ECG Interpretation Chapter 22 ECG Interpretation 1 Rate

ECG Interpretation Chapter 22

ECG Interpretation 1. Rate 3. Axis a. Atrial rate: PP interval 4. Hypertrophy b. Ventricular rate: RR interval 5. Blocks 2. Rhythm a. P wave b. PR interval c. QRS i. voltage (height) ii. width 6. Infarct 7. Ischemia

Standardization mark 10 mm vertical deflection = 1 m. Volt

Rate Ventricular rate (heart rate) RR interval Atrial rate PP interval 3 rd degree AV block

Heart Rate Calculation 1500 divided by the number of small boxes between two R waves • most accurate • take time to calculate • only use with regular rhythms • quick 300 divided by the number • not too accurate of large boxes between • only use with regular two R waves rhythm 10 multiplied by the number of R waves in 6 seconds • less precise • use with irregular rhythms • very quick 1 lg sq = 300 bpm 2 lg sq = 150 bpm 3 lg sq = 100 bpm 4 lg sq = 75 bpm 5 lg sq = 60 bpm 6 lg sq = 50 bpm

Rhythm Sinus rhythm - consistent P waves Atrial rhythm - irregular P waves Junctional/Nodal rhythm - no P waves, late P waves, or inverted P waves Ventricular rhythm - no P waves, wide QRS

AV Junctional Rhythms Retrograde P waves immediately preceding the QRS complexes in a. VR and II. Retrograde P waves immediately following the QRS complexes Absent P waves

ECG Waves P wave atrial depolarization ≤ 2. 5 mm in amplitude < 0. 12 sec in width PR interval (0. 12 - 0. 20 sec. ) time of stimulus through atria and AV node prolonged interval = first-degree heart block

P wave Tall = RAE Wide = LAE

PR Interval Long PR interval = first degree AV block Short PR interval = WPW Short PR interval with inverted P waves = ectopic atrial or junctional pacemaker

Classification of AV Heart Blocks Degree Block Uniformly prolonged PR interval Degree, Mobitz Type I Progressive PR interval prolongation 1 St 2 nd AV Conduction Pattern 2 nd Degree, Mobitz Type II Sudden conduction failure 3 rd Degree Block No AV conduction

Wolff-White-Parkinson Wide QRS due to early depolarization not due to a delay in depolarization Shortened PR interval Upstroke QRS complex is slurred; delta wave

ECG Waves QRS width 0. 12 second or less

Normal QRS V 6? V 1? Fig. 4 -6 V 1? V 6?

Normal Q waves • Septal r wave • Septal q wave

Q Waves Abnormal if wider than 0. 04 sec Leads I, III, a. Vf or leads V 3 - V 6. Greater than 25% of the R wave Note: Not all Q waves are abnormal, Not all Q waves are the result of MI.

QRS Width Wide RBBB or LBBB Premature ventricular beats WPW

QRS Voltage RVH LVH

Mean QRS Axis

Axis Deviation LEAD a. VF LEAD I (or Lead II or III) Normal Positive LAD Positive Negative RAD Negative Positive Intermediate axis Negative LEAD a. VR Positive (or Negative)

R Wave Progression

Transmural MI Ischemia Tall T waves (and/or reciprocal T wave inversion) ST segment elevation. Injury T wave inversion of the previously tall T waves Pathalogical Q waves Infarct (at least one small box wide or 11/3 the entire QRS height)

Overview LEAD AREA OF THE HEART V 1 -V 2 Anterior/Septum V 3 -V 4 Anterior Wall V 5 -V 6 Anterior/Lateral II, III, a. VF Inferior I and a. VL Lateral V 1 -V 2 Posterior (reciprocal)

ST Segments J point: end of QRS wave beginning of ST segment beginning of ventricular repolarization normally isoelectric (flat) changes, elevation or depression, may indicate pathological condition

Subendocardial Ischemia ST segment depression criteria 1 mm or more horizontal or downward lasts 0. 08 seconds depression of only the J point with rapid upward sloping are considered normal.