1. Systems of Care and Time Targets
1.1 Reperfusion Time Goals
Time to reperfusion is the single most important modifiable determinant of outcome in STEMI. The relationship between delay and mortality is approximately linear in the first 2-3 hours after symptom onset, with the greatest benefit from reperfusion occurring in the first 1-2 hours (“golden hour”).
| Metric | Target | Definition |
|---|
| ECG acquisition | ≤ 10 minutes from first medical contact (FMC) | Time from arrival at ED door (or EMS contact) to 12-lead ECG acquisition and interpretation |
| Door-to-balloon time (D2B) | ≤ 90 minutes | Time from hospital arrival to first balloon inflation/device activation at PCI-capable facility |
| First medical contact-to-device time (FMC2D) | ≤ 120 minutes | Total system time from FMC (EMS contact or ED arrival) to PCI device activation — includes transfer time |
| Door-in to door-out time (DIDO) | ≤ 30 minutes | For non-PCI-capable facilities: time from arrival at referring hospital to departure for PCI-capable hospital |
| Door-to-needle time (D2N) | ≤ 30 minutes | Time from hospital arrival to initiation of fibrinolytic therapy (when fibrinolysis is the chosen strategy) |
| Total ischemic time | Minimize | Symptom onset to reperfusion; <12 hours for PCI, <12 hours (ideally <6 hours) for fibrinolysis |
1.2 Reperfusion Strategy Selection Algorithm
| Clinical Scenario | Recommended Strategy |
|---|
| PCI-capable facility, D2B achievable in ≤ 90 min | Primary PCI (Class I) |
| Non-PCI-capable facility, transfer time allows FMC2D ≤ 120 min | Transfer for primary PCI (Class I) |
| Non-PCI-capable facility, transfer time would result in FMC2D > 120 min | Fibrinolytic therapy within 30 min of arrival (Class I), followed by transfer to PCI-capable facility for routine angiography within 3-24 hours (pharmacoinvasive strategy) |
| Symptom onset < 2 hours AND expected PCI delay > 60 min beyond fibrinolysis | Consider fibrinolysis even if transfer possible (Class IIa) — greatest benefit of early reperfusion |
| Symptom onset 12-24 hours with ongoing ischemia, hemodynamic instability, or electrical instability | Primary PCI still recommended (Class IIa) |
| Symptom onset > 24 hours, stable, no ongoing ischemia | PCI of occluded artery NOT routinely recommended (Class III — no benefit; per the OAT trial) |
| Cardiogenic shock | Emergent PCI regardless of time delay (Class I) |
2. Primary Percutaneous Coronary Intervention (PCI)
2.1 Key Recommendations
- Primary PCI is the preferred reperfusion strategy when it can be performed in a timely manner by an experienced operator at a high-volume center
- Radial artery access is preferred over femoral access (lower bleeding, lower mortality in STEMI based on the MATRIX and RIVAL trials)
- Drug-eluting stents (DES) are preferred over bare-metal stents (BMS) for all STEMI patients (lower restenosis, no increase in stent thrombosis in contemporary trials)
- Culprit-lesion-only PCI is generally recommended at the time of primary PCI; complete revascularization of non-culprit lesions should be considered during the index hospitalization or as a staged procedure (Class IIa based on COMPLETE, PRAMI, and CvLPRIT trials)
- Aspiration thrombectomy is NOT routinely recommended (Class III — no benefit; per TOTAL and TASTE trials)
2.2 PCI Quality Metrics
| Metric | Standard |
|---|
| D2B time ≤ 90 minutes | ≥ 75% of STEMI cases at PCI-capable facilities |
| Radial access utilization | Target > 50% (quality improvement benchmark) |
| Primary PCI volume | ≥ 200 PCI procedures/year per operator; ≥ 400 per institution for optimal outcomes |
| In-hospital mortality (STEMI with PCI) | Expected 4-7% (risk-adjusted) |
3. Fibrinolytic Therapy
3.1 Indications
