Sunday, September 18, 2011

LOCATION OF MI BY ECG LEADS

 LOCATION OF MI by ECG LEADS


Lead I      : Lateral          aVR :    ___                 VI : Septal                     V4 : Anterior
Lead II     :Inferior          aVL : Lateral                V2: Septal                     V5 : Lateral
Lead III   : Inferior          aVF:  Inferior               V3: Anterior                  V6 : Lateral


Lead aVR is a nondiagnostic lead and does not show any change in an MI.
An MI may not be limited to just one region of the heart . For example,if there are changes
in leads V3 and V4 (anterior ) and in leads I ,aVL,V5,and V6 (Lateral ),the MI so called an
anterolateral infarction.


Progression of an Acute Myocardial Infarction

An acute MI is a continuum that axtends from the normal state to full infarction.
   *Ischemia   = Lack of oxygen to the cardiac tissue,represented by ST segment
                        depression,T Wave inversion,or both.
   *Injury       = An arterial occlusion with ischemia,represented by ST segment elevation.
  
   *Infarction = Death of tissue,represented by a pathological Q Wave.




Clinical Tip ; Once the acute MI has ended,the  ST segment returns to baseline and the T Wave
becomes upright,but the Q Wave remain abnormal because of scar formation.


                                                       Anterior Myocardial Infarction

                                                    
   Clinical Tip :Anterior Myocardial Infarction frequently involve a large area of the
    Myocardium and can present with Cardiogenic shock,second degree AV Block type II,
    or third degree AV Block.

                                                  Inferior Myocardial Infarction

  Clinical Tip :Be alert for symtomatic sinus bradycardia,AV Block,hypotension,
   and hypoperfusion.

                                                   Posterior Myocardial Infarction





Clinical Tip: Diagnosis may require a 15 lead ECG because a standard 12 lead
does not look directly at the posterior wall.
                                  Left Bundle Branch Block

ClinicalTip :Patients may have underlying heart disease including coronary artery disease,hypertension,
cardiomyopathy and ischemia.
                                     
                                                   Right Bundle Branch Block

  Clinical Tip : Patients may have underlying right ventricular hypertroph,pulmonary
  edema,cardiomyopathy,congenital heart disease or rheumatic heart disease.                                           


 ST Segment Elevation and Depression

                               
Primary cause of  ST Segment Elevation
*Early repolarization ( normal in young adults )
*Pericarditis
*Ventricular aneurysm
*Pulmonary embolism
*Intracranial hemorrhage

Primary cause of ST Segment Depression
*Myocardial ischemia
*Left Ventricular hypertrophy
*Intraventricular conduction defects
*Medications (e.g digitalis)


Saturday, September 17, 2011

12 Leads ECG and Interpretation

                                               THE 12 LEADS ECG

       The most commonly used clinical ECG system is the 12-leads ECG.It consist of the following leads:
I  ,  II  ,  III ,aVR , aVL ,aVF ,V 1, V 2, V 3 , V4 , V5 , V6...Both limb and chest electrodes are used
to record 12-lead ECGs.

                                    Standart Limb Lead Electrode Placement

 Lead                         Positive Electrode                 Negative Electrode                     View of the Heart

   I                                    LA                                       RA                                       Lateral
  II                                    LL                                       RA                                       Inferior
  III                                   LL                                       LA                                       Inferior
  aVR                               RA                                      -                                            None
  aVL                               LA                                      -                                            Lateral
  aVF                               LL                                       -                                           Inferior

  V1 =               Right sternal border-4th ICS              -                                              Septum                                
  V2 =               Left sternal border  -4th ICS              -                                             Septum
                       
  V3 =               Midway between  V2 and V4            -                                             Anterior                                                     
  V4 =              Midclavicular line   -5th ICS               -                                              Anterior

  V5 =              Anterior axillary line -5th ICS             -                                              Lateral

  V6 =              Mid axillary line -5th ICS                   -                                              Lateral


         


Saturday, September 10, 2011

Reading ECG


     Most of  health professional has little understanding about how to read easily electrocardiography especially those who are not dealing with the ECG in their work place.However, learning how to read ECG rhythms and  to manage patients condition according to the ECG is absolutly needed. By learning ECG pattern we can interpret wich part of the heart are affected,and immediate action must be perform as soon as possible.
    Now we will learn together how to read tipically ECG pattern and interpretation.
     

