What causes SVT (Supraventricular Tachycardia) after a URTI (Upper Respiratory Tract Infection) in someone who consumes coffee?

Causes of SVT after URTI with Coffee Consumption

Supraventricular tachycardia (SVT) following an upper respiratory tract infection (URTI) in a coffee consumer is most likely triggered by the combination of physiological stress from infection and caffeine's stimulant effects on the cardiac conduction system.

Pathophysiological Mechanisms

• SVT may occur spontaneously or can be provoked by exertion, coffee, tea, or alcohol consumption in susceptible individuals 1
• Caffeine is a vasoactive substance that promotes the release of norepinephrine and epinephrine, potentially triggering arrhythmias in predisposed individuals 2
• Physiological stress from URTI can create a substrate for arrhythmias through:
  • Inflammatory mediators affecting cardiac conduction
  • Increased sympathetic tone due to fever or discomfort
  • Dehydration from fever or reduced intake 1

Role of Caffeine

• Caffeine acts as an adenosine receptor antagonist, which can:
  • Increase heart rate
  • Enhance automaticity in cardiac cells
  • Potentially trigger SVT in susceptible individuals 3
• Recent caffeine ingestion (within 4 hours) significantly reduces the effectiveness of adenosine in treating SVT, highlighting caffeine's direct impact on cardiac electrophysiology 3
• High concentrations of caffeine, particularly in energy drinks, have been associated with cardiac arrhythmias in case reports 4, 2

URTI as a Trigger

• Infection with fever is recognized as a pathological cause that can lead to physiological sinus tachycardia, which may trigger SVT in susceptible individuals 1
• Systemic inflammation from URTI can affect cardiac conduction properties
• Dehydration and electrolyte imbalances during infection may lower the threshold for arrhythmias 1

Pre-existing Conditions

• SVT most commonly occurs in young adults without structural heart disease 1
• Pre-existing conditions that may predispose to SVT include:
  • Dual AV nodal physiology (anatomic substrate of AVNRT)
  • Accessory pathways (substrate for AVRT)
  • Mitral valve prolapse 1, 4

Clinical Considerations

• SVT following URTI with coffee consumption typically presents with:
  • Sudden onset of palpitations
  • Possible shortness of breath, dizziness, and neck pulsations
  • Rarely syncope 1
• The diagnosis should be confirmed with a 12-lead ECG during tachycardia 1
• Vagal maneuvers are the first-line intervention for acute termination of SVT 1

Prevention Strategies

• While moderate caffeine consumption has not been definitively linked to increased arrhythmia risk in the general population, patients with known SVT may benefit from limiting caffeine during acute illness 2
• Energy drinks with high caffeine content should be avoided in patients with known arrhythmias 2
• Adequate hydration during URTI may help prevent arrhythmias 1

In summary, SVT after URTI in a coffee consumer is likely caused by the combination of physiological stress from infection and caffeine's stimulant effects, particularly in individuals with underlying susceptibility to arrhythmias.