Septic Cardiomyopathy

Septic cardiomyopathy is acute, reversible myocardial dysfunction during sepsis, affecting both ventricles. It is usually defined by a left ventricular ejection fraction under 45 to 50% or reduced global longitudinal strain, with ventricular dilatation and normal or low filling pressures. It occurs in 20 to 60% of patients with septic shock, depending on the definition and the timing of echocardiography.

Mechanisms

• Circulating cytokines (TNF alpha, IL-1 beta, IL-6) and complement fragments that depress contractility
• Excess nitric oxide and reactive oxygen species causing mitochondrial dysfunction
• Impaired calcium handling and adrenergic receptor downregulation
• Microvascular dysfunction and endothelial injury
• Catecholamine toxicity from high-dose vasopressors and endogenous release

Because the ventricle dilates, stroke volume can be preserved at a lower ejection fraction, so cardiac output may be normal or high. The dysfunction appears within 48 to 72 hours of onset and recovers over 7 to 10 days in survivors. Persistent or right ventricular dysfunction predicts worse outcome. Complications: low-output shock, pulmonary edema, arrhythmia (atrial fibrillation), myocardial injury with raised troponin and failure to wean from vasopressors.

• Persistent hypotension despite adequate fluids and vasopressors
• Cool, mottled peripheries with delayed capillary refill, oliguria and rising lactate despite adequate pressure
• Tachycardia, dyspnea, raised jugular venous pressure or crackles in some
• Warm shock early and a cold, low-output state later
• Red flags: lactate rising despite a mean arterial pressure above 65 mmHg, new arrhythmia, pulmonary edema and escalating vasopressor need

1. Bedside echocardiography repeated daily in shock: left ventricular ejection fraction under 50%, global hypokinesis, dilated left ventricle, reduced global longitudinal strain (less negative than -16%), right ventricular dysfunction (tricuspid annular plane systolic excursion under 17 mm) and filling pressure estimates.
2. Troponin and natriuretic peptide (raised but nonspecific), lactate and central venous oxygen saturation (below 70% suggests low output).
3. ECG: sinus tachycardia, ST and T wave changes, arrhythmia.
4. Advanced hemodynamic monitoring (pulse contour analysis, thermodilution or pulmonary artery catheter) when shock persists: cardiac index under 2.5 L/min/m2.
5. Exclusion of other causes: coronary angiography when ischemia is possible, and assessment for takotsubo cardiomyopathy, tamponade and pulmonary embolism.

Differentials: acute coronary syndrome, takotsubo cardiomyopathy, pulmonary embolism, tamponade, pre-existing cardiomyopathy and drug-induced myocardial depression.

1. Treat sepsis:
   • Antibiotics within 1 hour: piperacillin-tazobactam 4.5 g IV every 6 hours (children 100 mg/kg of piperacillin every 8 hours), or meropenem 1 g IV every 8 hours (children 20 mg/kg every 8 hours), adjusted to the likely source and local resistance.
   • Source control by drainage, debridement or removal of infected devices.
2. Fluids: balanced crystalloid 30 mL/kg IV in the first 3 hours, then further boluses of 250 to 500 mL only when dynamic measures predict responsiveness. Excess fluid causes pulmonary edema in a failing ventricle.
3. Vasopressor: norepinephrine 0.05 to 0.5 micrograms/kg/min IV to a mean arterial pressure of at least 65 mmHg. Add vasopressin 0.03 units/min IV to reduce norepinephrine requirement.
4. Inotrope for persistent low output or hypoperfusion despite adequate pressure and volume:
   • Dobutamine 2.5 to 20 micrograms/kg/min IV, titrated to cardiac index, urine output and lactate.
   • Epinephrine 0.02 to 0.2 micrograms/kg/min IV as an alternative.
   • Levosimendan 0.05 to 0.2 micrograms/kg/min IV without a bolus for 24 hours in catecholamine-resistant dysfunction (watch for hypotension).
5. Corticosteroid: hydrocortisone 50 mg IV every 6 hours when norepinephrine remains at 0.25 micrograms/kg/min or more for 4 hours.
6. Tachycardia after resuscitation: esmolol 25 to 100 micrograms/kg/min IV in selected patients with a heart rate above 95 beats a minute despite adequate filling, under intensive monitoring.
7. Atrial fibrillation with instability: synchronized cardioversion, or amiodarone 150 mg IV over 10 minutes then 1 mg/min for 6 hours then 0.5 mg/min.
8. Refractory cardiogenic component: venoarterial extracorporeal membrane oxygenation in selected patients.
9. Supportive care: lung-protective ventilation, renal replacement therapy as needed, and glucose control at 8 to 10 mmol/L.

Follow-up: repeat echocardiography at 7 to 10 days and at 3 months. If ejection fraction remains under 40%, start ramipril 1.25 mg twice daily and carvedilol 3.125 mg twice daily after stabilization. Counsel on recovery.