Cardiogenic Shock, Mechanical MI Complications & LVADs

Triage, SCAI Staging & LVAD Hardware Audit: Place on cardiac monitor, pulse oximetry, and cycle NIBP. If LVAD patient: auscultate precordium for continuous mechanical hum; use Doppler probe + manual cuff over brachial artery to measure Mean Arterial Pressure (MAP = first audible Doppler sound); inspect controller for alarms, battery power, and driveline integrity [1,2,3].

First-Line Vasopressor (Cardiogenic Shock / LVAD Hypotension): Start Norepinephrine at 0.05–0.5 mcg/kg/min IV (3.75–37.5 mL/hr of 64 mcg/mL bag for 80 kg). Target MAP ≥ 65 mmHg in standard CS, or MAP 70–80 mmHg in LVAD patients (never > 90 mmHg) [1,2,4].

Restores diastolic coronary perfusion pressure (CPP = DBP − LVEDP) via α vasoconstriction and mild β₁ inotropy with significantly fewer fatal arrhythmias than Dopamine (SOAP II) or Epinephrine (OptimaCC) [4,5].

12-Lead ECG & Immediate RUSH/Cardiac POCUS: Obtain 12-lead ECG within 2 min (identify STEMI/OMI, right ventricular infarction via V4R, or ventricular arrhythmias). Perform 4-view Cardiac + Lung POCUS to differentiate LV pump failure, RV shock, Papillary Muscle Rupture (acute MR), Ventricular Septal Rupture (VSR), Free Wall Rupture (Tamponade), or LVAD Suction Event [1,3,6].

Right Ventricular Infarction / LVAD Suction Override: Infuse a controlled 250–500 mL isotonic crystalloid bolus ONLY if lungs show A-lines (no B-lines) and LV is underfilled or RV is acutely dilated without pulmonary edema [1,3]. If LV failure with B-lines: Strictly withhold IV fluids [1].

Optimizes Frank-Starling preload in RV infarction or relieves leftward interventricular septal shift ("suction event") in an underfilled LVAD cavity without tipping a failing LV over the descending Starling limb [1,3].

Invasive Hemodynamics & Contractile Support: Insert a 20G radial or femoral arterial line (ultrasound-guided required in non-pulsatile LVAD patients) and central venous catheter. Draw arterial lactate, central venous ScvO₂, ABG, hs-Troponin, BNP, CBC, Coags, LDH, and plasma-free hemoglobin (if LVAD thrombosis suspected) [1,2,3].

First-Line Inotrope (Low Cardiac Index < 2.2 L/min/m² once MAP ≥ 65 mmHg): Start Dobutamine 2.5–10 mcg/kg/min IV (6–24 mL/hr of 2,000 mcg/mL bag for 80 kg; max 20 mcg/kg/min) [1,7]. Alternative (if on chronic β-blockers or severe Pulmonary HTN): Milrinone 0.125–0.375 mcg/kg/min IV (omit bolus) [1,7].

β-receptor stimulation (Dobutamine) or PDE-3 inhibition (Milrinone) increases intracellular cAMP and sarcoplasmic reticulum Ca²⁺ release, shifting the End-Systolic Pressure-Volume Relationship (Eₑₛ) upward and leftward [1,7].

Culprit-Vessel Revascularization & Mechanical Complication Unloading:
• AMI-CS: Activate Cath Lab for immediate Culprit-Lesion-Only PCI (avoid routine multivessel PCI in acute shock — CULPRIT-SHOCK) [1,8].
• Acute MR / VSR with SBP > 90 mmHg: Add vasodilator + place IABP / Impella / VA-ECMO as bridge to surgery [6].

Acute Mechanical MR / VSR Afterload Reduction (Once SBP > 90 mmHg on Inotrope): Add Sodium Nitroprusside 0.3–2 mcg/kg/min IV (7.2–48 mL/hr of 200 mcg/mL bag for 80 kg) + Dobutamine 5–10 mcg/kg/min [6].

Lowering systemic vascular resistance (SVR) reduces the impedance to forward aortic ejection, decreasing the regurgitant fraction across a ruptured mitral valve or left-to-right shunt fraction (Qₚ/Qₛ) across a VSR [6].

Airway Stabilization & Temporary Mechanical Circulatory Support (tMCS) Activation: Avoid premature RSI until pressors are running. If hypoxic respiratory failure or severe metabolic acidosis mandates intubation, use hemodynamically neutral RSI and activate the Shock Team (Impella CP / VA-ECMO) [1,9].

Cardiogenic Shock RSI: Pre-treat with Norepinephrine infusion running + Fentanyl 0.5–1 mcg/kg + Etomidate 0.15–0.2 mg/kg (12–16 mg IV) or Ketamine 0.5–1 mg/kg + Rocuronium 1.2 mg/kg (100 mg IV) [1]. Set PEEP at 5–8 cmH₂O (low PEEP 3–5 cmH₂O in isolated RV failure) [1].

Positive-pressure ventilation in LV failure reduces LV transmural afterload (Pₜₘ = PLV − Ppleural) and unloads the failing LV, whereas excessive PEEP in RV failure compresses alveolar capillaries and worsens RV afterload [1].