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

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

Cough syncope is classified as a distinct form of situational syncope within the broader category of neurally-mediated (reflex) syncope, and is not considered a form of classical vasovagal syncope according to current guidelines. 1

Classification of Cough Syncope

• Cough syncope is specifically categorized as "situational syncope" in the European Society of Cardiology (ESC) guidelines, which clearly distinguishes it from classical vasovagal syncope 2, 1
• The ESC guidelines explicitly list cough syncope alongside other situational triggers (micturition, defecation, swallowing) as a distinct subcategory of neurally-mediated syncope 2
• While both cough syncope and vasovagal syncope fall under the broader umbrella of neurally-mediated (reflex) syncope, they have different triggering mechanisms and pathophysiology 1

Key Differences from Classical Vasovagal Syncope

• Classical vasovagal syncope is primarily triggered by emotional distress (fear, pain) or orthostatic stress, with typical prodromal symptoms 2, 1
• Cough syncope is specifically and exclusively triggered by prolonged intensive coughing, often occurring in smokers with underlying lung disease 1, 3
• Loss of consciousness in cough syncope is a direct and immediate result following the cough, whereas vasovagal syncope typically has a more gradual onset with prodromal symptoms 1, 3

Pathophysiological Mechanisms of Cough Syncope

• The pathophysiology of cough syncope involves markedly elevated intrathoracic pressures induced by coughing, which differs from the emotional or orthostatic triggers of vasovagal syncope 3
• Several mechanisms have been proposed for cough syncope:
  • Diminished cardiac output from increased intrathoracic pressure, causing decreased systemic blood pressure and cerebral hypoperfusion 3
  • Increased cerebrospinal fluid pressure causing compression of cranial vessels 3
  • A neurally mediated reflex vasodepressor-bradycardia response specific to coughing 3
• Some patients with cough syncope demonstrate abnormal Valsalva maneuver responses with absent blood pressure overshoot and prolonged hypotension after coughing 4

Clinical Characteristics and Diagnosis

• The typical cough syncope patient is a middle-aged, large-framed or overweight male with obstructive airways disease 3
• Diagnosis of situational syncope, including cough syncope, can be made when syncope occurs during or immediately after the specific trigger (coughing) 2
• Cough syncope typically features rapid recovery within 1-2 seconds after the event 5
• In rare cases, cough-induced syncope may be associated with complete atrioventricular block, highlighting the importance of ECG monitoring during evaluation 6

Management Implications

• Since cough syncope is classified differently from vasovagal syncope, management approaches differ 1, 3
• Treatment of cough syncope primarily focuses on eliminating the underlying cause of cough, as removal of the trigger will eliminate the syncopal episodes 3
• Evaluation should include thorough assessment for potential underlying causes of chronic cough according to published cough management guidelines 3
• Physicians should be aware of this distinct form of situational syncope when evaluating patients with syncope and screen for possible underlying sources of cough 5