ELECTROCARDIOGRAM BASIC


An electrocardiogram reflects the electrical activity of cardiac cells and records electrical activity at a speed of 25mm/sec.
An electrocardiogram strip consist of horizontal square representing seconds and vertical representing voltage.
Each smaal square represents 0.04 second
Each large square represents  0.20 second.
P WAVE           :represents as atrial depolarization
PR INTERVAL : represents the time it takes an impuls to travel from atrial through the 
                           atrioventricular node bundle his and bundle branch of the purkinje 
                           fibers.Normal PR interval duration from 0.12 to 0.2 second                                                             
QRS COMPLEX:represent as ventricular depolarization.QRS complex duration 
                            from 0.04 to 0.1 second    
Q WAVE            :as the first negative deflection in the QRS COMPLEX and 
                             reflects initial ventricular septal depolarization.
R WAVE            :the first positive deflection in the QRS complex
S WAVE            :appears as as the second negative deflection in the QRS complex.
ST SEGMENT   :represents as ventricular repolarization.
T WAVE            :represents as ventricular repolarization and ventricular diastole
U WAVE            :follow the T wave ,prominent  U wave hypokalemia.
QT INTERVAL  :represents as ventricular refractory time or total time for 
                            ventricular depolarization and repolarization. QT interval measured 
                            from the beginning of the QRS complex to the end of the T wave. 


                                         


                                       
                                          

                                                                ECG GRID
 
                                           Left to right = Time and duration
                                           Vertical       =  Measure  of voltage < Amplitude >

                                                               P WAVE
                                          >Depolarization of atrial muscle
                                          >Low voltage (2-3mm in amplitude)
                                          >Duration <0.11 second
                                                             
                                                              Abnormal P WAVE
                                          >P=Pulmonal
                                            * tall peaked
                                            * right atrial enlargment secondary to pulmonary HTN
                                         >P=Mitrale 
                                           * broad notched
                                           * Left Atrial enlargement secondary to mitral valve disease
                                                            
                                                            QRS Complex
                                         >Depolarization of ventricles
                                         >Larger muscle mass
                                         >As high as  25 mm
                                         >Duration normal conduction <0.10
                                         >Amplitude >25 mm can mean chamber enlargement as 
                                            in ventricular hypertrophy 

                                                          QRS complex
                                        * Low amplitude
                                             - diffuse,severe coronary artery disease
                                             - pericardial effusion
                                             - hypothyroid
                                                
                                                         QRS Complex
                                         * 1st Negative deflection=Q Wave
                                         *1st Positive  deflection  =R Wave
                                         *Negative deflection after R Wave= S Wave
                                         *Positive  deflection after R Wave =R Prime
                                         *Negative deflection after S Wave = S Prime

                                                        ST Segment
                                         >Time between completion of depolarization and onset of 
                                            repolarization.
                                          - Normally isoelectric & gently blends into upslope of T Wave
                                          - Point where ST take off from QRS = J  Point 
                                          - Plays important role in diagnosis of Ischemic heart disease

                                                        ST Elevation
                                               * HALLMARK OF MI 
                                               *Slight elevation across entire tracing is normal especially 
                                                 in young male

                                                      ST Depression 
                                               * Indicative of Ischemia,Ventricular hypertrophy

                                                      T   WAVE 
                                          >Repolarization of the ventricles
                                          >Same direction as predominant QRS deflection
                                          >Abnormalities-usually inversion with BBB,hypertrophy 
                                                or AMI

                                                     QT Interval
                                          >Beginning QRS to the end of T Wave
                                          >Abnormalities : 
                                                  *Prolonged-commonly from drugs like Procan and
                                                     Quinidine or electrolyte imbalance
                                                  *Increased opportunity for R on T.ventricular re-entry
                                                    rhythms and sudden death.                   

ECG RHYTHM

In this section you will find the most common ECG pattern.
Normal Sinus Rhythm
Normal Sinus Rhythm
Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - (60-100 bpm)
  • QRS Duration - Normal
  • P Wave - Visible before each QRS complex
  • P-R Interval - Normal (<5 small Squares. Anything above and this would be 1st degree block)
  • Indicates that the electrical signal is generated by the sinus node and travelling in a normal fashion in the heart.
  • Clinical Tip :A normal ECG does not exclude heart disease
  • Sinus Tachycardia
    Sinus Tachycardia
    An excessive heart rate above 100 beats per minute (BPM) which originates from the SA node. Causes include stress, fright, illness and exercise. Not usually a surprise if it is triggered in response to regulatory changes e.g. shock. But if their is no apparent trigger then medications may be required to suppress the rhythm
    Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - More than 100 beats per minute
  • QRS Duration - Normal
  • P Wave - Visible before each QRS complex
  • P-R Interval - Normal
  • The impulse generating the heart beats are normal, but they are occurring at a faster pace than normal.
  • Clinical Tip :Sinus tachycardia may be caused by exercise,anxiety,fever,hypoxemia.hypovolemia.or cardiac failure.
  • Sinus Bradycardia
    Sinus Bradycardia
    A heart rate less than 60 beats per minute (BPM). This in a healthy athletic person may be 'normal', but other causes may be due to increased vagal tone from drug abuse, hypoglycaemia and brain injury with increase intracranial pressure (ICP) as examples
    Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - less than 60 beats per minute
  • QRS Duration - Normal
  • P Wave - Visible before each QRS complex
  • P-R Interval - Normal
  • Usually benign and often caused by patients on beta blockers  
  • Clinical Tip :Sinus bradycardia is normal in athletes and during sleep.
          
