Cardiology

Background

Obstructive shock is a form of shock characterized by decreased cardiac output due to a physical obstruction impeding either cardiac filling or ejection of blood. Despite preserved myocardial function, circulation fails due to impaired preload or increased afterload. Common causes include tension pneumothorax, cardiac tamponade, and massive pulmonary embolism. If untreated, it rapidly leads to tissue hypoperfusion, organ failure, and death. 


II) Classification or Types

By Mechanism of Obstruction: 

• Impaired Venous Return (preload): 

• Tension pneumothorax 

• Cardiac tamponade 

• Constrictive pericarditis 

• Superior vena cava (SVC) syndrome 

• Increased Right Ventricular Afterload: 

• Massive pulmonary embolism 

• Severe pulmonary hypertension 

• Increased Left Ventricular Afterload: 

• Aortic stenosis (critical) 

• Hypertrophic obstructive cardiomyopathy 

• Aortic dissection involving the ascending aorta 

III) Epidemiology 

• Sex: No strong predilection, but specific causes (e.g., PE more common in females with hormonal risk factors) may vary. 

• Age: More common in older adults due to comorbidities (e.g., cancer, atrial fibrillation, pericardial disease). 

• Setting: Often presents in critical care, trauma, or emergency departments. 

• Comorbidities: Increased incidence in patients with malignancy, coagulopathy, or cardiac disease. 

Etiology

I) What Causes It

• Tension pneumothorax 

• Cardiac tamponade (trauma, malignancy, pericarditis) 

• Massive pulmonary embolism 

• Constrictive pericarditis 

• Severe pulmonary hypertension 

• Critical aortic stenosis 

• Aortic dissection with tamponade 

• Intracardiac tumor/thrombus obstructing outflow 

II) Risk Factors

• Central venous catheters or mechanical ventilation 

• Known malignancy (esp. with pericardial involvement or PE risk) 

• Atrial fibrillation or prolonged immobility (PE risk) 

• Connective tissue disorders (aortic dissection) 

• Recent cardiac surgery or trauma 

• Hypercoagulable states (e.g., pregnancy, thrombophilia) 

Clinical Presentation

I) History (Symptoms)

• Sudden-onset dyspnea 

• Chest pain (pleuritic with PE or aortic dissection) 

• Syncope or near-syncope 

• Anxiety, restlessness 

• Severe fatigue, lightheadedness 

• Cough (with hemoptysis in PE) 

• Oliguria in advanced cases 

II) Physical Exam (Signs)

Vital Signs: 

• Hypotension (often severe) 

• Tachycardia 

• Tachypnea 

• Low oxygen saturation (in PE or pneumothorax) 

Cardiac Exam: 

• Distant/muffled heart sounds (cardiac tamponade) 

• Prominent jugular venous distension 

• Pulsus paradoxus (tamponade) 

• Loud P2 component (PE) 

Pulmonary: 

• Unilateral absent breath sounds (tension pneumothorax) 

• Dullness or hyperresonance on percussion 

Peripheral: 

• Cold, clammy extremities 

• Cyanosis or mottling in late stages 

• Signs of DVT (in PE) 

Differential Diagnosis (DDx)

• Cardiogenic shock 

• Hypovolemic shock 

• Septic shock 

• Myocardial infarction 

• Tension pneumothorax (if not initially identified) 

• Acute pericarditis or pericardial effusion 

• Pulmonary embolism 

• Aortic dissection 

Diagnostic Tests

Initial Tests: 

Bedside Ultrasound (POCUS): 

• Pericardial effusion with diastolic collapse (tamponade) 

• Right ventricular dilation (PE) 

• Absence of lung sliding (pneumothorax) 

• IVC plethora with minimal variation 

ECG: 

• Electrical alternans (tamponade) 

• Right heart strain (S1Q3T3 pattern in PE) 

• ST elevations in specific leads (if dissection involves coronary arteries) 

Chest X-ray: 

• Enlarged cardiac silhouette (tamponade) 

• Hyperlucent hemithorax (pneumothorax) 

• Widened mediastinum (aortic dissection) 

CT Chest with Contrast (CTPA): 

• Gold standard for pulmonary embolism 

• May identify aortic dissection 

Echocardiography (TTE or TEE): 

• Tamponade, PE, or severe valvular disease 

• Can identify obstructive masses or septal motion abnormalities 

Labs: 

• ABG: hypoxia, acidosis 

• Elevated lactate (tissue hypoperfusion) 

• Troponins (if RV strain or myocardial infarction) 

• D-dimer (screening for PE) 

Treatment

I) Medical Management

Immediate Stabilization: 

• Airway & Breathing: High-flow oxygen; intubation if needed 

• Circulation: IV fluids with caution (especially in tamponade or PE) 

• Vasopressors: Norepinephrine for hypotension 

Condition-Specific Therapies: 

• Tamponade: Emergent pericardiocentesis 

• Tension pneumothorax: Immediate needle decompression followed by chest tube 

• Massive PE: Systemic thrombolysis (e.g., tPA), catheter-directed thrombolysis, or surgical embolectomy 

• Aortic dissection: Blood pressure and heart rate control (beta-blockers), surgical repair for type A 

• Constrictive pericarditis: Diuretics; eventual pericardiectomy 

II) Interventional/Surgical

• Pericardiocentesis or pericardial window 

• Chest tube placement 

• Catheter-directed thrombolysis or embolectomy (PE) 

• Endovascular or open surgical repair (dissection) 

• Valve replacement (severe aortic stenosis) 

Patient Education, Screening, Vaccines

• Recognizing early symptoms (e.g., pleuritic chest pain, sudden SOB) 

• Importance of DVT prevention in high-risk patients 

• Compression stockings, anticoagulation as prophylaxis post-op or during immobility 

• Encourage mobility and hydration 

Vaccinations: 

• Influenza annually 

• Pneumococcal vaccination (esp. for those with underlying cardiopulmonary disease) 

• COVID-19 vaccination 

Consults

• Critical Care/ICU: For hemodynamic support and monitoring 

• Cardiology: If tamponade, PE, valvular obstruction 

• Cardiothoracic Surgery: For dissection or cardiac masses 

• Pulmonology: For PE management 

• Vascular Surgery: For aortic pathology 

• Hematology: For thromboembolic disorders 

• Primary Care/Internal Medicine: For long-term risk factor management 

Follow-Up

• After Resolution of Acute Episode: 

• Monitor for recurrence (especially in PE or tamponade) 

• Echocardiographic follow-up if cardiac involvement 

• Surveillance imaging in chronic aortic conditions 

• Ongoing Management: 

• Anticoagulation monitoring (for PE or atrial fibrillation) 

• Cardiac rehabilitation if post-op or post-shock recovery 

• Optimize chronic disease management (e.g., cancer, heart failure) 

• Education on red-flag symptoms requiring emergent care