SVT

Question 1

Avnrt

• pathogenesis
• investigations
• ecg
• treatment

Answer 1

Pathogenesis

• re-entrant circuit using dual pathway (fast conducting beta fibres and slow conducting alpha fibres) within or near av node
• av node divided into 2 pathways with vary conduction speed and refractory periods -> tachy initiated when appropriate times atrial complex is blocked one pathway and conducted down the other to ventricles -> impulse conducted and previous blocked Pathway recovers so impulse can now conducted uptoward atria -> reentrant circuit

Ix:
Ecg may not be that valuable as often occur within av node therefore atria and ventricles stimulate simultaneously -> p wave hidding in qrs

Retrograde p waves may be seen but usually lost ^

Treatment:
Acute - Valsalva or carotid massage (constant pressure directed posterior u against the carotid artery for 5-10s, Listen to Bruits before)
- these method enhance parasympathetic tone and can hasten arrhythmia termination

1st choice - if unresponsive to cabal maneuvers use adenosine
Fail - metoprolol, digoxin, dilutive my
Hemi dynamically unstable (hypotension, angina, hf) use electrocardioverison

Question 2

Paroxysmal supra ventricular tachycardia refers to? Most commonly which tachycardia account 50-60% of cases?
Heart rate range around?
Epidemiology?
Precipitating event?

Answer 2

Psvt refers to number of tachyarrhythmia, majority due to reentrant mechanism - avnrt is the most common (50-60% of cases)
Heart rate range around - 120-250/min
Epidemiology - female (70%), Third to fourth decade, commonly idiopathic
Precipitating event - alcohol, caffeine, stmpathimimetic amines

Question 3

Atrial fibrillation 
- epidemiology 
- symptoms 
- classification 
   Chronic/permanent, lone, nonvalvular, paroxysmal, persistent, recurrent, secondary

Answer 3

• epidemiology
  Most common sustain arrthymia, increases with age (10% of > 80 age)
• symptoms - palpitation, fatigue, syncope, precipitate or worsen hf
• classification
  Chronic/permanent, - continuous afib unresponsive to cardio version (don’t re attempt)
  lone, - 7 days or terminates only cd
  recurrent, - two or more episodes
  secondary - mi, cardiac sx, pulmonary disease, hyperthyroidism

Question 4

Atrial fib

• pathology
• ecg

Answer 4

Pathology

• initiation - single circuit re-entry +/- ectopic foci act as aberrant generator -> atrial tachycardia (350-600bpm)
• maintenance - atrial structural and elector physiological remodel further promote afib
• consequences - promotes blood stasis increase risk of thrombus formation

Ecg
- no organised p waves due to rapid atrial activity (350-600bpm) cause chaotic fibrillatory baseline

Irregularly irregular ventricular response (typically 100-180 bpm), narrow qrs

Wide qrs if aberrancy following long short cycle sequence (ashman phenomenon)

Loss of atrial contraction, thurs no a wave seen in jvp, no s4 auscultation

Question 5

Atrial fibrillation

- risk prediction for non-valvular

Answer 5

Risk of non-valvular afib via chads2

• congestive heart failure 1
• hypertension 1
• age > 75 1
• diabetes 1
• Stroke/ Tia (prior) 2

Chads2 score (stroke risk %/year, anticoagulant ion recommendation)
0: 1.9% low - aspirin 81-325 mg od
1: 2.8 low-mod - oral anticoagulants 
2-3: 4-5.9 mod - "
4-6: 8.5-18.2 high - "

Oral anticoagulate - warfarin (inr 2-3), dabigitran, rivaroxaban

Question 6

Afib mx

Answer 6

Race
- rate control
Beta blockers, diltiazem, verapamil
(Heart failure - digoxin, amiodarone)

• anticoagulation
  Warfarin, dabigitran, rivaroxaban, apical an to prevent vte
• cardio version
  24-48 hour, anticoagulate for 3 weeks prior and 4 weeks after cd

Unstable (hypotension, sick sinus syndrome, uncontrolled hf) - cd immediately

treat etiology

• ethology

Question 7

Mx of newly discover of afib

Mx of recurrent/ permanent afib

Answer 7

Newly discover

• anticoagulant if high risk
• episode is self limited and no associated severe symptoms - no need antiarrhythmics

Persist, 2 options

• rate control and anticoagulation
• cd

Recurrent/ permanent
Brief or minimally symptomatic - avoid abtiarrhytmic, rate control and anticoagulate is ok
If at least one attempt of cd and remain can be accepted (rate control and anti thrombotic

Abtiarrhytmic if:
No or minimal heart disease - flecainide, propafenone, sotalol
Lv dysfunction - amiodarone
Cad - beta blocker, amiodarone

Question 8

Atrial flutter

• what is it
• etiology
• ecg

Answer 8

Rapid, regular atrial deplorization from macro re-entry within atrium (most common ra), atrial rate 250-350 bpm, can occur with av blocks

Etiology
- cad, thyrotoxicosis, mitral valve disease, cardiac sx, copd, pe, pericarditis

Ecg - sawtooth flutter waves in inferior leads, narrow qrs

Carotid sinus massage (check for Bruits), valsalva or adenosine may decrease av conduction and bring out flutter waves

Question 9

Atrial flutter mx

Answer 9

Acute
Stable
Anticoagulant
Long term