Fibrinolytic therapy is indicated when primary PCI cannot be performed within the recommended time window:
- Symptom onset < 12 hours (greatest benefit within 0-6 hours; Class I for < 12 hours)
- STEMI diagnostic criteria met on ECG
- No absolute contraindications
- Expected FMC-to-device time > 120 minutes
- Door-to-needle time achievable within 30 minutes
3.2 Fibrinolytic Agents — Weight-Based Dosing
| Agent | Dose | Route | Bolus/Infusion | Fibrin Specificity | Adjunctive Heparin |
|---|
| Tenecteplase (TNKase) | Weight-based single bolus: < 60 kg: 30 mg; 60-69 kg: 35 mg; 70-79 kg: 40 mg; 80-89 kg: 45 mg; ≥ 90 kg: 50 mg | IV bolus over 5 seconds | Single bolus (most convenient) | High | Required (UFH or enoxaparin) |
| Alteplase (Activase, tPA) | 15 mg IV bolus, then 0.75 mg/kg (max 50 mg) IV over 30 min, then 0.5 mg/kg (max 35 mg) IV over 60 min; total dose ≤ 100 mg | IV bolus + infusion (90 min total) | Bolus + infusion | High | Required (UFH or enoxaparin) |
| Reteplase (Retavase) | 10 units IV bolus, followed by a second 10 unit IV bolus 30 minutes later | IV double bolus | Double bolus (30 min apart) | Moderate | Required (UFH or enoxaparin) |
Half-dose tenecteplase for patients ≥ 75 years: The European cardiology guidelines committee recommends consideration of half-dose tenecteplase in patients aged ≥ 75 years to reduce intracranial hemorrhage risk (based on the STREAM trial protocol).
3.3 Absolute Contraindications to Fibrinolytic Therapy
| Contraindication | Rationale |
|---|
| Any prior intracranial hemorrhage | Unacceptable risk of recurrent ICH |
| Known intracranial neoplasm, AVM, or aneurysm | Risk of hemorrhagic transformation |
| Active internal bleeding (excluding menses) | Will worsen hemorrhage |
| Known or suspected aortic dissection | Catastrophic if fibrinolytic enters false lumen |
| Significant head/facial trauma within 3 months | Risk of intracranial hemorrhage |
| Ischemic stroke within 3 months | Risk of hemorrhagic transformation |
| Intracranial or spinal surgery within 3 months | Risk of surgical site hemorrhage |
| Severe uncontrolled hypertension (unresponsive to treatment) | Increased ICH risk |
| For streptokinase: prior administration within 6 months | Antibodies reduce efficacy and increase allergic risk |
3.4 Relative Contraindications to Fibrinolytic Therapy
| Relative Contraindication | Clinical Consideration |
|---|
| Chronic, severe, poorly controlled hypertension | SBP > 180 mmHg or DBP > 110 mmHg on presentation (attempt to control before administration) |
| Ischemic stroke > 3 months prior | Weigh individual risk-benefit |
| Traumatic or prolonged CPR (> 10 minutes) | Increased bleeding risk but not absolute |
| Major surgery within 3 weeks | Surgical site hemorrhage risk |
| Non-compressible vascular punctures | Bleeding risk |
| Recent (within 2-4 weeks) internal bleeding | Weigh severity and timing |
| Pregnancy | Risk of placental hemorrhage; weigh maternal mortality risk |
| Active peptic ulcer disease | GI hemorrhage risk |
| Current use of anticoagulants (higher INR = higher risk) | INR > 1.7 or PT > 15 sec — increased hemorrhage risk |
| Prior exposure to streptokinase (if streptokinase is planned) | Use alternative agent |
3.5 Markers of Successful Reperfusion After Fibrinolysis
| Marker | Criteria | Timing |
|---|
| ST-segment resolution | ≥ 50% reduction in maximal ST elevation within 60-90 min of fibrinolytic administration | Most reliable non-invasive marker |
| Reperfusion arrhythmias | Accelerated idioventricular rhythm (AIVR), transient sinus bradycardia | Suggestive but not reliable alone |
| Chest pain resolution | Significant improvement or resolution | Supportive but non-specific |
| Early troponin peak | Peak troponin at 12 hours rather than 24 hours | Suggests early washout |
