• Ischemia Dynamics in Occlusion
• Dynamics of ST Elevation in STEMI
• Physiological Q Wave
• Infarction and Q Wave
• ECG and Post-Infarction Q Wave
• ECG and Decreased R Wave Progression
• Left Anterior Hemiblock and Old Anteroseptal Infarction

Ischemia Dynamics in Occlusion

• After occlusion of a coronary artery
• A STEMI infarction (sometimes NSTEMI) often begins to develop
• A myocardial infarction (necrosis) gradually develops in the myocardial wall
• Time intervals are individual for each patient
• Myocardial viability depends on collateral circulation
• Ischemia (<20min.)
• The myocardium is hypoxic (lacking oxygen)
• Hypoxia (occlusion) lasts less than 20 minutes
• It is reversible
• On the ECG there are hyperacute T waves
• Ischemic Damage (>20min.)
• The myocardium is hypoxic (lacking oxygen)
• Hypoxia (occlusion) lasts more than 20 minutes
• It is reversible
• On the ECG there are already ST elevations
• Infarction (>2hrs.)
• The myocardium is hypoxic (lacking oxygen)
• Hypoxia (occlusion) lasts more than 2 hours
• It is irreversible damage
• On the ECG a pathological Q wave begins to develop

Dynamics of ST Elevation in STEMI

• Only in STEMI infarction does the characteristic ECG dynamics of infarction develop
• Based on the ECG, the duration of STEMI infarction and the affected artery can be determined
• NSTEMI infarction does not have this characteristic ECG dynamics
• In fact, sometimes NSTEMI infarction can have a normal ECG

ECG Dynamics of STEMI Infarction

• In clinical practice, STEMI is categorized into 3 stages based on the ECG picture:
• Acute STEMI
• Shows ST elevation without Q wave
• Duration: minutes - hours
• Subacute STEMI
• Shows ST elevation and Q wave
• Duration: hours - days
• Old STEMI
• Shows Q wave without ST elevation
• Duration: > one week

Infarction and Q Wave

• Pathological Q wave is wider and deeper
• Occurs with transmural necrosis in STEMI infarction
• It arises due to an electrical window
• Mislabeling of STEMI as Q infarction
• NSTEMI can also rarely produce a pathological Q wave
  
  
• STEMI has 3 stages:
• Acute (No pathological Q wave)
• Subacute (Pathological Q wave present)
• Starts to form an electrical window
• Old STEMI (Has pathological Q wave)
  
  
• Pathological Q wave in STEMI arises
• Most commonly 9 hours after occlusion
• But it can appear as early as 2 hours after occlusion
• Rarely can appear:
• Several minutes after occlusion
• 24 hours after occlusion
• Timing of appearance depends on collateral circulation
• Pathological Q wave
• Does not necessarily indicate myocardial necrosis
• After reperfusion, Q wave can disappear
• Does not exclude acute infarction

• This Q wave does not necessarily indicate irreversible myocardial damage
• It reflects a disruption in action potential in the ischemic zone behind the occlusion

ECG and Decreased R Wave Progression

• After anterior infarction
• There is an electrical window on the anterior wall
• And decreased R wave progression occurs
  
  
• Decreased R wave progression is:
• Absent R (V1-V3)
• Absence of R wave (V1-V3)
• Or R wave in V3 < 4mm
  
  
• There is no consensus on ECG criteria

Subacute Anterior STEMI

• ST elevations on the anterior wall (V2-V5)
• Pathologic Q wave (V2-V3)
• Depth > 3mm
• Indicates occlusion of the LAD (left anterior descending artery)
• Represents subacute anterior STEMI
• Duration hours - days

Subacute STEMI of the Inferior and Lateral Walls

• ST elevations in inferior and lateral leads (II, III, aVF, V5-V6)
• Pathologic Q wave (II, III, aVF)
• Depth > 3mm
• Patient had occlusion of the dominant LCx (ramus circumflexus)
• ST elevation II > III
• Represents a subacute STEMI of the inferior and lateral - left wall
• Duration hours - days