Is coughing syncope a form of vasovagal (vasovagal) syncope?

Cough Syncope is a Form of Situational Syncope, Not Classical Vasovagal Syncope

Cough syncope is classified as a situational syncope, which is a specific subtype of neurally-mediated (reflex) syncope, but it is distinct from classical vasovagal syncope in its triggering mechanism and pathophysiology. 1

Classification and Pathophysiology

• Cough syncope falls under the category of "situational syncope" within the broader classification of neurally-mediated (reflex) syncope according to European Society of Cardiology guidelines 1
• While both cough syncope and vasovagal syncope involve reflex mechanisms that lead to hypotension and cerebral hypoperfusion, they differ in their triggers and potentially in their pathophysiological mechanisms 1, 2
• Classical vasovagal syncope is typically triggered by emotional distress (fear, pain) or orthostatic stress, whereas cough syncope is specifically triggered by prolonged intensive coughing, often in smokers with lung disease 1, 3

Mechanism of Cough Syncope

• Cough syncope occurs immediately after coughing and typically resolves within 1-2 seconds 4
• The mechanism involves markedly elevated intrathoracic pressures induced by coughing, which can lead to:
  • Diminished cardiac output causing decreased systemic blood pressure and cerebral hypoperfusion 2
  • Increased cerebrospinal fluid pressure causing increased extravascular pressure around cranial vessels 2
  • A neurally mediated reflex vasodepressor-bradycardia response to cough 2, 5
• Recent studies suggest cough syncope patients demonstrate a blunted chronotropic response to hypotension compared to vasovagal syncope patients, indicating different pathophysiological mechanisms 5

Clinical Characteristics and Diagnosis

• Typical profile of cough syncope patients: middle-aged, large-framed or overweight males with obstructive airways disease 2
• Cough syncope patients experience greater blood pressure drops and longer recovery times after coughing compared to controls or vasovagal syncope patients 5
• Valsalva maneuver testing can help discriminate among pathogenic mechanisms in cough syncope patients 6
• Diagnostic evaluation should focus on identifying and treating the underlying cause of cough, as elimination of cough will eliminate the resultant syncopal episodes 2

Distinguishing Features from Classical Vasovagal Syncope

• Classical vasovagal syncope is primarily mediated by emotional or orthostatic stress 1, 3
• Cough syncope is specifically triggered by coughing, with a direct and immediate loss of consciousness following the cough 1, 4
• The pathophysiology of cough syncope involves both mechanical effects of increased intrathoracic pressure and potentially different reflex mechanisms than those in classical vasovagal syncope 2, 5
• Patients with cough syncope show abnormal hemodynamic responses during Valsalva maneuver testing compared to those with vasovagal syncope 6

Clinical Implications

• Management of cough syncope should focus on identifying and treating the underlying cause of cough 2
• Thorough evaluation of potential underlying causes of cough is essential, as recommended in cough management guidelines 2
• Patients with cough syncope should be screened for possible underlying sources of cough, including obstructive airways disease 4, 2