3.6 Rescue PCI
If fibrinolysis fails (defined as < 50% ST-segment resolution at 60-90 minutes), rescue PCI should be performed urgently:
- Transfer immediately to PCI-capable facility
- Do NOT re-administer fibrinolytic therapy
- Class I recommendation for rescue PCI in the setting of failed fibrinolysis with ongoing ischemia
- Rescue PCI should also be considered for hemodynamic deterioration, worsening heart failure, or persistent ventricular arrhythmias after fibrinolysis
3.7 Pharmacoinvasive Strategy
The pharmacoinvasive strategy combines early fibrinolysis with routine angiography and PCI within 3-24 hours, regardless of whether fibrinolysis appears successful:
- Administer fibrinolytic therapy at non-PCI-capable facility
- Transfer to PCI-capable facility
- Perform coronary angiography within 3-24 hours:
- If < 3 hours: wait (unless rescue PCI needed for failed fibrinolysis)
- If 3-24 hours: routine angiography and PCI of culprit lesion
- Rescue PCI immediately if fibrinolysis fails
Evidence: The STREAM trial demonstrated that the pharmacoinvasive strategy (tenecteplase + transfer for angiography within 6-24 hours) produced similar outcomes to primary PCI in STEMI patients presenting within 3 hours who could not undergo PCI within 1 hour.
4. Antiplatelet Therapy in STEMI
4.1 Aspirin
| Parameter | Recommendation |
|---|
| Loading dose | 162-325 mg chewed and swallowed (non-enteric-coated) as early as possible (Class I) |
| Maintenance dose | 81 mg daily indefinitely (preferred over 325 mg for long-term use due to lower bleeding) |
| True aspirin allergy | Desensitization if feasible; if not, P2Y12 inhibitor monotherapy |
| Evidence class | Class I, Level of Evidence A |
4.2 P2Y12 Receptor Inhibitors — Comparison
| Parameter | Clopidogrel (Plavix) | Ticagrelor (Brilinta) | Prasugrel (Effient) |
|---|
| Drug class | Thienopyridine (prodrug) | Cyclopentyl-triazolopyrimidine (direct-acting) | Thienopyridine (prodrug) |
| Activation | Requires hepatic metabolism (CYP2C19) | No hepatic activation needed | Requires hepatic metabolism (single-step) |
| Onset of action | 2-8 hours | 30 min-2 hours | 30 min-1 hour |
| Reversibility | Irreversible | Reversible | Irreversible |
| Duration of effect | 5-10 days | 3-5 days (must be dosed BID) | 7-10 days |
| STEMI loading dose | 600 mg (if going to PCI) or 300 mg (if fibrinolysis) | 180 mg | 60 mg |
| STEMI maintenance | 75 mg daily | 90 mg BID | 10 mg daily (5 mg daily if < 60 kg) |
| For fibrinolysis | 300 mg load (age ≤ 75); no load if age > 75 (75 mg only) | NOT recommended with fibrinolysis (no safety data) | NOT recommended with fibrinolysis (no safety data) |
| Landmark trial | CLARITY-TIMI 28 (with fibrinolysis); CURRENT-OASIS 7 (with PCI) | PLATO | TRITON-TIMI 38 |
4.3 P2Y12 Inhibitor Selection in STEMI
| Clinical Scenario | Preferred Agent | Rationale |
|---|
| STEMI with primary PCI (general) | Ticagrelor or prasugrel preferred over clopidogrel (Class I, LOE B) | Superior outcomes in PLATO and TRITON-TIMI 38; faster onset, more potent, less variability |
| STEMI with fibrinolysis | Clopidogrel is the only validated option | Ticagrelor and prasugrel lack safety/efficacy data with fibrinolysis |
| Prior stroke or TIA | Ticagrelor or clopidogrel; prasugrel is CONTRAINDICATED | TRITON-TIMI 38 showed net harm (increased ICH) in patients with prior stroke/TIA |
| Age ≥ 75 years | Ticagrelor or clopidogrel preferred; prasugrel used with caution (consider 5 mg dose) | TRITON-TIMI 38 showed no net clinical benefit in ≥ 75 age group |
| Body weight < 60 kg | If prasugrel chosen: reduce to 5 mg daily maintenance | Higher bleeding risk at standard dose in low-weight patients |
