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)