SVT – Paroxysmal Supraventricular Tachycardia (PSVT)

1. Include all tachyarrhythmias that either originate from or incorporate supraventricular tissue in a re-entrant circuit
2. It is often used synonymously with AV nodal re-entry tachycardia (AVNRT), a form of SVT
3. Cause: accessory pathway (ectopic site) commonly above the bifurcation of His bundle 
4. Classification of SVT by site of origin and regularity
   1. Regular Atrial
      1. Sinus tachycardia
      2. Atrial tachycardia
      3. Atrial flutter
      4. Inappropriate sinus tachycardia
      5. Sinus node reentrant tachycardia
   2. Irregular Atrial
      1. Atrial fibrillation
      2. Atrial flutter (variable block)
      3. Multifocal atrial tachycardia
   3. Regular Atrioventricular
      1. AVRT
      2. AVNRT
      3. Automatic junctional tachycardia
5. Ventricular rate may be the same or less than the atrial rate, depending on the atrioventricular (AV) nodal conduction → affects degree of haemodynamic compromise
   1. Poor ventricular filling → ↓CO 

6. Clinically: rapid, regular tachycardia with abrupt onset and termination
   1. associated symptoms may include:
      1. Presyncope or syncope due to a transient fall in blood pressure
      2. Chest pain, especially in the context of underlying coronary artery disease
      3. Dyspnoea
      4. Anxiety
      5. Rarely, polyuria due to elevated atrial pressures causing release of atrial natriuretic peptide

7. ECG findings
   1. Fast regular p wave (160-250 bpm) 
   2. Regular narrow QRS complex: b/c it gets conducted down the normal pathway 
   3. Conduction down His-Purkinje faster than retrograde conduction
      1. narrow QRS waves appear before P waves – hallmark of PSVT
8. Not associated with stroke

Case: Jane is a 42 yr old women who teachers at the local primary school.  She attends your surgery at lunch time complaining of feeling light headed and dizzy.

1. What history would you take from Jane?

• Appreciate these symptoms could be caused from pathology to nearly any body system.
• PC: preceding factors, intercurrent illness, trauma, chest pain,, prior, onset, etc.
• PMHx: febrile illness, thyroid, syncope, stroke, Heart disease, arrhythmia, inner ear, endocrine.
• FMHx: for same
• Recent surgery’s.
• Mental health
• Meds, allergies, illicit drugs (withdrawal), alcohol, smokes.
• Nutrition
• Social/lifestyle/home/work/travel
• ?menstruation –menhorragia – anaemia??
• Pregnancy now?

Jane reports she has suffered these symptoms for one hour and has never had them before.  She is feeling palpitations and doesn’t feel well.  The only thing she was doing was drinking a strong coffee just before.  She has only recently come to town 2 months ago after splitting with her husband and as such has been under substantial stress.  She has no PMHx to note, smokes 5/day, drinks ½ a bottle of white wine most nights.  She exercises by walking/jog 3x per week.

2. What would your examination and GP accessible test include?

• General inspection – appearance, behavior
• Vitals, wt/ht.
• Skin: features of alcoholism or IVDU.
• Neuro: Pupils, Peripheral T/P/R/S/coordination – ?stroke, cerebral bleed, opiates
• Vision/hearing – check for vestibular causes.
• CVS: ECG ? arrhythmia, ACS, orthostatic intolerance
• Resp: LRTI, PE
• ENT: ears
• Endocrine: BSL, thyroid, addisons
• Abdomen
• MSE – depression/anxiety screen.
• GU – MSU dip stick.

Jane is afebrile, BP 95/60, HR tachy, no other features of thyroid dysfunction.

3. How do you interpret this ECG and what will be your management?

SVT is the rhythm

Non pharmacological

• usually one method should be attempted prior to pharmacological treatment in the stable patient
• Increased Vagal Tone
  • Modified valsalva – REVERT trial shows improved response to Valsalva manoeuvers if done sitting, sustained Valsalva for 15 secs(attempt to blow into 10ml syringe), then positioning flat and raising legs for 15 secs. This increased rates of cardioversion from 17% to 40%.
  • Carotid sinus massage – Patient supine with neck hyperextended, apply gentle pressure for 10-15secs.
    • Check for bruits first, do not perform if bruits present or at risk of stroke (age >65, Hx of TIA / CVA or risk factors present). Do not do bilateral massage simultaneously.revert approximately 30% of cases

MEDICATIONS

Verapamil

1. appropriate first choice in adult SVT without significant hypotension and narrow QRS
2. contraindicated in children < 1 year of age
   1. severe cardiac decompensation may occur
3. reversion rate
   1. 80% with 5 mg IV
   2. 95% with 10 mg IV
   3. the addition of vagal manoeuvres + Trendelenburg position can produce reversion with lower doses
4. progressively less effective for heart rates higher than 175 bpm
5. probably more effective than adenosine in patients with caffeine ingestion in previous 4 hours
6. pretreatment with 5 mL calcium gluconate 10% decreases hypotensive effects without decreasing efficacy