| High bleeding risk | Clopidogrel (least potent); consider shorter DAPT duration | Lowest bleeding rates among P2Y12 inhibitors |
| CYP2C19 loss-of-function carriers | Ticagrelor or prasugrel | Clopidogrel is a prodrug requiring CYP2C19 for activation; loss-of-function polymorphisms reduce efficacy |
| Cost-sensitive | Clopidogrel (generic available) | Significantly less expensive than ticagrelor or prasugrel |
4.4 Glycoprotein IIb/IIIa Inhibitors in STEMI
| Agent | Dose for Primary PCI | Notes |
|---|
| Abciximab (ReoPro) | 0.25 mg/kg IV bolus, then 0.125 mcg/kg/min (max 10 mcg/min) infusion for 12 hours | Monoclonal antibody; longest track record in STEMI PCI; not available in many countries |
| Eptifibatide (Integrilin) | 180 mcg/kg IV bolus (double bolus — repeat at 10 min), then 2.0 mcg/kg/min infusion for 18-24 hours | Reduce infusion to 1.0 mcg/kg/min if CrCl < 50 mL/min; contraindicated if CrCl < 30 mL/min |
| Tirofiban (Aggrastat) | 25 mcg/kg IV bolus over 3 min, then 0.15 mcg/kg/min infusion for 18-24 hours | Reduce infusion by 50% if CrCl < 30 mL/min |
Current role: The routine upstream use of GP IIb/IIIa inhibitors has been downgraded. They may be considered as bail-out therapy during PCI for angiographic complications (large thrombus burden, slow/no-reflow, threatened vessel closure).
5. Anticoagulation in STEMI
5.1 Anticoagulation for Primary PCI
| Agent | Dose | Notes |
|---|
| Unfractionated heparin (UFH) | 70-100 units/kg IV bolus (without GP IIb/IIIa inhibitor) OR 50-70 units/kg IV bolus (with GP IIb/IIIa inhibitor); target ACT 250-300 sec (without GP IIb/IIIa) or 200-250 sec (with GP IIb/IIIa) | Class I; most widely used; easily titratable; reversible with protamine |
| Bivalirudin (Angiomax) | 0.75 mg/kg IV bolus, then 1.75 mg/kg/h infusion during PCI; optional extended infusion at full or reduced dose (0.25 mg/kg/h) for up to 4 hours post-PCI | Class IIa; direct thrombin inhibitor; alternative to UFH + GP IIb/IIIa; lower bleeding but possible higher acute stent thrombosis (mitigated by extended infusion and pretreatment with potent P2Y12 inhibitor) |
| Enoxaparin | 0.5 mg/kg IV bolus at time of PCI | Class IIa; alternative to UFH for primary PCI; validated in ATOLL trial |
5.2 Anticoagulation for Fibrinolytic Therapy
| Agent | Dose Protocol | Duration | Notes |
|---|
| UFH | 60 units/kg IV bolus (max 4,000 units), then 12 units/kg/h infusion (max 1,000 units/h initially); target aPTT 1.5-2.0 × control (approximately 50-70 seconds) | Minimum 48 hours, up to 8 days or until revascularization | Class I; check aPTT at 3, 6, 12, 24 hours and adjust |
| Enoxaparin | Age ≤ 75: 30 mg IV bolus, then 1 mg/kg SC q12h (max 100 mg for first 2 doses). Age > 75: NO IV bolus, 0.75 mg/kg SC q12h (max 75 mg for first 2 doses). CrCl < 30 mL/min: 1 mg/kg SC q24h | For duration of hospitalization, up to 8 days | Class I; validated in ExTRACT-TIMI 25 (superior to UFH); dose adjust for age and renal function |
| Fondaparinux | 2.5 mg IV bolus, then 2.5 mg SC daily starting day 2 | Up to 8 days or until revascularization | Class IIb for fibrinolysis adjunct; if patient goes to PCI, additional anticoagulation (UFH) required due to risk of catheter thrombosis |
5.3 Anticoagulation After PCI — Post-Procedure
- In general, anticoagulation is discontinued after successful PCI unless there is another indication (LV thrombus, AF, mechanical valve, extensive anterior MI with akinesis)
- If ongoing anticoagulation is needed, see triple therapy considerations in Part 4
6. Adjunctive Therapy in STEMI
6.1 Oxygen
| Recommendation | Details | Evidence |
|---|
| Supplemental O2 if SpO2 < 90% | Titrate to SpO2 ≥ 90% (Class I) | AVOID-trial and DETO2X-AMI trial: routine oxygen in normoxic STEMI patients provides no benefit and may increase infarct size; do NOT administer oxygen if SpO2 ≥ 90% |
