Basics of EKG.ppt

Basics of EKG The Normal Conduction System PROCESS SA Node - Heart pacemaker; located in the RA; initiates next step PROCESS P Wave - Atrial depolarization and contraction PROCESS AV Node - Slows the depolarization of the atria; connects atria and ventricles electrically PROCESS QRS co...

Basics of EKG The Normal Conduction System PROCESS SA Node - Heart pacemaker; located in the RA; initiates next step PROCESS P Wave - Atrial depolarization and contraction PROCESS AV Node - Slows the depolarization of the atria; connects atria and ventricles electrically PROCESS QRS complex - ventricular depolarization; begins in Bundle of His PROCESS VENTRICULAR DEPOLARIZATION His Bundle Left Bundle Branch & Right Bundle Branch Purkinje Fibers VENTRICULAR DEPOLARIZATION • Q Wave - 1st downward wave of the complex • R Wave - 1st upward wave of the complex • S Wave - downward wave preceded by an upward wave PROCESS ST Segment - Initial plateau phase of ventricular repolarization PROCESS T wave - Rapid phase of ventricular repolarization Waveforms and Intervals NORMAL ECG EKG Leads The standard EKG has 12 leads: 3 Standard Limb Leads 3 Augmented Limb Leads 6 Precordial Leads The axis of a particular lead represents the viewpoint from which it looks at the heart. Standard Limb Leads All Limb Leads Precordial Leads Adapted from: www.numed.co.uk/electrodepl.html Precordial Leads Anatomic Groups (Summary) Rate • Rule of 300 • 10 Second Rule Rule of 300 Take the number of “big boxes” between neighboring QRS complexes, and divide this into 300. The result will be approximately equal to the rate Although fast, this method only works for regular rhythms. What is the heart rate? www.uptodate.com (300 / 6) = 50 bpm What is the heart rate? www.uptodate.com (300 / ~ 4) = ~ 75 bpm What is the heart rate? (300 / 1.5) = 200 bpm The Rule of 300 It may be easiest to memorize the following table: # of big boxes 1 Rate 2 150 3 100 4 75 5 60 6 50 300 10 Second Rule As most EKGs record 10 seconds of rhythm per page, one can simply count the number of beats present on the EKG and multiply by 6 to get the number of beats per 60 seconds. This method works well for irregular rhythms. What is the heart rate? The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/ 33 x 6 = 198 bpm The QRS Axis By near-consensus, the normal QRS axis is defined as ranging from -30° to +90°. -30° to -90° is referred to as a left axis deviation (LAD) +90° to +180° is referred to as a right axis deviation (RAD) Determining the Axis • The Quadrant Approach • The Equiphasic Approach Determining the Axis Predominantly Positive Predominantly Negative Equiphasic The Quadrant Approach 1. Examine the QRS complex in leads I and aVF to determine if they are predominantly positive or predominantly negative. The combination should place the axis into one of the 4 quadrants below. The Quadrant Approach 2. In the event that LAD is present, examine lead II to determine if this deviation is pathologic. If the QRS in II is predominantly positive, the LAD is nonpathologic (in other words, the axis is normal). If it is predominantly negative, it is pathologic. Quadrant Approach: Example 1 The Alan E. Lindsay ECG Learning Center http://medstat.med.utah .edu/kw/ecg/ Negative in I, positive in aVF  RAD Quadrant Approach: Example 2 The Alan E. Lindsay ECG Learning Center http://medstat.med.utah .edu/kw/ecg/ Positive in I, negative in aVF  Predominantly positive in II Normal Axis (non-pathologic LAD)  The Equiphasic Approach 1. Determine which lead contains the most equiphasic QRS complex. The fact that the QRS complex in this lead is equally positive and negative indicates that the net electrical vector (i.e. overall QRS axis) is perpendicular to the axis of this particular lead. 2. Examine the QRS complex in whichever lead lies 90° away from the lead identified in step 1. If the QRS complex in this second lead is predominantly positive, than the axis of this lead is approximately the same as the net QRS axis. If the QRS complex is predominantly