Cardiogenic Shock and Ejection Fraction
No, ejection fraction (EF) does not have to be decreased in cardiogenic shock, as cardiogenic shock can occur with preserved systolic function through different pathophysiological mechanisms. 1, 2
Definition and Pathophysiology
Cardiogenic shock is defined as a state of inadequate cardiac output to meet the demands of the tissues, resulting in end-organ hypoperfusion 1. While most commonly associated with reduced left ventricular (LV) systolic function, cardiogenic shock can occur through several mechanisms:
Reduced EF cardiogenic shock: The most common form, typically resulting from extensive myocardial necrosis (at least 40% of LV) or stunning of viable myocardium 1
Preserved EF cardiogenic shock: Can occur through several mechanisms:
Cardiogenic Shock with Preserved EF
Several clinical scenarios can lead to cardiogenic shock despite normal or preserved EF:
RV infarction: Can present with cardiogenic shock while LV function remains preserved 1
- Echocardiography may show RV dyssynergy, dilatation, paradoxical septal motion, and McConnell sign
- Decreased tricuspid annulus systolic excursion (TAPSE) is usually present 1
Mechanical complications: Free wall rupture, ventricular septal rupture, or papillary muscle rupture can cause cardiogenic shock despite preserved LV systolic function 1
Valvular disease: Acute severe mitral regurgitation can lead to cardiogenic shock with preserved EF 1
Normal EF low cardiac output shock: In some cases, the functional LV cavity size may be insufficient to maintain adequate cardiac output despite normal EF 3
Clinical Evidence
Recent research has provided insights into the relationship between EF and cardiogenic shock:
A 2022 study found that approximately 32.6% of patients with cardiogenic shock after acute myocardial infarction had mid-range EF (41-49%), and 32% had preserved EF (≥50%) 4
Patients with preserved EF cardiogenic shock had lower 30-day mortality (32%) compared to those with reduced EF (72.7%) 4
A 2024 study examining non-ischemic cardiogenic shock found that mechanical circulatory support was more beneficial in patients with LVEF ≤20% compared to those with higher EF values 5
Diagnostic Approach
When cardiogenic shock is suspected, immediate transthoracic echocardiography (TTE) should be performed to:
- Confirm the diagnosis and identify the underlying cause 1
- Assess ventricular function (both LV and RV) 1
- Evaluate for mechanical complications 1
- Rule out other causes of shock 1
If TTE is suboptimal, transesophageal echocardiography (TOE) may be indicated 1.
Management Considerations
Management should be tailored based on the underlying mechanism:
For reduced EF cardiogenic shock: Standard heart failure therapies and mechanical circulatory support may be beneficial 5
For preserved EF cardiogenic shock: Treatment should target the specific cause (e.g., surgical repair for mechanical complications, right-sided support for RV failure) 1, 2
RV function assessment is crucial, as 3D echocardiography-derived RV ejection fraction >24.6% has been associated with higher success rates of weaning from VA-ECMO and lower 30-day mortality 6
Clinical Pitfalls
Focusing only on LV ejection fraction: Reporting EF in isolation can be misleading in cardiogenic shock evaluation 3
Overlooking RV dysfunction: RV failure can cause cardiogenic shock despite normal LV function 1
Missing mechanical complications: Careful echocardiographic assessment is essential to identify mechanical causes of cardiogenic shock 1
Delayed diagnosis of preserved EF shock: The prognosis of acute cardiogenic shock with preserved EF can be favorable if promptly diagnosed and appropriately treated 2