  • Supraventricular Tachycardia (SVT) Abnormal
    Supraventricular Tachycardia
    A narrow complex tachycardia or atrial tachycardia which originates in the 'atria' but is not under direct control from the SA node. SVT can occur in all age groups
    Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - 150-250 beats per minute
  • QRS Duration - Usually normal
  • P Wave - Often buried in preceding T wave
  • P-R Interval - Depends on site of supraventricular pacemaker
  • Impulses stimulating the heart are not being generated by the sinus node, but instead are coming from a collection of tissue around and involving the atrioventricular (AV) node
  • Clinical Tip :SVT may be related to caffeine intake,nicotine,stress,or anxiety in healthy adults.
  •  
  • Atrial Fibrillation
    Atrial Fibrillation

  • Many sites within the atria are generating their own electrical impulses, leading to irregular conduction of impulses to the ventricles that generate the heartbeat. This irregular rhythm can be felt when palpating a pulse
    Looking at the ECG you'll see that:
  • Rhythm - Irregularly irregular
  • Rate - usually 100-160 beats per minute but slower if on medication
  • QRS Duration - Usually normal
  • P Wave - Not distinguishable as the atria are firing off all over
  • P-R Interval - Not measurable
  • The atria fire electrical impulses in an irregular fashion causing irregular heart rhythm
  • Clinical Tip: Atrial fibrillation is usually a chronic arrhythmia associated with underlying heart disease.
  •  
  • Atrial Flutter
    Atrial Flutter

  • Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - Around 110 beats per minute
  • QRS Duration - Usually normal
  • P Wave - Replaced with multiple F (flutter) waves, usually at a ratio of 2:1 (2F - 1QRS) but sometimes 3:1
  • P Wave rate - 300 beats per minute
  • P-R Interval - Not measurable
  • As with SVT the abnormal tissue generating the rapid heart rate is also in the atria, however, the atrioventricular node is not involved in this case.
  • Clinical Tip : The presence of atrial flutter may be the first indication of cardiac disease.
  •  
  • 1st Degree AV Block
    1st Degree Block
    1st Degree AV block is caused by a conduction delay through the AV node but all electrical signals reach the ventricles. This rarely causes any problems by itself and often trained athletes can be seen to have it. The normal P-R interval is between 0.12s to 0.20s in length, or 3-5 small squares on the ECG.
  • Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - Normal
  • QRS Duration - Normal
  • P Wave - Ratio 1:1
  • P Wave rate - Normal
  • P-R Interval - Prolonged (>5 small squares)
  • Clinical Tip: Usually AV block is benign,but if associated with an acute MI it may lead to further AV defects.
  •  
  • 2nd Degree Block Type 1 (Wenckebach)
    2nd degree Block Type 1
    Another condition whereby a conduction block of some, but not all atrial beats getting through to the ventricles. There is progressive lengthening of the PR interval and then failure of conduction of an atrial beat, this is seen by a dropped QRS complex.
  • Looking at the ECG you'll see that:
  • Rhythm - Regularly irregular
  • Rate - Normal or Slow
  • QRS Duration - Normal
  • P Wave - Ratio 1:1 for 2,3 or 4 cycles then 1:0.
  • P Wave rate - Normal but faster than QRS rate
  • P-R Interval - Progressive lengthening of P-R interval until a QRS complex is dropped
  • Clinical Tip : This rhythm may be caused by medications such as beta blockers,digoxin,and calcium channel blockers (see emergency medications).Ischemia involving the right coronary artery is another cause.
  •  
  • 2nd Degree Block Type 2
    2nd Degree Block Type 2
    When electrical excitation sometimes fails to pass through the A-V node or bundle of His, this intermittent occurance is said to be called second degree heart block. Electrical conduction usually has a constant P-R interval, in the case of type 2 block atrial contractions are not regularly followed by ventricular contraction
    Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - Normal or Slow
  • QRS Duration - Prolonged
  • P Wave - Ratio 2:1, 3:1
  • P Wave rate - Normal but faster than QRS rate
  • P-R Interval - Normal or prolonged but constant
  • Clinical Tip : Resulting bradycardia can compromise cardiac output and lead to complete AV block.This rhythm often occurs with cardiac ischemia or an MI.
  •  
  • 3rd Degree Block
    3rd Degree Block
    3rd degree block or complete heart block occurs when atrial contractions are 'normal' but no electrical conduction is conveyed to the ventricles. The ventricles then generate their own signal through an 'escape mechanism' from a focus somewhere within the ventricle. The ventricular escape beats are usually 'slow'
    Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - Slow
  • QRS Duration - Prolonged
  • P Wave - Unrelated
  • P Wave rate - Normal but faster than QRS rate
  • P-R Interval - Variation
  • Complete AV block. No atrial impulses pass through the atrioventricular node and the ventricles generate their own rhythm.
  •  
  • Bundle Branch Block ( BBB )
    Abnormal conduction through the bundle branches will cause a depolarization delay through the ventricular muscle, this delay shows as a widening of the QRS complex. Right Bundle Branch Block (RBBB) indicates problems in the right side of the heart. Whereas Left Bundle Branch Block (LBBB) is an indication of heart disease. If LBBB is present then further interpretation of the ECG cannot be carried out.
    Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - Normal
  • QRS Duration - Prolonged
  • P Wave - Ratio 1:1
  • P Wave rate - Normal and same as QRS rate
  • P-R Interval - Normal
  • Clinical Tip : Commonly ,BBB occurs in coronary artery disease.
  •  
  • Premature Ventricular Complexes
    PVC's unifocal
    Due to a part of the heart depolarizing earlier than it should
    Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - Normal
  • QRS Duration - Normal
  • P Wave - Ratio 1:1
  • P Wave rate - Normal and same as QRS rate
  • P-R Interval - Normal
  • Also you'll see 2 odd waveforms, these are the ventricles depolarising prematurely in response to a signal within the ventricles.(Above - unifocal PVC's as they look alike if they differed in appearance they would be called multifocal PVC's, as below)
  • PVC's multifocal
     
