Sinus Tachycardia

Introduction

  • Mechanism: Increased automaticity of the SA node
  • Defined as sinus rate > 100 bpm

Response to Adenosine

  • Gradual slowing of the tachycardia and then re-acceleration
  • Sinus nodal re-entry tachycardia will suddenly terminate

ECG Characteristics

  • Gradual onset & offset (driven largely by the autonomic nervous system)
  • P-wave morphology
    • Matches P-waves in sinus rhythm
    • Positive in I, II, aVF, and biphasic/negative in V1 [Should originate in the SVC-RA junction]
  • Presence of conditions that drives sinus tachycardia: i.e. pregnancy, effort, stress
Sinus Tachycardia: Note gradual acceleration and positive P-waves in lead II

Management

  • Must exclude POTs, sinus re-entrant tachycardia, focal AT from superior crista terminalis or RSPV
    • Sometimes need EPS to exclude sinus re-entrant tachycardia
  • The following are diagnoses associated with sinus tachycardia:
  • Physiologic sinus tachycardia (PST) 
    • Correct underlying cause, no specific therapy needed
    • Commonly: Hypovolemia, Anemia, Hyperthyroidism, PE, Pheochromocytoma
  • Inappropriate Sinus Tachycardia (IST)
    •  >100bpm at rest or minimal activity (out of proportion) – generally young female.
    • Holter – mean HR > 90bpm, exaggerated > 100bpm during waking hrs.
    • Prognosis benign, not associated with tachycardia cardiomyopathy
    • Therapy:
      • 1st Line: Lifestyle: exercise training, volume expansion, avoid stimulants
      • 2nd line:
        • B-Blockers (high doses needed) or
        • Ivabradine (usually with B-blocker to avoid paradoxical sympathetic increase)
  • Sinus Node Re-entrant Tachycardia (SNRT)
    • Re-entry circuit involving the sinus node
    • Unlike IST, these are paroxysmal episodes
    • Drugs:
      • B-Blockers are often ineffective
      • 1st line: Verapamil/Diltiazem (IIB), avoid in HFrEF
        • Can try amiodarone
    • 2nd Line: Catheter ablation if do not respond to drugs (IIA)
ESC 2019 Guideline: Management of sinus tachycardia
ESC 2019: Sinus Tachycardia
  • POTS
    • HR ≥ 30bpm when standing > 30s (or ≥ 40bpm in 12-19yo) [Usually females 12-19yo]
      • ABSENCE of orthostatic hypotension
    • 50% spontaneously recover in 1-3yrs
    • Many mechanisms described
    • Non-Pharmacologic:
      • Increase salt/fluid intake, increase blood volume (10-12 g/day salt, ≥2-3L/day) (IIB)
      • Exercise program (start with non-upright like rowing) (IIA)
    • Pharmacologic:
      • Midodrine TID daytime (IIB)
      • Propranolol 10-20mg (non-selective BB ideal to block Beta-2 receptor) (IIB)
      • Ivabradine (with BB) can be considered (IIB)

References:

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