Sinus Tachycardia




Physiologic Sinus Tachycardia

Background

  • P wave before every QRS
  • Regular PR interval
  • Normal P axis (0-90 degrees)
  • Adults: over 100 bpm. Children: over age specific range

Mechanism

  • Normal automaticity and depolarization, just increased rate
     

Etiology/Risk Factors

  • Fever
  • Anxiety/pain
  • Respiratory illness/hypoxia
  • Sepsis
  • Dehydration
  • Stimulant meds/drugs/caffeine
  • CHF (congestive heart failure)
  • Myocarditis
  • Drug withdrawal
  • Postural orthostatic tachycardia syndrome (POTS)
  • Pheochromocytoma?

Epidemiology

  • Extremely common in infants and young children due to anxiety component to getting vital signs or ECG completed
  • Essential component to recognition of sepsis

Diagnostics

  • History/Symptoms
    • Recent illness history, fever, med/drug history
       
  • Physical Exam/Signs
    • General appearance, vitals
    • HEENT: nasal congestion, JVD
    • Cardiovascular: pulses, perfusion, murmurs
    • Pulmonary/Chest: respiratory distress, tachypnea, crackles
    • Abd/GI/GU: liver down or not? Any pain?
    • Musculoskeletal/Nervous System: cause for pain, seizures, AMS
    • Skin/Extremities: perfusion, signs of infection
       
  • Labs/Tests
    • Work up is not for the tachycardia but for the suspected cause of the tachycardia if
      • Suspected to be pathologic and not behavioral (eg, anxiety, crying, etc)
      • From a known iatrogenic cause (eg, albuterol)
         
  • Imaging
    • Usually none, if concerned this may not be sinus tachycardia get an ECG
    • Again, imaging will depend on work up for any treatable cause

Differential Diagnosis

  • Don't forget sepsis

Treatment

  1. Never treat sinus tachycardia - treat the CAUSE of sinus tachycardia
    • Main goal is to identify and treat that underlying cause
    • Assess/correct dehydration
    • Correct anemia
    • Correct fever and identify source
    • Medication review (eg, Sympathomimetics)
    • Toxicology screening
      • Amphetamines, cocaine, TCAs
    • Pain/anxiety are always diagnoses of last resort
      • Search for a physiologic cause first
         
  2. Specific situational treatment
    • Consider Beta-Blockers for:
      • MI patients, CHF patients
      • Thyroid storm patients
    • Consider benzodiazepines for:
      • Cocaine overdoses
        • Avoid Beta blockers, esp. if hypertensive
      • Sympathomimetic overdoses
        • Amphetamines, methamphetamines
        • Ephedra
      • Panic attack, severe anxiety disorders
        • Minimal cautious use

Disposition

  1. Admission guidelines
    • Any admission in this case should not be for the tachycardia but an underlying cause which would fit it's own criteria for admission
  2. Consults
    • Cardiology if unsure about whether rhythm is sinus tachycardia
  3. Discharge/Follow-up instructions
    • Follow up with Cardiology may be warranted if
      • Tachycardia is positional
      • There is syncope or presyncope
      • Concerns for POTS

Inappropriate Sinus Tachycardia

Background

  • A persistent increase in resting/ sinus heart rate
    • Increase is unrelated / out of proportion to a stressor
  • Majority of patients are female (90%)
    • Most common age 26-50 years

Pathophysiology

  • Two possible mechanisms
    • Enhanced sinus node automaticity
    • Abnormal autonomic regulation of sinus node
      • Excess sympathetic tone
      • Reduced parasympathetic tone
  • Range of disease varies from asymptomatic to major disability
  • Risk of tachycardia-induced cardiomyopathy is small

Diagnostics

  • Non-paroxysmal tachycardia
  • ECG identical to Normal Sinus Rhythm (NSR)
  • 24-hr holter monitor findings
    • Persistent sinus tachycardia (> 100 bpm) during the day
    • Excessive rate increase with activity
    • Rate normalizes at night
  • Secondary causes must be excluded
    • Hyperthyroid
    • Pheochromocytoma
    • Physical deconditioning
    • Medication/drug effects
  • If cardiac dysrhythmia is suspected
    • Consider prolonged ECG monitoring and echocardiography
      • History, physical exam and ECG lack diagnostic accuracy

Treatment

  1. Initial/Prep/Goals
    • ABCs, monitors
    • Treatment is symptom dependent
  2. Medical/Pharmaceutical
    • First-line treatment
      • Beta- Blockers
      • Calcium-channel blockers
        • Verapamil
        • Diltiazem
  3. Surgical/Procedural
    • Radiofrequency catheter ablation
    • Surgical excision in sinus node

Disposition

  1. Rule out underlying pathology
  2. Follow up with cardiologist

Postural Orthostatic Tachycardia

Pathophysiology

  • Disorder of autonomic dysfunction
  • Defined as:
    • Excessive orthostatic tachycardia within 10 min on upright tilt
      • >30 bpm over baseline OR
      • >120 bpm
    • NO significant hypotension
    • NO overt autonomic neuropathy
  • Many possible mechanisms:
    • Idiopathic hypovolemia
    • Splanchnic RBC pooling
    • Autoantibodies to peripheral nicotinic Ach receptors
    • Intrinsic sinus node abnormalities
    • Viral infection
  • Two predominant forms
    • Central beta-hypersensitive form
      • Physiological baroreflex fails to terminate tachycardia
      • May be due to defective norepinephrine -transporter mechanism
    • Partial dysautonomic form (most common)
      • Mild peripheral autonomic neuropathy
      • Peripheral vasculature fails to constrict during orthostatic stress

Diagnostics

  • Symptoms
    • Highly variable
      • Palpitations
      • Presyncope, lightheadedness
      • Severe fatigue, exercise intolerance
        • May overlap with chronic fatigue syndrome
      • Tremors
      • Feel cold / cannot tolerate extreme heat
  • Diagnostic Testing:
    • Head-upright tilt test : within 5-10 min, see
      • Heart rate:
        • Heart rate increase > 30 bpm OR
        • Heart rate >120 bpm
      • Blood pressure:
        • NO orthostasis
      • NO known cause of autonomic neuropathy
      • Provocation of symptoms
        • Usually see NE levels >600 ng/ml
        • Excessive HR increase to isoproterenol infusion
          • >30 bpm increase to 1 mcg/min infusion

Treatment

  1. Sinus node ablative procedures NOT effective
    • No effect on symptoms
    • May worsen symptoms
  2. Most therapy is currently medical
    • Not yet well understood/ classified
  3. NONPHARMACOLOGIC Tx
    • Volume expansion (current mainstay of treatment)
      • 8oz (240ml) of H2O 5-8 times daily
      • 10-15 grams salt/ day
      • Sleep with head of bed elevated 4 inches
        • Increases renin secretion
        • Expands plasma volume
    • Resistance training + physical counter maneuvers
      • Thigh-length compression stockings
        • > 30 mmHg at ankle
  4. PHARMACOLOGIC Tx
    • Many agents and combinations available
      • Beta-blockers
        • Beta-hypersensitive POTS
        • Partial dysautonomic POTS
      • Fludrocortisone +/- bisopropol
        • Idiopathic hypovolemia
        • Requires high salt intake
        • Requires monitoring K+ levels
      • Phenobarbitol
      • Methylphenidate
      • Clonidine
      • SSRIs
      • Octreotide

Disposition

  1. Follow-up with PCP or cardiologist