Cardiogenic Shock

A 72-year-old male presents to the emergency department with severe chest pain and progressive shortness of breath for 4 hours. The pain is sudden in onset, substernal, crushing, radiates to the left arm and jaw, and is associated with diaphoresis, nausea, and vomiting. He has a history of hypertension, type 2 diabetes mellitus, ischemic heart disease, and heart failure with reduced ejection fraction, and is a current smoker with a 40 pack-year history. On examination, he appears pale, anxious, and diaphoretic, with a blood pressure of 80/55 mmHg, heart rate of 118/min, respiratory rate of 30/min, and oxygen saturation of 88 percent on room air. His extremities are cold and clammy with delayed capillary refill. Jugular venous distension is present, and lung auscultation reveals bilateral basal crackles. Cardiac examination demonstrates an S3 gallop, and urine output is markedly reduced. Electrocardiography shows ST-segment elevation in leads V1 to V4. Laboratory evaluation reveals elevated troponin and a serum lactate of 5.2 mmol/L. Bedside echocardiography demonstrates severe left ventricular systolic dysfunction with an ejection fraction of approximately 25 percent and anterior wall hypokinesis. Right heart catheterization shows a cardiac index of 1.7 L/min/m² and a pulmonary capillary wedge pressure of 24 mmHg. Diagnosis?

Diagnosis is Acute Myocardial Infarction Related Cardiogenic Shock (AMI-CS).

1. Definition

Cardiogenic shock is a clinical syndrome of end-organ hypoperfusion due to primary cardiac pump failure, typically characterized by:

1. Hypotension (SBP <90 mmHg or MAP <65 mmHg)
2. Evidence of hypoperfusion:
1. Oliguria
2. Altered mental status
3. Lactate >2 mmol/L
3. Hemodynamic evidence:
1. Cardiac index <2.2 L/min/m²
2. Elevated PCWP >18 mmHg (LV dominant shock)

Cardiogenic shock may occur without overt hypotension.

2. Etiology

2.1 Primary

1. Acute myocardial infarction
2. Acute decompensated heart failure

2.2 Mechanical Complications (Must Not Be Missed)

1. Papillary muscle rupture leading to acute mitral regurgitation
2. Ventricular septal rupture
3. Free wall rupture

2.3 Electrical

1. Ventricular tachyarrhythmias
2. Complete heart block

2.4 Other

1. Myocarditis
2. Severe valvular disease
3. Right ventricular infarction

 

3. Pathophysiology

3.1 Core Mechanism

1. Decreased contractility
2. Decreased cardiac output
3. Hypotension
4. Hypoperfusion

3.2 Compensatory Mechanisms

1. Sympathetic activation → vasoconstriction → increased afterload
2. RAAS activation → fluid retention → increased preload

3.3 Vicious Cycle

1. Increased LVEDP → pulmonary edema
2. Reduced coronary perfusion → worsening ischemia
3. Lactic acidosis
4. Multiorgan failure

4. Hemodynamic Profile

1. Decreased cardiac index
2. Increased PCWP (LV dominant shock)
3. Increased right atrial pressure
4. Increased systemic vascular resistance

PCWP may be normal or low in RV shock

5. Classification

5.1 SCAI Shock Staging

1. Stage A: At risk
2. Stage B: Beginning shock
3. Stage C: Classic shock
4. Stage D: Deteriorating
5. Stage E: Extremis

First 24 hours are critical

5.2 Phenotypes

1. LV dominant congested phenotype
2. RV shock
3. Biventricular cardiometabolic phenotype

6. Clinical Features

6.1 Core Features

1. Hypotension
2. Cold, clammy extremities
3. Oliguria
4. Altered mental status
5. Elevated lactate

6.2 Cardiac Findings

1. S3 gallop
2. Elevated JVP
3. Pulmonary crackles

7. Diagnosis

7.1 Laboratory

1. Lactate >2 mmol/L
2. Elevated troponin

7.2 ECG

1. ST elevation
2. Arrhythmias

7.3 Echocardiography

1. Reduced LVEF
2. Regional wall motion abnormalities
3. Mechanical complications

7.4 Hemodynamic Monitoring

1. Cardiac index <2.2
2. Elevated PCWP

7.5 Key Prognostic Parameter

CPO = (MAP × CO) / 451

1. Strong predictor of mortality
2. CPO <0.6 W indicates severe shock

8. Management

8.2 Hemodynamic Support

Vasopressor

1. Norepinephrine (first line)

Inotropes

1. Dobutamine
2. Milrinone (risk of hypotension)

8.3 Definitive Therapy

AMI-CS

1. Immediate PCI (life-saving)

8.4 Mechanical Support

Impella

1. LV unloading
2. Improves cardiac output
3. Mortality benefit in selected patients (DanGer Shock)

IABP

1. No routine mortality benefit

VA ECMO

1. Refractory shock
2. Biventricular failure

10. Key Clinical Insight

1. Acute MI + hypotension + hypoperfusion = cardiogenic shock
2. Low CI + high PCWP = LV shock
3. Requires:
1. Immediate recognition
2. Urgent PCI
3. Norepinephrine ± inotrope
4. Early mechanical support

11. Exam Level Pearls

1. Cold and wet patient = cardiogenic shock
2. Lactate >2 mmol/L = hypoperfusion
3. Norepinephrine > dopamine
4. PCI improves survival
5. Mechanical complications must not be missed