negative, than the net QRS axis lies 180° from the axis of this lead. Equiphasic Approach: Example 1 The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/ Equiphasic in aVF  Predominantly positive in I  QRS axis ≈ 0° Equiphasic Approach: Example 2 The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/ Equiphasic in II  Predominantly negative in aVL  QRS axis ≈ +150° Systematic Approach Rate Rhythm Axis Wave Morphology – P, T, and U waves and QRS complex • Intervals – PR, QRS, QT • ST Segment • • • • Rhythms/Arrhythmias • Sinus • Atrial • Junctional • Ventricular Sinus Rhythms: Criteria/Types • P waves upright in I, II, aVF • Constant P-P/R-R interval • Rate • Narrow QRS complex • P:QRS ratio 1:1 • P-R interval is normal and constant Sinus Arrhythmias: Criteria/Types • Normal Sinus Rhythm • Sinus Bradycardia • Sinus Tachycardia • Sinus Arrhythmia Normal Sinus Rhythm • Rate is 60 to 100 Sinus Bradycardia • Can be normal variant • Can result from medication • Look for underlying cause Sinus Tachycardia • May be caused by exercise, fever, hyperthyroidism • Look for underlying cause, slow the rate Sinus Arrhythmia • Seen in young patients • Secondary to breathing • Heart beats faster Atrial Arrhythmias: Criteria/Types • P waves inverted in I, II and aVF • Abnormal shape – Notched – Flattened – Diphasic • Narrow QRS complex Atrial Arrhythmias: Criteria/Types • Premature Atrial Contractions • Ectopic Atrial Rhythm • Wandering Atrial Pacemaker • Multifocal Atrial Tachycardia • Atrial Flutter • Atrial Fibrillation Premature Atrial Contraction • QRS complex narrow • RR interval shorter than sinus QRS complexes • P wave shows different morphology than sinus P wave Ectopic Atrial Rhythm • Narrow QRS complex • P wave inverted Wandering Atrial Pacemaker • 3 different P wave morphologies possible with ventricular rate < 100 bpm Multifocal Atrial Tachycardia • 3 different P wave morphologies with ventricular rate> 100 bpm Atrial Flutter • Regular ventricular rate 150 bpm • Varying ratios of F waves to QRS complexes, most common is 4:1 • Tracing shows 2:1 conduction Atrial Flutter • Tracing shows 6:1 conduction Atrial Fibrillation • Tracing shows irregularly irregular rhythm with no P waves • Ventricular rate usually > 100 bpm Atrial Fibrillation • Tracing shows irregularly irregular rhythm with no P waves • Ventricular rate is 40 Atrial Tachycardia • Tracing shows regular ventricular rate with P waves that are different from sinus P waves • Ventricular rate is usually 150 to 250 bpm AV Nodal Blocks • Delay conduction of impulses from sinus node • If AV node does not let impulse through, no QRS complex is seen • AV nodal block classes: 1st, 2nd, 3rd degree 1st Degree AV Block • PR interval constant • >.2 sec • All impulses conducted 2 nd Degree AV Block Type 1 • AV node conducted each impulse slower and finally no impulse is conducted • Longer PR interval, finally no QRS complex 2 nd Degree AV Block Type 2 • Constant PR interval • AV node intermittently conducts no impulse 3 Degree AV Block rd • AV node conducts no impulse • Atria and ventricles beat at intrinsic rate (80 and 40 respectively) • No association between P waves and QRS complexes Another Consideration: Wolfe-Parkinson-White (WPW) • Caused by bypass tract • AV node is bypassed, delay • EKG shows short PR interval <.11 sec • Upsloping to QRS complex (delta wave) WPW • Delta wave, short PR interval Ventricular Arrhythmias: Criteria/Types • Wide QRS complex • Premature Ventricular Contractions • Idioventricular Rhythm • Accelerated IVR • Rate : variable • Ventricular Tachycardia • Ventricular Fibrillation • No P waves Premature Ventricular Contraction • Occurs earlier than sinus beat • Wide, no P wave Idioventricular Rhythm • Escape rhythm • Rate is 20 to 40 bpm Accelerated Idioventricular Rhythm • Rate is 40 to 100 bpm Ventricular Tachycardia • Rate is > than 100 bpm Torsades de Pointes • Occurs secondary to prolonged QT interval Ventricular Tachycardia/Fibrillation • Unorganized activity of ventricle Ventricular Fibrillation