    Junctional Rhythms
    Junctional Rhythm
    Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - 40-60 Beats per minute
  • QRS Duration - Normal
  • P Wave - Absent,inverted,burried,or retrograde.Ratio 1:1 if visible. Inverted in lead II
  • P Wave rate - Same as QRS rate
  • P-R Interval - Variable
  • Below - Accelerated Junctional Rhythm
    Accelerated Junctional Rhythm
    Clinical Tip :Monitor the patient ,not just the ECG,for  clinical improvement .
    Ventricular Tachycardia (VT) Abnormal
    Ventricular Tachycardia
    Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - 180-190 Beats per minute
  • QRS Duration - Prolonged
  • P Wave - Not seen
  • Results from abnormal tissues in the ventricles generating a rapid and irregular heart rhythm. Poor cardiac output is usually associated with this rhythm thus causing the pt to go into cardiac arrest. Shock this rhythm if the patient is unconscious and without a pulse.
  • Clinical Tip :Consider electrolyte abnormalities as a possible etiology.
  •  
  • Ventricular Fibrillation (VF) Abnormal
    Ventricular Fibrillation
    Disorganised electrical signals cause the ventricles to quiver instead of contract in a rhythmic fashion. A patient will be unconscious as blood is not pumped to the brain. Immediate treatment by defibrillation is indicated. This condition may occur during or after a myocardial infarct.
    Looking at the ECG you'll see that:
  • Rhythm - Irregular
  • Rate - 300+, disorganised
  • QRS Duration - Not recognisable
  • P Wave - Not seen
  • Clinical Tip :This patient needs to be defibrillated!! QUICKLY
  •  
  • Asystole - Abnormal
    Asystole
    Looking at the ECG you'll see that:
  • Rhythm - Flat
  • Rate - 0 Beats per minute
  • QRS Duration - None
  • P Wave - None
  • Carry out CPR!!
  •  
  • Myocardial Infarct (MI)
    Myocardial Infarct
    Looking at the ECG you'll see that:
  • Rhythm - Regular
  • Rate - 80 Beats per minute
  • QRS Duration - Normal
  • P Wave - Normal
  • S-T Element does not go isoelectric which indicates infarction

Info
























ECG Component Time(sec) Small Squares
P Wave 0.10
up to 2.5
PR Interval 0.12 - 0.20 2.5-5.0
QRS 0.10
1.5-2.5