| Do NOT give routine oxygen if SpO2 ≥ 90% | Class III — no benefit | |
6.2 Nitroglycerin
| Parameter | Recommendation |
|---|
| Sublingual | 0.4 mg SL every 5 min × 3 doses for ongoing ischemic chest pain |
| IV infusion | Start at 5-10 mcg/min, titrate by 5-10 mcg/min every 3-5 min; max typically 200 mcg/min |
| Indications | Ongoing ischemic pain, hypertension, heart failure (Class I for symptom relief) |
| Contraindications | SBP < 90 mmHg or ≥ 30 mmHg below baseline; right ventricular infarction; use of PDE-5 inhibitors (sildenafil/vardenafil within 24h, tadalafil within 48h); severe aortic stenosis; hypertrophic obstructive cardiomyopathy |
6.3 Morphine and Analgesics
| Recommendation | Details |
|---|
| Morphine | 2-4 mg IV, may repeat at 5-15 min intervals; use with caution (Class IIb downgraded from prior Class I) |
| Concerns | Observational data suggest morphine may delay absorption of oral antiplatelet agents (clopidogrel, ticagrelor), slow GI motility, cause hypotension, and may be associated with larger infarct size. The international cardiology guidelines committee now recommends morphine only when other pain relief measures fail and pain is severe. |
| Alternatives | IV acetaminophen (1 g IV); titrated IV fentanyl (25-50 mcg IV, may repeat) has faster onset and less hemodynamic effect than morphine |
6.4 Beta-Blockers
| Parameter | Recommendation |
|---|
| Timing | Oral beta-blocker within the first 24 hours (Class I), provided no contraindications |
| IV beta-blocker | Consider in hypertensive patients without contraindications (Class IIa); metoprolol 5 mg IV × 3 doses at 5-min intervals |
| Oral agents | Metoprolol tartrate 25-50 mg PO q6-12h (then convert to succinate); carvedilol 6.25 mg PO BID; bisoprolol 2.5-5 mg PO daily |
| Target | Heart rate 50-60 bpm |
| Contraindications | Active heart failure / pulmonary edema; cardiogenic shock; SBP < 100 mmHg; HR < 60 bpm; PR interval > 0.24 sec; second- or third-degree AV block; active reactive airway disease; cocaine-associated ACS (relative — beta-blockers may worsen coronary spasm) |
| Key evidence | COMMIT/CCS-2 trial: early IV metoprolol in STEMI reduced reinfarction and VF but increased cardiogenic shock, particularly in hemodynamically compromised patients. NET benefit favored selective use, not routine IV beta-blockade in all comers. |
6.5 ACE Inhibitors and ARBs
| Parameter | Recommendation |
|---|
| Timing | Oral ACE inhibitor within 24 hours of STEMI onset (Class I) for anterior MI, heart failure, or EF ≤ 40% |
| Agents | Captopril 6.25 mg PO test dose → 25-50 mg TID; lisinopril 5 mg PO daily → titrate to 10-20 mg; ramipril 2.5 mg PO BID → titrate to 5 mg BID; enalapril 2.5 mg PO BID → titrate to 10 mg BID |
| ARB | Valsartan 20 mg PO BID → titrate to 160 mg BID (for ACE-I intolerant patients; VALIANT trial) |
| Contraindications | SBP < 100 mmHg; bilateral renal artery stenosis; serum K > 5.5 mEq/L; creatinine > 3 mg/dL (relative); pregnancy |
6.6 Statin Therapy
| Parameter | Recommendation |
|---|
| Timing | High-intensity statin initiated within 24 hours regardless of baseline LDL (Class I, LOE A) |
| Agents | Atorvastatin 80 mg daily OR rosuvastatin 20-40 mg daily |
| LDL target | < 70 mg/dL (some guidelines now recommend < 55 mg/dL per the European cardiology guidelines committee) |
| If LDL remains > 70 mg/dL on max statin | Add ezetimibe 10 mg daily (Class I); consider PCSK9 inhibitor (evolocumab 140 mg SC q2wk or alirocumab 75-150 mg SC q2wk) if still above target (Class IIa) |
7. Cardiogenic Shock in STEMI
7.1 Definition and Diagnosis
Cardiogenic shock complicates approximately 5-10% of STEMI presentations and carries mortality of 40-50% even with aggressive treatment.