Adenosine

1. first choice agent in SVT in
   1. infants
   2. patients with structural heart disease
   3. when borderline perfusion is present
2. Pharmacodynamics
   1. endogenous purine
      1. has specific receptors in the myocardium
   2. depression of SA & AV nodal activity
   3. antagonises cAMPmediated catecholamine stimulation of ventricular muscle 🡪 negative chronotropy & dromotropy
   4. direct agonist at specific cell membrane receptors (A1 & A2)specific action is only on the AV node
3. Pharmacokinetics
   1. spontaneous hydrolysis in the plasma
   2. no hepatic or renal excretion
   3. Onset 10seconds, duration 10 seconds, elimination T ½ 10 seconds
4. Indications
   1. SVT
      1. reverts 90% of patients in total
      2. 50% with first dose
      3. 15% recur after one dose
      4. progressively less effective for heart rates lower than 175 bpm
   2. diagnosis of narrow complex arrhythmias
      1. acts as pharmacological vagal manoeuvre
   3. diagnosis of broad complex tachycardia
      1. if SVT with aberrant conduction suspected
      2. however deaths reported when used in VT
5. Contraindications
   1. relatively contraindicated when additional sympathetic stimulation may be hazardous
      1. sympathomimetic induced SVT
      2. aortic dissection
      3. intracerebral haemorrhage
      4. APO secondary to hypertension
6. Adverse effects
   1. occur in 30% of patients
   2. duration usually < 30 seconds
   3. flushing
   4. dyspnoea
   5. chest pain
      1. anxiety
      2. may be severe
      3. feeling of imminent death
      4. reduced by pretreatment with midazolam
   6. bronchospasm
   7. bradycardias
      1. transient sinus arrest > 4 seconds occurs in 5%
      2. bifascicular block
      3. complete heart block
      4. more common in patients with heart transplants
   8. ventricular ectopy
   9. nonsustained monomorphic VT
      1. about 10 times the cost of verapamil
7. Dose
   1. rapid IV bolus followed by saline flush
   2. Adults: 3mg > 6mg > 12mg
   3. Children : 0.1mg/kg, repeat dose 0.2mgmg/kg
   4. give rapidly and follow with a 20 mL saline flush
   5. use of a 3 way tap helps to maximise speed of delivery
8. Interactions
   1. carbamazepine  increases the action of adenosine, and can cause additional AV block
   2. theophylline and caffeine inhibit adenosine competitively at the A1 receptor
   3. reduced reversion rate by approximately 20% if caffeine ingested within 4 hours of attempted reversion 

Electrical cardioversion

1. rarely required
2. must be synchronised
3. adults

1. monophasic 50  200 J
2. biphasic 20  100J
3. children

3. 1J/kg (revised upwards from 0.5 J/kg in 2015 ILCOR guidelines)
4. 2J/kg if unsuccessful

Prophylaxis of AVNRT

1. Single dose “pill in the pocket” oral therapy propranolol or diltiazem may be instigated by patient’s cardiologist for recurrent prolonged episodes
2. flecainide
3. digoxin and verapamil in combination
4. higher doses of verapamil needed to be effective (i.e. 80 mg three times daily)
5. radio frequency ablation if accessory pathway present

6. reduces recurrences within a year from 60% to 5%
7. also highly effective in nodal reentry SVT
8. 12% risk of precipitating complete heart block

Educate about PSVT:

Warn about triggers – stress, coffee, alcohol, smoking.

Teach what to do if another episode.

Cardiology r/v – echo, stress ECG, holter.

Ensure f/u

Managing SVT

1. Lifestyle Modifications:
   • Avoid Triggers: Common triggers include caffeine, alcohol, nicotine, and certain medications. Identify and avoid these triggers.
   • Stress Management: Practice relaxation techniques like deep breathing, yoga, or meditation to reduce stress, which can precipitate episodes.
   • Healthy Diet: Maintain a balanced diet, low in sodium and rich in fruits, vegetables, and whole grains.
   • Regular Exercise: Engage in regular physical activity, but avoid strenuous exercises that might trigger SVT.
2. Acute Management Techniques:
   • Vagal Maneuvers: Techniques like the Valsalva maneuver, coughing, or immersing the face in cold water can sometimes stop an SVT episode.
   • Medication: If prescribed, take medications such as beta-blockers or calcium channel blockers as directed by your healthcare provider.
3. Medical Treatment:
   • Medications: Long-term medication may be necessary to control heart rate or rhythm.
   • Ablation Therapy: In recurrent cases, radiofrequency catheter ablation may be recommended to destroy the area causing abnormal signals.
4. Emergency Situations:
   • Recognize Symptoms: Know when to seek emergency care—persistent chest pain, severe shortness of breath, or fainting.
   • Emergency Plan: Have an emergency plan in place, including access to emergency medical services if needed.

Regular Monitoring and Follow-Up

• Regular Check-ups: Keep regular appointments with your cardiologist to monitor your condition and adjust treatment as necessary.
• Holter Monitor: You may be asked to wear a Holter monitor or event recorder to track your heart’s activity over a period.

Patient Education

• Understanding Your Condition: Learn about SVT and understand your specific triggers and symptoms.
• Support System: Engage family and friends in your care plan so they can assist in case of an episode.

Important Tips

• Medication Adherence: Take your medications exactly as prescribed.
• Medical ID: Consider wearing a medical ID bracelet indicating your condition and medications.
• Health Records: Keep a record of your episodes, including potential triggers and symptoms, to discuss with your doctor.