Septic Cardiomyopathy (Sepsis-Induced Myocardial Dysfunction, SIMD)
Septic cardiomyopathy (SCM) is an acute, reversible myocardial dysfunction occurring during sepsis or septic shock(20–60% of septic shock patients), characterized by:
- Reduced myocardial contractility
- Ventricular dilatation
- Impaired response to fluid and catecholamines
- Usually recovers within 7–10 days in survivors
SCM occurs without acute coronary artery occlusion and is caused by complex inflammatory, metabolic, microcirculatory, and mitochondrial mechanisms.
Pathophysiology
SCM is multifactorial.
Mechanism | Most Important Details |
1. Cytokine-Mediated Myocardial Depression | TNF-α, IL-1β, IL-6, HMGB-1 cause negative inotropy, ↓ calcium sensitivity, and myocyte injury → ↓ myocardial contractility. |
2. Nitric Oxide (NO) Excess | Sepsis induces iNOS → excessive NO production, causing vasodilation, mitochondrial dysfunction, and direct myocardial depression → ↓ contractility. |
3. Mitochondrial Dysfunction | Oxidative stress inhibits ATP production, leading to energy failure and “myocardial hibernation” (reversible reduction in cardiac function). |
4. Calcium Handling Abnormalities | Reduced calcium influx, sarcoplasmic reticulum dysfunction, and decreased troponin sensitivity impair excitation-contraction coupling → ↓ contractility. |
5. Coronary Microcirculatory Dysfunction | Endothelial dysfunction, capillary leak, and microthrombi cause impaired myocardial perfusion despite normal epicardial coronaries → functional ischemia. |
6. Autonomic Dysregulation | Excess catecholamines and β-receptor downregulation lead to tachycardia, arrhythmias, and reduced response to inotropes. |
7. Myocardial Edema | Inflammation-induced capillary leak causes myocardial edema, reduced ventricular compliance, and diastolic dysfunction. |
Historical Triad of Septic Cardiomyopathy
Feature | Description |
LV dilatation | Increased LV end-diastolic volume |
Reduced EF | EF often <45–50% |
Reversibility | Recovery within 7–10 days |
Today SCM includes:
- LV systolic dysfunction
- LV diastolic dysfunction
- RV dysfunction
- Biventricular dysfunction
Clinical Features
No specific symptoms.
Suspect when septic shock patient develops:
- Persistent hypotension
- High vasopressor requirement
- Elevated lactate
- Low ScvO₂
- Poor perfusion
- Pulmonary edema despite shock
Biomarkers
- Troponin-Elevated in:40–85% of septic shock patients.Reasons:Membrane leak,Cytokine injury,Microvascular ischemia.Not necessarily MI.
- BNP / NT-proBNP-Usually elevated.Reflects:Ventricular stretch,Fluid overload,Cardiac dysfunction.Poor specificity.
Echocardiographic Features
- Reduced EF-Often:EF <50% but EF alone may be misleading because:Low afterload artificially increases EF.(GLS is more sensitive than EF for early detection.)Therefore EF may appear normal despite dysfunction.
- Global Hypokinesia-Most characteristic feature.Unlike MI:No regional wall motion abnormalities.
- LV Dilatation-compensatory mechanism.Allows preservation of stroke volume.
- Diastolic Dysfunction-Increasingly recognized..May occur even when EF normal.Associated with:Pulmonary edema
- Right Ventricular Dysfunction-Very common.Especially in:ARDS,Mechanical ventilation,High PEEP,Pulmonary hypertension
Differential Diagnosis
Condition | Distinguishing Features |
Acute MI | Regional wall motion abnormality |
Takotsubo cardiomyopathy | Apical ballooning |
Viral myocarditis | MRI findings |
Dilated cardiomyopathy | Chronic history |
Pulmonary embolism | RV strain pattern |
Management
There is NO specific therapy proven to reverse SCM.
Treatment is mainly supportive.(treat sepsis)
Role of Beta-Blockers
Recent concept.
Excess sympathetic stimulation may worsen injury.
Esmolol
May help when:
- Persistent sinus tachycardia (>95–100/min)
- Adequately resuscitated
- Stable vasopressor support
Potential benefits:
- Improved ventricular filling
- Reduced oxygen demand
Not routine therapy.