Diagnostic criteria (all required):
| Criterion | Threshold |
|---|
| Systolic blood pressure | < 90 mmHg for ≥ 30 min (or vasopressors required to maintain SBP ≥ 90) |
| Evidence of end-organ hypoperfusion | Altered mental status, cool/mottled extremities, oliguria (< 30 mL/h), elevated lactate |
| Cardiac index (if measured) | < 2.2 L/min/m² (without support) OR < 2.5 L/min/m² (with support) |
| Pulmonary capillary wedge pressure (if measured) | ≥ 15 mmHg (to differentiate from hypovolemia) |
7.2 SCAI Shock Classification
The cardiovascular interventional society’s shock classification provides a staging system:
| Stage | Name | Criteria |
|---|
| A | At risk | Not currently in shock but at risk (large STEMI, prior HF, tachyarrhythmia) |
| B | Beginning shock | SBP < 90 or MAP < 60 or > 30 mmHg drop from baseline; HR > 100; evidence of relative hypotension; beginning signs of hypoperfusion (elevated lactate, renal function decline) |
| C | Classic shock | Requires vasopressor or mechanical support to maintain SBP ≥ 90; frank hypoperfusion (lactate ≥ 2 mmol/L, cool extremities, oliguria, altered mental status) |
| D | Deteriorating | Failing to respond to initial interventions; escalating vasopressor or mechanical support requirements; worsening end-organ function |
| E | Extremis | Refractory cardiac arrest, PEA, refractory VT/VF; maximal support with ongoing hemodynamic collapse |
7.3 Pharmacologic Support
| Agent | Dose | Mechanism | Indications | Key Considerations |
|---|
| Norepinephrine | 0.1-0.5 mcg/kg/min (typical start 0.1-0.2 mcg/kg/min; max 0.5-1.0 mcg/kg/min) | Alpha-1 + beta-1 agonist | First-line vasopressor for cardiogenic shock with SBP < 90 (Class IIb, LOE B) | Preferred over dopamine (SOAP II trial: lower mortality, fewer arrhythmias) |
| Dobutamine | 2-20 mcg/kg/min (typical start 2-5 mcg/kg/min) | Beta-1 > beta-2 agonist | Inotropic support for low cardiac output with adequate blood pressure | May cause hypotension (beta-2 vasodilation); may increase myocardial O2 demand; tachyarrhythmias |
| Dopamine | 2-20 mcg/kg/min; inotropic range: 5-10 mcg/kg/min; vasopressor range: > 10 mcg/kg/min | Dose-dependent: D1 → beta-1 → alpha-1 | Second-line to norepinephrine; may combine with dobutamine | More arrhythmias than norepinephrine (SOAP II); avoid as sole agent in severe shock |
| Milrinone | 0.375-0.75 mcg/kg/min (loading dose 50 mcg/kg over 10 min — often omitted in shock due to hypotension risk) | PDE-3 inhibitor (inodilator) | Low cardiac output with elevated SVR; right heart failure | Causes vasodilation; use with vasopressor; renally cleared — reduce in CKD; long half-life (2-3 hours) |
| Vasopressin | 0.01-0.04 units/min (fixed dose, no titration) | V1 receptor agonist | Adjunctive vasopressor for refractory hypotension | Does not increase myocardial O2 demand; catecholamine-sparing |
| Epinephrine | 0.01-0.5 mcg/kg/min | Alpha-1 + beta-1 + beta-2 agonist | Refractory cardiogenic shock, cardiac arrest | Potent inotrope and vasopressor but increases O2 demand, arrhythmogenic; use as rescue |
7.4 Mechanical Circulatory Support (MCS)
| Device | Mechanism | Hemodynamic Support | Key Considerations |
|---|
| Intra-aortic balloon pump (IABP) | Counterpulsation: inflates during diastole (augments coronary perfusion), deflates during systole (reduces afterload) | ~0.5 L/min CO augmentation | IABP-SHOCK II trial showed NO mortality benefit in cardiogenic shock; downgraded from routine use; may still have role as bridge or with mechanical complications; Class IIa for refractory shock after pharmacoinvasive approach |
