus arrest Left or right bundle branch pattern Marked QRS widening (sine wave) ST elevation Ventricular arrhythmia and asystole ECG Interpretation: A Case-Based Review Case 9 A 19 year-old male college student with no known medical history presents to the university student health clinic complaining of episodic dizzy spells for the past two weeks. He describes episodes of lightheadedness and palpitations that occur for a few minutes and then spontaneously resolve. He attributed these to “finals week jitters” but he is now on summer break and the symptoms have continued. He tells you “I’m feeling dizzy right now”. Case 9 All of the following statements regarding this patient are true except … A. Carotid sinus massage may terminate this rhythm B. Intravenous adenosine may terminate this rhythm C. This rhythm may be amenable to cure with radiofrequency ablation D. This rhythm may not be amenable to cure with radiofrequency ablation E. This patient will require anticoagulation to prevent stroke. Supraventricular Tachycardias • Criteria – Regular rhythm – Narrow QRS complexes (unless pre-existing bundle branch block or aberrancy is present) – Rate > 100 bpm – Atrial waveform absent or appears retrograde • Differential Diagnosis – AV nodal reentry (most common by far) – Atypical AV nodal reentry – AV reentry A-V Reentry Case 10 A 42 year-old man with no medical history presents to an urgent care center with several hours of palpitations and a “rapid heart rate”. He tells you that he’s experienced two similar episodes over the past year but “they always went away before I could get to a doctor”. He denies any other symptoms and his current vital signs are BP 120/80 mmHg, HR 150 bpm, RR 14. He looks well and his exam is remarkable only for tachycardia. Last month the patient established care with a new primary care physician who, in view of his history of palpitations, arranged for a 48 hour Holter monitor and a surface echocardiogram. Both were completely normal. ECG Interpretation: A Case-Based Review Case 10 Which of the following statements regarding this patient is true? A. He requires long-term coumadin therapy to prevent stroke. B. He requires hospitalization for intravenous heparin and TEE-guided cardioversion. C. Catheter-based treatment of his arrhythmia has a high success rate. D. The antiarrhythmic drug of choice for this patient is amiodarone. E. His arrhythmia is not likely to reoccur following cardioversion. Atrial Tachyarrhythmias • Atrial Flutter – Sawtooth “F waves”, typically at 240-340 bpm – Typical flutter has negative F waves in inferior leads – F waves lack an isoelectric baseline • Atrial Fibrillation – Absent P waves or coarse, variable atrial “wavelets” – Irregularly irregular QRS pattern • Multifocal Atrial Tachycardia – Atrial rate > 100 bpm – Atrial waveforms with ≥ 3 morphologies – Variable PP and PR intervals – Seen often in patients with pulmonary disease ECG Interpretation: A Case-Based Review Case 11 A 65 year-old woman with type 2 diabetes, hypertension and hypothyroidism recently moved to your town and is seeing you today to establish care with a new internist. She presently voices no complaints and states that her blood pressures and blood sugars have been well controlled with HCTZ, lisinopril and metformin. She maintains an active lifestyle that includes walking, biking and swimming almost daily. Her ECG is shown. ECG Interpretation: A Case-Based Review ECG Interpretation: A Case-Based Review Case 11 All of the following are true about this patient except… A. Her ECG may represent a variant of normal. B. Her ECG may represent a prior myocardial infarction. C. Her ECG may represent age-related degeneration of the conduction system. D. Her ECG may represent structural heart disease. E. Her ECG may make the future diagnosis of myocardial infarction difficult. ECG Interpretation: A Case-Based Review Left Bundle Branch Block • Criteria – QRS duration ≥ 0.12 seconds – Broad, monophasic R waves in I, V5 and V6 – rS or QS in V1 – QRS-peak R wave duration >0.05 seconds • Seen in… – LVH – Myocardial infarction – Structural heart disease – Conduction system degeneration – Congenital heart disease – Almost never occurs in normals ECG Interpretation: A Case-Based Review Right Bundle Branch Block Criteria - QRS ≥ 0.12 seconds - rsR’ or rSR’ in V1 and/or V2 - QRS-peak R duration > 0.05 seconds in V1 and V2 - Wide, slurred S waves in I, V5 and V6 Seen in normals, hypertension, rheumatic heart disease, cor pulmonale, degenerative conduction disease, Ebstein’s anomaly. ECG Interpretation: A Case-Based Review What Should I Focus On? • ECG manifestations of systemic and non-cardiac illnesses – Thyroid disease – Pulmonary Disease • ECG manifestations of electrolyte disturbances – Potassium – Calcium • Relationship between the surface ECG and coronary artery distribution • ECG manifestations of structural heart diseases and their corresponding physical exam findings – Secundum ASD – Mitral Stenosis ECG Interpretation: A Case-Based Review Good Luck! Acknowledgement Dr. Michael Faulx, MD,FACC