What is active ongoing ischemia on an EKG (electrocardiogram)?

Active Ongoing Ischemia on EKG

Active ongoing ischemia on an EKG refers to dynamic electrocardiographic changes—particularly ST-segment elevation, ST-segment depression, or hyperacute T waves—that occur during chest pain or anginal equivalent symptoms and indicate real-time myocardial oxygen deprivation requiring immediate intervention. 1

Classic ECG Manifestations of Active Ischemia

ST-Segment Elevation Patterns

• ST-segment elevation ≥0.1 mV (1 mm) in two contiguous leads (or ≥0.2 mV in leads V1-V3) represents transmural ischemia from acute coronary occlusion and mandates immediate reperfusion therapy 1, 2
• Hyperacute T waves may precede ST-segment elevation in very early presentations, appearing as tall, peaked T waves in the distribution of the occluded artery 1
• The ST-segment changes must be dynamic and correlate temporally with symptoms—this distinguishes active ischemia from chronic patterns like left ventricular aneurysm 2, 3

ST-Segment Depression Patterns

• Horizontal or down-sloping ST-segment depression ≥0.05 mV in multiple leads indicates subendocardial ischemia and high-risk coronary disease 1, 3
• Isolated ST-depression ≥0.05 mV in leads V1-V3 may represent posterior wall myocardial infarction (a STEMI equivalent) and should prompt evaluation with posterior leads V7-V9 1, 2
• Up-sloping ST-segment depression with positive T waves is increasingly recognized as severe left anterior descending artery obstruction 3

High-Risk Ischemic Patterns

• Widespread ST-depression (≥8 leads) with ST-elevation in aVR and/or V1 suggests left main or multivessel coronary obstruction, particularly with hemodynamic compromise 1
• This pattern requires immediate coronary angiography regardless of troponin results 1

Atypical ECG Presentations Requiring Urgent Recognition

Conduction Abnormalities Masking Ischemia

• Left bundle branch block (LBBB) prevents standard ST-segment interpretation; look for concordant ST-elevation (ST-elevation in same direction as QRS complex) as a marker of acute MI 1, 2
• Ventricular paced rhythms similarly obscure ST-segments and may require urgent angiography based on clinical suspicion alone, or pacemaker reprogramming if the patient is not pacemaker-dependent 1
• Right bundle branch block (RBBB) typically does not prevent ST-segment interpretation, but persistent symptoms with RBBB warrant prompt management 1

Non-Diagnostic Initial ECGs

• Some patients with acute coronary occlusion present without diagnostic ST-elevation, particularly with circumflex artery occlusion, vein graft occlusion, or left main disease 1
• Ongoing chest pain despite medical therapy is an indication for emergency coronary angiography even without diagnostic ST-segment changes 1
• The initial ECG may be normal or non-diagnostic in up to 55% of acute MI cases, necessitating serial ECGs at 30-60 minute intervals 4, 5

Clinical Context and Diagnostic Approach

Temporal Correlation is Essential

• Active ischemia requires symptoms (chest pain or anginal equivalents) occurring simultaneously with ECG changes 1
• Repeat ECGs during pain episodes can capture dynamic changes missed on initial tracings 1
• Continuous ST-segment monitoring detects ischemia in an additional 16.2% of acute MI patients compared to single ECGs 4

Immediate Management Priorities

• Patients with ongoing ischemia and hemodynamic compromise require immediate coronary angiography regardless of ECG or biomarker findings to prevent life-threatening arrhythmias and limit myocardial necrosis 1
• Defibrillator patches should be placed in cases of ongoing ischemia until urgent revascularization is performed 1
• Two-dimensional echocardiography can identify regional wall motion abnormalities within minutes of coronary occlusion, supporting the diagnosis when ECG is equivocal 1, 2

Common Pitfalls to Avoid

Misinterpretation of ST-Elevation

• Do not confuse ST-elevation from left ventricular aneurysm, pericarditis, or benign early repolarization with acute coronary occlusion 2, 5
• Left ventricular aneurysm shows persistent ST-elevation without dynamic changes or symptom correlation 5
• Pericarditis typically shows diffuse ST-elevation with PR-segment depression 3

Delayed Recognition of STEMI Equivalents

• Posterior MI and left main occlusion patterns are frequently missed because they don't show classic anterior ST-elevation 1, 2
• Always obtain posterior leads (V7-V9) when inferior ST-depression is present with ongoing symptoms 1, 2

Monitoring Duration

• Continue ECG monitoring for at least 24 hours in suspected acute coronary syndrome, or until 12-24 hours event-free 1, 2
• Arrhythmia monitoring should continue uninterrupted until there is no evidence of ongoing modifiable ischemia or hemodynamic/electrical instability 1

Prognostic Significance

• Prehospital ECG evidence of ischemia independently predicts adverse hospital outcomes, with patients 1.55 times more likely to experience complications compared to those without ECG ischemia 6
• Even transient, asymptomatic ischemic episodes detected on continuous monitoring are significant markers for unfavorable short- and long-term outcomes 1