| Impella (2.5, CP, 5.0, 5.5) | Axial flow pump across aortic valve; active LV unloading | Impella 2.5: 2.5 L/min; Impella CP: 3.5-4.0 L/min; Impella 5.0/5.5: 5.0-5.5 L/min | Provides superior hemodynamic support vs IABP; access via femoral artery (2.5, CP) or axillary artery cutdown (5.0/5.5); complications: hemolysis, limb ischemia, aortic regurgitation, device migration; no definitive mortality benefit in RCTs |
| TandemHeart | Percutaneous LA-to-femoral artery bypass via transseptal puncture | 3.5-5.0 L/min | Provides hemodynamic support; requires transseptal puncture; bleeding and limb ischemia risks |
| Extracorporeal membrane oxygenation (VA-ECMO) | Percutaneous or surgical veno-arterial bypass; oxygenation + circulatory support | 3-7 L/min | Provides both respiratory and circulatory support; useful in refractory shock, cardiac arrest (eCPR); complications: limb ischemia, bleeding, hemolysis, LV distension (may require venting); ECLS-SHOCK trial (2023): no mortality benefit with early ECMO in AMI cardiogenic shock |
7.5 Emergent Revascularization in Cardiogenic Shock
- Primary PCI is the cornerstone of cardiogenic shock management in STEMI (Class I, LOE B)
- Culprit-lesion-only PCI is recommended during the initial procedure (CULPRIT-SHOCK trial: culprit-only PCI was superior to immediate multivessel PCI in reducing 30-day composite of death or renal failure requiring dialysis)
- Staged complete revascularization may be considered after stabilization
8. Mechanical Complications of STEMI
Mechanical complications typically occur 1-14 days after STEMI (most commonly 3-5 days). They are surgical emergencies with high mortality.
8.1 Overview of Mechanical Complications
| Complication | Incidence | Timing | Presentation | Diagnosis | Management |
|---|
| Free wall rupture | 0.5-2% of STEMI (declining with primary PCI) | 1-14 days (peak 3-5 days); early rupture also possible within 24h | Acute: sudden PEA/death; Subacute: tamponade (hypotension, JVD, muffled hearts — Beck triad) | Echocardiography: pericardial effusion with/without tamponade; hemodynamic collapse | Immediate pericardiocentesis for tamponade (temporizing); emergent surgical repair; volume resuscitation; avoid inotropes that increase wall stress |
| Ventricular septal defect (VSD) | 0.2-0.5% | 1-14 days (peak 3-5 days) | New harsh holosystolic murmur + thrill at left lower sternal border; acute heart failure; cardiogenic shock | Echocardiography with color Doppler: left-to-right shunt across septum; step-up in O2 saturation from RA to PA on right heart catheterization | Hemodynamic stabilization (IABP, vasopressors); emergent surgical repair (mortality 20-50% even with surgery); percutaneous closure considered in select cases |
| Papillary muscle rupture | 0.5-1% | 2-7 days | New holosystolic murmur (may be soft if severe — “silent MR”); acute severe pulmonary edema; cardiogenic shock | Echocardiography: flail mitral leaflet, severe MR with eccentric jet; no step-up in O2 sat (distinguishes from VSD) | Afterload reduction (nitroprusside if BP tolerated, IABP); emergent surgical mitral valve repair or replacement |
8.2 Distinguishing VSD from Acute MR at Bedside
| Feature | Post-MI VSD | Acute MR (Papillary Muscle Rupture) |
|---|
