Table of Contents
Cough syncope is an uncommon yet serious complication of chronic coughing that can pose a significant health risk. Early recognition, thorough diagnostic assessment, and proper guidance on driving restrictions are essential to ensuring both patient safety and public well-being.
Epidemiology & Risk Factors
- Typical Patient Profile:
- Middle-aged, Persons with a higher body weight with a history of smoking and COPD.
- Also reported in asthma patients (pediatric cases) and those with chronic bronchitis.
- Precipitating Factors:
- Paroxysmal coughing fits (often vigorous, prolonged).
- Increased intrathoracic pressure (e.g., forced expiration, Valsalva-like maneuvers).
Clinical Presentation of Cough Syncope
- Syncope Timing:
- Occurs suddenly or within 3–5 sec after coughing.
- Prodromal Symptoms:
- Lightheadedness, visual blurring, or dizziness.
- Associated Features:
- Tonic-clonic movements (10–47% of cases) → May mimic seizures.
- Rapid recovery (seconds) without postictal confusion.
- Prognosis:
- Mostly benign, but 1–2% mortality in patients with underlying cardiovascular disease.
Pathophysiology of Cough Syncope
Several theories explain cough syncope:
1. Peripheral Vasodilation (Sharpey-Schafer, 1953)
- What happens: Hard coughing makes blood vessels suddenly widen
- Effect: Blood pressure drops fast (“cough → ↓BP”)
- Result: Brain doesn’t get enough blood → fainting (“syncope”)
Reduced Cardiac Output (Gastaut et al., 1966)
- What happens: Coughing squeezes chest veins so hard that less blood returns to heart
- Effect: Heart pumps less blood (“↓Venous return”)
- Result: Brain blood flow drops (“cerebral hypoperfusion”) → pass out
Increased Brain Pressure (Kerr et al., 1961)
- What happens: Cough jams fluid pressure inside skull (“↑ICP”)
- Effect: Squeezes brainstem (like a concussion)
- Result: Temporary “shut off” switch for consciousness
Brain Blood Flow Stops (Mattle et al., 1995)
- Proof: Special ultrasound (TCD) showed middle brain artery flow actually stops during cough
- Like: Pinching a garden hose completely for a few seconds
- Why it matters: Even brief stops can cause fainting
Neck Artery Slowdown (Desser et al., 1973)
- Proof: Measurements showed neck arteries slow down 18-62% during cough
- Like: Partially kinking that garden hose
- Important: Proves coughing directly reduces brain’s blood supply
| Mechanism | Proposed By | Key Findings |
|---|---|---|
| Peripheral Vasodilation | Sharpey-Schafer (1953) | Cough → ↓BP → Syncope |
| Reduced Cardiac Output | Gastaut et al. (1966) | ↓Venous return → Cerebral hypoperfusion |
| Increased ICP ("Concussion") | Kerr et al. (1961) | Cough → ↑ICP → Brainstem compression |
| Cerebral Circulatory Arrest | Mattle et al. (1995) | TCD shows MCA flow cessation during cough |
| Carotid Blood Flow Reduction | Desser et al. (1973) | ↓Carotid velocity (18–62%) during cough |
Most Likely Mechanism:
- Combination of ↑intrathoracic pressure + ↓cerebral perfusion due to:
- Impaired venous return (reduced cardiac output).
- Vasovagal reflex (peripheral vasodilation).
Diagnosis of Cough syncope
1. Electrocardiogram (ECG)
Purpose: To detect arrhythmias or conduction abnormalities that may cause syncope.
Key Findings to Assess:
- Atrial Fibrillation (AF): Irregularly irregular rhythm, absent P waves.
- Heart Block:
- Prolonged PR interval (>200 ms) → 1st-degree block.
- Dissociation of P waves from QRS complexes → 2nd/3rd-degree block.
- Prolonged QT Interval (QTc >450 ms in men, >470 ms in women) → Risk of torsades de pointes.
- Right Axis Deviation & P Pulmonale (tall P waves in II, III, aVF) → May suggest pulmonary hypertension.
2. Echocardiogram (ECHO)
Purpose: To assess cardiac structure and function.
Key Features to Evaluate:
- Pericardial Effusion/Inflammation (e.g., tamponade, pericarditis).
- Left Ventricular (LV) Function (e.g., LV hypertrophy, cardiomyopathy, ejection fraction).
- Pulmonary Hypertension (PH):
- Elevated right ventricular systolic pressure (RVSP).
- Right ventricular hypertrophy (RVH).
- Valvular Disease (e.g., aortic stenosis, mitral regurgitation).
3. Cardiac Event Monitor (Holter/Loop Recorder)
Purpose: To capture intermittent arrhythmias not seen on a single ECG.
Indications:
- Suspected paroxysmal AF, bradyarrhythmias, or tachyarrhythmias.
- Syncope with palpitations but normal initial ECG.
4. Tilt Table Test
Purpose: To diagnose autonomic dysfunction (e.g., vasovagal syncope, postural hypotension).
Procedure:
- Patient is tilted upright (60-80°) while monitoring HR and BP.
- Positive test: Sudden BP drop ± bradycardia reproducing syncope.
5. Neurological Workup (If Red Flags Present)
Red Flag Symptoms/Signs:
- Headache, blurred vision, focal weakness, paraesthesia, or seizure-like activity.
Investigations:
- Urgent Brain Imaging (CT/MRI):
- Rule out stroke, mass lesion, or subarachnoid hemorrhage.
- EEG (if seizure suspected):
- Syncope can mimic seizures (e.g., convulsive syncope).
Clinical Approach
- High-Risk Features (Urgent Workup):
- Sudden collapse, no prodrome, abnormal ECG, or structural heart disease → Cardiac workup first.
- Low-Risk Features (Stepwise Evaluation):
- Prodromal dizziness, situational triggers → Tilt test or autonomic evaluation.
- Neurological Red Flags → Immediate imaging.
Management & Prognosis
Treat Underlying Cause
- COPD/Asthma Control:
- Smoking cessation, bronchodilators, corticosteroids.
- Antitussives (e.g., codeine, dextromethorphan) if chronic cough.
2. Lifestyle & Safety Measures
- Avoid driving until cough is controlled (risk of accidents).
- Sit or brace during coughing fits to reduce fall risk.
3. Prognosis
- Excellent with proper management.
- Recurrence rare if pulmonary disease is treated.
