Management of ST Depression MI in Lead V5
ST depression in lead V5 during myocardial infarction should NOT be treated with fibrinolytic therapy unless there is evidence of true posterior (inferobasal) MI or associated ST elevation in lead aVR, and management should prioritize primary PCI with dual antiplatelet therapy and anticoagulation. 1
Critical Initial Distinction
Fibrinolytic therapy is contraindicated (Class III: Harm) for ST depression except when true posterior MI is suspected or when associated with ST elevation in lead aVR. 1 This is a Level of Evidence B recommendation that must guide your initial reperfusion strategy decision.
Reperfusion Strategy
Primary PCI (Preferred Approach)
- Primary PCI should be performed within 120 minutes of first medical contact when available, as this is the preferred reperfusion strategy for patients presenting with ST depression MI. 1
- If the patient is hemodynamically stable, use radial rather than femoral access to minimize bleeding risk. 2
- Consider reduced doses of anticoagulants during the procedure to mitigate bleeding complications. 2
Fibrinolytic Therapy Considerations
- Only consider fibrinolytic therapy if primary PCI cannot be performed within 120 minutes AND there is evidence of true posterior (inferobasal) MI or ST elevation in lead aVR. 1
- If fibrinolysis is used, initiate treatment as soon as possible after STEMI diagnosis, preferably in the pre-hospital setting, using a fibrin-specific agent (tenecteplase, alteplase, or reteplase). 1
Immediate Pharmacotherapy
Antiplatelet Therapy
- Administer aspirin 162-325 mg loading dose (oral or IV if unable to swallow) immediately without contraindications. 1
- Add a potent P2Y12 inhibitor before or at the time of PCI: prasugrel or ticagrelor preferred, or clopidogrel (300 mg loading dose if <75 years; 75 mg if ≥75 years) if the others are unavailable or contraindicated. 1
- Continue dual antiplatelet therapy (DAPT) for 12 months after PCI unless there are contraindications such as excessive bleeding risk. 1
Anticoagulation
For Primary PCI:
- Unfractionated heparin (UFH) as weight-adjusted IV bolus with target ACT of 250-300 seconds (HemoTec) or 300-350 seconds (Hemochron) without planned GP IIb/IIIa inhibitor. 1
- Alternatively, bivalirudin 0.75 mg/kg IV bolus followed by 1.75 mg/kg/h infusion, with or without prior UFH treatment. 1
- Enoxaparin is preferred over UFH with GP IIb/IIIa receptor antagonist in patients at high bleeding risk. 1
- Fondaparinux is NOT recommended for primary PCI (Class III: Harm). 1
For Fibrinolytic Therapy (if applicable):
- Anticoagulation for minimum 48 hours, preferably for duration of hospitalization up to 8 days or until revascularization. 1
- Enoxaparin IV followed by subcutaneous (preferred over UFH) according to age, weight, and creatinine clearance. 1
Clinical Assessment and Risk Stratification
Evaluate for Posterior MI
ST depression in V5 may represent:
- Reciprocal changes from inferior MI (which has better prognosis and does not indicate additional ischemic territory). 3
- True posterior (inferobasal) MI requiring fibrinolytic therapy consideration if PCI unavailable. 1
- Additional lateral ischemia associated with more extensive infarction and multivessel disease. 4
Echocardiographic Assessment
- Perform routine echocardiography during hospital stay to assess LV and RV function, detect mechanical complications, and exclude LV thrombus. 1, 2
- Patients with persistent ST depression in V5-V6 after anterior MI may have restrictive LV filling patterns with elevated filling pressures. 5
Ongoing Management
Maintenance Antiplatelet Therapy
- Continue aspirin 75-100 mg daily indefinitely. 1
- Maintain DAPT with aspirin plus ticagrelor or prasugrel (or clopidogrel) for 12 months. 1
- Add a proton pump inhibitor (PPI) in combination with DAPT for patients at high risk of gastrointestinal bleeding. 1, 2
Additional Pharmacotherapy
- Initiate oral beta-blockers once hemodynamically stable, particularly in patients with heart failure or LVEF <40%. 1, 2
- Start ACE inhibitors within 24 hours in patients with heart failure, LV systolic dysfunction, diabetes, or anterior infarct. 1, 2
- Begin high-intensity statin therapy as early as possible with LDL-C goal <1.8 mmol/L (70 mg/dL). 1, 2
- Consider aldosterone antagonist in patients with LVEF ≤40% and heart failure or diabetes who are already receiving ACE inhibitor and beta-blocker, provided no renal dysfunction or hyperkalemia. 1
Post-Fibrinolysis Strategy (if applicable)
- Transfer to PCI-capable center immediately after fibrinolysis. 1
- Perform angiography and PCI of infarct-related artery between 2-24 hours after successful fibrinolysis. 1
- Rescue PCI is indicated immediately when fibrinolysis has failed (<50% ST-segment resolution at 60-90 minutes) or with hemodynamic/electrical instability. 1
Common Pitfalls
- Do not administer fibrinolytic therapy to patients with ST depression without confirming true posterior MI or ST elevation in aVR, as this increases harm without benefit. 1
- Avoid IV beta-blockers in patients with hypotension, acute heart failure, AV block, or severe bradycardia. 1
- Do not use fondaparinux as sole anticoagulant for primary PCI. 1
- ST depression in V5 with extensive involvement (≥4 mm or ≥7 leads) indicates high mortality risk and requires aggressive management. 6