| Murmur location | Left lower sternal border | Apex, radiating to axilla |
| Thrill | Often present | Usually absent |
| PCWP tracing | Normal or moderate V waves | Giant V waves |
| PA O2 saturation step-up | Present (> 5% increase from RA to PA) | Absent |
| Echocardiography | VSD visualized on color Doppler | Flail leaflet, severe MR |
| Territory | Anterior (apical VSD) or inferior (basal VSD) | Inferior MI (posteromedial papillary — single blood supply from PDA) » anterior MI (anterolateral papillary — dual supply from LAD + LCx) |
9. Arrhythmias in STEMI
9.1 Ventricular Arrhythmias
| Arrhythmia | Clinical Significance | Management |
|---|
| Ventricular fibrillation (VF) — primary | Within first 24-48 hours; does NOT independently predict long-term mortality if occurs early | Immediate defibrillation per ACLS; amiodarone 150 mg IV bolus for recurrent VF; lidocaine 1-1.5 mg/kg IV bolus alternative; correct electrolytes (K > 4.0, Mg > 2.0) |
| Ventricular fibrillation — late | After 48 hours; associated with poor prognosis and need for ICD evaluation | Revascularization optimization; electrolyte correction; ICD evaluation before discharge |
| Sustained ventricular tachycardia (VT) | Monomorphic VT > 30 sec or causing hemodynamic compromise | Hemodynamically unstable: immediate cardioversion. Stable: amiodarone 150 mg IV over 10 min, may repeat; then 1 mg/min × 6h, then 0.5 mg/min × 18h. Alternative: lidocaine |
| Non-sustained VT (NSVT) | Common; does not require specific antiarrhythmic therapy unless causing hemodynamic symptoms | Monitor; optimize reperfusion and electrolytes; beta-blocker when hemodynamically appropriate |
| Accelerated idioventricular rhythm (AIVR) | Rate 60-100 bpm; common reperfusion arrhythmia; benign | No treatment needed; sign of successful reperfusion |
9.2 Bradyarrhythmias and Conduction Disease
| Arrhythmia | Association | Management |
|---|
| Sinus bradycardia | Inferior MI (vagal response); early reperfusion | Atropine 0.5-1.0 mg IV if symptomatic; temporary pacing if atropine-refractory |
| First-degree AV block | Inferior MI | Usually benign; monitor |
| Second-degree AV block — Mobitz Type I (Wenckebach) | Inferior MI (AV nodal ischemia) | Usually transient; atropine if symptomatic; temporary pacing rarely needed |
| Second-degree AV block — Mobitz Type II | Anterior MI (infranodal/His-Purkinje ischemia) | Higher risk of progression to complete heart block; transcutaneous pacing standby; transvenous pacing often needed |
| Third-degree (complete) AV block | Inferior MI: junctional escape (narrow QRS, rate 40-60, often transient). Anterior MI: ventricular escape (wide QRS, rate < 40, poor prognosis) | Inferior + narrow escape: atropine, temporary pacing if needed; usually resolves. Anterior + wide escape: emergent temporary transvenous pacing; high mortality; consider permanent pacemaker evaluation |
| New LBBB or bifascicular block | Anterior MI; suggests extensive infarction | Monitor for progression; transcutaneous pacing standby; transvenous pacing if progresses to high-grade block |
9.3 Supraventricular Arrhythmias
| Arrhythmia | Incidence in STEMI | Management |
|---|
| Atrial fibrillation | 10-20% of STEMI | Rate control (beta-blocker if no HF; amiodarone if HF or hypotension); anticoagulation if persists > 48h; cardioversion if hemodynamically unstable |
| Atrial flutter | Less common than AF | Same principles as AF |
References